I think this thread has enabled us to build a useful reference source that suggests that many of the Aerokits model boats that have a large keel on them would benefit from having them cut-off (or at least reduced in depth) to improve their steering performance when used with radio control.

The deep keels can be helpful when the models are being used as "free runners" when they have no radio control and are set to run "straight" in the traditional pond model tradition.

As a "straight runner" model the deep keel can be a benefit as it will help to keep the model running "straight" and this may be why this feature was included in the design at the time?

This same "resistance to deflection" that the deep keel provides is the reason that we have experienced "strange handling" problems when running our Aerokits models under radio control.

The Aerokits range was drawn-up many years ago - probably at some time during the 1950's when few of us could afford to buy a radio control system, so most of them would have been run as traditional "straight runners" across the local model boating lakes.

When the early 'galloping ghost" type radios first became affordable to some devout model boat enthusiasts, they merely clicked the rudder to the left or the right and back to the neutral position again to cause a non-proportional deflection of the models progress across the pond......and so the stability that the deep keel provided could still be regarded as an asset rather than a problem.

It was only much later when proportional radio control was fitted to almost every Aerokits model boat that was being run under IC or electric power that these "strange handling" problems were noticed as the rudder and the deep keel came into conflict with each other.

The intended action of the deep keel was trying to keep the models direction nice and straight and the rudder (now under proportional control) was fighting against it to produce a nice proportional turn to the left or right.

With more power being so easy to add to these early model boat kits they began to run faster and this is when the conflict between the deep keel designs and the proportional rudder control began to generate "strange handling" problems such as the nose wanting to dive when the rudder was turned to the RIGHT - this being especially noticeable if the model was being turned into choppy water or another boats wake.

Removing (or at least reducing) the deep keel from these models will improve the performance and help (at least) to remove any of the problems that I experienced with my own Sea Commander before the "penny dropped" and the true reason for the problems was realised.

I have spent many hours and made lots of changes to my Sea Commander to try to find the reason and the cure for the nose diving actions that it suffered.

Removing the deep keep is such an easy "fix" that does not have to be done when the model is being built. It is so easy to cut off the area of the keel along the line of the hull where it meets the prop shaft, and this simple modification can vastly improved the performance of the model when it is being run under radio control.

Bob.

Hi All
I checked the plans of the Sea Rover and it has the same large keel as the Sea Commander. Mine Sea Rover keel was very poor state, so I cut it off and added a 4x4 mm strip from bow to the prop tube. Only a small triangle piece of plywood from the prop tube to the prop.
The boat handles like a dream!!!
Harry

Hi Zooma
My 46" crash Tender has a 420 kv brushless on 6 S and a 2 blade 52 mm prop. RPM about 10000 !!! So I have a 5055-700 kv brushless and on 4S about 10360 rpm. So that's my base start. As for spray rails I am not planning on adding them, but chine rails, yes.

Harry

Hi Harry,

I always thought that it was a bit strange to specify a 17" long 4mm prop shaft on such a large Classic Model Power Boat.

Swapping the 4mm shaft for a 5mm Maxi-shaft will be one of the first jobs on my Sea Queen restoration followed by a good motor mount to fit a brushless out-runner.

I am not so sure about the size of propeller yet, but 50mm could be a good size to start with, but when the boat can be run for the first time, the experimentation will start!

Making a set of strakes for the Sea Queen is something that I may consider doing as they do make the otherwise "bland" looking hull a bit more interesting.

Fitting chine spray rails and deck edge strips from two laminates of 1/8" x 1/4" obechie hardwood will be fitted (this has always been a "standard fit" on all my Classic Model Power Boats).

My Sea Queen does not have any chine edge spray rails fitted, so maybe the original builder of this model did not like them?

I did fit some fairly substantial strips of wood to the engine bay floor skins of my Sea Commander to help stop any "drumming", but I had not thought about adding any to the two rear-most cabin floor skins, but being a much bigger model it would make sense so I will fit some.

This will be a nice slow restoration project that I will fit in-between my other builds - in particular the Sprite Plus that has had no attention at all over the Christmas holiday period !

Bob.

Hi Zooma
I checked the plans and the keel is far less than Sea Commander. So the modified Commander keel on my boat is about the same standard on the Sea Queen.
Ordered the whole 5 mm drive plus a 50 mm 3 blade and a 52 mm 2 blade prop. I removed the decks, saved the side ones. The bow deck is getting replaced. I think I can save the fixed forward cabin roof and the forward cabin roof.The stern roof section can be saved also. I have re-glued all the hull and removed the nails. Next is installing stringers to the two stern section to stop drumming from the thin plywood skins.

Canabus🤞

Just a little TLC and it should be a runner Harry 🤣

I also have an old Sea Queen that needs a bit of the same - maybe they could both get to run during 2026?

.....then we can report back on the claim that the Sea Queen does not have the same handling problems as its smaller sibling the Sea Commander.

Merry Christams,

Bob.

Well lads, I will sea if my Sea Queen handles as well ???
It 's just a bear hull at present with lots of nails.
Harry

I have just re-found this short online video of a Sea Queen that suggests that the Aerokits Sea Commander and Sea Queen models were based on a boat called the "Sea Rover" that won an off-shore race in 1960/61...but it doesn't say which off-shore race......

...but I knew that I had heard this claim somewhere before, but I couldn't remember where I had heard it

If true, this would be a very good result for a model that some still think was based on a Norfolk Broads cruiser .

I only included this here as there was some mention about the suitability of this design for fast running when I was experiencing the handling problems that formed the reason for this thread.

Either way, my own Sea Commander (Kopy Kommander) is now running beautifully at speed and looks very much at home making white water!

Bob.

I ran my Sea Commander (Kopy Kommander) yesterday afternoon with the keel now almost completely removed and it performed flawlessly.

The boat is now a pleasure to drive and has no longer has the tendency to nose dive when turning RIGHT into choppy water or a wake.

It has taken a long time and lots of “false leads” as every suggestion offered was followed-up and tested in the search for a solution, but the most simple fix was to chop-off the keel and that was the only one that made a substantial difference.

The strakes that I added during the building of this Sea Commander replica do not affect the nose diving and so they can stay and continue (in my opinion) to enhance the appearance of the boat.

The wedge that was added to the stern makes no real difference either, and so it has been left on as it is now part of the history of of the boat, and in its developed “grooved” form it looks as good as the strakes.

I have left the commercially available “large” size rudder fitted (I forgot to refit the “medium: size rudder) so that is how it is running now, but I didn’t think that the change of rudder size (or the use of a “shaped” rudder) made much difference either.

The two layers of roof lead that I cut and shaped to hook behind the rudder post have stayed as I like the attitude of the boat as it rides when it is planing.

The two large 2C 7600mah LiPo cells remain either side of the motor to give balance and ballast so that the boat “sits” nicely in the water.

The boat has still only ever been run with a single 2C LiPo connected (the second LiPo is only carried to balance the boat left to right) and this produces plenty of power to use on the small Southport boating lake.

The only remaining “curiosity” that remains to be resolved is the “gurgling” sound that comes from the propeller when the rudder is turned (either left or right).

This “gurgling” sound is best heard when the boat is being driven closely away from me, but once identified it can be heard at any speed and anywhere when the rudder is deflected to the left or the right.

The may (or may not) be caused by the three rows of strakes on either side of the hull (?) and it does not detract from the boats much improved handling in any way……..but it does remain as a curiosity.

When the chance to test drive another Sea Commander arises (it is unlikely to have any strakes fitted) I will listen and observe to see if it also has a similar “gurgling” sound when the boat is turned to the left or right (but disappears when the rudder is returned to the straight ahead position).

Bob.

That's interesting Harry, I didn't know that your Jotika Sea Commander also suffered from the infamous Sea Commander nose dive.

I tried moving the battery position during the testing on my Sea Commander and it didn't seem to make much difference to the bows digging in. If I turned RIGHT into choppy water the bows would dig in where ever the batteries were placed.

At the moment I have gone back to running with a pair of batteries mounted side by side in the engine bay and it works well.

When I run with the batteries under the cockpit floor the boat ran with the bows quite high in the air - but they still dug-in when turning RIGHT into choppy water!

With the keel chopped away (like yours) the problem has disappeared - maybe my strakes are helping?

I am still running with the two layers of roofing lead behind the rudder post - maybe that is helping too?

Bob.

Hi All
I have two positions for the battery. One is about under the
wheelhouse floor and the other is far more to the stern.
The forward setup makes the bow dig in on the turns.
The stern mount has as in the pictures has the bow sitting up high, but the boats spot on.
Harry

You are spot-on with your observation Will - mine now drives like Harry's does.

It turns nicely into the turns (left or RIGHT) and leans into them beautifully.

My Sea Commander is now running with minimal keel left on it - the same as Harry's 👍

Bob.

With Harrys Sea Commander, you can see it leaning into the turns, which yours wasn't before was it Bob, plus as you say, you can see the stern slipping out with the rudder input at speed.

Hi Harry,

Thanks for sharing the latest pictures of your Sea Commander "doing its thing" on your local water in Tasmania .

Your Sea Commander runs with its nose fairly high out of the water when it is on the plane and running fast - just like mine does!

Now that I have chopped the keel off of my Sea Commander (same as yours) it has become a very different boat to drive and enjoy!

Bob.

Great shots Harry. They clearly show the stern moving sideways when turning which Bob's wouldn't do because of the deep keel. This was then forcing the bow to turn sharper than what usually happens and throwing up all that water which was causing him those issues.

No sooner said than done Roy 👍

I have started a new thread to cover "Early Radio Control Experiences" that I have started with my own first radio control system that I had to save up for weeks to buy in the 1960's.

Meanwhile, this thread continues to get good support for what must be one of the most popular Classic Model Power Boats ever made - the Aerokits Sea Commander,

Bob.

Hi all, this is a great thread! Now we are talking about early RC experience.😍

Could we start a new thread with that subject? I still use all the old (proportional) stuff myself. With 18 Tx's and many more rx's no reason to go to 2.4 Ghtz.
Roy

Hello All Sea Commanders
A few Pictures from last Saturday.
I was driving like it was stolen in a double figure eight.
35mm 1250kv, 3S lipo and a 40mm CNC prop.
Harry

Post moved to early RC experiences thread.

Ha, I am in Rawtenstall Duncan, so we live very close to each other 👍

Yes Rossendale Models was on the main road in Rawtenstall, and King Cobra Racing had a unit in Helmshore before buying one closer to Rawtenstall on the Burnley Road near to Crawshawbooth.

Both model business's are now sadly closed, much like the one in Deansgate, they are all sadly missed,

Bob.

Yes I live in Helmshore. Was your shop on the main road in Rawtenstall? If it was, it is a great shame it is no longer there just like the one in Manchester I worked in that that is no longer there!

Thanks for sharing your pictures with us Duncan - the more Classic Model Power Boats that we can show here, the better 👍

I see that you added an alloy wave breaker and a pulpit to your Sea Commander - they do look good !

I also worked in a local model shop - Rossendale Models - not too far away from you!

Bob.

Hi Bob, I must have been about 14 or 15 at the time. I use to wash cars on a Sunday morning in order to save enough cash to buy a second hand radio control set! It was non proportional with two switches which you had to switch on and off for short periods of time to steer and also adjust the speed. There was no way I could afford a proportional set which were several hundreds of pounds back around 1966! My bedroom always had a smell of diesel because to me it was too valuable to keep it in the garage! I stored it on top of my wardrobe. I now regret having sold it but the diesel engine was rather trouble some to start! I also had to save up to buy my own full size bicycle. How things have changed! 😂
The Sea Commander was secondhand so I didn't build it but I did a lot of modifications including using, for example, silver foil around the windows. When I was about 15, I started working in The Model Shop on Deansgate in Manchester on Saturdays and during school/college holidays This is where my Dad bought the boat from as a present after I had a serious eye operation in East Grinstead (about 240 miles from home) because they couldn't do the operation in Manchester. I was in hospital for 5 weeks but my Dad could only have 3 weeks holiday. So I had no visitors for 2 weeks! So the boat was for me being brave in hospital all on my own. When I was about 20, I built the already part built Aerokits RAF Crash Tender for my brother's birthday but after a few years he 'fell out' with it so he gifted it back to me! You have seen the video of this Crash Tender running on our pond on this thread. Hope you like the pictures of the boat from the mid 1970's - taken from colour slides. A trip down memory lane for me !😀😀

That is a brilliant memory to have Duncan, you have painted it so well that I can see you (in my mind) standing there in the middle of the pond watching your Sea Commander encircle you!

The deep keel will have given your boat really good stability to help it encircle your position with as little deviation as possible....until the ratchet sprung loose!

Did you ever add radio control to your Sea Commander at a later date?

..........and do you have any picture of your Sea Commander that you can share with us?

Bob.

Yes in the 60's my Sea Commander was set with a turning circle on the racket tiller! I had a pair of waders and I used to stand in the middle of the pond watching it go round. One time the ratchet sprung loose with the vibration of the 3.5cc diesel engine. The consequence was it crashed into the concrete side of the pond and damaged the bow!

Ha - I can just imagine taking your model boat on a London tram to the local model boating lake Roy.

The Sea Commander would fit across the tram seat very nicely.

Model boating was very popular before the war and again back in the 1950's and 60's before radio control became so readily available and affordable.

Bob.

Hi Bob, I think the straight runner would have been max. 40 inches.
This was the width of a seat on the old London trams! This is where the restricted length came from.

They were often low s/s to stop wind deflection and again relatively fast. A low power motor would allow for too much time on the course and time to drift off course.

Many pre-radio boats had a ratchet tiller and would be set to go in a wide half circle.

The competitons would attract dense crowds pre-war and back in the 50s and early 60's.
Roy

Straight Runner?

Dave mentioned in a previous post on here that the Sea Commander may well have designed by Les Rowell at a time when a lot of Classic Model Power Boats were still being used as "straight runners" without radio control.......and is why it had such a deep keel to help it run straight.

This made sense as a lot of the olde Classic Model Power Boats that I have bought to restore over the years came with a ratchet fitted to the rudder, and I remember seeing these rudders with ratchets advertised in the same Keil Kraft catalogues as the Sea Commander at that time.

One of the first things that got thrown away every time I took these old models apart to work on restoring them was the ratchet, so although I have had had quite few of them - I did not have one left to take a picture of.

Here is a picture of one of these ratchets that I found fitted to a 36" Classic Model Power Boat that also has an old Mabuchi electric motor fitted to it to further identify it as being a "straight runner" from the 1960's time period.

As a matter of interest, one of the LesRo Rapiers that I am currently restoring came with a very lower power electric motor and was fitted with a ratchet rudder, so it had obviously been run without any radio control - probably as a pond boat?

Bob.

Good idea Chris - send them the link so they can also see all the other things that were tried and didn't work as it may save them a lot of hassle and time by not having to try them all - especially when the solution is so simple and easy to apply to any pre-built model or kit.

The large keel can also be seen on other designs from the same pen that may benefit from either reducing or removing the keel completely.

The LesRo Sportsman has a large keel, and one of the first things that I did was to reduce its depth quite considerably as I started to restore it.

Apparently the Aerokits 34" Crash Tender also suffers in a similar way to the Sea Commander, so this information may be of interest to owners of other Classic Model Power Boats?

Bob.

I've already advised someone on a Facebook group who is about to start building a Sea Commander to reduce/remove the keel.

Hi Chris, I am fairly confident that this will be the last change that will be needed to my Kopy Komander to improve its overall handling and specifically to stop the nose diving when it turns RIGHT into any form of choppy water.

Leaving some of the keel showing ties-in with the strakes that I fitted when I was building the boat, and it actually looks much better than the original Aerokits (over-sized) keel did too.

I know that the underside of the boat is not usually visible, but I do really like the look of this hull with the added strakes, and I am so pleased that adding them did not do anything to adversely affect the handling of this boat.

When the boat is running at its usual cruising speed (and not being thrashed specifically to cause the nose dive for the videos) the strakes help to lift the boat up onto the plane at quite a low speed, and the way that they turn the water away from the bows in an ordered series of mini-wakes as the boat drives past at low speed is very pleasing.

The "anti-torque wedge" that was fitted early in the testing is still fitted with its shape being the one that was developed to give less effect that the original large flat shape, but has enough effect to counter any torque induced twist.

I am not sure if the wedge is actually "needed", but since it is not causing any problems it can stay fitted as part of this particular boats history......and it adds to the "interesting" under-water hull shape!

The wedge may actually be of some genuine value (?) as the powerful brushless motors that I am using do give a lot more power than the types of ic engines (up to 10cc) that could have been used back in the 1960's when this boat was probably one of the most popular large kit-built model boats that could be seen on the local model boat clubs waters, but either way it is staying on this boat as I have no plans to remove it.

I think it safe to say that I have never spent as much time working on the parts of any model boat that would not normally be seen!

No other model boat that I have had since the 1960's when I first started making, restoring and driving Classic Model Power Boats has ever needed this amount of development to get it to run "properly".

I think these tests have proven that the Aerokits Sea Commander design does not work well with the currently available proportional radio control systems and brushless motors if its original large keel shape is not reduced in size.

Some of the other Aerokit and LesRo Classic Model Power Boat designs that come from the same pen also share this same over-sized keel shape that was possibly (?) designed to give stability to the models when being driven as "straight runners" with no radio control (and much smaller motors), or with the simple single channel radio systems that were beginning to appear around the time that these early kits were being produced.

As a firm supporter of Classic Model Power Boats I do have some other models from this era that also have an overly large keel shape. I will be reducing them in depth to help them cope with the radio and power systems that we currently use.

It may be seen as sacrilege to the purist Classic Model Power Boat enthusiast to chop away some of the original keel shape, but I think it far more important to present these lovey original deigns working at their best when they are out on the water.

Sharing these findings with others that may be experiencing similar strange handling problems with their own Classic Model power Boats may even help to ultimately promote their more regular use !

.........especially as the problem can be so easily corrected - even on a boat that is fully built and has been in use in its original large keel shape for years !

Bob.

That looks good now as the prop should get a good, uninterrupted flow of water to it now.

I have left a small amount to keel showing proud over the bottom skins Dave - probably similar to what Harry has done with his Jotika Sea Commander.

This increases to just over 5mm where it joins onto the underside of the prop shaft.

I am hoping this will be the last change that is needed to the underside the hull so that I can give it a decent rub down to get everything nice and smooth before treating it to a nice coat of paint.......but I will test it again first !

Bob.

Harry - that's a very useful snippet as I am building (very slowly between other projects) a Jokita Sea Commander at the moment.

I will definitely trim the keel back to be level with the lower skins as the evidence now appears conclusive.

Dave

That's good Harry, it sounds like when you removed the keel from your Jotika Sea Commander you left about the same amount of keel left that I have on mine (see picture below).

The performance of my Sea Commander (Kopy Kommander) improved no end after I chopped away some of the keel, and now I have chopped off quite a bit more so that it is now probably about the same as yours?

I am looking forward to running my Kopy Kommander again as I really like this Classic Model Power Boat and I think the handling is now more or less "sorted".

Bob.

Hi All
Oh, boy, I cut a section of 25mm x 470mm long off the keel which left about 5mm below the prop shaft.
Well, well, well, the Jotika( yes it's a Jotika) Sea Commander handles double fiqure eights at half speed.
Like on rails !!!
So that's dusted off my handling problems.
So back to the Spearfish Police boat.
Harry

Hi Bob

Will be interesting to see what happens on the water. The first reduction of the keel seem to make a big difference on the turning so next step will be interesting. As I still have a "Factory" one I will be watching with interest.

Adam

A few minutes in the workshop (shed) with my razor saw, and the depth of the keel has been reduced still further.

I also reduced the size and changed the shape of the prop shaft tube support to reduce any problems that may have been causing the propeller to "gurgle" at times.

Some red paint has been slapped on over the exposed wood to protect it when it goes out to play again, and hopefully this will be the last major change to the hull to make the Sea Commander run as well as it can.

The wedge has also been left on as it was not removed for the last test run and did not appear to cause any problems.....so it can stay.

Bob.

Thanks Roy.

I have not been home this week and the only two rudder blades that I had with me was a standard size “medium” and a standard size “large”.

The “medium” blade has already had a little concave trim on its rear part of the blade (not much) and the “large” rudder is still full size.

I am expecting the “medium” size rudder will be large enough to work well once I have removed all of the keel, but when I return to the water with it in a week or so, I will bring some tools with me to make further small adjustments to the blade until it works well.

Bob.

Re the rudder, on my little Huntsman I reduced the width of the rudder progressively until it had a minimum effect. So rudder movement has a gentle effect and the turns are smooth and easy.

Roy

Rudder Testing.

The Kopy Kommander was run again today with the smaller keel that was tested on Sunday, but this time with a large size rudder.

The boat was nice on the water - possibly a little more “twitchy” than it was on Sunday, so the medium size rudder was refitted and the boat was sent out again.

This time the steering had lost its “sensitivity” and it still steered well enough, but the burbling propeller noises returned with bubbles being seen in the wake.

My theory on this is that the remainder of the large keel is still enough to challenge the authority of the medium rudder and affect the flow of the water around the propeller.

This weekend, I will have the chance to remove the rest of the keel and tidy-up the underside of the hull.

I wont get the chance to test the hull after the keel has been completely removed for another week, but my guess is that the boats handling will be still further improved and the authority of the medium size rudder will also be improved.

The burbling noise from the propeller should hopefully also disappear along with the fine bubbles that can be seen in the wake.

The hull is pictured as it was run today with the depth of the keel reduced, the large size rudder, and the modified anti-torque wedge still fitted.

Bob.

Interesting, I wasn't aware of the differences as I have only seen completed Sea Commanders and haven't been able to poke about inside any of them.

The cutouts in the bulkheads under the deck is puzzling, more work and no useful wood saved, so it could be to make running wires more easily, it is hard to think of any other reason just now. I suppose a small reduction in weight is a good thing, but in this case it is probably not enough to be noticeable.

Here is a picture of the template I made to cut my keel from, and the shape drawn onto the 4mm plywood ready to be cut out.

This shape was taken directly from the original Aerokits plans.

Bob.

Thanks Dave.

There are some differences that i have spotted straight away.

The bulkheads have cut-outs under the deck area, and the two keel doublers on the bows have been replaced by one (larger) single piece that has been notched-out to give a positive location for the pair of lower chine stringers.

I can see nothing that would make any difference to the handling of the boat in these pictures, and I am not sure why Jotika hollowed-out the bulkheads under the deck area, but it could be handy for threading cables through possibly?

A picture of the keel could be helpful to see if they have removed the depth of it at all?

I located my upper and lower chine stringers on a modified breast hook and a pair of lower breasthooks that I made to strengthen the bows.

I see that Jotika have modified their kit breasthook - just like mine !

The Aerokits breasthook is designed to have the pair of upper stringers wrapped completely around it on both sides.

The modified breasthook removes the need to shape the top pair of stringers around the outside of it as they end short - only part way around.

A pair of the lower breasthooks were made and given to Adam to fit as he builds his Aerokits Sea Commander.

I can also see some sort of interlocking around the cockpit floor area that is not present on the Aerokits original.

Bob.

Hi Bob & co.
Here are a few pictures I took this morning of the Jotika kit of the Sea Commander that I started on New Year's Day 2023. Since then, I have done very little to it.
I have tried to show the area around the bow in case anyone can spot any differences between the Jotika version and the original Aerokits one.
The clamps are there to hold the parts in place while I get around to making sure they fit.

After seeing more of the photos you have posted I can see that it clearly is a planing hull. Should have picked up on that before….duuh! Guess I was looking at the cabin arrangement topside & assuming it was the typical displacement/semi displacement hull found on cruisers.BTW, I can see your after keel surgery pic that the current rudder needs to remain as is.
Thank you for posting all your efforts & experimentation in this thread.
It’s been a good ride indeed!

I had never seen a Sea Commander with strakes, so I thought that I would fit a set to my Kopy Kommander as I was building it because I thought they would look good .

….. so I made some triangular hardwood strips and fitted a set to my Kopy Kommander.

For a while I was worried that fitting strakes to this hull had been the cause of the nose diving that the boat had when turning RIGHT.

I was so relieved when I found out that it was a common fault with the Sea Commander - and even happier when it was so easy to fix…..although it took a lot of testing for other possible causes until the keel was found to be the cause !

I think Dave had it right when he suggested that the deep keel was originally designed for the boat to be a “straight runner” when the over sized keel would help to keep it on a predetermined course.

Steering the boat by radio control was fighting against the keel that was still trying to keep the boat running straight !

We got there in the end , and I didn’t need to remove my strakes !!

Bob.

Looks good in that shot. No strakes I notice.

One for you Dave, a Jokita Sea Commander at speed.

Here is a picture that Harry sent some years ago of a club members “SLEC” (Jotika?) Sea Commander at speed.

I wonder if it is the same one that he bought recently?

Bob

I managed to find some old pictures of Harry’s first Sea Commander in Tasmania.

Firstly as it was when he first sold it in 2018,

Later, what it looked like after he bought it back in 2023.

..and what it looked like after it had been restored.

Bob.

Yes, I've used sub breasthooks or chine formers as they are called in a number of my builds. Either to wrap the chine stringers around or to replace them.

Another tip with the breast hook is to cut the end of the cut out at an angle to restrain the stringers and put a hole in the breast hook so that you can get a clamp in. I came up with that after struggling but no doubt it isn't a new idea.

Photos are from my Swordsman build.

Good idea, Bob, I'll try to remember to take a few snaps when I am next upstairs in my modelling room.

Unfortunately, that will also reveal just how untidy it is in there!

I remembered making a pair of sub-breasthooks on my Kopy Kommander to strengthen the bows, so I have cut a pair for Adam to fit to his build.

These sub breasthooks also make it easier to fit the chine wall stringers at the bows and as this is his first ever model boat build I thought it would help.

I also made the breast hook for my Kopy Kommander using the same idea of locating the stringers into a notched cut-out, but I only did this as I had to cut all my own parts in any case and I am not so sure this was as good an idea as the pair of sub breast-hooks was?

Bob.

Hi Dave,

It would be interesting to see some build shots of your Jotika made Sea Commander kit as they suggest that they have “improved” it in some ways from the Aerokits original.

It would be easy to compare their interpretation with the original Aerokits version that I have just been looking at on Adam’s building table.

With both kits being in the construction stages, any obvious differences would be easy to spot.

I think I may also have some build pictures of my Kopy Commander which was based on the Aerokits original that could be used as a comparison too.

Bob.

Yes, I expect he built his from the same kit I have spread out on my bench at the moment, the intention of my post was to save people wasting time looking for a Sea Commander on the Slec website.

It’s probably the Jotika copy Sea Commander that Harry was thinking of Dave?

Of course, the copy kits could be re-branded as SLEC in Tasmania……..but more likely Harry just guessed wrongly at who made the kit that his boat was made from.

I doubt that Harry actually built the boat himself so he would not have seen the kit box etc to know the manufacturer, but he did know that it was not an Aerokits original and noticed the differences between them both.

Bob.

Bob, I don't think SLEC have ever made a Sea Commander or Sea Queen kit. The pair that I have were made by Jotika.

Which is quite strange, as SLEC produces all of the smaller Sea series of Aerokits models.

Hi Harry, I know you mentioned previously that your newer SLEC version of the Sea Commander did not handle as well as your original one did.

Maybe the difference was only caused by the size of the keel?

Let us know how it goes with the keel cut down to 5mm .

Bob.

Hi Lads
As I sold my kopy Kommander which handled very well.
On test my SLEC one I found it very sentive in the steering, so checking in my pictures I found the Kopy had only the triangle support between the prop shaft and the hull. So I cut off the keel down to about 5mm at the prop end but still leaving a bit of the keel. So it's all painted up for Saturday for testing.

Hi Chris,

My Remora, Suzie Q, Swordsman, Rapier, Javelin, in fact all the boats and flatties that I have ever owned and run have a triangular fillet support inserted and bonded in between the underside of the hull and the propeller shaft tube.

Some have also had a similar fillet inside the hull to support the shaft between its underside and the keel.

I have never used ‘P” brackets (or prop shaft clamps) on any of my boats as I prefer the blended-in look, and on my fast electrics, the streamlined look works better and does not produce any turbulence or drag.

24hour Araldite is used to bond the fillets and this has never failed on any boat over the last 60 + years that I have been using this technique.

On some of my boats, I have also had a little P38 filler smoothed around the joints and blended-in to give a really nice slick look to the blend lines on some of my fast boats …..or when I had some mixed filler left over that needed a good home 😎

Some of my previous boats have been run and/or raced in the sea, on rivers and canals as well as the more usual boating lakes and all of them have clocked up high mileage - and often as a fair speed !

My Kopy Kommander will soon be the latest addition to the streamlined fillet fleet (the fillet will be the only part of the keel that will be left!).😋

Bob.

That's an interesting article. With my faster models I think I will stick with my usual solution! First photo.

Do you think I'll be OK with my Fairey Fisherman at high speed? Only joking. Might have to fit a bigger prop though! Second photo.

Bob, I did ask somewhere if your Remora and Rapier had triangular prop shaft supports but as they handle well they obviously don't cause any issues.

You can really get into the weeds of fluid dynamics if you do a web search like “prop/keel interactions”. I found this reference that is non-mathematical & should adequately serve our model building needs. It’s a bit disappointing that they didn’t go into a deeper discussion when they described interaction between a deep keel & two bladed prop & dive into a bit of fluid dynamics. I’ll continue to look for something along those lines.
And now to include the reference.

https://southernboating.com/engines/inboards/hull-prop-relationship/

Not Anger Management !

Thanks Chris, the boat has certainly seen some action during the testing, and the hull is definitely in need of some cleaning-up and a fresh coat of paint - especially below the water line.

I will remove the rest of the keel and tidy the shape of the prop shaft support while I am at it.

The wedge shape has been refined and didn’t seem to cause any obvious problems during the last test when it was still fitted, so I will tidy that up and leave it fitted as it is now part of the boats history.

One final test this week will be with the hull as it is now (with the half keel) and the original medium size rudder re-fitted to see if it still runs as well with the smaller rudder blade.

After this final test, the boat can enjoy a more sedate life with no more vicious testing strains being inflicted on her.

One observer at the club on Sunday watched the testing with interest and was fascinated to understand what we were doing and relieved when he was reassured that it was not an exercise in “anger management” 😂

Bob.

Great to see the improvements to the performance when turning and especially the more natural leaning in for a boat of this type.

I doubt that removing the rest of the keel will make that much more difference given the big improvement so far but I agree it should improve the flow even more to the prop and why bother with it anyway as it doesn't appear to offer any useful purpose. So away with it I say!

On some turns a lot of water is still being thrown off at the bow but I think that is down to the shape of the bow (the Rapier is much sleeker for instance) which you can't do much about and you will have to accept as a characteristic. It seems worse obviously when going into waves so you can't be too hard on the poor old girl for that!

I know you are now happier with the handling and performance and if/when you remove the rest of the keel be rest assured you have done everything within reason to bring about the improvements.

Nice lick of paint and then just enjoy it for what it is, an improved Sea Commander.

You could be right about the large keel contributing to the Sea Commanders straight running ability Dave, and that would make sense if it was advertised as being suitable for free running.

I remember running around to the other side of the boating lake in Victoria Park in Bath when I was a young boy to try to catch my small electric model power boat before it hit the other side.

Fortunately I was a lot younger and fitter then, and my toy boat was not very fast!

The Keil Kraft catalogue of that time also showed a brass rudder assembly with a ratchet under the tiller arm to allow the rudder to be set in one position before being released as a straight runner, so boats like the Aerokits Sea Commander were indeed also intended for straight running without radio control, as well as with radio control for those that were fortunate enough to own a radio control system.

If they had suggested cutting the keel off when the boat was going to be used under radio control, it would have saved their future customers a whole lot of head scratching.

Maybe Keil Kraft who distributed the kits could have updated the user advice too?

As a matter of interest I have a LesRo Rapier waiting for restoration that had one of these same ratchet rudders fitted and was powered by a small Mabuchi motor that would have struggled to get up to walking speed! Another straight runner from the same sort of time period.

Regarding your comments about the boat being designed as a displacement hull, I think that highly unlikely.

Les Rowell had been designing hard chine model boat kits for many years as they were easy and quick to make by the average modeller at home with minimum tools or skills.

In his many years of designing r/c model boats I have never seen any that were not specifically designed for hard chine construction.

Without the large keel, we have yet to discover the design parameters that the Sea Commander now has………..but it is looking MUCH better 👍.

Bob.

I am wondering whether the Sea Commander is being pushed beyond it's original design parameters. Looking at an early 70s Keil Kraft handbook, it is described as being suitable for free running or radio control, powered by 1.5 to 5cc engines.
Could it be that initially the keel was used as an aid to keeping the boat on a straight course for those who used it for free running, who may well have been the majority of those building it?
Another thought (I'll have to give up thinking) is that it might have been originally intended as a displacement hull, but built using flat sheets of ply for reasons of production which has made it look like a typical planning hull with chines instead of a smooth rounded displacement hull.

The Kopy Kommander was run today with a longer rudder (painted black to easily identify it) than I had used before.

I fitted this (large size) rudder so that it was lower in the water to extend below the huge keel that the Aerokits design had. I should have removed it after cutting off half of the depth of this keel - but I forgot!

During the rush to get the boat onto the water before the heavy rains that were due to arrive at any time (and my very cold fingers) the decision was hastily made to leave it on - even though the previous (medium size) rudder was in the “orange box” shaped boat stand that I carry the boat on !

I should run the boat again with the original (medium size) rudder fitted before making any further changes …..but I was so impressed with the way that the boats performance had been transformed by halving the size of the keel that I may have trouble restraining myself from wielding the razor saw again and chopping the remainder of the keel away !

I will also remove the propeller and the 5mm inner prop shaft to give me a clear access to remove the extended swage of the prop shaft support as this is quite close to the propeller and may be interfering with the propeller’s action in the water?

I am hopping that this will be the last under-hull changes that will be needed to completely cure the Sea Commander’s Strange Handling (the title of this blog).

This will no doubt come as a great relief to those that are truly sick to death of constantly see the subject crop up so often on this forum.

………but for those that actually own a Sea Commander (or those that intend building one in the near future) this article will be of great value as it shows how a simple fix can be easily made to any (new or old) Sea Commander to transform it handling .

It may also help owners of other Aerokits model boats that have the large keel that seems to have been a common design feature throughout most (but not all) of the Aerokits range of model boats kits. 👍

Bob.

That is very illuminating! To lean over and into a turn the rear part of the boat has to slide sideways under the influence of the rudder.
With a large keel area the keel is trying to maintain the course of the boat so when the rudder angle alters the forces on the keel maintain her more upright but the hull above the water can only then act on the centrifugal forces and go the other way.

I have not thought of that before. My little Huntsman has hardly any length of keel and slides easily and leans into the turn.

Anyone agree?
Roy

Hooray!👍 That looks great Bob. I’m glad it runs completely counter to what I thought it would! The wake looks the way it should; flat behind the stern, bow wave prox halfway down the side. Now I will have to try to understand the prop/keel interaction.🤔 Did I completely miss something? Was the hull rolling to port when you were doing a turn to Stb’d & vice versa?
Well on you; problem solved!

When we arrived at the club lake this morning, there were some members cars parked-up, but there were no boats on the lake !

Usually we move up the lake to get as far away from any other users as possible when we start to abuse the boat to force it to enter into the Sea Commander Nose Dive, and we also make sure that we do not run near any other boats so that our testing does not spoil anyone else’s boating pleasure.

But with an empty lake and rain clouds ready to burst, we got the boat into the water as fast as we could.

The first thing that was very noticeable straight away was that for the first time, the boat actually leaned inwards when making a left or right turn.

This was very reassuring and looked much better. The oversize keel on the standard Aerokits Sea Commander was obviously stopping the boat from leaning into a turn, and by keeping the boat upright we had been experiencing some strange handling - including on one accession when the boat actually tipped outwards onto its side !

With the handling already much improved I then entered into giving the boat as much serious abuse as I could - to get it to nose dive - but I failed !

The boat did drop its nose close to the surface and picked up some spray on the foredeck, but I couldn’t actually force it to dive under the water.

The boat is still running with approximately half of the original designs keel still in place.

Another thing that was noticed was that the water cooling outlet was pushing water out at any speed (previously despite being checked for any blockages, it hardly worked).

This suggested that the propellers water flow has been seriously impeded previously by the over-sized shape of the standard kits keel.

The improved wake and reduced “burbling” from the propeller at low speed also suggested that this could be the case.

My Kopy Kommander is now much nicer to drive and trimming away half of the keel has much improved its performance in every department.

The Sea Commander (copy) now drives like a boat that has a lot more performance available…but it still has the tenancy to drop its nose when turning RIGHT (when being abused), so my testing is not quite finished yet……but it is very close to making this a truly “vice-free” Classic Model Power Boat that is a pleasure to drive.

Bob.

I'm with you with regards building v running. Though I'm always excited when I'm undertaking the first lake trials.

Apart from my water-jet and outboard projects all of my builds have been to scale (well close to!) being my Fairey builds which in the main are sports cruisers, so designed for speed, though I don't go too mad!

I really have to apply self-restraint with my River Cruiser though as the hull is derived from the Huntress and would easily plane!

Photos shows my Dave Milbourn built Huntress and my River Cruiser going at the speed it should do.

“Trouble is with models is that they can be easily over powered/ motored and therefore driven at higher than scale speeds and also asked to do sharp manoeuvres in water conditions that a full-sized boat wouldn't do or be able to do! Or even the crew being able to withstand! Folks soon get bored with tootling around unless it is a model obviously designed for slow speed, like a tug or river/pleasure craft and the temptation is to give it some beans!

It's made for an interesting discussion though and exercised our brain cells and it will be interesting to see what, if any, difference results from Bob removing the keel.”

Chris,
It certainly has made for a brain exercising experience. I’ve learned a lot & it’s caused me to recall some things I had forgotten.
I completely agree with your comment regarding overpowering & wanting to go faster. My sense is that is an issue for Bob. The only place I have seen a wave deflector is on model warships. Warships may encounter mountainous seas!
The keel reduction will be interesting to me. My sense is that it will make matters worse. The keel is intended to improve tracking & turning stability particularly for round bilge hulls. But from the discussions herein it seems to have worked for others.
My builds are all scale in nature. So for me making the model as true to type in appearance & performance is the goal. I generally have to slow mine down. If I’m honest I enjoy building more than running.
Bob; we anxiously await your keel trial.

Morning Chum - yes, they do apply to sail and power but my understanding is that the hull speed only applies to displacement hulls as stated in your second link? There is a point at which more power doesn't meaningfully increase speed but with planing hulls it does.

I do agree that the SC does seem to be a bit of a hybrid though. It would have been better if it had been advertised as a river cruiser rather than an ocean going cabin cruiser and having Sea in its name. There is still that question mark over the wave deflector as well which implies the model was designed for a bit of speed.

Trouble is with models is that they can be easily over powered/ motored and therefore driven at higher than scale speeds and also asked to do sharp manoeuvres in water conditions that a full-sized boat wouldn't do or be able to do! Or even the crew being able to withstand! Folks soon get bored with tootling around unless it is a model obviously designed for slow speed, like a tug or river/pleasure craft and the temptation is to give it some beans!

It's made for an interesting discussion though and exercised our brain cells and it will be interesting to see what, if any, difference results from Bob removing the keel.

Bob, do your Remora and Rapier have the triangular piece between the prop shaft and hull?

Chris, I’m an engineer, not a naval architect but those principles are physics-based & apply to all hulls, sail & power. Their individual impacts may vary depending on the hull form& function.
Of course I could be misguided but from pics I’ve seen the SC hull to me defines the shape of a displacement hull. Hull forms of the displacement type I’ve viewed, 1:1 & model include variations of the extensive keel. Added to that is the SC appears to be designed as a cruiser. 1:1 cruisers do not plane since that is not their function. I’ve never seen an overturned SC so maybe the hull is a hybrid between a displacement & planing hull.

Of course I could be all wet!😀😀

Chum, don't those links apply to displacement hulls though? Whilst the speeds being attained are probably above the scale speed (even though there isn't a full-size boat) the readiness for the SC to come up onto the plane would suggest that it was designed as a planning hull despite the big keel.

The same applies to the aforementioned Sea Scout which has a ridiculously large and unnecessary keel! Even my little Fairey Faun, which is based on a real boat and is a displacement hull by comparison only has a small keel.

Thanks, Bob, I will build it with the keel and make the decision before the finishing.

Bob, in a nutshell, hull speed is the max speed the hull can run before handling issues occur. Adding power after hull speed has been obtained only forces the hull’s stern down. I realize that your vids are at a higher speed than you normally run and your’s squats in your latest one.
Glynn Guests’'article & subsequent site comments are talking about stability. The old adage of keeping things above the deck light is a great rule to follow.
So, there you are. Factors creating your issue include prop torque, hull speed, stability, prop speed & pitch, type of hull, weight distribution, etc. etc. 🤔🤔

Thanks for the additional reading matter Chum444 - my small olde brain is already fully torque twisted to beyond its limit……but I will enjoy reading them and try to expand my limited knowledge base.

I have no idea how fast my Sea Commander (Kopy Kommander) can run at when it is flat-out, mainly because I have never timed it, but also because I seldom run it flat out .

I like to drive my boats quite quickly as I like to see some realistic white water and a nice wake…and I enjoy driving them.

There are some owners that like to push their boats to the absolute limit and run than at crazy speeds. That is not what I ever want to do with any of my Classic Model Power Boats, but I accept that some do and seem to get a lot of pleasure from it.

Bob

Hi Dave,

Good to know that you have retrieved your part built Sea Commander from the loft and that you are going to get it finished and on the water.

Well done !

From what I am hearing and finding out so far, it is looking like the boat would be better off without the extended keel.

Just how much to remove has yet to be tested on my boat, but all the signs are from others that have chopped the keel is that the boat could be better without any of it, but I have only gone part way to date and look forward to finding out for myself.

Another fast Sea Commander is something to look forward to seeing as I am sure that you will enjoy driving it as it is a superb model that only has the one fault that is being worked on here to correct.

Hopefully I will have an answer for you about the keel before you get to the painting stage !

The keel is easy to remove at any stage and so building it with the full keel still present is not going to be a problem - in fact it is probably easier to chop it off of the finished hull with the skins already fitted.

It is also good to see that you are going to be using a brushless motor that will probably give your boat the same sort of performance as my own!

Something to look forward to - far better than the fast electrics that we have both recently “dumped” - at least for the time being……….😂

Bob.

I got my part built Sea Commander down from the loft yesterday. Just the the bulkheads, keel, and cabin sides in place so far. Do you think I'd better off planing the keel so it is flush with the bottom skins before finishing it or wait and see how it behaves on the water first? I am thinking of either a 3542 or 3536 brushless, both 1000kv and probably 2S lipo to start with. Any opinions or suggestions of any other motor/battery combo?

Thanks for sending the plans for the Aerokits Sea Scout, Will - much appreciated.👍

Maybe they could also be added to the Classic Model power Boats thread as anyone interested in it may not find it on this thread?

The Sea Scout plans clearly show an extended keel - just like the Sea Commander has (from the same Aerokits stable) and the video that we have seen of Harry’s old one in Tasmania suggests that it has similar handling problems too!

The common denominator is the extended keel - something that Harry has cut off of his Sea Rover, and that appears to to be running well without it !

Maybe I should have chopped off all of the keel ?, but the reduced depth version will be tested tomorrow to see if it has helped at all, and if it has (but not completely solved the problem) I will chop the rest of it off when I am next at home.

The prop shaft support also looks a bit close to the propeller, so I may increase that space a little too as that may also be crowding the propeller as well.

Bob.

Bob, some additional reading material while you are traveling. I’m sure you have either timed or calculated how fast the Kommander is traveling. Is it beyond hull speed? How doors it compare to the real boat’s cruising speed?

https://rcratings.com/rc-boat-speed-calculator/

https://www.omnicalculator.com/sports/hull-speed

The Sea Scout definitely has a fairly long keel, that is quite deep towards the stern, just like the Sea Commander.

Will

That little white boat was probably the one that I thought was an Aerokits Sea Scout Chris.

I also noticed the “similar” handling traits to my Sea Commander. I think that model has a keel on it as well !

Bob.

That cat Sophie looks good on the water. What's the little white boat at the start? It has similar characteristics to the SC in that it leans outwards on turns and throws a lot of water up at the bow. Bit choppy for the small models though.

Hi
That's my old Sea Scout and The Sea rover has no keel only a wedge between the prop shaft and the hull.
That Incat is 1200mm x 500mm running old Graupner jet drives but with 35mm 750kv brushless which is about scale speed, but we may test it on 4S lipos which will add 3000rpm!!!
Harry

Thanks Harry, nice to see your Aerokits Sea Rover going well towards the end of the video…and an Aerokits Swordsman too ?

Did I spot an Aerokits Scout earlier in the video?

As a matter of interest, has your Sea Rover got a deep keel on it like my Sea Commander had (before I chopped it off)?

Bob.

https://rctoystasmania.com/forums/topic/saturday-sailing-24/

Thanks PhilH. I hope that we have at last stumbled onto something that may help more than anything else that has been tried to date.

Thanks for the link Chum444. Your link will give me something interesting to read while I am away (currently travelling).

Your comments and observations are now very similar to my own Chris and I am hoping that some of the clues to the "freaky" handling on my Sea Commander do indeed stem from the very deep keel shape.

If I can see any improvements, the next time I drive the boat (planned for this Sunday) I would be more than happy to remove the remainder of the keel that is in front of the propeller.

Wouldn't it be nice if this simple fix was all that was needed?

Bob.

Looking better underneath now you have trimed the keel lets hope it sails better good luck with you trials .
Philuk👍

Found what I have been looking for. See

https://www.rcgroups.com/forums/showthread.php?3416337-Stability-how-to-avoid-ro

Nice one Bob! You do have to wonder what LR was thinking when he designed this model? I didn't realise from the earlier photos just how deep the keel was approaching the prop! Perhaps, being described as an ocean going cabin cruiser rather than a sports cruiser it was only intended to run at relatively slow speeds?

OK, not all sea going vessels have to be fast but the hull shape at the stern does suggest it was designed to plane, unlike a displacement hull, and so I don't think it was unrealistic of you to think it should handle some speed which is supported by others running the boat in videos. And the more I think about your comments concerning the wave breaker (or whatever it was called) on the cabin roof makes me think it was a sticking plaster. Scenario could have been that the design was too far advanced and the kit was ready for release when the "characteristic" was experienced? Why else would you stick something on the roof which is completely out of keeping with the design of the boat and the boat was a cabin cruiser designed for slow speed? All conjecture of course! 🤔

Will the next step be to remove all of the keel in front of the prop shaft?

Yesterday I almost chopped some of the keel away from my Sea Commander...

......and today I found myself looking at it again, but with my razor saw in my hand, and the next minute, it's not quite as deep as it was a few minutes earlier!

There is still some keel left, but I thought I would test this first to see if it makes a difference....but I am already asking myself if it needs to have any keel at all?

The propeller should certainly get to see a bit more water in front of it, so that may help to reduce the gurgling noises?

The picture of my old Sea Queen (waiting for restoration) shows that it had been running with even less keel than I have left, so there is a lot further to go with my Sea Commander and its keel trimming...if I can see any improvements.

I had already fitted a larger rudder, but I think I will swop the original one back now that I have taken so much of the keel away so I am not testing too many things at the same time.

The wedge has also been re-profiled to be less efficient (and look better), but a wedge may not be needed at all now?

The underside of my Sea Commander is starting to look a bit rough now following the various experimental ideas that have and are still being tried and tested.

It has been drilled and plugged twice to re-position the pick-up and rudder. It has had a wedge fitted (and now modified), and some of the keel has been sawn away.

I am reluctant to spend too much time re-establishing the paintwork just yet (other than to keep the wood dry with some sort of covering) but once I have either found a solution (or given up), the boat definitely needs a bit of a make-over !

Bob.

Funny you should say that!

I have been looking at my Sea Commander tonight and was wondering if the deep keel was the cause, or at least not helping the problem with the strange burbling noises coming from the propeller.

I almost chopped some of the keel away as its bulk could be shielding the propeller and not allowing the hull to be as agile in the water as it could be?

Tomorrow I will take a quick look at an old See Queen that I have and possibly saw away some of the keel on my Sea Commander to reduce its depth.

..........it could be interesting........

Bob.

Chris I think you
added a lot when you talk about the full length keel. So, the speed of the prop, the driveshaft angle relative to the bottom of the hull, & the keel all contribute to the issue facing Bob. Adding Bob’s comment about the shape of the bow to the above reinforces my sense that the hull configuration won’t support very high speeds.

Well I couldn't help myself! Had to Google the larger Sea Queen which does lean in a bit and guess what, either no keel at the bow or some photos show a small one which percentagewise is smaller than that on the Sea Commander.

Drawing shows no keel at the bow. 🤗

Oh, and just noticed, the chine rails curve up.

Second drawing is the SC which does show the keel at the bow, and in fact the keel is much larger as it approaches the stern - so there are some difference between the Commander and Queen. Perhaps with the SC the resistance of the hull is greater than that of the rudder! So causing it to lean out. Never mind tripping over the keel towards the bow!

As per our earlier comments, I like you, use the line of the bottom and side skin abutment to position the chine rails, though on one of my Faireys I did curve up a bit at the bow. Not very noticeable as the join of the skins wasn't too much of an angle and the colour camouflages it. Funnily enough I did come across a SC for sale which has got the chine rails rising at the bow which illustrates your point. You can see the joint of the skins below but it's not too bad.

I'm preferring to do this rather than tackle the front windows on my Faun build! I'm making them in mahogany and they are like those on the Sprite Plus, vee forward, leaning back and with a curved roof. But slightly more complicated as the cabin sides are at an angle as well. Back to them in the morning!

One thing I keep forgetting to mention! The keel that runs almost all the way to the bow. It's the only planing boat that I've seen that has that detail. 🤔

Could that be contributing to the problem, well the leaning out, even if not the TSCD? Perhaps as the boat is turning the keel stops the bow from sliding sideways and "trips" the hull up causing it to lean outwards on a turn? I seem to remember that planing hulls lean inwards because the force from the rudder is stronger than the resistance of the hull whereas with displacement hulls and ships the resistance of the hull is greater and therefore wins which causes the vessel to lean out. Given how flat the hull is with the SC there is no way it should be leaning out? Perhaps it is the keel and not just the part towards the bow? Why is it so deep approaching the prop shaft? I can understand it with displacement hulls as the keel often contains the prop shaft within it. The SC is never going to lean much of course due to that flat hull at the stern. The more I think about it the more I think the keel could be the problem or at least a major part of it.

Also, it's fairly wide and blunt and could be contributing to the amount of water being flung up.

Where's the clutching at straws emoji when you want one?!! 😁

Thanks for your continuing contributions and thoughts.

For what it's worth, the strange handling and TSCD makes absolutely no sense at all to me.

Deep Vee hulls (I much prefer them!) handle very differently and lean "in" to a turn, and are much more predictable.........and just a lot nicer to drive!

My Sea Commander stays flat 99% of the time - but it can lean outwards during a RIGHT hand turn, and on one occasion when running quite fast with the wedge fitted it actually went a little further and leaned on its outside edge! (seen on video) .

My Remora does not have a deep vee hull either, and was designed to be a low speed "steering boat", and yet it flys around the lake at any speed with no abnormal behaviour - in fact it is very safe and predictable.

One thing that I have not "majored" on yet is the way the Sea Commander propeller does not seem to be getting too much of a "grip" on the water.

It burbles around and makes bubbles and the wash does not look like other boats that I have driven either.

Maybe the underside water dispursion of the hull has been spoilt by my addition of the strakes, and this in turn causes this strange sounding "gurgling" from the propeller?

Having said that, the boat goes very well for the low power in-runner with only 2C batteries, so the prop is certainly delivering the power OK.

Even more baffling to me...that make's three with hurting heads........so far.......

Bob.

Chris, that makes two of us with hurting heads. If the boat actually dives under the first wave as I believe Bob has indicated, the short period of the waves allows no time for the hull to regain any buoyancy before it encounters 2nd & succeeding waves. Things go downhill (get wetter) from there!

Prop walk and torque (due to motor, shaft and prop) are two different things with prop walk only effective at very slow speeds and so I think that it is torque having the most significance here. My understanding is that for a left-hand/anti-clockwise prop the effect would be to push the stern to port due to prop walk and roll to starboard due to torque. This doesn't fit with the slight roll to port we see in the videos though which is confusing me!

I'm not convinced about the water over the angled area of the tilted hull though as the hull is still pretty well upright and most water seems to be being deflected away. Be different with a deep vee hull which rolls into turns.

Anyway, my head hurts now and will wait to see what further testing brings! 🤕 😀

Bob. From my view the forward spray rails have no effect on your issue. Allow me to say it more forcefully. They are not the cause nor are they adding to the issue; they have too little surface area. Forward spray rails are meant to deflect the spray created when running in a head sea; nothing else.
Note the upward curved spray rails on my racing lobster boat; such rails are not uncommon over here on different types of hulls. They do the job of deflecting spray. BTW, they played no part in the hull’s rollover at higher speeds. Q
Of course I could be misguided but your issue is prop walk(torque). The solution is to slow down & run at scale speed. With some hulls you can get away with greater than scale speed. The trick is to find the upper limit for what the hull can handle. With some hulls ( reference your barge bow comment ) that speed may not be very high.
The prop walk along with the force created by the rudder vector cause the bow to take the first head sea over the angled area of the tilted hull. That forces the bow downward & deeper into the next wave. The sequence will continue until the boat sinks from resulting water incursion.
Okay. That’s more than my two cents worth!
Realizing that your vids demonstrate extreme speeds, if you haven’t done so already, ramp your speeds up slowly, turn, then stop increasing speed when the first hint of a dive occurs.

Phew! Another of my long-winded posts.😉

Have a look at this video , the quality is appalling, all my good quality videos have been lost , but you will see what I am talking about. Its a 4 foot veron huntsman, deep v hull, with the chine things under the hull, and an improved spray rail that goes the length of the hull. its powered by brushless, and 6 cells lipo, with gps eagle tree data logging, its 25mph, and is over the speed that the hull feels safe. Look at the turns, left are perfect, right are choppy, the torque roll is massive, even in a straight line its on the verge of flipping when flat out, but what a ride!
I wanted speed, and its a very heavy old girl. It has a 3 blade cleaver brass prop. I experimented with x50, x45 x55 props on a 5mm shaft. S props don't give speed, x do. I measured the amp draw between the props. The spray rail was very important, you will see the bow planes at speed, it cant dig in if its planing. Many trials with centre of gravity, using battery placement archived the ride at speed, see only the bow is planing, its not got the front half of the hull in the air, its very balanced with the lipos , but balanced for speed. An rc plane will crash if the cog is only millimeters out, the saying is a tail heavy plane has one flight. Same principles apply with a fast boat. Also, throttle management is important, you can hear the motor tone changing to maintain a fast right turn. I still think your rudder is playing a part in the issue. Your turns are very flat compared to my Huntsman I cant understand why. Something that has been mentioned is the angle o the shaft, the prop needs to be close to the hull, so its pushing forward, not upwards, Here is the proof you can get a scale boat to go fast! I think I will come visit Southport lake, I'm not that far away!

https://youtu.be/XBK7ZfsqlGs?si=-Yn79ZSDXpH9JESd

Chine Rails.

Hi Chris, on every hard chine construction boat that I have ever made or restored the chine rails run along the natural joint of the bottom skins and the side skins.

To raise the chine rail at the nose above this natural position would leave the nose that is left under the raised chine rail position looking very odd.

Some of our deep vee hulls could be a lot more tolerant of this, but the Sea Commander has a (comparatively) barge like bows shape that would not really look very good at all.

Planked and round bilged hulls could also accommodate an artificially high chine rail at the bows, and some boats (like my Remora pictured here) have naturally very high chine rails at the nose.

I will take a look at any idea offered, but to do this idea justice the bows of the boat would need to be rebuilt to accommodate the required shape change, and I am not convinced (at this moment) that this is the answer.

Once the bows drop below the water then the chine rails and the strakes begin to work more like they would on a submarine, but I would prefer to find a way to stop the bows going under water in the first place……..if I can….

Bob.

Hi Chris,

I think all the commercially available moulded propellers have the same choice of pitch (S or X).

A finer pitch prop would be nice to try (if they existed) as would a 3 bladed prop in the correct sort of size range .

The 5mm prop shaft that I have fitted does restrict the choice of propellers that I have to choose from, but I never thought for one moment when I was building this boat that it would need so much time just to get it to drive properly without TSCD.

Changing the battery position is not a problem.

I made an extended lead to enable the batteries to be plugged in under the cockpit deck and left it in the boat so it can be used at any time.

I will have another go at moving the battery and/or batteries back again, but the boat already goes up onto the plane very fast and rides quite nose high so we will see what happens this time.

I know from my fast boats that buying a metal prop (even of identical dimensions) gives a very different result, so I would be reluctant to get one made until I have a better idea about what could work.

Bob.

Hi Bob, again I know that you tried moving the batteries further back before and I think you said it didn't make much if any difference? But didn't Harry say that ideally the balance point should be around a third along from the stern? If so, this might explain the tendency for the bow to drop quickly when power is reduced?

You said earlier, that the prop turns anti-clockwise and therefore I think if torque was the problem then you have put the wedge on the correct side. But maybe the roll that you experienced wasn't initiated by torque but by prop walk to the right and up due to the pitch of the prop. So yes, it would be interesting to see what a 3 blade results in.

You could always give the model a treat to off-set all the trauma it's been through and get it a nice brass/bronze prop which are readily available for the sizes you want!

But it sounds as though you will soon have the ideal test mule! 😁

Hi Chris, I recently sold a new and unmade Sea Commander to a friend who is starting to build it this week.

The boat will be built with a “clean” hull, (ie no strakes) so sometime soon we will be able to compare them directly.

The balance point of the boat is more of less half-way along its length being approximately in line with the end of the large cabin side window.

As the batteries are carried side by side in the main cabin, this balance point does not change when the batteries are removed (just tested!).

The two shaped lead weights fitted in behind the rudder axle post have been back in place for some time.

The bow does drop rapidly when the boat slows down, and once the side strakes are under water the TSCD begins!

Regarding your previous comments about the wedge - I have given this a lot of thought and given my brain some torque twisting about it too.

With the propeller turning to the right (when viewed from behind) it is not the torque that causes the front right hand side of the boat to dive it is anti-torque (?).

This is why I did not fit the wedge on the left hand side of the boat as this would have further encouraged the TSCD.(?)

I would still like to find a 3 bladed prop to fit my M5 prop shaft - ideally a choice of 40, 45 and 50mm sizes to experiment with as the propeller is the device that causes the torque transfer into anti-torque that gives the twisting force to the boat.(?).

I will re-shape the wedge and reduce its depth and surface shape as (in theory) it should be working in our favour - but not with the shape as extreme as it is(?)

Meanwhile, the point that seems to be lost (at times) as this thread develops is that the TSCD was first seen when the boat was running at a very low speed as I was slowly manoeuvring the boat to return to the lakeside for recovery after it had completed its run.

I do somethings fear that this important point has been lost on some when they see the videos deliberately inflicting this TSCD, and think that it must be “normal behaviour” !

Nothing could be further from the truth. The boat is always driven with full care and courtesy for other users that are on the water at the time.

Any testing is done away from any other water users and if/when any other boats should stray into the same area the test is immediately aborted and the boat is moved away so as not to interfere with other users enjoyment.

The Sea Commander does have a small handling fault that may not be experienced by those that do not run their boats for the number of hours that mine clocks up, or indeed in some of the same conditions that mine experiences, but it can be a worry when first seen.

I can live with this problem and know how to safely drive out of it….but the point is that I shouldn’t have to….and I am enjoying trying to find a simple fix that myself and others may find helpful.

Bob.

Overlapped with Roy's post but I've sort of mentioned the boats attitude with my comments.

I know that you have added additional weight in the stern but did you ever see what the balance point was? In most circumstances it does get up onto the plane easily but sometimes it does look as though the bow drops too readily.

At the speeds you are using to purposely create the issue I would expect the boat to be on the plane and yet when it dives it doesn't which for me still points to water getting above the chine rails (passing wake or choppy water/waves) and driving the bow down which I still think isn't helped by the chine rails not curving up towards the bow. I also think it is due to a combination of things including the prop effects/torque.

Ideally, and to take a more scientific approach, you could do with another Sea Commander and start from first principles. Start off with a basic hull and try that. Then add the chine rails curving at the bow. Then add strakes/spray rails stopping short of the chine rails and reduce them in section at the bow to reduce the potential for ploughing.

Or are you going to be more brutal once you have changed the wedge position to try that! 😀

Hi Zooma I always like to see experimental work in progress. My own thoughts are to get the attitude right when the boat is in the water. Then slow her down so that the desired attitude is maintained with the minimum power required.

I have used battery voltage and type of battery although I do not use LiPos, prop size and even switch motors to achieve this.

Just recently with a relatively slow but heavy fishing boat (24 inches loa) I tried different batteries (weight considerations) prop size and eventually changed the drive motor to another of the same power but smaller dimensions to give better access inside.
All awaiting testing, the weather is not cooperating!

Roy

Just to reassure and verify, the excess speed and violent manoeuvres displayed in some parts of the research videos are deliberately made to try to encourage TSCD (the nose dive), something that can occur AT ANY SPEED, but it can be made to happen more easily at speed if the water is not choppy enough to cause the effect often enough to analyse at normal speeds.

Turning slowly into choppy water can be just as effective, but we don’t have any really choppy water to show this with at the moment and I want to try to find the cause and a solution sooner rather than later.

Trying to cause the nose dive is the only way to see if the various ideas that have been suggested and tried tried have worked without having to wait for bad weather, or a fast boat passing to generate a wake.

The videos are shared in an attempt to gain any helpful input into what would appear to be a recognised handling problem that can affect all Sea Commanders (and the shorter 34” RAF Rescue Tender) from the same kit maker.

I provided the answers to the questions posed by Chum444 along with the additional description and some thoughts about the possible cause and cure.

The hull tipping sideways was definitely caused by the combination of the size and depth of the wedge - and the speed being used when turning RIGHT, but it was worth doing to see the effect that it would cause and to confirm that it did not remove the boats natural desire to nose dive when being turned RIGHT into choppy water.

Roys experience is a valuable contribution as he experienced the same problem with tipping to the side with a smaller craft that went a stage further and actually sunk (glad it was recovered OK Roy).

Just to recap, I am not doing any of this research to make the Sea Commander go fast, I am trying to stop it wanting to nose dive when it turns RIGHT into choppy water, and this has been witnessed at much lower speeds in choppy water or another boats passing wake.

I like to drive my Classic Model Power Boats quickly enough to look good (when conditions permit and other water users are not affected) but I also enjoy driving them at slower speeds too - I just enjoy driving them at any speed and under all conditions!

I will continue to experiment when I get the chance, but I will continue to enjoy driving my Sea Commander and accept that the design has a natural desire to nose dive under certain water conditions when turning RIGHT only.

Bob.

Im guessing that at least a part cause of the aerated water you're seeing behind the boat, is due to the strakes making air bubbles remain under the boat, until they exit at the end of the strake at the transom?
Depending on prop and motor suitability, there could be some cavitation, but whether that's caused by the prop/motor combo, or could it be because of the air that the strakes are holding under the hull?

Will

The prop is cavitating because its pitch is too great. I would try same size prop with half the pitch. Don’t increase the rpm as that defeats the purpose of less pitch.
Regar ding the hull, you need a V or modified V hull to minimize effect of wake when it catches up to the hull when you slow down.
Unfortunately either of these modifications will have effect on the prop torque. Since it happens at any speed I am completely puzzled since it only happens turning to Stb’d. Have you checked the distribution laterally?

I like your TSCD acronym!

Hi Chum444, yes the rudder probably is close to being hard over, and the throttle is open.

This does not reflect the usual way that this boat is driven, it is being provoked to demonstrate the problem of the nose diving when being turned RIGHT into choppy water.

The hull turning onto its side was a surprise as we have never experienced this before, but it does show how sensitive the hull is to any change in the water conditions……and the wedge?….but the boat was run several more times after this event (the wedge has not been removed) and it was not possible to repeat this side roll.

Even when driving much more normally with gentle progressive steering and smooth throttle inputs, a minor change in the water surface can cause “The Sea Commander Dive” (TSCD as it is now being refereed to) without warning.

TSCD can and does happen at any speed, but is more likely when going faster - and is why these videos are generally shot at faster speeds.

We did notice and comment (in a later video) that the propeller sounded like it was bubbling and turning in air and not in the water.

The wake does not look “proper” - I agree.

My colleague suggested that the hull looked like it was generating a lot of air. If this is the case then it could be stopping the hull getting “wetted” properly and this in turn could affected the handling of the boat.

Further tests will include running a smaller prop at higher revs - this may not exactly follow your observation regarding the prop not being able to handle the revs…….but maybe a smaller prop can?

The stern is a flat surface, as you suspect.

This could be converted to a rounded surface in the same way as a frame is built and covered by a ply skin on my Swordsman build (pictured here) if it would help?

Basically this copy Sea Commander has become a research vessel to try to find the reason (but more importantly the cure) for a problem that this very popular model suffers from.

Bob.

I completely agree with Roy & Oxford Dave. I’m surprised it didn’t roll on its side & sink before. Again, one cannot ignore physics. The combination of the rudder’s force vector & the motor torque at higher speed is more than the hull was designed for.
As I mentioned in one of my early posts, one of my lobster boats when set up for racing exhibited extreme prop torque. It flipped onto its side and would have sunk had I not immediately killed the throttle when I saw it.

I have to agree with Roy - these boats were never intended to be fast, just pottering around the pond while marvelling at the miracle of radio control!

Hi all, my two penworth!
If you want to run at that speed then make the rudder narrower.
Second the hull is going too fast and is beyond its' speed envelope.
In proportion my smaller Huntsman started out going even faster and was basically uncontrollable. She had just 10% of hull in the water and was flying rather than planing.

Eventually she did exactly what your model has done turned on her side and dived down underwater. She then ran beneath the waves turning round and round and beyond RC control. After about 30 seconds she surfaced and stopped.

That is when I decided she needed to slow down. The motor was a fast 380 with a 1 : 2 geardown driven by an ex-camera 6 volt NiCad. It was difficult finding the right power to weight ratio but she works very well now.

I have not exagerated what happened, there was a witness but he died a while back.
Roy

A couple of questions & then some observations.

1. When turning right are you hard over to Stb’d with the rudder?
2. Are you making the turn with the throttle wide open?

A. In these videos your wake does not look proper. It should be flat when coming the stern without the white water (which are bubbles) showing. The white water is an indicator of prop cavitation. Said another way the prop cannot handle the RPM’s imposed on it.
B. The stern rising when you slow down is normal. It’s your stern wake catching up to the slowing boat. Your hull looks to be flat in the stern which accentuates the effect. Since one can’t defy the laws of physics, there is nothing that will stop this phenomena.

Better remove that wedge! And try it on the other side?

Near Capsize?

…..and just when we thought we had seen everything…………….

This second video shows the boat turning up onto its side…something we have never witnessed or recorded before.

Bob

At the Southport Club lake today my Sea Commander was run with the wedge fitted on the rear underside of the hull at the back and on the right hand side (when viewed from behind).

As Chum444 suggested, the rudder needed some adjustment initially for it to run “straight” so a few clicks were dialled-in to achieve this.

Initially the boat looked good and the wedge appeared to be working well, but given the same water conditions that always seem to encourage the now infamous “Sea Commander Dive” the boat did its own “thing” and attempted to dive under water when it was turned RIGHT into choppy water……like it always has done !

I drove the boat at various speeds and noticed that when slowing down quickly, the rear of the boat tended to lift and the nose dived down - if it was then turned to the RIGHT at this same time it would then start to sub-marinate !

No change (either positive or negative) had been achieved by fitting the wedge.

As the rain began to come down quite hard we decided to call it a day as some of the other “tweaks” that I had planned to try would be more comfortable done without having water running down my neck - but they include fitting a longer (deeper) rudder, more propeller testing, and running at higher revs with a smaller propeller and changing from my regular 2C LiPo to a 3C LiPo battery.

As for the wedge……..well it may as well stay put as a curiosity and as part of the boats development history in its attempt to cure “The Sea Commander Dive”.

I will improve the visual shape and finish it properly so that it looks better when the underside of the hull is re-finished.

Bob.

No worries Dave, it is easy to miss the odd post on this thread as it has attracted so-much attention.

The Sea Commander is a very popular Classic Model Power Boat.

Lots of good theories have been offered and I am trying to respond to all of them to see if I can find a way to remove “The Sea Commander Dive”.

I will keep trying, but have to admit that I have done nothing yet that has influenced this strange behaviour significantly one way or another.

Bob.

Sorry, Bob, I missed that post. It will be interesting to see how my Sea Commander behaves, but there is a fair bit of work to do to it before it meets the water!

Hi Dave,

If you read the last comment before yours on here you will see that I admitted to a typo and that my propeller turns to the left (when viewed from behind) so it rotates anti-clockwise as normal.

Like you, I also come from background of running ic engines (in the 1960’s) and they only run anti-clockwise ……although I have had the occasional one fire-up and run in reverse when it had been over-fueled !

It will be interesting when you get your Sea Commander finished to see if you can find a cure for the nose dive that seems to be a fairly common occurrence with them when they turn RIGHT into choppy water.

The boat does not have to be driven into the turn fast, it can also happen at fairly low speeds too, but can be deliberately started by slowing down very quickly and then turning RIGHT.

The similar sized 34” Aerokits Rescue Launch reportedly also does the same thing, but again there are no reports of the larger version doing it!

Curiously, the larger sized Sea Queen has no reported occurrences of this happening either, and as previously noted, Les Rowell never added the large “wave breaker” to the Sea Queen either, so maybe (like us) he also failed to find a cure for it either?

It is fun trying to find the reason why the Sea Commander has this curious wish to sub-marinate when turning RIGHT into choppy water - and even more fun trying to find a cure for it…..other than driving very slowly in calm water - or avoid turning right 🤣

Bob.

I'm with boatshead on this, coming from an i.c. modelling back background, I still expect a single prop to rotate anti-clockwise.
I have a framed up Sea Commander in the loft, bought the kit in 2021, started it in 2023 and haven't touched it since. I hope to complete it next year (along with a dozen or more other projects!).

Sorry Thomas, it was a typo (now corrected) - my prop turns to the left when running (anti-clockwise) so your fears about me fitting the wedge on the wrong side of the hull remain.

I will be setting off to the lake shortly……

Bob.

Hi Zooma,
I didn't realise that you was running your motor clock wise.
I have always run anti clock wise as be fore I have always run IC engines.
So when I fitted electric as I had the props from previous use I had run my motors the same way, anticlock wise.
So you may have a good reaction with your wedge that you have fitted. 🚤🚤🚤🚤
Good luck, I look forward to your results.
I hope you have got it right and I am wrong with the way I ran my motors.
Regards BOATSHED. >> (Thomas) Happy boating.🚤🚤👍👍

Hi Stephen,

The Sea Queen is the larger boat and from comments received to date it does NOT suffer from the same desire to dive when turning RIGHT into choppy water.

Of these two, it is only the smaller SEA Commander has this unusual handling trait.

Bob.

ON my large Sea queen it hasn't these habits are we all getting con fused which boat is which as they look the same all by aerokits some clarification of these types is needed ive all ways been an advocate to have a to z of boat types and who made them it seems to me with all these knowledge and a great website it could be added a chap who owns a model train site has built one up in 16mm scale locomotives look at anything narrow gauge website

There could be an unintended benefit. When running ahead with neutral trim, the boat may, emphasis on may, drift to Stb’d due to the drag force created by the wedge. That would require some trim to port in order for the hull to track straight. The when turning to Stb’d the trim to port will reduce the rudder angle to Stb’d which may, again emphasis on may, reduce the diving.

At this stage I am happy that I didn’t spend too much time on painting the wedge…….🫣

Bob.

Well Bob, look at it this way: you won’t learn when you’re any younger. 😊

Waiting in anticipation!! 😀😀
Hope the weather isn't too bad for the sail

Hi Thomas, from what you say I have made a mistake - easily done in my case.

I admit that I have had some problems coming to grips with torque and anti-torque and wound myself up completely - possibly in the wrong direction.🤣

When viewed from the rear, the prop turns to the left, and when the boat turns to the RIGHT the nose wants to dive.

My simple logic was that the ramp (mounted on the right) should help to lift the nose when it dives when turning RIGHT…….but I could be so wrong……..

I have fitted the ramp now, so it would be a bit of a shame not to test my (possibly dubious) theory, so it will be run this way tomorrow morning.

The result could well be that I have made the problem considerably worse, but either way, the effectiveness of the ramp of that size will be seen.

Let’s hope I haven’t made the boats natural desire to sub-marinate even worse!

Either way, we will enjoy the experience and learn from it ……..and the video could be hilarious 😎

Bob.

Hi Zoom,
I have not been on your page for a few days.
I have just seen that you have fitted the wedge on the sratboard side of the boat.
Ifnthe post side is diving then surely it would be fitted on that side of the boat. I have coppied and pasted the paragraph from my pevious post for you again that I was tols to fit it. I would be curious first to see how she reacts to how you have fiitted it when you run it if you go out this weekend.
The paragraph is below.
Happy boating this weekend and I look forard to your new video in hope for you🚤🚤🚤.
Good luck.🚤🚤
PS, I am NOT picking fault or judging you, just suggesting.👍


He said to me a good Idea would be when he saw it was to remove all the forward part of the rudder, it was a bit deeper than the prop. and to also add a small wooded wedge glued on the under side of the port side of the hull,
This acted as a type of fitted trim tab so to speak.
It was only about 2.5" long, 3/4" wide and 1/2" deep at the end part of the wedge.
Similar to a door stop? if you get my meaning.

The local weather forecast for tomorrow is looking a bit bleak with winds and rain expected to last all day.

…ideal conditions for testing the SEA Commander in as turning RIGHT into choppy water is when it starts to nose dive.🙄

If the wedge idea shows any promise, it will certainly have a good opportunity to show it tomorrow.

Bob.

Thanks Roy,

I agree that the wedge does look a bit severe - especially when viewed from behind.

The first drive will be interesting!

Seeing what attitude it drives at when in a straight line will be the first thing I am concerned about ….

If I get past that first hurdle OK, the most important thing will be what happens when the boat is turned to the RIGHT into choppy water.

Bob.

Hi Zooma I had a 'Bobby' if you remember it about 20 inches long. It had a 540 with a 30mm dia prop and it went really fast but had a tendancy to react to the torque involved.

I started the wedge off at 0.25inch and 0.75 width using P38 and gradually it was filed down to just about 1/8th inches deep and that was enough.

Take it easy on your first run the wedge looks rather much!
regards Roy

The wedge doesn’t look so bulky when viewed from the side.

Once it is sanded down properly and painted it may not look too bad at all.

Let’s hope it works !

Bob.

Hi Thomas (boatshed),

The first wedge that I have made is to the measurements that you suggested.

The hairy looking lump of plywood that I have used has been sealed with superglue and will be sanded smooth with each subsequent coat of my home made pink undercoat.

I will bung some red gloss on it before sailing to protect the wood.

At this stage I have not taken any great care of the paintwork as the wedge may need to be removed or modified depending on what it does during testing.

I scraped away the paint in the area that the wedge will cover, glued it on with superglue and reinforced it with some brass nails.

The wedge should be possible to remove to adjust the size and shape if necessary, but should hold on well enough if it works as it is.

1/2” thick visually looks a bit too much, but without testing we will never know, and your measurements will make a good start to this latest round of experiments to try to cure the dreaded nose diving symptoms that my boat displays after turning RIGHT into choppy water.

Thanks for your contribution to this thread and for reminding me of yet another thing from years ago that I had forgotten about using on fast ic powered boats 😊

Bob

Hi Stephen T, and welcome to this thread aimed at those that own or have an interest in the Aerokits SEA Commander....and for those that enjoy contributing to solving a common problem that this design has.

The Aerokits SEA Commander shape complete with its WAVE BREAKER does not look too much like a river cabin cruiser to me, but I admit to not studying river cruisers too much over the last 60 years of enjoying my Classic Model Power Boat models.

Maybe you have seen a river cruiser that looks a bit like the SEA Commander......but probably not one with such a large WAVE BREAKER fitted?

Irrespective of what style of craft Les Rowell used to inspire the final shape of the SEA Commander, it has ended-up as being a boat that looks like it could tackle the open sea and the model certainly performs well.

Many SEA Commander owners have pushed their boats much faster than I am running mine at, but my model has a strange handling quirk that is (I am told) also shared with the same size Aerokits Fire Launch that can display similar problems when turning RIGHT into choppy water.( I don't have the smaller 34" Fire Launch so I have not experienced this problem for myself).

I am really happy with my SEA Commander and I like the way it looks and performs (apart from the nose dive that is NOT speed related).

If I can find a way to overcome its desire to dive when turning RIGHT into choppy water (I have now proven that it does not have to be driven very FAST for this to happen!) I will be very happy to share the solution with other SEA Commander owners (and Fire Boat owners) that have the same problem with their models.

Trying to remove this "quirk" from an otherwise good performing model boat is proving to be an interesting challenge that I am really enjoying trying to achieve.

Today I made a wedge to fit the outside rear of the hull to see if it will work on the SEA Commander as well as it has done on some ic powered model boats in the 1960's and 1970's.

If the wedge can be developed in size and shape to work it would be a simple fix that would be very easy to replicate for anyone else that would like to correct this problem with their own similar sized Aerokits model boats.

My only interest in this project is to make my own SEA Commander handle as nice and as well as any of my other Classic Model Power Boats.... and I have had a LOT of them since I started making, restoring and driving them since the 1960's.

I am not pushing my SEA Commander any more than any of my other Classic Model Power Boats .........and they do NOT (none of them) have this problem of attempting to enter a dive when turning RIGHT into choppy water, so it is a real challenge to make this model into a nice easy handling boat that has safe neutral handling even when turning RIGHT into choppy water.

Bob.

These boats are river cabin cruisers not power boats reading all these comments are you trying get more out it than the hull shape will let you

I wouldn’t remove the forward strakes. Doubt very seriously they contribute to the problem. The wedge might create just enough drag on the port side to greatly reduce the effect of the prop torque. Were it me, I would spend some time experimenting with size & location. A possible downside is that you will need to add starboard trim to get the hull to track straight.
Your comment that this a narrow hull jumps off the page at me. How narrow is the beam? A long hull with a narrow beam doesn’t have enough wetted hull surface to counter the prop torque.
Ain’t this fun?

Thanks Roy,

I will see how the boat runs with the wedge first and then make a decision to follow this up and remove the front part of the strakes if needed.

Making one significant change at a time usually works best and identifies most accurately which change worked .

Bob.