Hi Harry,

We used to off-set the water scoop pick-up tube to the right of the prop shaft back in the days of fast ic powered model boats to counteract the torque, but I have never off-set the prop shaft.

Some of my fast flexi-drive-shaft equipped flatties have an off-set rudder with the water pick-up included in the rudder blade.

I also like speedway and supported the Bristol Bulldog’s, Exeter Falcons, Poole Pirates and Swindon Robins when I lived in various places in the West Country, but since moving up north our local team is Bellevue in Manchester (also the home of the National Speedway Stadium).

My all time favourite rider was Ivan Maugher and our best local team captain was Phil Crump.

Bob.

Hi Zooma
The old speedway saying, GO HARD OR GO HOME !!!!
I drive my boats the same as EWE !!!
The best handling boat is the Spearfish in cornering and a straight line both in rough and calm water(if setup right).
I off set my prop shaft to the right side of the rudder because of prop thrust.
Harry👍

Regarding the cheeky comment from ChrisF suggesting that the cause of my strange handling problem was my “throttle hand”.

…..I admit to driving all my classic power boats quite quickly at times (fast) as I like to see them make “white water”.

However, I drive all of my Classic Model Power Boats “with enthusiasm” and enjoy seeing them perform well and in a scale like way (OK maybe slighter faster at times 🤓).

As I have a variety of different Classic Model Power Boats to drive (along with some quite fast flatties etc) I appreciate that they do not all perform in the same way and drive them accordingly.

However, the ONLY Classic Model Power Boat that I have driven since the 1960’s when I first started driving (and racing) them that has displayed this strange nose diving quirk has been my Sea Commander!

This is not all bad news as now I have gotten used to it (and even know how to “encourage” it to perform in this way), I sometimes deliberately drive it into this situation as it looks so spectacular with the decks awash and partly submerged forcing the “wave breaker” to display its effectiveness (it does work!).

Having admitted to the above, and seen other Sea Commanders behaving in exactly the same way (depending on speed and water conditions), I am not really worried about it at all……but I would still like to understand why this particular design handles so uniquely differently from any other Classic Model Power Boat that I have ever driven or experienced over the last 60 years or so of “enthusiastic” driving with the same “throttle hand”. 😎

Yup, I think some hull designs cope with the phenomenon described by Chum444 much better than others.

The LesRo Rapier hull just shrugs it off, whereas the Sea Commander hull copes with it noticeably badly.

Bob.

Re latest post by Chris F. When you slow down in a real boat the bow is pushed downward by the remnants of the boat’s wake. Happens when the wake, which is now faster than the hull’s speed, catches up to the stern. The flatter the hull’s deadrise is in the stern the more the bow will be forced downward. Analogous to slow running in a following sea.
Same thing happens with model boats.

The problem's with Bob's throttle hand! 🤣

From your post after the prop shipping cost post it’s beginning to sound like there might be a problem with the hull design. Hopefully not.

I forgot to mention it at the time, but since it is still bothering me, the cost for sending the spare plastic propellers to me that I bought locally recently was £6.50.

This is a standard delivery charge from my favourite supplier of model boat bits and pieces and is worth remembering when only a small lightweight item (such as a plastic propeller) is needed.

It is less expensive to buy these things and have them posted from China, but I always support my local supplier whenever possible.

Bob.

Thanks for your thoughts Will, this has been something that was previously suggested by Chris as he experienced a similar thing on his Huntsman 28 testing and guessed that his spray rails may have been “digging-in” as the bow drops.

I think the problem is worsened on the Sea Commander as it barges it way through the water when the bow drops back down from riding on the plane.

At first I did wonder if the strakes were also contributing to this, but if you read my previous post starting “Two Sea Commanders …” the other boat that did not have any strakes acted in the same way.

To date I have seen a few Sea Commanders in action, and unless they are being driven very slowly (many are!) they all display the same action.

The difference seems to be magnified when dropping from a high speed run (when the bows naturally drop) or when turning into a wake wave or very choppy water at low speed and then opening the throttle to power into them.

I will continue to experiment with various things including the placement of different weights in different places and also test the effect of running a smaller prop that produces less torque that may or may not also contribute to this strange nose diving effect.

At this stage I am not convinced that sanding away (or removing) the spray rails at the bows will help to remove this strange willingness to dive down into the water under certain conditions, but I am considering picking up a cheap used Sea Commander to test run a plain hull with no spray rails or strakes fitted to see if it handles any differently with the same power, propeller and weight distribution etc.

I have also read the article that Chum444 offered as a reference.

Bob.

Yeah, we did mention that in one of the posts I think Will and could be likely as the bow drops so much when coming off the power.

I noticed it a bit when doing water trials with my Huntsman 28. Not to the extent that Bob's model does but just a bit of a snatch when turning sharply. The chine rails don't turn up much at the bow. I just turn slower and more gently now! 😀

Things might alter when the build is finished and the weight distribution changes a bit.

Bob, I've just had a thought. Your spray rails, could it be possible that when you tip the boat into a turn, that the inner spray rail dips below the water and due to hull shape, is at enough of an angle to cause it to drag the bow down?
In most situations, straight running etc, the spray rails will be doing what they're designed to do, but do they have an adverse effect if they dip under the water?

I could be completely wrong, but was just a thought that I had.

Will

You might find this article & it’s reference to other similar articles useful.

https://www.aeromarineresearch.com/publications/PBR_feb2015.html

Hi Stephen, I have “spray rails” along the sides of my Sea Commander as well as strakes along the bottom skins.

The chine rails terminate at the bows and the strakes terminate where they blend in to the chine rails.

Your spray rails stop short of the bows on your Vivacity - do you have a picture of them on your Sea Commander by any chance?

Maybe where they stop has some bearing on how they affect this problem that seems to “dog” all Sea Commanders?

Bob.

I fitted them to my vivacity as well as that did the same thing its just simple strip just up from the water line

That’s interesting Stephen, could you add a picture of them here please as maybe you have found the answer for us?

Bob.

I have fitted a pair of spray rails to each side and it no longer digs in the bigger boat hasn't got this issue

Hi Stephen,

if you read the recent thread "Two Sea Commanders on the lake today" (just two threads before this one) you can see that both boats acted very much like each other.

At this moment in time, I am thinking that this strange handling is a trait that affects all Sea Commanders.

I also have a Sea Queen and I am interested to see what happens when this model is restored and driven in similar conditions as I have also heard reports that they do not have this same problem.

The Sea Queen kit never came with the distinctive 'wave breaker" either, so maybe Les Rowell was also aware of this when the enlarged model prototype was tested?

Bob.

I have a old sea commander and for some reason that ive never figured does the very same thing as on the sea queen no matter how rough doesn't doo this is its bigger size that stops this happening

Just collected the different sizes of M5 propellers from home and look forward to testing them on the Southport Club lake this weekend.

Bob.

Two Sea Commanders on the lake today.

I will be driving home early this week to check my wood stock to see what I may need to order for the Sprite Plus project that Chris is drawing at the moment……and hopefully pick up those propellers!!!

At the lake today was another Sea Commander that was going quite well so I was able to watch and make some comparisons with the handling characteristics of my own Kopy Kommander,

Both boats handling was very similar, mine was a bit faster but I was more interested in the way they reacted when they were turned and when they slowed down quickly.

The first thing I noticed was that the other Sea Commander sat a little lower in the water and was not as fast to get up onto the plane, but when it did, its bows did not ride quite as high as mine above the water.

Both boats tended to plough their way through the water when not on the plane rather than parting the water and elegantly riding over it like the deep vee hulled boats would do, or skate across the water smoothly like the Vic Smeed Remora, so that is a characteristic of the design - more like a barge!

Once actually up on the plane both boats ran as smoothly as anything else and both boats were also quite quick, but as the throttle was closed the boats bows dropped quickly downwards into the water easily flooding the fore decks.

This could look quite spectacular, and I admit that once I knew that the boat could take this treatment time after time I quite enjoyed seeing it perform under such a weight to water and shrug it off ! I imaged a similar shaped boat at sea in rough weather acting exactly the same.

The “wave breaker” that is part of the Sea Commander design earns its keep and certainly works well (the other boat did not have the wave breaker fitted).

Both boats tended run “dirty” by that I mean that they don’t run cleanly in the water - they make a lot of bow wave when they are not up on the plane.

My boat has strakes and these can be seen to be working in the water at any speed and are probably why it lifts up onto the plane so quickly and easily…..and maybe why it keeps the bows a little higher too?

My wife observed that the bows on my boat naturally ride higher that the other boat whose bows never lifted as much as mine did.

This could be due to the strakes working or the fact that it sits a little higher in the water that the other one that I was trying to compare it with, but I removed the second layer of lead from the rear compartment to see if it made any difference to this…and it didn’t.

More testing next week when I have a choice of propellers to experiment with as maybe less torque and more revs could change the handling charactoristics too?

With the smaller propellers I can also try running 3C LiPos to take advantage of the greater revs and less torque. I have only ever run 2C LiPos in the Kopy Kommander to date.

I should also mention that the other Sea Commander was much prettier than mine and had more detail work too, so the next time I see it I will take some pictures of it to show what a nicely finished and presented Sea Commander should look like !

Bob.

I ordered the propellers from my favourite supplier who lives partway up a Welsh mountain (he told me this a long time ago).

Things don’t always go to plan (they were also sent to the wrong address) but when the props arrive (at my home address) sometime soon, I will drive home to collect them.

The weather has turned off a bit so maybe the weather will have improved by the time the propellers arrive, so it could turn out to be a positive rather than a negative 🤓

Bob.

That's blooming frustrating Bob 🤞
Fingers crossed they arrive soon, then the 'fine tuning' can begin/continue.

Will

My selection of propellers has still not arrived so I was unable to do any testing on my Sea Commander (copy) last week…….and I drove home to see if the props had been delivered — but still no joy!


When the M5 props do arrive, combined with the old 2BA ones that I already have (both these thread sizes fit the same), I will have a good selection to play with:

S60, S55, S50, S45, S40,S35.

X55, X45, X40, X35.

That size range will cover anything that I already own or have in build or restoration at the moment when combined with any brushless motor (in-runner or out-runner) that I have to use.

Should make an interesting test session as I always use the same size water-cooled engine mount in all my boats so swapping and comparing different motors in different hulls is quick and easy.

I also hold an appropriate sized spanner and Allen key on magnets inside each hull so I can change props or lube the prop shaft alongside the lake without having to carry a tool box or search for the correct sizes of tools for the job.

Bob.

That makes sense Will, I am not at home to measure my Aerokits original (1971) version, but as you suggest - the re-kit is probably the same size 👍

Bob.

Bob, I've just checked and the modern version of the Fast Patrol launch is 20" long, so i presume the original is too 🤷‍♂️

Hmm, it could well be 16", I can't remember. Something in my head said it was 20", but I'm more than likely mistaken 😂

As far as I know Will, Aerokits only made the one version of their Fast Patrol Launch?

I think mine is 16” long (I am away at the moment and so I can’t cannot check it) and looks very much like yours that you have so kindly added to the Classic Model Powerboat thread.

Bob.

Bob. Which Fast Patrol boat is that you've got, is it the small 20" version? If so, I've got one of those too.

Will

I have ordered a selection of props to test on my Sea Commander copy.

I thought I had a few spare props to choose from, but most of them were red coloured and come from the 1960’s and 70’s.

Although they would still be perfectly good to use (2BA props can fit onto M5 prop shafts) they were all X50 and above as they were used with IC engines that have motor torque than revs.

To my surprise I also found quite a few 4BA propellers from the same sort of time period. These can be used on any of my models that have a 4mm propshaft (they fit perfectly), but the only boat that I have currently running with a 4mm propshaft is my Remora, and the prop that I am currently usuing on that boat works a treat - so I wont be changing it.

Some of my smaller project boats may end up with a 4mm shaft, and my Aerokits Fast Patrol boat already has a 4mm shaft fitted, so I am pleased that I dug-out this old box of propellers as they could come in handy.

I also found a good selection of BRASS propellers (yes I did make and sail scale models back when my eye sight was able to see the very small details better).

These BRASS propellers are mostly 3, 4 and even 5 bladed. I will take a picture of them to see if they are of any interest to anyone on here before putting them on eBay.

Another box of old propellers revealed a small selection of props for use on fast surface piercing boats that have the notch for “dog-drive” to fit flexi-shaft drive systems. Some of these are brass and some are plastic, and are good spares to my fast “flatties” (is this term still used for the “plastic fantastics” ?).

My delivery of new M5 props has not arrived yet so unfortunately I wont be able to test them this weekend, but hopefully they will arrive very soon as I am looking forward to see how the different sizes perform on my Kopy Kommander.

Bob.

As long as you're enjoying the boat now, you've put so much effort into building it, and now sorting the handling.
I'm really pleased with the outcome Bob.

These two strips of lead gave the best balance for the Kopy Kommander and didn’t move during testing.

I will tidy-up the installation and then move on to testing smaller size propellers….and also 3C LiPo batteries.

Bob.

Hi Will, yes, if you check the first pair of videos you can see where we started with the single lead weight fitted.

The first two videos were run at speed, the second two were run at a lower speed, and the final video was run with TWO weights - at all speeds.

The progress can be seen and the end result is that I am very happy with the handling of the Kopy Kommander now - and it also has good turning and an excellent performance on a 2C LiPo battery.

The endurance is better than I get on the same cells with my Rapier, but I am keen to try a smaller size prop, and possibly using a 3C LiPo with an even smaller prop to see how if affects the performance, handling and the duration.

Those two old delaminated cabin sides that you gave me have ended up being built into a good copy of the Sea Commander that I am very happy to own and run.

I am VERY pleased with it - thank you for unwittingly starting all this by giving me those scrap oddments from a broken boat.

Building this boat has been a challenge that I really enjoyed.

Bob.

Well done Bob, looks like a great result, and an easy fix too.
Are you happy/pleased with the handling of the Kopy Kommander now?

Will

Hi Harry,

Thanks for your input, your idea of adding a little weight to the rear of the hull has allowed me to trim the balance of the boat slightly, and this was enough to make it handle nicer and avoid the nose diving that could be induced under certain conditions - although most times the boat drove really nicely.

Regarding your choice of power, I am only running a 2C 7600mah LiPo and that gives me enough speed to use on our small boating lake in Southport.

Even with such high capacity Overlander LiPo batteries, I am not getting especially long run times (although they are probably twice as long as these same cells give me in my Rapier) and I am thinking about reducing the size of the propeller to allow the motor to rev more freely and reduce the workload.

I will find some alternative M5 propellers to test and see how I get on with them.

Your choice of 35mm props on your Sea Commander seems small, but with more cells used the smaller the prop needs to be (with the same motor), so it will be interesting to see how mine runs with a smaller prop.

I do have 3C LiPo batteries that I can use, so I may test them with a smaller prop and see how they perform for speed and duration, but for now I will stay with the 2C LiPos for my prop testing.

Good to see your Sea Rover pictured here - do you have any of your restored Sea Commander to share with us?

Bob.

I cut 4 pieces of lead sheet to use in the testing of the Kopy Commander, but only ended-up using two of them.

I have just weighed these last two pieces of lead and they weigh 265g, so allowing for the small notch I cut out to fit around the back of the rudder shaft, and the corners that I clipped off they probably weighed closer to 260g for the pair.

This information may be helpful to anyone else who builds a Sea Commander.

There as a possibility that the strakes that I added have contributed to the strange nose diving that it was possible to induce under certain conditions.

Another possibility is the weight distribution that I have, but from what I can see (and have been told), most Sea Commander owners have placed their batteries (lead acid/Nicad/NiMh/LiPo) under the cockpit floor, and after testing various other options, I am happy that this is the best location for them.

Anyway, for now, I am very happy with the way my copy Sea Commander drives with these two small weights added behind the rudder post so I can now relax and just enjoy driving it.

Bob.

Looks like the problem solved with a nice floating bow over the waves. Time to up the kv's or battery.
My Kopy Kommander is running 35mm 1100kv on 3 and 4S Lipo.
My Sea Commander 35mm 1450kv on 3S.
We are just into Spring with rain and more rain.
Back from Brisbane as our second great granddaughter had her first birthday.
Hope to get back into finish restoring my Sea Rover and start on my first new kit build, a Lesro Sprite.

Harry aka Canabus

By now the rain was coming down heavier and the car park was emptying, so with the lake more or less deserted, we decided to run one last test with the second weight added on top of the first weight.

We sheltered under the rear hatch of the car and fitted the second weight.

The boat was put back into the water, but as there was very little else on the water by now we decided to stay closer to the car at the end of the lake and run it from there.

This final video shows that the second weight works even better than running the boat with the single weight fitted.

Now that I am happy with this small addition, I will bend the weights a little more to fit into the contours of the hull even better - although there is no sign of any movement with them fitted the way that they are - it will look a little neater!

Bob.

Two more runs were made in an attempt to cause the nose to dive at different speeds as my “cameraman/observer” (Adam) and myself thought that the boat was more likely to nose dive at slower speeds.

The last run with the single lead weight fitted was made at a gentle to moderate cruising speed where the boat now looked to be well balanced and looking good.

…..and the weather continued to deteriorate….

Bob.

Hi Will, the Sea Commander (Kopy Kommander) was driven on the the Southport Club lake this morning with the lead weight fitted as shown in the previous picture.

The idea worked quite well - so thanks Harry!

I have video taken of the first two runs with the single weight fitted.

My friend Adam (a newcomer to r/c model boats and who is about to build the original Aerokits Sea Commander kit that I acquired recently) took the videos on my iPhone and suggested that the weight had also changed the sound of the boat - possibly making it sound more “dampened”.

The first run included some reasonably fast runs with lots of erratic steering inputs to try to cause the nose diving attitude that we are trying to cure.

The weather today is windy and increasingly wet with rain getting stronger as the day goes on - so good conditions for this particular test!

As the morning went on there were less and less boats on the lake as their owners headed for cover - or mostly went home!

Not many r/c boaters like to get their boats wet 😂

The climatic conditions are playing-up with the TV reception and the videos have not downloaded from my iPhone onto my iPad yet (atmospheric intervention?) but as soon as they do I will show them here.

Bob.

It will be interesting to hear your thoughts after the next run of the Kopy Commander, and if this additional weight in the stern has made any difference to the strange handling trait.

Will

Here is the first strip of lead fitted in the rear compartment of the Sea Commander.

The lead has been slightly shaped with finger pressure to conform a little to the inside shape of the hull.

Hopefully, this minor shaping combined with the notch to locate it against the rear of the rudder post will keep it in position during the testing.

If this lead weight works, it can be shaped (by taking advantage of its softness) even more to fit the into contours of the hull.

Any additional layers of lead that may be added can also be shaped in this way, although some sort of adhesive would probably be added in due course to ensure a permanent fit.

Bob.

Following-up on Harry’s suggestion of adding weight to the rear of the hull, some strips of used lead sheet were cut ready to fit as far back as possible in the rearmost hull compartment.

There is a small space between the rudder post and the transom that could be used to place the weight at the back in the hull ready to test.

There is not too much room to slide the lead strips over the top of the rudder shaft (and under the rear deck), but one strip was fitted here and a notch was cut in it to anchor it against the rear of the rudder post to stop it moving around when the boat is being driven.

The two strips of lead are shown here - but only one will be fitted to start with to see if it can make any difference. The other piece will be taken to the lake tomorrow and can be fitted if it looks like the idea will work better with more weight.

Bob.

Thanks Harry - good to hear from you.

I will take some lead strip back with me so I can try weighting the rear of the boat and see if it helps.

Stay safe,

Bob.

Hi Zooma
Move weight to the stern(battery) bothe my Sea Commander's would close to getting up the plane at that speed.
As for turning they turn on a dime !!!

Thanks JB and Will,

I will keep experimenting until the cause of this strange phenomenon becomes clear - then it will be possible to remove it.

The chances are that it will end up being something so obvious that it has been staring me in the face all along - but for now, I can’t see what it is.

I will keep the updates and thoughts coming because they may be helpful to someone else in the future!

Bob.

Bob, I was going to say, the only difference between your Kopy/Sea Commander and probably a majority of the others on the water, is in fact the strakes. Whether or not they are causing the issue is a hard one to say, but in theory they shouldn't. Having a keel, the hull wouldn't slide on the surface at all, so shouldn't have a loading on the top faces of the strakes.
Keep experimenting, that's all that you can do really, but I'm sure you'll get to the bottom of it.

Will

Hi Will (and Chris),

I will check to see if I can get the centre of gravity any lower than it already is, but I think it is probably as low as I get get it already?

The problem that Chris, yourself, and myself have is, that we are all used to the way that the deep vee hulls lean inwards during a turn ( and contributes to why we like them so much) whereas the more conventional hull shapes tend to stay much flatter as they turn.

I have got it right with my Remora (or at least Vic Smeed did) and I have done nothing to impair its handling by driving it fast and it still sits very flat on the water.

The Sea Commander has got me beat at the moment as I have used the Aerokits prop shaft length and angle so I don’t think I have done anything in the building to cause the nose dive tendency that this boat has.

I am passing my new Sea Commander kit on to a friend and neighbour who is new to model boating and the kit will be built as intended (without strakes) but it will have similar power to mine.

There are other Sea Commanders in our club, but none of them are driven fast enough to be able to make any helpful comparisons (sensible cautious owners) so I will continue to explore all options until I get it right.

I only run 2C LiPo cells, but I have 3C an available, so I will try this with smaller props to give me the revs rather than the torque.

Having said that, I am only running a standard 45 prop at the moment, so it is not exactly over- propped for a 34” cabin cruiser.

The more I think about it, the more suspicious I become about where the the chine rails and the strakes meet at the bow.

I love the way this area looks, but maybe (just maybe) at low speed the water gets over these and it causes the boat to nose dive under their direction?

I can try to further blend away the chine spray rails and strakes at the nose of the bows to reduce this possibility……but I will try to find another cause if I can…..because I really like how they look and the way they direct the water away from the hull at any speed….other than a slow turn into a heavy wake or choppy water !

Bob.

Hi Bob, keep at it, you'll have it sorted at some stage,- like a lot of things with models, sometimes it's a process of elimination. Videos are really handy for seeing what's going on. I've sorted a number of issues with my planes and boats over the years, by studying videos of them in action when I get back home. (like spotting a few with my latest semi scale yacht)

JB

Hi jbkiwi, and thank you for taking the time to contribute with your helpful thoughts.

Congratulations also for running a Stiletto, I also have pair of scaled up Stiletto boats, but mine are Rapiers 😂 (!) with a same hull offshore racer (LesRo Javelin) almost ready for action and a Stiletto on the bench being prepared for restoration.

As you can guess, I am a big fan of these LesRo deep vee hull designs - as well as the Swordsman and other Fairey designs, so my Sea Commander copy (Kopy Kommander) is a bit of a departure from my area of understanding as the deep vee hulls have entirely different handling characteristics.

With that in mind I followed the Aerokits plan as far as the prop shaft length and angle was concerned so it is basically “kit standard”.

I have written on the Kopy Kommander thread about my extensive tests regarding moving the ballast to different positions to try to resolve this desire for the hull to nose dive under certain conditions, but to date nothing I have tried and tested has made any difference or helped to improve this problem.

I have used flexi drive on most of my really fast boats over the years and understand the theory you have shown so clearly regarding the benefits of having a flat drive.

Something else I need to try before removing the prop shaft and making any dramatic changes to the drive, is to experiment further with smaller propellers.

My reasoning is that there are probably more Sea Commanders out there than almost any other model power boat, and some of them will have been driven as fast (or faster) than I drive mine.

One of the reasons for creating this thread was to try to attract comments from other Sea Commander owners, who will (most probably) also be running their boats with the kit designated prop shaft length and angle - but to date this thread has not attracted any Sea Commanders owner/drivers who have a similar fast boat set-up.

………but I hope it will…….

Meanwhile, here is a short clip of my 39” Rapier that may be of some interest to you?

I can see the roll outwards but not much throttle was being applied and I think that was just due to a change of mind when steering or maybe a wave? It is difficult to say.

The model does stay very flat when cornering, though it's not going very fast in the video, unlike my Faireys which lean quite a bit due to the deep vee hull.

Bob, I was going to say something similar to JB, but without the technical part (as I hadn't thought of that), as I too thought that I saw it roll outwards on one of the turns. I had wondered about the centre of gravity, but JB's reasoning is probably more likely than mine.

Will

Hi Bob,
Just some observations and suggestions. I noticed that it rolled outwards on a turn at one stage in the video, this is usually caused by too steep a propshaft angle, which can cause the bow to dig in on turns. Best I can describe it is,- If you make an imaginary arc from your propshaft to the bow, you will notice that there are 2 points the boat is trying to operate on,- the prop and the bow. The prop is trying to push the boat up at the angle of the shaft, (taking weight off the stern) and the weight forward of the prop is pulling it down at the bow, which causes the boat to want to torque roll on the bow.

Not usually that noticeable in a straight line, but in turns you will probably notice it only does it in either a left or right turn, (depending on which way the prop rotates) - looking from the stern, if the prop is rotating left, the boat will roll right and vice versa. The best drives are either cable or stinger drives, as they can be set to push parallel to the surface of the water (or bow trimmed up or down) for best performance. You can move weight to the stern in your case, which may help reduce the problem, but it would be better if you could minimise the angle somehow. Looks to run fine in most areas, just the turns causing problems. Have you tried turning the other direction to your normal direction,- might help if you are turning against the torque ?

Another way which might help, is to use a smaller prop to reduce torque roll, and spin it faster (higher KV motor). I use a 25mm prop on the Stiletto, with a 1600kv 37x56 outrunner on 3s to make it run as it does, and it's restricted to 75% throttle.
My scaled up Stiletto uses a cable drive, and you can see how stable it is, as it keeps the bow up and the stern down on the planing surface.
JB

I will try to take a video of the Sea Commander at speed later this week as it looks really good when it is up on the plane like a really well balanced boat should.

The thread on my Kopy Kommander explains the various different battery positions tested, and none of them made any change to this desire to submarinate as it turns into a wake or choppy water when travelling more slowly.

The boat runs with a pair of hard cased 7600mah LiPo batteries under the cockpit floor and probably weigh less than a lead acid battery would.

The battery’s fit one on each side to balance the boat as well as giving it the best ballast tested to date.

Only one 2C battery powers the boat at a time and it has plenty of power for the size of lake it is running on.

It could be that the chine rails dig in at low speed and try to pull the boat downwards until the buoyancy overcomes it ?

Another thought(like noses everyone has one) when you slow down just before the first wave the boat’s stern wake might be lifting the stern & pushing the bow down. Try slowing down a bit earlier before taking on head waves.

Only as a trial you might try taping a bit more ballast weight after in the stern. It looks to me from the bow wave that she’s heavy in the bow. But that’s merely my thinking. Of course you should try it at speed with the temp ballast to be certain she still planes properly.

Apart from this strange quirk of nose diving after decelerating and turning into a wake or choppy water, the boat handles and performs really well.

I will try to find some video of it at speed where it really performs and handles perfectly.

These two pictures were taken seconds apart.

The boat had just slowed from a fast run and was turning as it was decelerating ready to take off again.

The boat goes onto the plane very quickly, has no water inside it at all and all the components inside to boat are firmly fixed and do not move.

When stationary the boat floats nice and level.

Some things to consider.
- At rest in calm water how does the boat sit?
Does it appear to be bow down even slightly?
- Are all of your components in the bilge tightly
secured, particularly the battery.
Might be a ballast issue or an issue of weight shifting in the bilge when underway. After hitting the first wave it sounds like the boat starts to porpoise.is the CG too far forward?
One last thought after absorbing one or two waves on the bow is there water in the bilge?

I have never had that issue with mine, very easily onto the plane and is quite happy to take on the wash from other boats.

What battery are you using and where located? Originally I used a 12v gel which fitted neatly under the helmsman’s floor, however now use either NIMH or a 3cell lithium. Even the gel battery did not affect the performance with no diving.

It certainly does seem strange as that appears to be going straight there. Usually a model would be up on the plane so that wouldn't happen.

Certainly an impressive curtain of spray!