Yes, that would work. At present though am making steady progress in getting all three screws running. if that optimism is unfounded may well use your suggestion
Rowen

You could use just two motors for running and fit the 3rd screw to a dummy shaft for judging etc. Yes?????👍

Hi Doug,
Thanks.
Yes, there was a trim tab. To avoid your enjoyment of future epistles, all will be revealed in the fullness of time
The motor control circuit is also something I am thinking about. For my current test program am going to use a simple 1 control - 1 motor.
Do not know of the name Tasmanian Devil, the guy who has been very helpful is called Michael.
You are probably right, think it could be "overmotored", but that will be revealed in the tests.
Rowen

Great stuff Rowen, Good progress 👍
Interesting, didn't realise they had a trim tab! Are you going to fit one?
You're probably right about the battery. Usually 3 batts adding up to the same capacity (Ah) of a single weigh at least around 20-25% more.
Only advantage I can see would be weight distribution; two at the sides would help to dampen rolling.
Depending how you set up the ESCs and controls the 3rd motor can actually work like an overdrive or turbo 😉
You've got some mighty meaty motors there anyway so I would expect performance on two engines to be pretty good. Switch in the 3rd for 'Emergency Ahead' 'Throttles through the gate Number One'!
Your contact wasn't our 'Tasmanian Devil' by any chance? 😉
A very resourceful and helpful guy👍 Ciao 😎
PS I totally agree; if the original had 3 screws (or x of anything else for that matter) then so should the model - that's what 'scale' is about ain' it😉

Thanks for your advice. Guess am stuck with the water jacket style now, will see how they work.
Was intrigued by these rubber ones though, they have an internal scroll which defines the water path. Rather like a coil.
Intend to make the small ESC wire mods you and Doug recommend. Thanks

Hi Rowen,
I have had water cooling on all my patrol boats running at 12Volts, whether brushed or now brushless.
For the brushed motors I have used aluminium tube coils with water pickups between the propellers and rudders. I did try water jackets a couple of times but found too much friction loss and therefore lack of flow.
For the newer brushless outrunners I use a brass tube soldered to a brass plate across the front of the motor fitted between it and motor mounting bracket.
I agree with Doug with regards to the disconnection of the red wires on the ESC's. This is now common practice, especially if you have an external receiver battery.

Hi Rowen,
snag with the ESCs is that bY connecting all 3 red leads to the the RX you are shorting the outputs of all the Battery Eliminator circuits together.
If they are not protected by fast diodes you may do serious damage to the ESCs 😡 The RX only needs one supply anyway. if you are going to use a separate RX battery then DEFINITELY disconnect all 3 ESC red leads!
Cheers Doug 😎

Thanks all for the responses.
Donnieboy - have thought out the plumbing, which is simplified by using a cooling pump. See future episodes!
Doug - appreciate the concern regarding the red ESC wires. Have been trying to understand the rationale behind that theory. if all ESCs share a common input voltage, i.e. from one battery, what would the connection of multiple red wires do? Can understand if there were several unique power sources, but that is not the case here.
Perhaps with your electronics background you can explain.
Colmar - Used the angle on the scale drawing. if it were good enough for Vosper, should be good enough for me! Think it close to 7 degrees anyway.
Think short shafts with oilers should help. Have heard of bushings running dry and seizing with these high speed motors.
The initial props are scale versions of the originals. Rather suspect they will not prove to be ideal. Have purchased some 2 blade racing style props for a future test. They have a much coarser pitch and are designed for high speed motors.
Intend to use plastic props initially as they are cheap enough to experiment with. Perhaps others have a comments on the cavitation question?.
Incidentally, this is my first high speed boat too, but there is much of information on both this web site and Model Boat Mayhem for guidance.
Posting questions always generates useful information. Look widely though at all types of fast models, MTBs, RAF launches, E Boats etc. - it has all been done before!

Hi - This will be my first fast boat build and thoroughly enjoying yours :o) The layout is superb. Great advice keeping the prop shafts short which would have completely escaped me! I also note the long oilers added. Also, is there a particular angle for setting them to (7 degrees I've read)? As for minimising cavitation is there a general preference for props?
Sorry if my Q's are basic but really quite new to it all.

Neat installation 👍👍
Don't forget to disconnect two of the red supply leads from the RX if the ESCs have BEC !!! 😲
Cheers Doug 😎

Nice installation of the electrics.Easy access.It might be better to plan the water cooling right now just in case something gets in the way.

Evenin' Rowen,
So far so good, nice job👍
Let me go through your comments one by one😉
1) "Moved the battery towards the stern and, at speed, the forefoot lifts slightly clear of the water. The plane is now almost flat. The battery is not well positioned when near the bow."
Battery in the bow is almost always bad news🤔 too much weight forward of the CoG or natural balance point when planing.
2) "The 2S battery used was a 4000mAh 30C; suspect this battery does not have the capacity to operate the model. Every motor will run up smoothly until a second one is operated. The first motor then “stutters” and a fuse might blow, this could be indicative of a power surge. Any comments from the electronic experts among the group would be appreciated."
First the battery: you may be right. Especially with 3 x4500 kV motors Since you are using 3 ESCs how about feeding each one from a slightly smaller (lower weight) battery? Precondition of course is that all three are equally charged to the same voltage and capacity AND have the same (or very very similar) internal resistance! Complicates the issue of course and motors with a lower kV rating and one power source may well be the better solution😉
Second the 'stutter': How and when did you switch in the second motor?
If the first was still at 'Full Ahead', i.e. 'Pedal to the metal!, I might expect the battery voltage to dip and then recover with the sudden additional load and a sharp rise in total current drawn. But no particular excuse for a sudden current rise in the first motor ! Where was the fuse that blew? I suspect in the primary supply lead from the single battery🤓 since with brushless motors you can't fit individual fuse in their supply leads like you can with a brushed motor. BUT you can to the ESCs feeding them!!! You can't get a power surge from a battery, not like a surge on the mains network due to lightning etc! But you can get a voltage dip and recovery if you suddenly present it with an additional load😲
3) "The 3S battery was 10,500mAh and 40C; with this battery all three motors can be run at full speed together and fuses do not blow. it was also very heavy at 1700g, holding the model down."
All run up together to full speed or 'switched in' as described above?
There's a big difference between a gradual increasing of load on a power source and a sudden step increase!
4) "The motors are 4500 kV. On refection, think a slower motor around, perhaps 2000 kV would have been a better choice."
I did think at the outset that 3 x 4500kV was perhaps a little ambitious😲
2000 - 2500 sounds much better, and more controllable👍 Then you could also get good performance results with a single battery of capacity lower and weight 👍 The function of the third (centre) motor for 'action speed' would also be more pronounced👍
5) "Would concur with comments by others that a simple single or two bladed propeller layout for this model is probably best - that is unless you want to capture the true scale layout. The centre propeller seems to have little effect on overall performance, (see above re 4500kV motors- Doug😉) although it will power the model quite nicely when operating by itself. Have had several suggestions about how best to use the centre propeller. Will think about them and decide later how to do this when I start to finish the model."
As a 'Scale Purist' (as far as my skills and tools allow!) personally I would frown on the use of 2 blade props, much less only a single prop. Do that in a fictitious power boat if you will, but for 'Brave Borderer' ? 😡
Do her justice please😉
Many three screw (😲) boats (including the full size originals of this era) only used the third motor for additional manoeuvring speed in action situations.
My personal experience of FACs (Fast Attack Craft) and FPBs (Fast Patrol Boats) over the last three decades shows me that the three screw configuration has been largely dropped, especially since the introduction of much more powerful engines such as improved diesels and gas turbines. Many use a combination of diesel, for cruising, and gas turbine for 'action speed', so called CODAG, COmbined Diesel And Gas turbine.
6) "The 2 blade Hi – speed propellers both increased performance and current draw. The model is more than fast enough with the original scale layout."
As I believe the 2 blade props were of larger diameter (and perhaps also of larger pitch) than the 3 bladers the higher current draw is a logical conclusion! Stick with the scale config! 👍👍👍
7) "Will purchase a lighter, 3 S battery as that seems the best choice for performance and weight." 👍 but don't overdo it to the other extreme by reducing weight and therefore capacity too much😲 You want a decent sailing time don't you?
8) "Testing using the bare hull with a minimum of detail worked well. For a models with a complex power train, this is a good approach as access to the internals can be gained easily. Nothing worse that finishing a boat carefully just to find the performance disappointing. Then having to to rip it apart to make major modifications or adjustments!"
Heartily agree 👍👍👍
Bon chance mon ami😊

Thanks. Agree, with the wisdom of hindsight this wound have been s better appproach. Anyway, have learnt a lot from this project and enjoyed it

You would actually be better off with motors that have a KV rating of less than 1000. I have a 48" Elco PT with three 780 KV's on three cell lipo's, 40mm 3 blade props, scale planning speed is obtainable at approximately 45% throttle. Very little load on motors, no cooling necessary on motors or ESC's.
You will also find low speed operation much more manageable.

Hi. Thanks for your comments.
Before I started the BB did some canvassing of the net to find other builders. The drivetrain remarks were particularly interesting. The consensus seems to be that building three screws, as is scale and as I am determined to do, is the most complex and that for performance it is better using either single or two.
Once deviating from scale bigger propellers also work better. I have rather limited my options with being determined to capture the original layout though.
The vessel is being scratch built on a hull from MTBHulls, of which I am well pleased. The HK source is HobbyKing, often find their products are on backorder, but usually only take a few days to arrive. in this case have been advised it will be rather longer.

If its of any help I run a all wood Perkasa with one motor (came from a old battery power tool) powered with a lead acid 12 volt, so as you can imagine its heavy.

But she will plane as per any photo you can find on the NET. 😊

You state that you are waiting for parts from HK, is your BB a Hooben model ?. I purchased one of these and found the moulding of the transom to be atrocious and the company's customer service to be non existent.

Hi Rowen, you could always use small cable ties to hold the ESC wires down. The motor wires then look after themselves 😉
Look forward to some pics / vids of the Teakwood in action👍
G'night, Doug 😎

Doug,
Thanks for the comments, you are probably right on all counts. The loose connection was more than likely caused by moving the wire to get it lined up once installed and the movement released it slightly.
Rather like the terminal block idea though as it holds the wires in place, can now guard against looseness and corrosion by careful assembly. However, am mulling over the gold connectors suggestion, probably have some weeks to come to a conclusion! They are much lighter than the block too.
The motors are on back order, am now resigned to waiting for them. it does give the opportunity to park the Brave and get some running time on my Teakwood, which has hardy moved this year.
Rowen

Hi Rowen, Bad luck🤔
Not necessarily a short, maybe just very high current draw due to the 4500kV motors and a dodgy connection adding resistance.
In the wet stuff you have of course a load on the propellers which you don't have on the bench/bank, hence the higher current draw through the ESCs.
I did wonder before about the 3 x 4500kV !!
Since I went brushless I always use only 3.5 or 4mm gold bullets to connect them to the ESCs. Suggest you do the same and remove the corrosion susceptible screw connections.😲
Surprised the motors weren't available😲 I recently bought some, also 28mm,and some EScs for my PTB and they were here in 4 days! Oops, sorry, did I buy the one's you wanted 🤔