Following the improvement gained on my RTTL installation, decided to do the same to my Brave Borderer - again on the bench.
Removing the "Brake" feature on Fwds/ Rev definitely smooths the transition and gives better control.
Looking forward to trying on the water where the resistance should give a further improvement. Afraid my access priviledges to our indoor test tank have been restricted!

Omitted to mention after RTTL, on the bench!

Doug, one of your earlier messages mentioned programming the ESC Fwd/Rev to not include the brake function.
This is contrary to advise had previously been given. However, intended to test properly once our local ponds reopen as could help the controlability of brushless powered models.
At something of a loose end due to these virus strictures, decided to test it on my RTTL hull.
It does "soften" the Fwd/Rev action, making the motor more tractable.
Will reprogram my Brave shortly but am confident a similar improvement can be achieved.

"I have learnt a lot about both brushed and brushless motors.👍😀"
Glad to help Peter.
We all had to learn when brushless started to take over the market.
Although their advance seems recently to have stalled a bit wrt boats😊
I went round this learning loop a couple of years ago, prompted by some excellent starter advice from Canabus in Tasmania!!
For the fly boys of course they are the Bog's Dollox, as Steve so eloquently describes such superior qualities😮
For us boaties brushed still have a place in large high displacement hull scale ships. And subs, which don't need to be sprinters, although my Type 1A U25 IS with two 385s on 12V 😁
For the faster Deep V type planing hulls brushless (plus Lipo for the not faint of heart!) must be the way to go.
Happy building and sailing folks, whoever your motor God is😉
Stay safe and be alert - the world needs Lerts now more than ever!!
Cheers, Doug 😎

Thanks Doug, been watching this correspondence with interest.
Will now reprogram to eliminate the brake function, had once been advised to use it. After the ice goes and will try it and let you know the effect.
Had already arrived at the "soft start" setting by trial and error. It was an improvement, but the brushless motors are still erratic on part throttle..
Have toyed with the idea of changing out a brushed for a brushless to see the effect on performance. Rather as you have done.
I have this fetish about building accurately, so could not even dream of changing out propellers!
Theoretically brushless should give a lower power consumption than a similar brushed in the same vessel. Same speed and prop.
Unfortunately the temptation is to use the increased performance and power consumption goes up.
I have an inline voltage/Current/wattmeter and with a 550 size brushed motor, current consumption is usually under 5 Amps.
Using 2800 and 1100 kv brushless outrunners 20-30 Amps on a 3S cell is fairly normal. Periodically a 30A fuse may blow, but these are very conservative as the ESCs are 50A.
My Brave Borderer goes well with 2 x brushless, the high power consumption is worth it for the exhilaration!

Thanks for all of your help. I have learnt a lot about both brushed and brushless motors.👍😀

PS Peter,
"I reckon that 1000kV and a 40mm prop are probably at the very top end of the useable combination range."
Apropo combination_
If your motors get too hot to touch and draw a lot of amps (which I don't really expect) then you have two choices-
1 Reduce the size of the prop.
Fitting a prop with a lower pitch might help but not as much as reducing the prop diameter.
NOTE to our prop aficionados; I'm not absolutely certain about the pitch, contributions welcome!👍
My reasoning being that lower pitch means that the prop has less work to do per rev so allowing it to rev more freely and putting less strain on the motor = less current and heat! Corrections welcome if necessary. I.e. if someone knows better and has the math to prove it!😉

2 Fitting a beefier motor;
i.e. a fatter motor with more torque and probably a little lower kV.
Props are cheaper 😉
Cheers Doug😎

Hi Peter,
There's lots more math and tech behind what I wrote but I tried to boil it down to the essentials.
Around 8kg was about what I'd figured for the all up deadweight👍
So I reckon that 1000kV and a 40mm prop are probably at the very top end of the useable combination range.
Attached is the spec table for the Graupner brushed Speed motors.
Looks like they suggest the model 3302, Speed 600 BB Turbo (Vroom vroom Maisie!) nominal 12V. That's listed at 17500 rpm at nominal 12volts off load. 17.1A max drain on load😮 Max efficiency probably around 60% or less.

A 1000kV brushless will have an efficiency more like 80%, thus draw less current for similar performance as the 600 but still have power in reserve, do 11100 rpm or more off load on a 3S Lipo, and produce more torque than the 600.😊 More torque means you can swing a larger prop.
So my bet is that underwater, i.e. on load, the brushless will produce more torque, thus revs and thrust, than the 600.
Don't have a formula for drop in revs On Load I'm afraid🤔
Two of 'em acting together should provide more than enough Oomph.
Nough said?😉
Cheers, Doug 😎

Thanks Doug.
A very good answer to a question I dared not to ask as I thought it wold be a complex answer. Now I know what the numbers mean.
If I were to go the brushed route, they would run on 3s LiPo`s. 12v version.
The finished boat has a displacement of 8kg. Does this affect your kv judgement.
40mm props are supplied.
Thanks.
Peter.👍

Hi Peter
"suggested 600 motors"
Hmm! That depends on WHICH Speed 600 was suggested!
There are several versions, from 7.2 to 12V and off load RPM from 14300 to 21500😮 So which spec to use as a basis for choice of a brushless???

My choice would be a pair of 750 to 1000kV brushless.
Prop size significantly affects current drain and speed.
Often a bigger prop simply sucks more current with no performance gain.
Maybe the contrary in fact.
Size of brushless motor:-
They are quoted as xxyy, in my Sea Scout 2830 (Outrunner by 'Propdrive' HobbyKing). That means 28mm diameter and 30mm stator length.
Relevance?
The larger the diameter or the longer the stator size the greater the torque but usually lower kV. (Revs per Volt OFF LOAD)
So for tug pulling perhaps a big fat, long outrunner with kV 250 or so.
For max speed a short, slim motor for hi revs for the competition racers.

I reckon for your Lifeboat a decent compromise between start torque (to overcome the boats inertia) and a good speed would be a pair of something similar to the 2830 1000kV I used in my Sea Scout.
I only had one in a 28", 2kg boat, your boat is bigger 'n 'eavier so two should do the job nicely😊
Also recommend a pair of the Quicrun ESCs to drive them. Type Hobbywing Quicrun 16BL30 or current equivalent. They're good for 30A but I don't think the motors I suggest will ever draw more than 10A in your boat, WITH THE RIGHT PROP SIZE! Prob. 35 - 40mm MAX.
Get the Programming card to go with it as that easily enables you to switch off the irritating Brake function and to set the Start to Soft, which eliminates the problems Rowen had with 'jump starts' and slow speed manoeuvres.
I run my Sea Scout on a 4Ah 3S (11.1V Nom) battery which gives me well over an hour runtime and great performance. See my Boat Harbour, Blog and Video Gallery for trials videos!
If you can fit one similar battery per motor I think you'll be a very happy sailor😊😊 You can always throttle back!😮⚡😭
Enough ramblin'😮 Hope this helps more than confuses 😉
Pics show my Sea Scout 'Engine Compartment' and differences between old motor and prop and the new😉
Bon chance mon ami👍
Cheers, Doug 😎

Fully agree Haig👍
My results converting the Sea Scout to brushless (1000kV) were very similar to yours.
I junked the old 2 blade 40mm prop and Decaperm, put in a 1000kV brushless and a 30mm 3 blade prop and she now goes like stink (plenty of Grunt as I believe you say down there😉) and comes easily up on the plane, which she NEVER EVER did before.
Consumption was never more that 7 to 8Amps.
Motor never got more than 'lukewarm'. (Whoever Luke is!🙄)
See Sea Trials here-
https://model-boats.com/blogs/28209
or here

Full trials report in my Boat Harbour and Build Blog and the Video Gallery with info on batteries tried and performance results.
Cheers, Doug😎
BTW Rowen; I got round the 'scalded cat syndrome' of the brushless by using the programming card to set the 'Start' function of the Quikrun ESC to 'Soft'. Have never had any problem with slow speed manoeuvring.😊

I have both Brushed and Brushless motors in my patrol boats and MTBs. I was somewhat misled by the catalogues quoting large Amp ratings and power outputs of the brushless motors. What I did was to mount an on-board video camera to focus on an ammeter connected to one of the brushless motors in my La Combattante missile boat and drove around the pond trying a couple of different size props. With one prop type the motor used 6 amps and with the other it used 8 amps. The motors are KEDA are quoted at 240 watt and 800kV from HobbyKing. Using 6 and 8 amps that is 72 and 96 watts respectively. They were powered by 9 x NiMH batteries approx 12V and 9AH for each motor. The boat performs beautifully and similar in performance to my Fairmile D that has 2 x Graupner 700 12V motors and the same batteries. My conclusion is that for similar boat performance on the water the power consumption for the brushless motors was similar if not better than the brushed motors (that are more inefficient). In some ways this is common sense that one would use similar power output for similar water performance. You can get brushless motors that are much more powerful than brushed, however if you want similar performance on the water then battery life with brushless is a little better. This is my experience. There are videos of both boats that I have previously posted if you want to check them out.

The other advantage of brushless that I forgot to mention is that the combined current draw of your two brushed motors will less that 10A. The two brushess will exceed 30A.
This makes battery life much better with brushed and also fusing simpler.
I fuse all motors and find that the 30 or 40A lantern style fuses preferred are not readily available in these larger capacities. 10 A are easy to come by.

Thanks Peter, that would be my choice too.
If you think the speed is inadequate (very much doubt it will be) there are ways of increasing voltage and thus speed.
Brushless are great, but predominately in racing and planning hulls. From my experience, not scale displacement types.
Good luck, I think you will be satisfied.
Drop us a note eventually to let us know your thoughts.
Rowen

Thank you Rowan. I have found this most useful and will probably go with the suggested 600 motors. 👍

I have built a Tyne class at about 32"; similar style hull with 2 x 550 brushed motors and 30mm screws. Performance is fine.
Have friend with a similar Tamar to yours, 2 x 550 with 35mm, performance is again fine.
If I were making that model would use brushed motors. That way you will have adequate top speed, great controllability and with good slow speed performance.
Have used several brushless motors in planning hull models. Top speed is great, but slow speed and control erratic. Some of my experiences are described in my Brave Borderer blog.
Often going from forwards to reverse and back is difficult and one motor might change direction whilst the other does not.
Almost impossible to dock without damage, and thus retain your friends!
If you want a displacement hull model that performs around scale speed and is easy to use, would recommend brushed power.
Hope another member will add their thoughts as mine could be wrong. Have discussed my experiences with others though and am advised they are not unique.

Thanks Rowen.
The model is a Tamar Class Lifeboat. It is 1M long by 320mm beam. The supplied props are 40mm diameter although the kit designers say these are slightly smaller than the scale size.
Peter.

Good question!
With a brushed motor the rule of thumb is use a motor with an outside diameter about the same size as the propeller.
My current build has 35mm propellers, so chose 37mm Turnigy watercooled brushless motors. If anything they seem too fast, but as it is a planning hull will be OK.
The more important value is the motor "kv" rating, the prop rpm is directly related to voltage x kv. What kind of model are you building? Is it planning or displacement?
Might be better with brushed motors if not a performance vessel. Brushed motors are more tractable and better to control; would be reluctant to fit brushless to a slow speed displacement hull.
Would also try to keep the brushless to as low a kv value as possible, most model propellers develop their highest performance below about 10,000 rpm. This does depend on prop size and style though.
Hope somebody else can offer some type size correlation, but I have not found one.

Thanks for the help.
Just one further little question though. The plans state two 600 brushed motors or brushless of similar level. Please can you tell me, say at 11.1 volts, which brushless might be similar but a little faster.
Thanks. Peter.

Well Pete,
My experience (apart from in price) has been outrunners are the more suitable for boats!
Either way they go like the clappers and in the right boat well worth the trouble.
Rowen

Well Peter, I have tried both brushless motors, and without a doubt, I always use Inrunners, in all kinds of vessel, they are the easiest motors to water cool, straight from the inlet, to the motor then into the ESC, and then out, dead simples. Yes, they are a little more expensive, but well worth the less trouble.😊


Cheers, Pete

Thanks for the help.

Have tried both and out runners are more suited to driving water propellers.
Hobby king have several water cooled ones available and water cooled mounts are also available.
The water cooled motors seem to be adequately cooled with even slight water flows. Have never tried a fan but am sure will help.
From my experience, my LIpo batteries get discharged rapidly so overheating has not been an issue. Tend to use a smaller battery to minimize weight, perhaps to larger one could give more of a problem.

Out runners are the way to go, as size for size they have more torque. Inrunners are more suited to high speed race boats etc.

For cooling to you could either fit a small fan (on the motor shaft or separately) or use a water cooled motor mount.

Chris