3 Motors RC Boat

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3 Motors RC Boat

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14 July 2020 at 11:04 #89954
William Dawson 1
Participant
@williamdawson1
Hello All

I was hoping to get some help with how to set up a 3 brushless motor configuration for my RC Boat. I've had this boat since I was 12 and it was sat in my loft for 10+ years. Recently I've taken it down and decided to an upgrade! I'd like to do a 3 brushless motor setup but I do not how I would do this. I used to race RC Cars so I understand ESC, Servos, Radio receiver and the rest but I've never attempted to go more than one motor. How would I go about fitting 3? Appreciate all help and Feedback! Can upload pictures of the boat if it helps with the thread. Look forward to any and all responses!

Thank you
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14 July 2020 at 11:04 #2937
William Dawson 1
Participant
@williamdawson1
I have a RC boat with three brushed motors and I would like to change it to Brushless
14 July 2020 at 11:34 #89955
harry smith 1
Participant
@harrysmith1
Hi William

Can we have more info on the boat, size, props please.

With brushless motor you require a ESC for each motor for a start and a set of Y leads to connect them together to run of one channel.

The brushless motor are far more powerful than the brush motors.

I found that out my dropping a 35mm 2400kv one into a RC car(the old motor was a hot 540).

So on 2S Lipo I had 17280 rpm but a power jump from 90 Watts to 550Watts( dam fast).

I have had it on 3S (26640 rpm) and it's totally insane !!!!

So watch the power ratings with three in one boat !!!

Harry Smith
14 July 2020 at 13:38 #89961
Byron Rees…(Ron)
Participant
@byronrees-ron
Hi William,

You should have very little trouble swapping 3 brushed for 3 brushless motors in your boat. I have now done this to nearly all my models (26 of them!!!) As Harry (above) says you will need to buy a separate speed controller for each motor, so it is vital that we know what the ,model is, what the current motors are, and if it went OK with them or not, or even if you don't know.

A brushless motor equivalent to what is in it at the moment will be quite a bit smaller but may fit the existing mounts which will hopefully maintain the propshaft to motor line-up.

You will have to solder up a three way lead from the receiver to power each controller, as I have never seen one supplied ready made (I could be wrong) This is unless you want the two outers paired and the middle one on a separate stick, as in say…some torpedo boats.

So once we get some actual details of what we are playing with here, we can all make suggestion which will hopefully help you.

Cheers…Ron.
14 July 2020 at 15:47 #89967
Kev.W
Participant
@kev-w
Component Shop do a 3 way splitter lead.
14 July 2020 at 17:54 #89971
William Dawson 1
Participant
@williamdawson1
Hi All!

Already the responses are giving me some interesting potential ideas to turn this into a speed demon!!

The images attached below show the boat in question as well as its current setup, in my opinion, it's a pretty rubbish setup. It was essentially a kids toy in all fairness but I can just see it being far superior to this. I can see it being modified such as cutting some of the plastic away to make the hatch bigger and more accessible as well as to get more space as well. I'm not scared to modify it as I'm an engineering student and worked in Motorsport for the past 4 years now so I'm not afraid to get properly stuck into it.

I am grateful off the feedback given and I think I will now start to build a plan of how this is going to be built, my only worry really is the material the boat is made off. it's like a 3/4mm thick plastic and what worries me is that any bigger motors may just churn the plastic up and ultimately sink it! which obviously something that must be avoided.

Anyway, I look forward to more responses and will be very appreciative all of your thoughts and feedback!
14 July 2020 at 19:26 #89976
ashley needham
Participant
@ashleyneedham69188
William.

I would be inclined to rip the lot out and fit just one motor.

Would be adequate and save a fortune on esc, leads and motors.

As it is configured, I could see the outboard prop cavitating as it goes into a tight turn.

Ashley
14 July 2020 at 20:14 #89978
William Dawson 1
Participant
@williamdawson1
Would cavatation be a issue for RC boats? What if the propellers were metal?
14 July 2020 at 20:33 #89979
Colin Bishop
Moderator
@colinbishop34627
I would agree with Ashley One motor would give you all the perfornance you need and far cheaper.

Colin

Edited By Colin Bishop on 14/07/2020 20:33:53
14 July 2020 at 20:47 #89980
ashley needham
Participant
@ashleyneedham69188
I will stick my neck out and say that virtually ALL fast r/c speedboats (this sort of hull) use single motors/props.

You might want two or three props for specific models…ie scale torpedo boats etc, but otherwise….

Cavitation can affect all prop sizes big or small.

Your boat has three props as it is a ready-to-run type and it looks sexy in the packaging. Lots of RTR boats have two props, but they do not have rudders, control being by differential prop speed (cuts down costs).

Some of these hulls are very nice and can be made to go very well with replacement motors.

Ashley

Edited By ashley needham on 14/07/2020 20:47:29

Edited By ashley needham on 14/07/2020 20:49:17
14 July 2020 at 22:32 #89986
William Dawson 1
Participant
@williamdawson1
Ahh okay noted! In that case I suppose what I could do is cut out the middle prop and fill the gap to smooth it out and then replace the 2 outer props with new motors. Would a rudder be better to use in that set up?

I understand that one prop can give good performance and it will be cheaper but to be perfectly honest I'd very much like to turn this into a speed machine! Just a speed freak personally
14 July 2020 at 22:37 #89987
Empire Parkstone
Participant
@empireparkstone
Scale torpedo boats? well my 1/24 S-boot ran on 3 x MFA 850's it now runs as fast if not faster on 1 brushless. I would think if not bigger than the one in post definitely lot heavier
14 July 2020 at 22:59 #89989
Charles Oates
Participant
@charlesoates31738
Just to add my two Pennyworth, I totally agree with Ashley, a single motor and rudder is the way to go for speed. Twins are useful for scale appearance, torque, especially in large scale models and gobbling money. There's a good reason virtually all fast models do it this way……it works.
14 July 2020 at 23:18 #89993
Kev.W
Participant
@kev-w
I'm not a "speed freak" but I do like my boats to have the performance of the life size versions.

When it comes to my tugs, then speed is not important, pulling power is, but I do own an original 'Ripmax Interceptor 650' speed boat, this was fitted with a 540 brushed motor as standard, now this was to be my "Fun" boat, so knowing nothing but what I have read on here, I stuck a Turnigy 2200kv outrunner in it, with a 35mm sports prop, using 2200mah 3S lipos, …………. it goes like a bat out of hell, doesn't compete with the proper sports gear, but come on, for the price, it's a bundle of hooliganistic fun on a Sunday morning. Who said 'plastic fantastic' is just Chinese rubbish.
15 July 2020 at 07:46 #89994
ashley needham
Participant
@ashleyneedham69188
Kip. The Turnigy (28mm?) 2200Kv motor puts out 340 watts max….your probably bog standard 540 put out….40?? 50 ??or, lets be silly….100Watts.

No wonder it goes a bit better!

Ashley
15 July 2020 at 09:29 #90000
Empire Parkstone
Participant
@empireparkstone
My Replacement is One Turnigy 3648 1450kv outrunner
15 July 2020 at 09:29 #90001
harry smith 1
Participant
@harrysmith1
Hi Guys

Lets stop pussy footing around !!!

One brushless motor, ESC, Battery and prop .

From Hobbyking, a Turnigy X2845-1980kv( 792Watts on 5S), but drop down to 3S (21978rpm un loaded).

A 45Amp car ESC.

Prop 32mm 2 blade.

Lipo battery 3S 2650mah 30C.

Speed about 45KPH !!!

I have this setup my Sea Hornet (640mm), but the motor in an older 1900kv.

Harry Smith
15 July 2020 at 10:41 #90004
William Dawson 1
Participant
@williamdawson1
I'm very grateful for everyone's input to this thread, it has definitely improved my knowledge on the hobby as a whole. I can see why single prop would work well and the more people that are vouching for it the more I am leaning towards this setup. Also, I see Harry has said 45kph which is quick but what would be needed to go to 160kph or anything close to 100mph? and also a rudder setup will be okay for this? I've seen model sport and hobby king sell metal rudder kits which I may just buy along with a high torque servo.

Again very grateful for all the input and look forward to any further input

Will
15 July 2020 at 10:49 #90005
William Dawson 1
Participant
@williamdawson1
Ahh added note as it is an idea I have had. I notice that a lot of setups are motor connected straight to the prop shaft. Has anyone ever see a gear setup i.e. gear on the motor and gear on prop shaft? I can calculate out the gear ratios and how much RPM this should increase the prop rotations by but has anyone ever done this? or is it a case of it'll just break the gears and spend more time replacing gears than anything else.
15 July 2020 at 11:01 #90006
harry smith 1
Participant
@harrysmith1
Hi William

A 100mph that is serious setup and money !!!

That boat would not handle it at all !!!

No one uses gear up setups, straight drive very high powered brushless motor .

In Lipo batteries 90C plus on 6 to 8S !!!

Check out offshore electrics forum.

Harry Smith
16 July 2020 at 09:23 #90028
Malcolm Frary
Participant
@malcolmfrary95515
Speed requires power. Any motor will give its power as a combination of speed and torque. More speed, less torque.

Gearing down, much favoured by tug modellers, allows for a relatively small fast spinning motor to turn a large prop with lots of torque.

Gearing up, I have not heard of anybody bothering. Motors are easily available that can spin a direct drive train beyond any rpm where it might survive. Any gearing has losses,. Gearing down, nobody really notices, gearing up, the losses mount and become very noticeable very rapidly. Putting a any motor in a situation where it tries to deliver more torque than it can deliver results in smoke coming out of the motor as the insulation on the windings melts.

Boat speed. A model boat needs to travel at the speed of its real counterpart divided by the square rot of the scale. A 1/4 scale model of a 100mph real thing would need to go at 50 mph in the real world. A 1/6 scale model of a 200mph boat would need to be doing 81mph. That figure was worked out a long time ago for somebody wondering about doing a K7.

On a model, that, just as in the full size, means a large, well engineered motor. Similar standard drive train. A power supply that can supply the very large current involved for long enough without vapourising itself.
16 July 2020 at 10:36 #90032
Chris Fellows
Participant
@chrisfellows72943
One thing that hasn't been mentioned is that hull doesn't look suitable for very high speeds anyway, as it is too short and wouldn't be stable. Race boats tend to be long and thin.

Chris
16 July 2020 at 11:18 #90036
Dave Cooper 6
Participant
@davecooper6
William – if it isn't a rude question, how big is your water ? Have a look on Youtube at some of the really fast racing boats. They cover an awful lot of water in a very short space of time…

I see you're into motorsport – how do you fancy jumping straight from a Formula SAE into an F1 car ! (I found it difficult enough going from FF2000 to F3).

Seriously, even though you're experienced in R/C cars, I would plan a more gradual progression and leave the really quick stuff for later.

Have fun,

Dave
16 July 2020 at 13:45 #90040
Charles Oates
Participant
@charlesoates31738
Those are my thoughts too, it comes down to walking before you can run. Experience comes with time and practice, then most of the questions will have been answered on your learning curve.

I also notice that no one has mentioned 3rd party insurance, top performing boats can be dangerous if miss used, or something goes wrong. Imagine a 100 mph boat hitting the bank. Lots of bits of metal,, glass /carbon fibre shards, the motor and lipos going into onlookers.yuk. that's why a debris and wildfowl free water is ideal.

If speed is your thing then go for it,I used to love it, but tread carefully.

Chas
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