I am looking for help with Yaht - RC Groups
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Sep 27, 2012, 03:43 AM
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I am looking for help with Yaht

Hello, guys.

I am building a Yacht.
the plan was on my local forum but the thread in dead.. So i am asking for help here .
The build is going well but i have problem with the hardware i am looking for advice which motor, speed controller and prop to use.. no need for some high speed.. It doesn t matter if it is outrunner or inruuner something not too expensive..

Here are some specifications:
the length is one 1m, weight don t now currently
shaft is standard not flexible 30cm long, ruder is 45*68mm with standard servo.
battery is LiPo 4s 4500 mah
Thank you for any advice or proposals for which hardware to use..

here are pictures from previous month...

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Sep 28, 2012, 09:39 AM
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Zmajcek 13- First off were are you located, as this will affect the shipping charges for good ordered. For a model of 39 in length with a modified V bottom (planning hull), you have to make some decisions on motors and running hardware.

First since the model is a built model and not a fiberglass hull, what is the weight of the hull, deck, and cabin, before we start picking the power for the model.
Last edited by frankg; Sep 29, 2012 at 01:07 PM.
Sep 29, 2012, 08:42 AM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
For the size prop and battery, a 700 to 900 Kv Brush-less out-runner motor 36mm or 42 mm or an equivalent brushed motor such as a 700 with a 2:1 gearbox would be my recommendation.


Sep 30, 2012, 08:18 AM
Registered User
Hello thank you for help guys
I am from Slovenia (Europe). Most of the hardware i need is ordered from Hobby king or Leaders Hobby.
Today i have managed to do some work and weiht the yacht. Current weiht with battery installed is 1,9kg so finsihed shouldn t have more than 2,5kg. O yes and the shaft is 4 mm
here are some pictures from progress :
tested the waterproof - no leakage

install servo for rudder

finished the bodywork - primary coloring is finished
Oct 01, 2012, 07:22 AM
Boaters are nice people.
Hi zmajcek13,

Good to hear there are no leaks.

I have a few remarks though:
- the propshaft angle is rather steep, but, as long as you don't want the boat to plane, that's not (such a big) problem, if the boat has to plane, expext handling issues, as the bow is goint to be pushed down.

- the servo set-up is flawed, when using two rods, they need to be parallel, this is causing friction and may even push your ruddeshaft out of it's position, or damage the servo.

As for the motor; does it have to be brushless?
As Nick suggested, a 700 motor, either geared down, or a 700BB Torque in direct drive would suffice.
Even cheaper would be a motor from the scrapyard, a motor that turns the fin in front of the radiator has more than enough torque to turn a big prop, on 4S you wouln't need watercooling either and you can run the motor with a (relatively) cheap car ESC.

The motor in the picture is such a fan motor from a car:

I added brushtab- and can cooling, as I plan to run it on 24V.

Regards, Jan.
Last edited by pompebled; Oct 03, 2012 at 06:03 AM. Reason: typo.
Oct 02, 2012, 01:13 PM
Registered User

Thanks for help and replies. I am sorry for a late replies but I have a severe lack of time so

For the servo i have removed rode so its s only one now (friend already warned mee )
For motor yes brushless because a last brushed motor and speed regulator I saw
was 4 years ago hobby is not new to me but i am mostly in aircraft section.
Most the material is home servo,balsa,speed controler.. There is juts problem for motor and prop size...
for airplanes is drive calc easy to use just searc for motor a propeler 30 min of work
is there for boats propeler anything like that?
Last edited by zmajcek13; Oct 02, 2012 at 01:46 PM.
Oct 02, 2012, 04:58 PM
Boaters are nice people.
Originally Posted by zmajcek13
is there for boats propeller anything like that?
Hi Z,

No, there isn't, for boats it's mostly experience and knowing how fast you want the boat to run.

What is the maximum size of the prop that will fit under the boat?

Regards, Jan.
Oct 03, 2012, 02:23 AM
Registered User
I am thinking about this motor:


speed controller 60 Amp.

the space between center of the shaft ant the hull is 2,5 cm so max. 5cm diameter propeler it fits on.
Last edited by zmajcek13; Oct 03, 2012 at 02:28 AM.
Oct 03, 2012, 05:54 AM
Boaters are nice people.
Hi Z,

A friend of mine burned that motor up in a much smaller boat (60 cm), turning a 45 mm prop in surfacepiercing drive.
I don't think it has sufficient torque to turn a 45mm underwater prop without overheating.

I'd suggest an outrunner like this:

On 4S you'll have over 10.000 rpm at the prop, which can be a rather coarse pitch too.

Regards, Jan.
Oct 04, 2012, 05:08 AM
Registered User
Thank you P,

i will go for it with jour advice and put it in this motor:

http://www.hobbyking.com/hobbyking/s...er_770kv_.html it should be enough for weekend ride on the lake. O i forgot to mention that the boat is intended to my better half she was one day looking at the computer when is was reading local forum..
And she get really interested in boats so i decide it to built her one
That is way no need for hi speed

thank you guys again posts will be updated as the build goes on. but because i don t have much free time is all work done trough the weekend, so don t give up.
Oct 08, 2012, 12:58 PM
Registered User
Here it is bodywork finished now starts waiting for motor so that work keeps on pictures are bad quality because are taken with phone..
But that is final look yust a several layers of coat and that it is.. Here are some pictuers:

With Regards Matjaz
Feb 04, 2013, 03:43 PM
Registered User
Project almost finished some small work still needs to be done .. but the most is over here are some pictures ..
This is it

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