custom rc boat

[1rclovinkid]

im building a custom boat from wood, im new to boating but here is my idea. im going to use the hpi 18ss motor and the spur gear from a nitro mt,rs4 from the spur gear will com the drive shaft from the rs4 as well that will go to another drive cup that will hold the prop. my questions are how should ai balance the weight of the boat exactly even more toward the back or front. the strearing servo is basically the same as any other rc cars set up 2 rudders 2 pivot points.

also do i have to run a marine cooling head

[DESTROYER_MAXX]

yeah you'll have to get the water head for the engine because there is nothing that the motor is pullin so it will heat up quicker

[nitrosport182]

Sounds like an interesting project. How are you going to handle the exhaust ?

[F_R_E_D]

Normaly a prop shaft is attached directly to the engine and prop size is changed rather than gearing. If you can find some thin copper tube/pipe you can wrap that around the cooling head and attach a water pickup from that to the rudder. ( seen it done on a force .15 worked OK ). weight ballance is probably best set to around centre then adjusted once in the water.

[SUT_User]

lay down the engine, harder to flip that way. A direct drive would probly be the easiest way to go instead of gearing. It would be lighter too.

[1rclovinkid]

thanks guys i will take all of your ideas into consideration, as far as the exaust i will use a stampede dual stinger set up that will exit from the top back of the boat

[cyclesoul]

you dont need a cooling head if the hull has an open cockpit. As long as there is airflow over the engine, you will be fine. Fred is correct in that wrapping the head in copper or alloy pipe with a water pick up on the transom of the hull will also work.
Boats also normally have a heavier flywheel than cars/trucks to stop them from stalling to easy when you put them on the water (with direct drive anyway, if you run a clutch ignore this!!!) normally you throw them forward in the water with a little throttle, this helps avoid cavitation and also engine stalling. To stop a direct drive boat you have the carby set up so that a little brake closes the carb, cutting the motor

[cyclesoul]

oh yeah,COG from what I have read is normally around 30% from the rear, or about a third of the way from the back of the boat for most hull types. There are exceptions though, like hydro planes (miss bud style) and riggers.

One rudder is enough, normally on the right side looking at the back of the boat, make sure it is at least 1 inch longer than the depth of the prop.

One more thing, surface drive is the go for your drive setup with the prop shaft coming out close to the bottom of the V on the transom. This way when on a plane the boat only has about half the prop in the water, making it much faster.