Totally unrelated subject. I’m scratch building a large radio controlled speedboat / cruiser. It has a planning bottom at the back and should go like stink with the motors I’ve fitted. I need to know (roughly) where it should balance so that I can work out where to install the cradles for the battery packs. I suspect that it should be too the rear rather than just in the centre, i.e. over the planning section of the hull. I have angled the props at 25 deg so it shouldn’t pitch up on power.

Would anyone have an idea??? Last thing I want is it doing a cartwheel a 40mph…

[Edited on 13/12/06 by macnab]

its not easy to say without seeing as there are so many variables.

However, a good method if you are capableof running in water is to temporarily fit the batteries in using blue tac. Then you can test the batteries in different places and get the very best setup for the configuration you have. Once you have found the sweet spot make the cradles to fit that exact position.

I used to race both FSR-V (multi) and FSR-O (offshore) but, as said above, it's difficult without seeing. Is it surface or submerged drive? A side-on photo showing the hull profile, prop / rudder location etc would help.

cheers dudes,

I'll get a couple of pictures tonight and see what you think though its very similar to this boat
Rescued attachment boat.jpg

oh yeh and I modelled the bottom on one of these...
Rescued attachment torpedo boat.jpg

Is that last pic of a Nasty Class? Tasty boats!

[Edited on 13/12/06 by Ian Pearson]

hmm not sure of the class, their on the web for sale in america I think, resting on a river bank. Bit past it now as the wood planking has rotted away some with huge holes in the side.
Rescued attachment lineup.jpg

I've been building R/C model boats for years (my wife says centuries), including high-speed electrics, Chris-Craft inboards, etc., and as a general rule for a planing hull, the boat should balance at a point approximately 1/3 of the way forward from the transom. This is a good starting point, and all mine ended up extremely close to that in the end. If you start off that way, then ballasting will be very easy in the end.