outrigger plans part 2

jasonspeedy · Feb 11, 2004

I need the smart model boaters to help me out here. I'm building a gas rigger from scratch, but i have some questions about lengths and ratios. Firstly, what is the proper length from the prop to the wetted surface of the sponsons. Secondly, at what percentage of the length should the motor be mounted. So many boaters talk about boat length, but I feel like overall length is a mute point, since you could in fact have 3 feet of nose in front of the sponsons, or vica-versa. I think the real numbers are the ones I asked about. Any advise is appreciated.

wswatzell · Feb 12, 2004

I wish i could help you out with the #'s you are looking for, but i just don't know that much about riggers of that size.

jasonspeedy · Feb 12, 2004

Any possibilty that the ratio's are proportional? I've built .21 riggers that handle well. I've been testing a .60 rigger that's giving me problems, in some part due to its lack of weight...but now i wonder if my dimensions are also wack.

wswatzell · Feb 12, 2004

They might be. I would think that a 60 rigger & a Gas rigger would be close to the same, only having the tub a little wider to acomidate the wider engine. I might be wrong though.

jasonspeedy · Feb 12, 2004

Okay, so imagine this. Point A is the wetted surface at top speed (which happens to be miserably small on my boats), and point B is the prop. I think this is the effective boat length. All of that other stuff is "along for the ride" to quote my best buddy in the whole wide world. So at what percentage of this length should the center of mass/cg/motor be? Anyone...Anyone...Bueler...Anyone?

wswatzell · Feb 12, 2004

Well this is according to John Finch "Advanced R/C Boat Modeling"

"Generaly, outriggers have a CG that's behind the the Sponosons at a distance of about 15% of the measurement of the after-plane"

I hope this helps a little, like I said, I really don't know much about rigger design.

Mike G · Feb 12, 2004

I don't think "length" matters, your CG in % or in relation to your turnfin is going to determine how the boat handles. Larry from Jims builds a 48" gas rigger while I think mine is about 42". Remember the gas engines don't have the same power to weight ratio as the little nitro guys, ie. your planing surfaces might need to be a bit bigger to lift the tub out of the water.