Model Boat Design

[sail fast]

I am in the process of making modifications to an existing design and need info on righting moment formula. I need to reduce total weight by at least 2.5 lbs. and can do so by lengthining(sp) the keel.This will shorten the waterline length.
sail fast

[daiquiri]

This guy is a model boats designer/builder and he knows his stuff:
http://www.boatdesign.net/forums/pro...edschmidt.html
You can ask him for info you need.

[Paul Kotzebue]

If you're changing length, weight, and keel depth, finding an equivalent righting moment (which changes with heel angle) is much more than applying a formula.

I suggest getting a copy of "Principles of Yacht Design" and read the chapters on hydrostatics and stability. You're going to need to do some research.

[Doug Lord]

Originally Posted by sail fast

I am in the process of making modifications to an existing design and need info on righting moment formula. I need to reduce total weight by at least 2.5 lbs. and can do so by lengthining(sp) the keel.This will shorten the waterline length.
sail fast

====================
Is that on a 36/600? That will be hard to do-especially if yours is already one of the light boats at around 5-6lb! I'd suggest a new design with the max wl length and narrowest hull possible. I don't remember: is movable ballast still illegal? Thats one solution but it would make a boat that would require more channels and lots of practice to sail well-but it would be a rocket.
Again, in the old days(10 years ago) light boats were around 5-6lbs with an 80% B/D ratio-4-to 4.8lbs of ballast. Losing 2.5lbs from a boat like that will be tough-and likely impossible without either a wildly deep keel or movable ballast. We can guesstimate how deep the keel has to be for a skinny 36-to lose that much weight and have the same RM would probably require an 18" keel going to 36". If I were you I'd contact Lester Gilbert or Graham Bantock and see if their research has revealed negatives other than the obvious ones for that kind of keel length on a 36" hull. Both those guys were helpful to me in the old days.
Good Luck!

[sail fast]

The boat I need to loose weight on is a Pointing 36 by Amen, it is a 9.5 lb boat and looks like a Mistral by Bob DeBow. The Keel is a good 6" shorter than my CF TalonII which is less than 5lbs.
Sail Fast

[sail fast]

Originally Posted by daiquiri

This guy is a model boats designer/builder and he knows his stuff:
http://www.boatdesign.net/forums/pro...edschmidt.html
You can ask him for info you need.

My name is sailfast and by this website you are a model bouider, are they AMYA Class boats? I have been building and sailing them since 1991 and in 1944 sailed those that were equiped with steerimg vanes.

sail fast