17 foot boat - sail & keel weight - how much?

That hull is a perfect candidate for a tri. But i would suggest you make the out-riggers removable if you still want to transport it easily.

Personaly I would stick each pontoon 8' out to the side and half the length of the main hull. I would make it thinner than the main hull, maybe 1:10ish?

Ok let me revise this a little. My instinct would suggest two 10foot long, 1 foot wide pontoons, maybe 1.5 feet tall. 8 feet out to each side. I would also whack a decent amount of sail on, 120sqf minimum, with the mast at about the forward 3rd. Dont make the mast too tall but give her a nice big jib and main. I think a daggerboard would still be useful for high wind, go fast situations. 3 foot sounds fine. But a little thinner than that 2x4 you have sitting there. Glass the daggerboard to save it from trouble, maybe also make it a kick-up dagger board if you intend to beach it. The cabin sounds fine (not particularly useful at that beam, especialy with the daggerboard) but if you decide to have it, you really do need those outriggers because you are raising the center of gravity.

Take it all with a grain of salt and do what you want, I'm no professional.

 

vince your suggestions look good to me.

i suspect you're right about the keel but i'll probably keep the 2x4 since it's already glassed, sealed, and hinged - unless i get a bunch of volunteer help from some where. so far this whole thing's been done single handed and i've already spent so much time on that keel.

alright it's 1 pm and i still need breakfast. thanks for help and ahve a good day.

 

now that's a nice pair of pontoons

ty

so, hypothetically, if the boat weighs 600 lbs fully loaded then i'd want the pontoons to displace 600 lbs, and at 8 lbs per freshwater gallon i'd want 75 gallon pontoons. there are 7.5 gallons per cubic foot. so i'd want pontoons with a volume of 10 cubic feet. probably 10 feet long (as the other poster sugests) 1 foot wide, but about 2 feet deep. that was a good estimate he gave.

alright thanks everybody i'll take these things into consideration and put it together.

 

If you're not planning to hike out (climb out on the windward side), then you'll have to sail your boat at a considerable angle of heel in order to realize much stability, and you'll probably want about half the total weight of the boat to be ballast. If you give yourself a way to get your weight out to windward, you improve the situation considerably.

Let's say you want to be able to sail your boat flat, using two people's weight exclusively to keep the boat level. Since the boat is level, no righting force is being generated by the ballast or the hull shape. Lets say you and a friend total 333 pounds, and you can sail with your combined center of gravity 3 feet off centerline. You're then generating 1000 foot-pounds of righting moment. Now lets say the center of effort of your sailplan is 12'-6" above the center of lateral resistance. 1000/12.5 = 80 pounds of sail pressure. Conveniently, you generally want to size your sail based on 1 sq. ft. = 1 pound of sail pressure. On that basis, you want to be carrying about 80 sq. feet of sail.

Now lets say you are willing to sail at a heel. For each 1 degree of heel, the additional righting moment will be:

RM1 = b(Awp^2)/(10*L) + (GB*Disp/57.3)
(approximately correct for most common hullforms)

Variables:
RM1 = righting moment at 1 deg of heel
L = waterline length in feet
b = waterline beam in feet
Awp = waterplane area in square feet
Disp = weight of vessel, ½ load condition, in pounds
GB = vertical distance from the center of gravity to the center of buoyancy, in feet, ½ load condition. (NOTE: IF THE CENTER OF GRAVITY IS ABOVE THE CENTER OF BUOYANCY, THIS VALUE IS NEGATIVE)

On a boat with a narrow waterline beam the additional stability as you heel won't amount to much unless your center of gravity is below the hull, but a low center of gravity will give your boat a steadier feel than it would have with no ballast, and ballast will make the boat easier to right in case of a 90 degree capsize.