> I am building a wood frame skin covered kayak, with no plans except for
> the photos of the plywood structural pieces that my 3/4 by 5/8 ash strips
> are to be screwed to. I took the pictures and blew them up some and scaled
> them to give me a pretty good approximation of size. now, I am making the
> kayak wider, possibly 30" for increased stability in the water and
> because I am 280lbs will the wider shape give me more stability? or am I
> going about this wrong. not understanding hull design I don't know what
> effects the changes will have

Think of this more as hull experimentation than hull design. Nothing wrong with experimenting, but the phrase `trial and error' is used a lot more often than something like, say, `trial and success'.

When you enlarge things so that the beam is 30 inches the size of all your frames will also increase. If you space them at the distance specified for the original boat the shape will not be the same as the original design. You'll get a boat which is wider and deeper. This may, or may not improve your stability.

Your weight will affect the stability, too. Once you get aboard the boat is going to sink deeper in the water than it would with a lighter paddler. Keeping your weight as low as possible in the boat lowers your center of gravity, and increases your feeling of stability. but it does this at the expense of freeboard, or the amount of the boat that is above the water line.

If you increase the width enough you will not sink so far down in the water. If you have a wide and also a tall boat the wood work sitting above the water will only weigh more, cost more to cover, and possibly catch the wind a bit more. At its worst, though, it should still be less of a wind grabber than most canoes -- so the handling should be acceptable.

If you are worried about your weight being more than that of typical paddlers, you might also consider using wider and thicker (stronger) strips of wood. you might go up an 1/8th or a 1/4 inch on these. This would seem reasonable since you were also enlarging the frames. Or, consider using a few more, so the canvas is spread over more of them, and they can share the pressure.

Just some ideas for you. Paul Jacobson