Jim Woodward ) writes:

If, what you mean, is to just increase the length 50%, with no change
in beam or height (draft plus freeboard), then you stand a chance, but
even this will be less than ideal. You might get away with adding two,
maybe three feet, but I wouldn't do seven. It probably won't be
strong enough and it will be too narrow.

but he can't make a boat 50% longer by making the pattersn for the plywood
panels 50% longer.


Better look for similar designs that are 21'. You'll be much happier.

indeed. if he wants to play with the dimesnions and see what haapens, and
if he has a table of offsets for the design, he could download a copy of
the free hard chine boat program from www.carlsondesign.com. that program
will calculate numbers. I belive it will also draw new patterns for the
bigger boat.

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