On Sep 25, 5:31 pm, Wm Watt wrote:
On Sep 25, 3:08 pm, Davej wrote:

They both have the same 17" waterline beam. Looking at the curves I
can't see anything that hints that the "hull speed" is increased for
the 22 ft design.

It may not. There is a famous case of two canoe racers who built
themselves a long boat thinking they would leave the competition in
their wake but finished well back because the longer boat weighed
more. They weren't aware of all the effects adding length has on
performance.

I'm sorry I don't have John Winter's KAPER formulae to show how weight
enters the math but you can find some of his writings atwww.greenval.com
where canoes are sold from his designs, also some of his publications.
Perhaps the first page ofwww.greenval.com/shape_part2.htmlwill
explain it, although I regret the KAPER formula does not appear. I've
only used KAPER once to check out a design of a sailboat based on a
canoe I built for myself and cannot find the formulae among my notes.
Also look at part1.html and part3.html for his complete "Shape of the
Canoe". Apparently Green Valley sells an updated edition online which
includes a copy of KAPER.

Most of my boat calculations have been for sail power where
displacement is a big factor. Displacement is the total weigth of both
boat and contents. Canoes and kayaks, being light dispalcement boats,
don't perform the same as sailboats and motorboats. That's why
Winter's modified the formulae.

Hope that helps.

Well, I found out I was not preparing the models correctly. The
waterline has to be manually adjusted before the curves are valid. The
corrected models are;

http://home.att.net/~galt_57/c014.yak
http://home.att.net/~galt_57/c022.yak

And now the long boat has superior drag for all speeds above 4 knots.
As you mentioned this still leaves the problem of constructing a long
boat that is very light weight...