: I've built a 17' Guillemot and a 14' Great Auk with the help of
: Nick's book and this forum. Many Thanks to all!!

: To give myself a little more stability in the G17, I increased the
: size of the three center forms (stations 7, 8, and 9) by 10% and
: increased the two adjacent forms, fore and aft, by 5% (stations
: 5, 6, 10, and 11). It turned out great.

: Now I'm thinking of further modifications for my next Guillemot. I
: really like the lines and shape, but I want to turn out a
: shorter 14 foot version, keeping with the increased sized center
: forms to maintain volume. I plan to use Nick's formula for
: turning the 17' Auk into a 14' Auk (pg 185) by gradually
: reducing the spacing by 1/2 " for each form. I imagine I
: will have to add some height to the forms in front of the
: cockpit for foot room.

: My questions:

: 1) Will I have enough volume/displacement for a 195lb paddler?
: 2) How would I determine the center of buoyancy for the proper
: placement of the cockpit?
: 3) Are there other concerns/considerations I haven't thought of?

: Any and all advice would be greatly appreciated.

: Thanks in advance, Dan

1) If you adjust dimensions proportionally in each of the 3 axis of the kayak here is a formula to determine the new displacement.

(new displacement) = (new length) / (design length) x (new width) / (design width) x (new height) / (design height) x (design displacement)

Length you are adjusting 17’ to 14’ or a proportion of 14/17 = .824
And width adjust from 24” to 27” or a proportion of 27/24 = 1.125
And height you are not adjusting for a proportion of 12/12 = 1.000
So .824 x 1.125 x 1.000 = .926 so the new design displacement would become 222 x .926 = 206 lbs.

2) The COB moves the same proportion as the length i.e. (COB station) x .824

3) Your 195 lb CG (just you the paddler) is real close to 12" in front of your back (when seated in paddling position) which also needs to shrink the same .824 factor to 12" x .824 = 9.888" to not relocate your CG in your new scaled down kayak length. But you will not shrink any time soon, so your back will still need to be 12" back from the new CG loaction in your new kayak. Your back needs to be 12 - 9.888 = 2.112" aft of the proportioned backband location (station) in the new kayak.