Brian Whatcott ) writes:

The next best structural approach is a zig zag of diagonals along the
top. Still not practical.

Thinking of Frank Lloyd Wright, and out of curiosity, I tried a tight rope
around the top of the molds before posting the query, crossing before and
aft of the paddling position to leave that space open. Rope too elastic.
Arrangement too restrictive.

Getting a shade more practical: if you can introduce a box section
along the keel, or two box sections along each chine that will provide
adequate stiffness. If you could build in those two box sections
along the gunwhales, they would stiffen the hull in probably a most
practical way.

The 1/4" thick skids dry fit before, were glued on last night. Gluing made
an improvement to stiffness this morning. Don't know why . I've cut out a
second 1/4" layer of skid thickness for the centre portion of the boat to
strengthen the bottom but it should also improve twisting rigidity.

You will be aware that an approach which approximates this stiffening
approach is often used with open top glass hulls:
the gunwhale folds in, then down to make a channel.
Not as stiff as a box, but usable.

Yes! Side decks. I'd forgotten about those. Probably not here due to weight
but it's certainly something to keep in mind. Also reminds me now that
canoes have those ladder gunwales for stiffness with lightness. A bit of
fiddly work with lots of small pieces but certainly another possibility.

Thanks for all the suggestions.

I can make the boat okay for paddling now. I'd like to put a sail on it
later and then I'll have to think more about reducing hull twist.

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-FreeNet email must have "notspam" in subject or it's returned