Question:
I have dreamt up this crazy idea about building a powered Double canoe
wooden pontoon boat(similar to a Hawaiian double canoe). The basic
idea is this...
Build two 16' light weight reinforced stitch and glue canoes, once
completed fill the hulls with polyurethane foam and apply a top cover
or lid on each canoe.
Next connect the two canoes with 3x3 for 4x4 hardwood support braces.
Then lay the 10' x 8' floor on top of the support braces. There would
be 3' of pontoons hanging out of each end.
I will build the motor mount for a 30 or 40 hp outboard directly
behind the flooring.
Above the floor is just seating railing a bimini top, a bamboo, grass
hut, island theme.
My questions are as follows:
* Can this be done?
* I would like a top speed of about 25-30 mph is it possible?
* would filling the canoe with foam cause excessive weight?
* is a 30-40hp mhp to much? not enough?
Answer:
-whatever you come up with, please post it (or email me). I'm
working on coming up with something similar (except the speed.) 5-15
knots would be fine for me... I want a moveable swim platform. There
are a couple old designs on the web, Pontune
(http://www.svensons.com/boats/Pontune/) comes to mind. I've also been
working out the mechanics for a simpler vessel. Dow buoyancy billets
can be shaped with a nichrome wire and that is on the drawing board, as
is a simple 3/8" ply (or 1/8" hardboard stitch and glue epoxy
encapsulated) pontoon. These could be filled with pourable foam or just
made watertight.
In my notebook, I have worked out the displacement for a pair of 2'w by
1'h by 12'l (for a 10' by 8' platform). The span would be about 5 feet
and 2x4's spaced at 12" centers would be sufficient to support the deck.
With a 2x6 attached to the inside edges of the pontoons, there is the
right space for 2x4's for joists. I forget offhand but the working load
is somewhere around 900lbs (leaving 6" of freeboard on the pontoons)
after the weight of the lumber. It would require a cooperative crew...
i.e. they couldn't all be sitting on the forward edge or one side when
underway.
-I remember that Bob Hicks' wonderful little magazine, "Messing About In
Boats" had a story about someone who built a boat very similar to what you
describe. Two canoe-like pontoons on which stood an enclosed deck. The story
included pictures and, I think, drawings. I believe it was about five years
ago.
For those unfamiliar with MAIB, Bob's phone in MA is 978-774-0906.
He not only doesn't have a web site, he doesn't even have a telephone
answering machine.
-I think the general idea will work, BUT be careful about using any kind of
"canoe design for the pontoons if you want to get the kind of speed you
suggest. Canoe hulls are generally of the "displacement variety" , designed
for efficient propulsion at relatively low speeds. ie wide in the middle
and pointed at both ends. This places the center of bouyancy near the
center resulting in poor trim if a large motor is placed at one end.
Proper pontoons for your purposes should have roughly parallel sides.
tapered at the front and a flat bottom, at least at the aft end
