A few years ago, I started bowfishing some, and my flatback canoe wasn't quite stable enough to feel comfortable standing up and shooting a compound bow, at night, at carp moving rapidly through a small area lit up by a battery and 6 automotive flood lights. I started to build some pontoons to stabilize the canoe, but abandoned that when I only bowfished a few times. So the pontoons hung in my basement for a few years. Then I gave the canoe to my friend Mark, who cut it up and modified it(see thread "Widening an Existing Boat").
Earlier this summer we went on a family vacation and the resort we stayed at had pedal boats that we could borrow. My kids LOVED them. Well, a few weeks later, I'm working in the shop downstairs, saw those pontoons, and everything clicked. We need to have a pedal boat.
A little math first to see if it's got a chance of working. The 2 pontoons are 6 feet long, 9" wide at the bottom and about 11" at the top. About 10" tall. Pretty much rectangular boxes. A little math shows about 9 square feet of wetted area, so .75 cubic feet of displacement per inch of immersion. So around 45 pounds per inch of draft. Structure weight probably 60 pounds, plus 100 pounds of kid would require about 4" of draft. That's reasonable. My 185 pound carcass would need another 2 inches of draft leaving very little freeboard. Better deck over the tops so they don't get flooded. If this had been intended to be a paddle boat from the beginning, I'd have gone 8 feet long and an inch or 2 wider.
Pardon my slacking on early construction photos, this just sort of happened as I figured it out.......
Upside down view:
Pontoons are 1/4 plywood, flat bottomed. I experimented a little with how much camber was needed in the bottom of the side panels to make it fit up, I think it was about 3/8" or so. A few spacers to spread out the top center areas a bit and get some curve in the panels, zip tied, spot welded with putty. Once they dried, I taped the seams and used scrap cloth to cover the insides. glued a 1/2"x1 or so rail around the top and ends, then sanded it flat so I could glue the tops on. Glued in a couple substantial (2x4) crossmembers where the cross arms will be. then topped it off with another piece of 1/4".
Width is just under 48 so it's easy to toss in the back of most vehicles.
Monkeyed around a bit with seat locations, pedals, paddle wheel location, etc to keep the front to rear balance reasonable and get a lot of seat adjustment range so it can be used by little kids or adults. then glued up some cross pieces from pine and cedar, added a longitudinal member for mounting the pedals, and glue it together. Wrapped it all in light fiberglass (10oz on the hull bottoms, 4-6oz on the rest according to what I had left over from previous projects.
I got ideas for the bike parts design from http://www.atomiczombie.com - a website for low $ home made custom bike building. The pedals and crankset came from a 20" kids bike that I got for $10 on Craigslist. I cut out the part of the frame I needed, welded up a couple little holes in it from where extra tubes joined, and then epoxied it into the front longitudinal beam. that beam is made of 3 pieces of 3/4" lumber, so I cut out the middle piece with a jigsaw to fit the frame ends, then notched the outer wood with a chisel and grinder, clamped it up straight, and glued it all together. Filled the gaps around the bike tubes with some epoxy later on. I'll get better pics of that soon.
Graphite coated the bottoms. Let my daughter pick out the topsides color (BRIGHT red). Will update with pics of the seating arrangement and mechanicals as I build them.
2 coats of graphite a few hours apart looks pretty good. Still some areas where the weave isn't filled in real well, but it's a solid coating. I'm leaving it. This is a "git 'er done" kind of deal.
