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post #49 of Old 07-01-2013
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Re: Motor vs Rowing inflatable dinghy...

Originally Posted by copacabana View Post
Smurphy, I went through the same thought process a while back. I wanted to build a decent nesting dinghy that rowed well, could carry 3 or 4 adults and that was stable and not too heavy. I thought about using divinycell sheets for stitch and glue construction. A former member here pointed out that I probably wouldn't save any weight since the divinycell sheets had to be saturated with resin and sheathed with cloth inside and out. It seems that quality thin 4mm or 6mm ply has a lot going for it in both weight, stiffness and strength. Long story short, I searched around for plans and found Danny Greene's Chameleon, a 10ft nesting dinghy that weighs 100lbs, rows and tows well and is very stable. I'm actually building it right now and the design is very nice. I wouldn't say it's the easiest dinghy to build (it has a bow locker, aft buoyancy tanks and other fiddly things to build), but it is well within the abilities of an amateur builder. I wanted to reduce the weight a little so I used slightly thinner ply (but quality Brazilian hardwood marine stuff) and slightly lighter cloth. I'm hoping it will weight 80 to 90 pounds when finished. This means each section will be a very manageable 40 to 45 pounds to raise on deck and lower into the water. My stupid inflatable must weigh this much...
The plywood seems to be the greatest percentage of weight in the usual stitch & glue process. What I'm thinking of doing is using 1/4" polyisocyanurate foam (if I can find it that thin) to establish a shape. With a couple of layers of Kevlar over exterior and interior, using some large, taped corner fillets, it should be possible to build an extremely light and strong boat. As in the Adirondack Guideboats, which were designed to carry for miles through the woods, caned seats would also reduce weight.

I may just try this using the pram I mentioned above as a plug, eliminating the need for a core except for the transom.

Alberg 35: With a philosophical flourish Cato throws himself upon his sword; I quietly take to the ship.
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