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A Simple Plywood Hull

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Total Posts: 3

Joined 2011-11-01

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Firstly, thank you Administrator and Moderator for the excellent new site format and for all your hard work!

For some time now I’ve been working on concepts for cheap and easily built hulls for the “financially challenged” boater.  I don’t have the money or the time to spend on a nicely built craft these days and I’m thinking sustainable and accessible here as well – let’s design something which poor folk here and around the world can use to get out on the water, for work and play.

I’m talking about using regular plywood and basic lumber if possible.  Think quick-and-dirty, rough-and ready.

For my first experiment, using the “stitch-and-glue” method, I built a one-sheet plywood boat, which, though impractically short and horrible in performance, did actually work.  I used scrap plywood, wire clothes hangers, caulk, and 2x4s.  I spent less than $10 on this boat.  Pictured below.

Now I’m working on a 16’er.  The criteria as follows: (1) The hull must come out of 2 sheets of 4’ x 8’ plywood butted together end to end.  And (2) the basic construction must be low-tech – that eliminates the use of epoxy, fiberglass, and substances typically used in stitch-and-glue building.  I’m not against such substances, not at all, just can’t afford them. But also, is that stuff even available in the third world?

To avoid the problem of finely crafting a keel and stems of constantly varying angles to seat the side panels I’m trying a dead upright keelson and stems made of 2x4s with the sides (bedded with something) screwed or nailed right onto it, from stem to stem.  Then – “torture” the plywood – spread it open to a beam of 2’ amidships.  This results in rather hollow “clipper” style ends and a lot of flat area for lateral resistance.  See the tiny model pictured below.  The dashed line indicates the 2x4 keelson and stems on the inside.

Pictured last is a larger model in 1/16th scale.  The side is 1/64” inch thick, representing ¼” plywood.  There is also a “bullnose” type cutwater of solid wood.

I would bed the sides to the keelson with whatever I have access to.  Ideally some modern waterproof sealant such as 3M 5200 or Rule brand Sealant, although this might be prohibitively expensive or not available.  I would even consider tar(?), pitch(?), or asphalt(?) although I’m not really familiar with those things.  Worst case scenario, slather the joint with lots of wet paint and maybe even some tar paper before fastening the sides with lots of fasteners.  (I have used Weldwood Plastic Resin glue with good results in the past although it is not truly waterproof.)

There will, of course, be a gripe where the stems meet the keelson, also of 2x4.  Lots of mating area for the side panels and the keelson.

My next model will be bigger to test things further.  Any thoughts, anyone?  I just want to get boating again – and in a multihull!

Best regards,
Robert Sky
(Wavetyer)

[ Edited: 13 August 2014 02:29 PM by Wavetyer ]

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A proa rig concept here:
http://www.wavetying3.blogspot.com

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Total Posts: 664

Joined 2011-11-16

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The secrete life of Banka - Youtube

Semi dugouts, The new think

This seems like somethink along your line of thought?!?

Nice models. I like the simplicity and your “make it work” attitude. 2x4s and plywood, some nails and paint can make a nice proa.


Cheers,
Johannes

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Simple, efficient and fun!

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Joined 2011-11-11

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Memories…..reminds me of my first proa ACDC made for a $50 boatbuilding/race contest.

Two sheets $10 ply (back when $10 bought halfway decent ply) big tube of construction adhesive and the like.
Article on Duckworks isn’t available at the moment due to their upgrade but here’s a picture of the model and the drawing.

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Joined 2014-06-28

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Hi Robert,
I like your whole down-home approach. Nice models too.

A couple of thoughts…

I just paid $22 for one tube of 5200 just the other day! Great stuff, but those wee tubes add up quick!

To keep the budget low and strength high, how about just small fillets of thickened epoxy, covered with 2 inch fibreglass tape?
It would come in at about the same price as anything else (probably less) and be plenty strong.

Good luck and have fun with the build,
claudio