Need some ideas - plywood problem

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Need some ideas - plywood problem

Post by taxmasta » Sun Aug 12, 2018 8:32 pm

So here’s my current problem that I need advice on. The above picture shows my sides stitched up to the bottom, but the problem is at station one, which is about 2.5 ft back from the bottom of the stem. At sheer level there’s supposed to be an athwartships beam 4’6” long. The station along the bottom is only 45 inches in width, so obviously this beam is meant to give outward flare to the hull. The problem is that for the life of me, I can’t bend the plywood out that far. The flare at that section now is actually none - the sides come straight up. I’ve tried several things, and just can’t seem to bend the plywood out the required 9 inches in total.

Has anybody had this problem before, and if so, what did you do to fix it?

I’m considering just cutting 6 inches off the beam and settling for less flare if I can’t figure it out.

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Re: Need some ideas - plywood problem

Post by JimmY » Mon Aug 13, 2018 3:40 pm

I tend to frown upon second guessing the designer, being an engineer. So, I would recommend not trying to change the shape of the hull. With those upright sides it looks like it would plow through the water rather than plane nicely.

Have you thought about trying a different assembly sequence? Maybe stich the sides together with the athwartships beam, and then add the bottom. Maybe use some long zip ties to work it around and pull the edges together? Maybe undo the bow until the beam is in. Also, have you double checked all the parts against the plans? Also, it looks like when the sides are flared out, the bottom would need to curve up at the bow and stern. Can you weigh down the center of the bottom and block up the bow and stern? I skimmed through the section on Stich and glue in the Plywood Boat Building book, but didn't immediately see anything to address your situation.

I haven't built a stich-n-glue boat, but I have bent plywood to fit my frame and I did stay at a Holiday Inn last night. :D
Nothing says poor craftsmanship like wrinkles in your duct tape!

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Re: Need some ideas - plywood problem

Post by TomB » Mon Aug 13, 2018 4:41 pm

I think Jim's onto the issue. The tug have a reverse a stem that curves forward then back to sheer creating a bulbed bow. So after confirming the plywood is cut to plan (I bet you've checked a bunch of times already), I'd suggest cutting the stem ties, install a thwart at station one, and then torture the plywood into shape from keel to sheer along the stem. Clamps used a wrenches and ratchet straps would be my tools of choice.


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Re: Need some ideas - plywood problem

Post by chugalug » Tue Aug 14, 2018 12:23 pm

:D Wouldn't hurt to drape some towels on ply and apply boiling water.seemed to help on my Bo-jest. :D
Working on regular-sized Bo-Jest

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Re: Need some ideas - plywood problem

Post by JasonG » Mon Aug 27, 2018 10:46 am

You could cut a piece of plywood with the top measuring the required 54" and the bottom 45". Cut it about a foot or so wide so it forms a trapezoid wedge you can force athwartship to persuade the plywood out far enough to install your beam. Wedge it just behind were your beam will go. You will probably have to reinforce the wedge with a cheap regular old 2x4

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Re: Need some ideas - plywood problem

Post by JasonG » Tue Aug 28, 2018 10:02 am

I also noticed a bulkhead in these construction pictures that would help solve your problem. I had to use a temporary bulkhead in my Dyno jet build to help form the plywood into proper shape.
Here's the link to his construction photos if you haven't seen them. I know pictures helped me a lot. ... ll-florida
thumbs_tugalong18-conklin126.jpg (15.62 KiB) Viewed 3992 times

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