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Author Topic: New ply bowed  (Read 2148 times)

tobyker

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New ply bowed
« on: January 12, 2009, 12:08:00 AM »

Can't find an answer to this on the "wood" thread, so here goes. I bought a nice piece of Orbit 6mm ply 12" x 48" a couple of days ago from my LMS. It looked quite flat, with maybe a very slight "s" bend, but it had been displayed on end in a rack in the shop. I laid it flat under the bed when I got home - on looking at it now it seems to be bowed along its length. As I want to cut a 3' keel out of it, it would be nice to start with it straight. Will I do any good by damping it and weighting it on a flat surface? Presumably the stuff was made straight, so how can I get it back to its original state?
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tigertiger

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Re: New ply bowed
« Reply #1 on: January 12, 2009, 01:56:09 AM »

A couple of thoughts spring to mind.

I would guess it is about humidity in the wood..

If you have central heating, put the board outside, garage if you have one, or maybe the loft.
I also stack weights on mine to keep it flat. In the shop it remains flat due to the other boards on top of it.

I know once I cut it it will revert to a bend. So I know I must work fairly fast in getting the hull to a point where it is all semi rigid.
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Ramon

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Re: New ply bowed
« Reply #2 on: January 12, 2009, 04:17:14 PM »

Tobyker,
I definitely wouldn't dampen it. What's probably caused the bend is the fact you laid it on a flat surface. This has allowed the top surface to dry out relative to the underneath and contract, hence the bend.
You may never get it all out but turning it over and weighing down the ends for a couple of days may reduce it. If you have something that will cover it completely eg a piece of MDF and you can leave it long enough to stabilise it should revert somewhere back to it's former self. Once happy store it on edge if possible.

Dampening it will just create the same problem only probably worse as it's the absorbtion of moisture in the atmosphere in it's previous environment that is the culprit.

Hope that is helpful - Ramon
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tobyker

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Re: New ply bowed
« Reply #3 on: January 12, 2009, 11:01:44 PM »

Thanks chaps. I have laid it (and the 1/8th sheet I bought today) on a flat steel shelf in the garage witha couple of heavy boats on top. I supose really they should be laid on battens so the air can circulate all around them. Under the bed it was on quite a thick pile carpet so I'd have thought the underside shouldn't have retained all that much moisture. We'll see how it goes.
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