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A plywood question

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A plywood question

#1

A plywood question

mike recchione

>I normally wouldn't bring up the subject of plywood in polite company, but we're all adults here, and I need help. Besides, there's hand tool content in here as well.

I'm building a small aditional workbench for my garage shop, and I decided to go with a variation of Drew Langsner's "chairmaker's workbench" from "The Chairmaker's Workshop". The top was intended to be four 2'x4' quarter sheets of 3/4" oak plywood, laminated to make a 3" thick top.

I bought all the materials a few months ago, then got really busy with work and didn't have time to complete the bench. I brought the plywood into my basement from the garage about three weeks ago, and since then a couple of the sheets (stored totally flat, on my workbench) have warped significantly. I didn't think plywood was supposed to do that, but there you go.

My question is this: If I were to go ahead and laminate them, clamping them flat on my benchtop, is it likely that the two warped sheets would cause the entire top to warp, or is there a reasonable chance the top would stay flat once it was glued up?

Hand tool content: The bench will be used to do carving and chairmaking with handtools in my garage during nice weather. I always wanted a workbench in front of a window...sigh.

TIA,

- Mike

Re: A plywood question

#2

Re: A plywood question

Moses Yoder in White Pigeon, MI

>Pywood stored outdoors has a fairly high moisture content, and when brought indoors normally will dry out some. Plus, the manufacturers are cutting costs as much as they can, which means a higher moisture content than it probably should have to start with. If stacked in such a way that one surface can dry out and the other not then it will definitely warp a lot, and it can warp a lot overnight. We have been dealing with this at my day job lately. I would suggest flipping the pieces over so they go back to flat before laminating them, as just glueing the pieces together if they are significantly warped will end up with a bowed top.

Re: A plywood question

#3

Re: A plywood question

mike recchione

>Thanks, Moses.

What you say makes sense. The worst piece is the top one, which exactly meets the conditions you stated.

- Mike

Re: A plywood question

#4

What Moses said...

Christopher Fitch @ Memphis

>Just orient the pieces with the warp facing away and glue/clamp them up. I advise using large cauls too.

Re: A plywood question

#5

Re: A plywood question

Don Thompson - Cutler Ridge, Florida

>Do you really need 3-inches? I have an auxilliary bench the top for which I made from two layers of 3/4 ply glued together, (with 3/4 inch poplar edge banding) that is pretty heavy and sturdy.

If you use all four sheets, put the bowed sheets on the outside, opposing each other, with the cup up. I would add screws, from the bottom.

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