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Need a stiffener for a large panel

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Forum topic by DickB posted 09-05-2014 12:24 AM 491 views 0 times favorited 5 replies Add to Favorites Watch
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DickB

63 posts in 984 days


09-05-2014 12:24 AM

I’ve made several of these large lake maps, about 2ft x 4ft, using select pine and have had no issues. The main panel is made from two 12” boards edge glued, and the frame typically 1×4, mitered joints held together with biscuits, with a routed slot in which the panel floats.

I made a larger one, about 3ft x 5 ft, and the project has warped. The 1×4 frame has not been sufficient to control warpage in this case.

I’m thinking I need to build a honeycomb-like subframe to be installed behind the project, not hexagonal but rectangular or square – maybe 8” squares? – out of 3/4” Baltic birch. The subframe would be hidden, but hopefully provide the necessary stiffness to prevent future warpage. (hopefully I have described this well enough to be understood.)

Any comments or suggestions?

-- Dick, http://www.carveshop.com


5 replies so far

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Rick M.

4021 posts in 1045 days


#1 posted 09-06-2014 05:49 AM

First I would nail down why it warped. Common causes are: too wet, finished only on one side, left in the sun, left on a concrete floor. Tables are bigger than that and do not warp if they are dried and finished correctly.

-- |Statistics show that 100% of people bitten by a snake were close to it.|

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oldnovice

3774 posts in 2033 days


#2 posted 09-07-2014 10:47 PM

One thing that causes warping is not applying finish to both side of the panel.
The unfinished side will absorb moisture expand and bow to the finished side.

-- "I never met a board I didn't like!"

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dhazelton

1196 posts in 961 days


#3 posted 09-07-2014 11:05 PM

You could always screw a couple of angle iron ribs to the back. But if the wood wants to move it will just split.

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dhazelton

1196 posts in 961 days


#4 posted 09-08-2014 12:54 PM

...or do your glueup out of more boards of a smaller width. Will be more stable.

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DickB

63 posts in 984 days


#5 posted 09-13-2014 10:32 PM

Thanks for the replies.

I removed the frame and found that the main panel was not warped after all, which leads me to believe that I messed up the frame when I built it.

BTW finish was applied to both sides, wood was dry, not in sun. I do often use glue ups of narrower boards, but in this case I want the grain to match as closely as possible and take care when laying out and choosing wood to do so, and use wider stock for that reason.

-- Dick, http://www.carveshop.com

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