I am working on a plan that calls for a cherry panel that is 12 13/32″ wide by 21 3/4″ tall by 1/2″ thick with a 1/4 rabbit on the edge to fit into a 1/4 slot in the rail & stiles that are 1″ thick. My question involves the calculation of the lateral movement of the panel. Is a 1/16 left & right allowance enough for movement, or should I increase the slot dept to say 3/8″ and allow for 1/8″ movement. Is there some type of formula to use? I’m in the midwest where it can be humid in the summer, and I’m afraid if I short the distance I’ll pop the joints this summer? Thanks.
Government’s view of the economy could be summed up in a few short phrases:
If it moves, tax it. If it keeps moving, regulate it.
And if it stops moving, subsidize it.
If it moves, tax it. If it keeps moving, regulate it.
And if it stops moving, subsidize it.
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Worst case for a cherry panel that wide would be about 3/8" total difference between "very dry" (20% relative humidity, 4.5% moisture content) and "very humid" (80% relative humidity, 16.0% moisture content). Realistically, allowing for 1/4" is probably fine.
Lee Valley sells a Wood Movement Reference Guide for only $8. Joe Bob says, "Check it out."
-Steve
Go http://www.woodbin.com and click on the "on line calculators". Then click on the "Shrinkulator". It will calculate the expansion/contraction. Input species, range of relative humidity or equibrium moisture content based on where you live and the staring width. The output will be the expansion/contraction range you can expect and should allow for. Keep in mind that you must estimate where you are in the range when you do your construction. In summer, the panel will be at its maximum width while in winter it will be at is narrowest. In spring and fall it will be somewhere in between.
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