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Thread: How much 'slack' in 6" * 22" solid wood panel

  1. #1
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    How much 'slack' in 6" * 22" solid wood panel

    I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

    IMG_4517.jpg

    The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

    1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

    2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

    Thanks as always,
    Mark McFarlane

  2. #2
    Yeah, 1/8th is plenty for such good wood and small space.

  3. #3
    The length isn't going to change dimensions any appreciable amount.

    According to the USDA FOrestry products you can expect seasonal moisture changes in the ranges shown on this map.moisture-content-ranges-usda.jpg
    Lee Schierer
    USNA- '71
    Captain USN(Ret)

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  4. #4
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    Lee, is that map showing EMC indoors, or outdoors?

  5. #5
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    Quote Originally Posted by mark mcfarlane View Post
    I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

    IMG_4517.jpg

    The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

    1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

    2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

    Thanks as always,
    On the time scale wood cares about, humidity barely changes in Houston. See here. You basically have a 4% RH change over the year. So, as long as your piece stays outside, given QS White Oak is a very stable wood to start with, you're going to see very little movement at all.

    And even if you were in a place where here are 15% plus RH swings, with your materials and dimensions you'd be OKith the 1/8" for width. Length isn't going to change measurably at all.

  6. #6
    I believe it is out doors, but here is a link that is definitely for outdoors
    Lee Schierer
    USNA- '71
    Captain USN(Ret)

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  7. #7
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    Quote Originally Posted by Lee Schierer View Post
    I believe it is out doors, but here is a link that is definitely for outdoors
    Yep. I was assuming that when the OP wrote he was building "a small outdoor shelf," that it was permanently outdoors, under a roof. Obviously if it's indoors or moving back and forth, it's a completely different story.

  8. #8
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    Permanently outdoors, at least during my lifetime.

  9. #9
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    My theory on fitups like this is I fit the panel exactly to fit. I can normally use the molding cuts on the outside to get the dimensions. Then once it is done and verified I cut one blade width off on two sides. So about 1/8" off in both dimensions.
    Bil lD

  10. #10
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    With the internal panel floating in the frame, regardless of humidity change, I would expect essentially no seasonal movement in the whole panel.

  11. #11
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    Thanks everyone for sharing your experience on this question.

    Sorry I have been slow to respond. I've been really sick with some severe flu-like symptoms for a couple days. I actually pulled muscles in my back due to the most violent vomiting I have ever witnessed. Hopefully I'll be back in the shop in a couple days after I rehydrate and get some nourishment onboard.
    Mark McFarlane

  12. #12
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    Quote Originally Posted by mark mcfarlane View Post
    I'm building a small outdoor shelf out of solid QSWO. The shelf will be on a covered porch, but subject to Houston's high humidity and temp swings. I built a prototype side today out of plywood just to verify my design aesthetic. Pic is attached below.

    IMG_4517.jpg

    The two ~ 3" W * 22" T* 1/4" solid QSWO panels on each side sit in a 1/4" deep groove in the prototype, making a final panel of ~ 6" * 22". The back will be a similar design, but maybe 28" W * 22" T with 4 or 5 panels with beaded edges on one side. FWIW, loose tenons (Dominos) will hold it all together.

    1) Is 1/4 deep enough for the grooves that the panel floats in, or should I go 3/8".

    2) How much 'short' should I cut the panels for expansion/contraction? 1/8" off length and width?

    Thanks as always,
    I finished milling all the wood and built the frame today. I put in my prototype panels with 1/8" of L-R play.

    The sides are made from two panels, so at least for now (before finish is applied) the two panels slide independently so they can potentially leave a gap (or a crooked gap) in the middle as per the attached picture below. Not really what I want. What should I do? Order some 1/4" Space Balls and cut them in half ?

    IMG_4522.jpg
    Mark McFarlane

  13. #13
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    Apr 2010
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    Houston, Texas area
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    Thanks everyone for the help on this project. I ended up using 1/4" space balls from Woodcraft, and cut them in half so they were 1/8".

    Here's the finished project. Turned out to be too nice to put outdoors, as originally planned .


    McFarlane Shelf-3.jpgMcFarlane Shelf-2.jpgMcFarlane Shelf.jpg
    Mark McFarlane

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