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  1. #1
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    RE: Tensile strength of woods...pine vs poplar

    With the diagonal on each support bracket, I think your biggest issue is going to be anchoring it to the wall.

    I would definitely add a skirt piece along the front beneath the table top to add strength to the top.

    I think 4" material would be sufficient for the diagonal as well as the piece on top running along the wall.

  2. #2
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    RE: Tensile strength of woods...pine vs poplar

    Eschew those doubts - drive them out - tell them "Out, doubt!"

    Nah, it'll be fine. Ain't nothing you've drawn there that'll get so much as a chance to warp... and the 4" stock is probably overkill. That basic triangle is about as stable a thing as you might see without horses. :)

    I do like the thought of lapping the t-beam's top member over the ledger... and ALSO the thought of adding skirting to the front edge to stiffen the workspace.

    If you glue those brackets together, they won't EVER fail ya.

    -- Tim --



    Dance
    Like nobody's laughing
    :)


  3. #3
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    RE: Tensile strength of woods...pine vs poplar

    I would also put a piece across the front of the desk not only for strength but it will give the appearance of a much thicker top. Like is done on counter tops.

  4. #4
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    RE: Tensile strength of woods...pine vs poplar

    Thanks for the input guys.

    I would like to put a structural skirt on there - only thing is if I make it with the intent to support, I would use at least a 4" - and then I'll be smackin my knees under it. I can't see anything less than 4" (or 3") doing much good.

    Isn't there some chart or something for plywood deflection at certain supported widths?

    I guess the next best thing is I'll go test a piece of scrap supported at 32" with some extreme weight in the middle...

    Yes, the supports will be screwed to the studs. I understand your fears about the pocket screws but I've been experimenting with that and I have full confidence. If the butt joint is perfectly square it is surprisingly very strong.

  5. #5
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    RE: Tensile strength of woods...pine vs poplar

    Well as for the skirt, a 1-inch wide skirt is better than none and a 2-inch skirt is better than a 1-inch. A 3-inch is better still.

    David C.

  6. #6
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    RE: Tensile strength of woods...pine vs poplar

    Yep, what Dave said. As a test pick of a 1 X 2 pine piece and note how easily it bends if you try bending it perpendicular to the 1" dimension. Then try the 2" (both nominal dimensions BTW) dimension. And when it is glued to the underside of the top, it combines the strength of both thicknesses.


  7. #7
    Joe Lyddon
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    RE: Tensile strength of woods...pine vs poplar


  8. #8
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    RE: Tensile strength of woods...pine vs poplar

    Phil,

    Personally, I'd go with torsion box contsruction a lot stronger and "cleaner" looking; no need for any bracing.

    "Pine" is pretty generic, amongst the hundreds of species their properties can vary by quite a bit. There are several books on wood identification and properties out there, books by Hoadly and Arno are the first that come to mind. Additionally, the U.S. Forestry Service's Center for Wood Anantomy Reasearch is another excellent resource.

    Dano

  9. #9
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    Tensile strength of woods...pine vs poplar

    Below is a sketch of the supports I plan to build for my built in "L" shaped desk in my new basement office. These supports will be placed every 32" along the wall. I plan to use 3/4 maple veneer plywood for the desktop. While most of the desk wont be supporting any significant weight, it will be holding my 50+ lb 22 inch CRT monitor (and a 17" flat panel monitor next to it).

    I'm worried if I use pine that in time it will start to warp from the weight? Would poplar be worth the extra $$$ or is the difference (if there is any) going to be negligible? The depth of the desk is about 3 feet, ~ 3.5' at the corner where the monitor will be sitting.

    Also, would anyone have an opinion on using 4" vs 6" boards on the angle and upper vertical piece?

    And one more thing :) Do you think 32" between supports will be enough to maintain a flat desktop? Or should I add a vertical piece across the front of the support?

    Full of doubts...Trying to save money...this room is becoming very expensive :(

    Edit: I should note that I plan to use pocket hole joinery to put this together

  10. #10
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    RE: Tensile strength of woods...pine vs poplar

    I think you'll be fine as you've drawn it.

    The t-beam on the top will be plenty stiff. The width of the vertical piece is not really an issue, because it is going to be fastened to the wall, correct? It needs to be wide enough to serve as a base and a fixing point for one end of the t-beam and the knee brace.

    I'd suggest considering a few changes. If the t-beam is just pocket screwed to your horizontal ledger, then you are relying solely on the fasteners to resist the pulling force that a load on the desktop will exert. Why not allow the top of the t-beam to overlap the ledger (you would have to let it into the ledger if you want it to remain flush), this way the ledger, which is fastened to the wall will bear much of the load directly.

    I'm not very impressed with the structural strength of pocket screws in applications where forces are pulling the joint in a direction parallel to the screws, there just isn't that much wood held by the screw heads.

    If I were you I'd add a vertical piece to the back, forming a triangular frame lap-jointed at the corners that can be screwed on from the rear trough the vertical piece that is screwed to the wall.

    Here's a sketch of what I mean...

    David C

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