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Small Cabin Forum / General Forum / how to flatten warped (cupped) seating
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bobrok
Member
# Posted: 13 Aug 2016 16:12
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Hope it's ok to post this question. A little break from the ordinary.
Boat related and the boat is part of my cabin experience , so here goes.

After a couple of decades my rear seat boards have developed a cup, or sag, that I would like to address as part of a restoration I'm doing.
If I can flatten these I will install some sort of support underneath, but for now my concern is how to do this without breaking the boards.

They are 2 piece construction and mahogany. Can a few of the woodworkers here suggest a best way to do this?
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bldginsp
Member
# Posted: 13 Aug 2016 16:36
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Only thing I could suggest is to run 3/8-1/2 inch kerfs on the underside every inch along the width, or less, then screw on cross supports.

Or start with new lumber, and don't use flat sawn as it is more prone to cupping. Use quartersawn, or rip flat sawn into 3" wide pieces, alternate the tree center side, and glue them together. This cancels out the cup effect.

Just
Member
# Posted: 13 Aug 2016 17:24
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Lay the concaved side down on some wet rags . let the sun shine on the convex side ,,. should flatten out .. then place some angle iron strips on the under side to hold it strait in the future .

bobrok
Member
# Posted: 13 Aug 2016 17:46
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Well, thanks, guys. I knew you'd chime in!!!

Both good ideas.

Just, I was actually thinking about wetting down the boards, or totally soaking them, and using weights to encourage them to flatten.

But I was also wondering if a heavy application of some sort of mineral oil would encourage softening, too.

Worst cast scenario, I guess I could cut them as you suggest, bldginsp, and reform them.

As always, thanx guys!

Steve_S
Member
# Posted: 14 Aug 2016 09:42
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I second with Just... I would say damp not dripping wet and let pressure from weight & gravity do it for you... could take a couple of days but no splitting or anything. The drying them flat in shade afterwards till they go back to normal ambient humidity.

Mahogany is pretty porous, so watch the moisture... when it's 100% dry maybe Tung Oil or Danish Oil would be better than topping it with a hard finish like Poly.

bobrok
Member
# Posted: 14 Aug 2016 15:04
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Thx Steve_S.
When 1st built I used a marine oil finish of some sort over the stain. That was 25 years ago and I don't remember exactly what I used.
Going to do my research again. Can't argue with 25 years of service!
No poly!!!!!!!

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