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Riveted plywood to aluminum?

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Dana

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Any plywood lighter than polyester fabric is going to be a lot weaker than the fabric. Also the plywood won't give like fabric as the structure flexes. Repairs would be more difficult, too.

Dana
 

BoKu

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How about the idea of riveting a plywood wing skin to aluminum wing ribs? On a fabric covered homebuilt.
I think that you'll find that the allowable bearing stress of the plywood is so low that, unless you use Rivets Of Unusual Size (ROUS), you will see fretting and fastener tear-out at rather low load factors.

Thanks, Bob K.
 

pictsidhe

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Plywood would be better buckling wise than aluminium skins. Might be good as a monocoque. As Boku said, it's bearing stress isn't great. Instead of big rivets, use a zillion of them, or rivet and glue. Fun if repairs needed.
 

PTAirco

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Metal and wood have been mixed in many weird and wonderful ways and in the case of the DeHavilland Hornet in a very successful way. Using the strengths of each to their best advantage. But they had a very clever engineering department behind them and chemists working on glues (Redux) and lots and lots of testing. Doing it the homemade way might be less successful. If you look at the design as a mainly wooden structure with metal reinforcement, you might be more successful.
 

buzzypeterson

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I remember in my minimax wiggling the wing on a preflight and noticing the cabin wasn't moving with the wing. Turns out the plywood and the metal glue joint would not hold. That gave me the idea of riveting wood, there was a very slick looking T tail single seat light 2 stroke powered plane with a plywood skin. It was glued to aluminum. Anyway I'm just brainstorming.
 

Jon Ferguson

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I think that you'll find that the allowable bearing stress of the plywood is so low that, unless you use Rivets Of Unusual Size (ROUS), you will see fretting and fastener tear-out at rather low load factors.

Thanks, Bob K.
Rivets of unusual size... I don't think they exist...
 

Autodidact

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I've thought of this, too. But really only as a non structural wing leading edge, for example. Look at the Ercoupe wing structure; the torsion and drag loads are reacted by the warren truss formed by the ribs and spars. Now replace the partial D-tube leading edge with plywood and that's what I was thinking basically. Metal dents easily; the wood either breaks or doesn't, and it can be cut out and a patch glued in. I haven't done any weight studies, so I don't know if it is workable for a 103, for example.
 

PTAirco

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I've thought of this, too. But really only as a non structural wing leading edge, for example. Look at the Ercoupe wing structure; the torsion and drag loads are reacted by the warren truss formed by the ribs and spars. Now replace the partial D-tube leading edge with plywood and that's what I was thinking basically. Metal dents easily; the wood either breaks or doesn't, and it can be cut out and a patch glued in. I haven't done any weight studies, so I don't know if it is workable for a 103, for example.
I think the leading edge on the Ercoupe is taking more than its fair share of the torsion loads; it isn't just a fairing. I agree , for a non-structural leading edge, there are better materials than thin metal, but not in a case like the Ercoupe.
 

Autodidact

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I think the leading edge on the Ercoupe is taking more than its fair share of the torsion loads; it isn't just a fairing..
Then I don't understand how; it is not a complete D-tube and doesn't extend back to the spar on the lower surface. Can that react to torsion any better than a bent angle? (It would help with the anti-drag loads, though...)
 
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Norman

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Rivets of unusual size... I don't think they exist...
Sure there are. We call them "drive nails" and in my former line of work we used them to attach posts to concrete patio slabs. The most common size I used is 1/4" diameter X 2" long. They look just like big pop rivets. We set them with a 14 oz framing hammer :gig: If you need something much bigger expanding bolts are better
 
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