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Old Dec 25, 2009, 03:44 PM
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Riverside, California, United States
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Plywood is manufactured for it's shear strength. If you took regular hardwood and nailed it to the shear wall of a house for example it would split easily.
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Old Dec 25, 2009, 03:59 PM
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Cody, WY
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Originally Posted by joe manor View Post
Plywood is manufactured for it's shear strength. If you took regular hardwood and nailed it to the shear wall of a house for example it would split easily.
And plywood has more stability. I could see a solid piece of wood swelling a lot more while sitting in the sun.

Adam
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Old Dec 25, 2009, 05:39 PM
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Rexburg, ID
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Originally Posted by joe manor View Post
Plywood is manufactured for it's shear strength. If you took regular hardwood and nailed it to the shear wall of a house for example it would split easily.
No, plywood is manufactured for it biaxial strength, and for its dimensional stability. It has the same shear strength as the wood it is made of. But, as you point out, less tendency to split due to moisture variations (because of the cross-plies).

I hate to pull rank on you, but I have a PhD in mechanics of composite materials. Although I'm still learning. I'd be happy to see any data you have to the contrary.

As far as the build thread, it may happen in the coming years. I'm founding a collegiate team with the goal of fabricating a plane capable of taking the Idaho record, currently held by Tauno and an Opus.

But allow me to express myself in awe of what you have accomplished. I'd be pleased if my students could benefit from your (and others') experience.

-David
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Old Dec 25, 2009, 05:59 PM
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Australia, NSW, Sydney
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Why not a solid lump of carbon and be done with it
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Old Dec 25, 2009, 06:29 PM
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Merry Christmas Joe. Its abnormally wet here instead of our normal heatwave.Brrr!

John
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Old Dec 25, 2009, 06:44 PM
Stay in it!!!!
Riverside, California, United States
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Originally Posted by rothlisburger View Post
No, plywood is manufactured for it biaxial strength, and for its dimensional stability. It has the same shear strength as the wood it is made of. But, as you point out, less tendency to split due to moisture variations (because of the cross-plies).

I hate to pull rank on you, but I have a PhD in mechanics of composite materials. Although I'm still learning. I'd be happy to see any data you have to the contrary.

As far as the build thread, it may happen in the coming years. I'm founding a collegiate team with the goal of fabricating a plane capable of taking the Idaho record, currently held by Tauno and an Opus.

But allow me to express myself in awe of what you have accomplished. I'd be pleased if my students could benefit from your (and others') experience.

-David
Thanks David. Maybe I will try the solid wood sometime. When I was at the lumber yard they had some very light mahagony that would have made this even easier. Think that would do the trick?
Do you know how to calculate compression and shear loads for my model?
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Old Dec 25, 2009, 06:46 PM
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Originally Posted by OZPAF View Post
Merry Christmas Joe. Its abnormally wet here instead of our normal heatwave.Brrr!

John
I hate the cold too. Nothing a good build session cant fix. Must work faster.
We decided to build a rock wall the other day when we were waiting for the wind. Kept us warm and sore for days.
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Old Dec 25, 2009, 07:39 PM
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My building rate will never keep me warm.I sort of have a reputation of the reverse.
cheers
John
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Old Dec 25, 2009, 08:43 PM
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San Diego, CA
Joined Apr 2004
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Quote:
Originally Posted by rothlisburger View Post
No, plywood is manufactured for it biaxial strength, and for its dimensional stability. It has the same shear strength as the wood it is made of. But, as you point out, less tendency to split due to moisture variations (because of the cross-plies).

I hate to pull rank on you, but I have a PhD in mechanics of composite materials. Although I'm still learning. I'd be happy to see any data you have to the contrary.

As far as the build thread, it may happen in the coming years. I'm founding a collegiate team with the goal of fabricating a plane capable of taking the Idaho record, currently held by Tauno and an Opus.

But allow me to express myself in awe of what you have accomplished. I'd be pleased if my students could benefit from your (and others') experience.

-David
David,
If the plywood shearweb was made from +- 45 Deg plywood instead of 0-90 plywood would that be a better way to use plywood for a shearweb?
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Old Dec 25, 2009, 08:47 PM
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???
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Old Dec 25, 2009, 08:47 PM
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San Diego, CA
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Did I mention I have a bad case of ShopBot envy??
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Old Dec 25, 2009, 08:47 PM
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It's yours anytime you want to use it Jason.
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Old Dec 25, 2009, 08:58 PM
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I appreciate that, Cause I'm a DS Junky..... if you know what I mean!
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Old Dec 25, 2009, 09:02 PM
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Plywood is manufactured by slicing or rotary peeling thin [<2.5 mm] sheets of material [veneer] from a flitch or log and then laminating three or more veneers into a rectangular sheet perhaps 1200 mm 1200 mm for very thin sheets otherwise 1200 mm 2400 mm. Laminating an odd number of plies [3, 5, 7 ...] reduces warping while increasing the number of plies increases the resistance to shearing forces.
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Old Dec 25, 2009, 09:06 PM
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Dale Thompson's Avatar
Cupertino CA
Joined Aug 2005
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Originally Posted by joe manor View Post
???
If I get the idea, when ripping the Ply strips treat it just like carbon cloth.

Cut some Ply strips at 0-90 and some on a 45 deg to the wood grain.
Treat the grain just like carbon tows.

When gluing the stack they can be alternated, then CNC as before.

Now the question is, will it really make a difference or just rip up a lot of plywood?
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