Strength Q?

[xnatex]

Where does the strength come from in a deck? I mean, obviusly it's the amount of plies, but does the adhesive play a role in it too? Does the amount of layers make a difference? And I'm talking strictly wood. (I know fiberglass, and carbon, etc.. will help.)

For an example, using 1/8 and 1/4" birch.

Board 1 - 1/8" 3 ply birch
1/4" 5 ply birch
+ 1/8" 3 ply birch = 1/2", 11 plies, 2 glue layers

Board 2 - 1/4" 5 ply birch
+ 1/4" 5 ply birch = 1/2", 10 plies, 1 glue layer

Board 3 - 1/8" 3 ply birch
1/8" 3 ply birch
+ 1/8" 3 ply birch = 3/8", 9 plies, 2 glue layers


The wood used in 1 & 2 each adds up to 1/2 an inch, but board 1 has 11 plys with 2 layers of glue. So obviously it'd be stronger right?

But what about board 3 compared to board 2, it only has 9 plys with 2 glue layers. If you were judging by plies it would obviously be weaker, but does the extra layer of adhesive make any difference?

I'm definately over thinking this right now, but just thought I'd post this to see what everyone else thought.

[shapeshifter]

if by strength you mean modulus of fracture... seems to me that you aren't taking into account the existing glue layers of the plywood being laminated. obviously you do not have any control over the glue and the quality of wood within the plies but all that being equal i guess i can take a stab at the problem...

...then again all the numbers are swimming around my head and makin' me dizzy.

the way i've been taught is that when correctly executed the glue line is stronger than the wood itself. answer your question? (you may just want to stop reading here)

be that as it may, there are a lot of variables in this equation:

the quality of the wood throughout the initial plies (as mentioned above)
the quality and type of glue within the initial plies (ditto)
the orientation of the wood within the initial plies (another thing you don't have any control over)
about the only thing you have any control of is the elements that bring the existing plies together (there's your weakness)

depening on your laminating, materials, techniques, and environmental conditions as well as the variations in curvature you are attempting to achieve. the glue seam probably wouldn't be quite as good as if it were to be laminated from veneer.

since we are discussing a "two dimensional" structure where the top layer and the bottom layer are essentially parallel, without the extenuating limits of variables that aren't in your control, if you compared the strength of different thickness of similar materials the thicker material would obviously be stronger. one that has more glue layers would have a higher modulus of flexibilty which could be misconstrued as "strength" but the higher density of the glue would also add weight. now when you delve into "three dimensional" structures where the top layer has little relation to the bottom layer except at the edges that strength can greatly exceed the properties of the material/proportion equation. the danger being that more likely than not strength can be greatly decreased because of design limitations.

soooooo... to answer your question:

i really don't know.

[NLC]

Amen brother Skinny .

[shapeshifter]

...the "craftsman"...

heard that.