Are diffuse-porous woods more resistant to delamination than ring-porous woods? I'll try to say that in engineering terms. Do diffuse-porous woods have greater radial tensile strength than ring porous woods?

Will someone please help this man, so I can figure out what the **** he's talking about?

Thanks.
=)

I'll try to make sense of my question.

Ring porous: Trees that have prominent vessels in earlywood and minimal vessels in latewood. Typically in areas outside of the tropics?

Diffuse porous: Trees that have vessels that are produced year round. Typically in the tropics?



We are looking at transverse views. In other words if you looked at the stump of the tree you just cut. Does it not look like that the ring porous tree might have a weaker bind between earlywood (where all the vessels are) and the latewood (where hardly any vessels are)?

I heard that most peg failure was when the post with the mortise delaminated because of the tie that was in it had to much tension on it. If the diffuse porous is stronger..........

just brainstorming.

Ooohhhhh....
cool.

so what, you gonna build something out of teak or something???? Somebody told me a story the other day about a boat crate that was made out of 10x10 teak timbers... Apparently teak is not so valuable in the areas where it is native, something like our poplar...

I'll stick my neck out and say if the pegs are breaking out of the mortise, then design or big wind is at fault, not wood.

I worked in one shop where we made pine furniture. Our hardware came in on mahogany pallets, go figger.

We have both types commonly in our forests. Ring porous would be Ash, Oaks, Locusts, Hickories, Walnut, etc. Diffuse porous are the Maples, Poplar, Cherry, Beech, etc, with a less distinct difference in the size of the vessels from earlywood to latewood.

I was first thinking you were asking about tension perpendicular to grain, ripping the board apart widthwise. It sounds like you are asking about horizontal shear, the fibers slipping past each other when the wood is bent. Within the safe working loads orientation doesn't matter, I think there was a small difference in testing to failure.

I think you want to read chapter 4 in the Forest Products Labs "Wood Handbook" if you haven't. Table 4-1 is bending my mind right now, "Elastic Constants of various species"...gee thanks

There are 3 growth rate/density relationships;
1. Ring porous hardwoods. Density tends to increase as the growth rate increases. Hickory and ash tool handles require a low number of rings per inch to be strong, over 30 per inch is a reject ash handle. The vessels are smaller but there are more of them.

2. Softwoods with prominent latewood. Density tends to decrease slightly as the growth rate increases. The correlation is weak and does not exist in some species.

3. Diffuse porouse hardwoods and softwoods without prominent latewood. The density has little direct correlation to growth rate.

If nothing else is known, density rules, use the heavy peg. Whether the pore is in a ring or diffused doesn't matter as much as how much wood is there, wood has weight. Void content of the wood is what determines specific gravity more than anything, well, maybe extractives in that teak. The heavy club is usually the strongest.

Grain orientation does have some strength variables radially vs tangentially. We don't use design values for radial or tangential though, the numbers aren't that different and so they call it "perpendicular to grain" whether a piece is loaded radially or tangentially.

That said, every kid knows how to orient the grain on a bat to avoid shattering it.

Don, sorry I chose poor words. Your initial thinking on my thinking was right. not peg failure, but the post failing.

Thanks

P.S. Just trying to understand the wood, that all........

The easy out;

NDS 3.8.2 Tension Perpendicular to Grain
Designs that induce tension stress perpendicular to grain shall be avoided whenever possible (see references 16 and 19). When tension stress perpendicular to grain cannot be avoided, mechanical reinforcement sufficient to resist all such stresses shall be considered (References 52 and 53)

The references 16&19 are to the ASTM methods of determining strength grades
52 is to the Wood Handbook
53 is to the AITC Timber Construction Manual

Better call the other pegged brace compression

As far as which orientation is better, I've been thinking about that, and your question to TG about the star check.
Ring shake shows that there is a cleavage plane in the growth ring plane you were concerned about. The star check that radiates from the heart is another common cleavage plane, along the medullary rays. Ring porous woods seem to my memory to have larger more pronounced rays and surface check more easily, thats ray checking.

I vote for rift sawn, but my trees aren't that big, a peg goes through several orientations. Kinda justifies just calling it perpendicular without saying radial or tangent, usually you can just say some form of perp.

The wood Handbook doesn't give grain orientation for its tension perp numbers. A quick scan doesn't show a distinct disadvantage in that regard ring porous or diffuse. Density does seem to pretty directly correlate, denser woods seem to have better strength than lighter woods. Softwoods really drop off in tension perp, about half the strength of the hardwoods.

If you roll all that together and apply the suggested references to modify the ultimate strength numbers in the wood handbook the allowable design values in tension perp are going to be below 100 psi for most hardwoods and in the tweens for softwoods the way I read it.

I'm just a carpenter Mo, feel free to give that all the regard it deserves


This link shows rays crossing oak cells, sort of shows how they interrupt the fabric.

http://botit.botany.wisc.edu/images/130/Wood/Quercus_Wood/Radial_Section/Ray_MC.html