wood strength of oak or fir

I don't think you can go wrong with pressure treated southern yellow pine. Fir will be fine too. Don't waste your money on oak unless you're sure it's white oak.

Very wrong, assuming we're talking heartwood not sapwood. The tyloses in white oak (absent in red oaks) make it very rot resistant, similar to black locust and walnut. According to USDA Wood Handbook, "An important use of white oak is for planking and bent parts of ships and boats, heartwood often being specified because of its decay resistance." Which is exactly my experience.

Thanks for the correction. My main point is that unless you're certain you're getting white oak, it's best to stay away from oak for anything that needs rot resistance. Note that white oak is used in boatbuilding primarily for its strength, not its rot resistance.

Another small problem with pressure treated wood. Are you thinking CCA, which is no longer being made? Or ACQ, which apparently eats most fasteners in a matter of months.

That and the problem with disposal of any pressure treated wood, makes my decision to use naturally rot resistant wood easy. No problems with my useage for the last 25 yrs. Ma Nature got it right.

Now, if this guy is trying to replace the stringers, I'm guessing from the description, on his hayrack, 3 2x6 treated pines screwed together on each side should do him just fine.

--->Paul

Tell ya what'd look sharp is redwood.

Boy, I dunno. That fir is some pretty tough stuff; I sure wouldn't be afraid of using it.

Allan

Southern Yellow Pine (850 PSI) 1.0
Red Oak 0.68
White Oak 0.71
Hem-Fir 0.68
Spruce - Pine - Fir 0.59

Oak is more rigid but doesn't have the bending strength of southern yellow pine. After learning about this most of my construction is with treated southern yellow pine. It resist rot, is stronger, and is more readily available in my area.

That's a different slant, to my way of thinking.

I.E. Compare all the 100 year old barns sprinkled around the country side.

Those with the bowing roofline and are falling down were most likely built with the softer pine; and yes, they are "bending".

Those that are still standing straight & strong were built using the tougher, harder fir.

Bending is the last quality I would want for construction if I was building something to last for a long, long time; although I know it is the most popular. But still, pine is the softest wood going.

Also, you failed to mention, it is by far the cheapest.

Allan