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Need opinion

Started by Dugsaws, June 22, 2003, 07:57:35 PM

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Dugsaws

I have a customer who wants some 10x12x10 timbers, and he didnt think that yellow poplar would be strong enough for the 10 foot span, and also what size diameter log it will take to get that size timber. I told him I thought y.p. would be strong enough, any help would be appreciated.
Doug

DanG

Somebody, and I'm thinkin' it was DonP, posted a great chart on the strength of different woods a while back. I checked the Knowledge Base and didn't find it. I thought it oughta be there. ???  If you do a little digging and come up with it, let it be known so it can be added to the KB.  I'm sure the adequacy of the timber will depend on the sort of load it is supporting. :P
"I don't feel like an old man.  I feel like a young man who has something wrong with him."  Dick Cavett
"Beat not thy sword into a plowshare, rather beat the sword of thine enemy into a plowshare."

biziedizie

What sorta load is it holding? Is it just supporting a truss system? Is it going to support a live load? Does it have to be a 10x12 or can you cut the beam down to 2x material and laminate it?
  I've seen big timbers crack and twist and even seen one snap in two if they are installed wet.

    Steve

Don P

Click on the link below, I've put some calcs on webspace Jeff provided. Its listed as "Beam Calculator".
It does math for a uniform loading, like a beam supporting joists or trusses that are evenly spaced along the beam. It is not meant for point loading, need to work one up, my neighbor's barn is going to have 2 point loading trusses on poplar beams over bays.
This was meant for "guesstimates" and of course an engineer should check it out. Poplar is the bottom of the pulldowns, I couldn't find good shear numbers for many species poplar among them, I would stay down in the 65 psi range or below. Poplar does check pretty good in big timbers.

https://forestryforum.com/members/donp/CalculatorIndex.htm

I plugged in some numbers real fast. A 120" 10x12 seems to be limited by shear. It was good for 17,500 lbs in bending and deflection but the shear didn't look good til it was down around 10,500 lbs. Those numbers were generated off dry wood samples. Wet wood has half the strength of dry.

Ron Wenrich

I have a calculator to solve the size question.  Problem is, I can't attach a file.  You need a minimum of 15.6 inch log.  That will give a beam with no wane.

Bending strength for poplar is similar to basswood, aspen, cottonwood, catalpa, sassafrass, hemlock and sycamore.  I don't have good numbers.  It is better than white pine.

If a white pine replacement, then you should be OK.  If an oak replacement, then I'd stay with oak.
Never under estimate the power of stupid people in large groups.

Wudman

The attached link is to the USFS Center for Wood Anatomy Research.  It gives some technical data for Yellow Poplar.

http://www2.fpl.fs.fed.us/TechSheets/HardwoodNA/htmlDocs/liriodend.html

Wudman
"You may tear down statues and burn buildings but you can't kill the spirit of patriots and when they've had enough this madness will end."
Charlie Daniels
July 4, 2020 (2 days before his death)

Mtnjack

Dug try these out for your sizes they are real handy. Side of square inscribed in circle =Dia x .70711    Dia of circle ciremscribed about the square = side x 1.41421     Where to make your first cut  square divided by dia divided by 2   Hope this helps let us know. Mtn Jack

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