Another mill shed, but with a beam question....

[MotorSeven]

Since i built the extenstion for the LT15, I had to make a beam for the front of the mill shed. I cut and skidded a 29' poplar log, and milled it to 28'(as far as the mill would go) finishing the 4 cuts with my 361. It's about 11x11"'s centered over the heart.
I plan on spanning about 28', am I nuts?

Oh and I got to use my new 60" Logrite peavy...wow, what a nice tool!













RD

[backwoods sawyer]

Are you planning any bracing to shorten the span? What kind of snow do you get in your area? I am not an engineer, but for the size of roof that you will be supporting, the fact that it is an out building, I would be inclined to think that you would be ok with it. If it tends to sag a bit you can always add a removable post to help carry the load.

[MotorSeven]

Yes, Knee braces on each end. Less than a foot of snow average. Roof will be 14' wide, tin on lathing & I will pitch it as steep as I can.
I hadn't considered a removable post...thanks!

RD

[beenthere]

If this is a clear span of 28' under the beam, you will likely need something above it to hold up the middle (or support posts below it to do the same thing).

I'd be surprised if the beam would support itself over time, just supported at the ends.

Can you build a truss over the top of it, like a gable end?

[MotorSeven]

I could do a truss, but was hoping to get away without one........... ;)

RD

[Jasperfield]

You can use posts on your rebuild. Your present design will fail.

The beam not only has to support its own weight, but at least half that of the entire roof structure, the tin, and 6+ inches of wet snow.

I believe it would be much cheaper to revise now rather than later.

[bandmiller2]

I've never used poplar isn't it a light brittle wood??When ever I have to carry a load over a span I use oak preferably white,it may bend but won't brake.You could truss your beam with wire cable and turnbuckles attach at each end with a block in the middle.Make up a good support post for the middle when expecting snow put it under.Frank C.

[MotorSeven]

Would this be better: I split this beam into 3-3 & a half inchx11 boards, turn the grain opposite, then put 2 - 3/4 plywood strips alternating the ply joints the entire length & screwing thm all together in a sandwitch?.  So I would have: 3.5 "Pop, ply, 3.5pop, ply, 3.5pop...= a 11x12" "laminate type beam. I thought about the temp post, but I am not liking the idea of removing/installing it every time I mill.

RD

[Warren]

MS,

I am not an engineer, so my comments may be worth what you pay for them... ;D  But, without some serious knee bracing/trussing, I don't think you will be happy with the result.  My understanding is that you get much better vertical loading on a long horizontal span by adding to the height of the beam, versus thickness.  Since you have a serious chunk of poplar, if you choose to resaw and laminate with plywood, you might want to consier making the final dimensions taller, and not as thick, maybe 22"x5.5" etc.  Will still need the knee braces, but better vertical loading.

Or, take a look at other ways to "skin the cat",  Such as, how 'bout a 28 ft long shed with an 8 ft cantalevered over hang over the saw ?  This would give you zero posts to block moving materials onto or off the saw ? I think Arky did something like this to one of his mills at one time.  Might even be pictures posted somewhere on the Forum...  But not for sure...

Given the sharp job you did on the mill extension, I have confidence you will arrive at a similarly suitable solution for your mill shed as well.

-w-

[beenthere]

Would this be better: I split this beam into 3-3 & a half inchx11 boards, turn the grain opposite, then put 2 - 3/4 plywood strips alternating the ply joints the entire length & screwing thm all together in a sandwitch?.  So I would have: 3.5 "Pop, ply, 3.5pop, ply, 3.5pop...= a 11x12" "laminate type beam. I thought about the temp post, but I am not liking the idea of removing/installing it every time I mill.

RD

Yes, it would be "better".  Good enough?, I doubt it.

But, might be you will want to try it, and feel better knowing first hand if it will work...or not.

[MotorSeven]

Thanks for the replies. I will ponder everything today while this storm pummeles us with rain >:(
W-cantalever is a good idea, but it won't fit...I'm backed up to a creek w/ a levee running it's length.
Steel is another option. My local steel supplier has some special ordered trusses that never got picked up...waiting for a price. I also have here on the farm a few 40' 12" bridge I-beams. This would be overkill and a wast of a premium bridge beam....but...it's here and was free.  Hmmmmm..........

RD

[Bruce_A]

Use roof flashing under that plywood with 2-1-2 nailining schedule to 5".  Will really increase the strength and doesn't cost an arm and a leg.

[Papa1stuff]

MS , If you don't want to use those 12" beams ,I would be glad to come and get them! ;D ;D

[MotorSeven]

"MS , If you don't want to use those 12" beams ,I would be glad to come and get them!"

No way...I'm hoarding thos babies! :D

[moonhill]

I must say I would go with the cantilevered idea.  Putting braces on the ends will help with the racking but won't do much with the load, 28' is just a long span with out some support from above or below. 

If you had a second or even a third long timber you may try stacking them with shear keys in between them, you may want advice from an engineer even at that.  Scroll down to page 655, some other interesting examples as well. 

http://books.google.com/books?id=e1swAAAAMAAJ&pg=PA653&lpg=PA653&dq=wooden+keyed+beams&source=bl&ots=04g64ycekB&sig=iSHo66zNSWqDY0brawwqO7NH6aE&hl=en&ei=DbG-SsKhHpPU8QaF7aGpAQ&sa=X&oi=book_result&ct=result&resnum=1#v=onepage&q=wooden%20keyed%20beams&f=false

Tim

[Hilltop366]

If I remember correctly when you double the width of a beam you double the load it can carry,

if you double the hight it will be 6 times the load it will carry.

I'm thinking a few flat trusses on the open side of shed (boxed in with plywood), and one running down the ridge
(it can be much taller where there is more room)

[mike_van]

RD, I also think this plan will fail. Better options are found by searching google for 'open span building' 'plywood rigid frame' a quick search came up with this from North Dakota    http://www.ag.ndsu.nodak.edu/abeng/plans/Construction1.htm

[bandmiller2]

RD Moto,28' is a tall order for any wood beam corner braces each end can get it down to 20'.Two short heavy pieces of angle iron at 90 degrees on the top end of the beam.cable run down to the middle block below the beam,on each side.Turn buckles to preload the beam,in outher words the cables carry alot of the load and the beam is more or less a spreader.The post in the middle I mentioned is only for when you expect a heavy snow load or your not going to use the mill for a wile.Frank C.

[Papa1stuff]

"MS , If you don't want to use those 12" beams ,I would be glad to come and get them!"

No way...I'm hoarding thos babies! :D

:( :( :( :(

[MotorSeven]

Ok guys, I am going to go with steel. I'll update when I decide Beam or truss, and if doing steel I "mise well" go with a bigger mill shed right?  8)

RD

[Papa1stuff]

Bigger is better smiley_swinging_board

[clif]

I do not know how to link this, but you might look at posts titled "Timber framed small plane hangar" here on the FF.
ps how do I post a link?

[mike_van]

Large jet airplane hangar might have enough room. Might I said!  :D

[moonhill]

My building has 2, one on each end, aircraft hanger doors, 30'x16', they bi-fold.

http://www.bifold.com/

This is not the company I used but it does show a wide use of the door, I did not see mill buildings as an example.

Tim

[shortlumber]

I realize you have made your decision, but I'm sure others will read this.

It would take a 10x16 structural select (the best of the best) in poplar to make that span at a 40psf load.

Knee braces nailed to the post do make a significant difference as does using a 3+ ply built-up girder.  

Steel is the only sensible way to go on this one.