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Author Topic: How much bow is acceptable-2  (Read 1244 times)

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Offline Jim_Rogers

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How much bow is acceptable-2
« on: March 18, 2014, 12:38:42 pm »
Last weekend I had a workshop here at the sawmill yard/shop.

We worked on a sill and some floor joists.

After the guys left and since we worked on the sill, I've been walking by it.

It appears that this sill has bowed some more since we finished chopping out the drop in floor joist pockets.

Here is a shot of a joist in a pocket:

 

 

Today I wanted to see how far it (the sill) was out.

I took my red chalk line and snapped a line down the top surface from one corner post stub tenon pocket on one end to the other end corner post stub tenon pocket.

If the piece was straight the center post stub tenon pocket would be in-line:

 

  



 

It is over 1/2" out of line. To me this sill is not acceptable.

I could cut each floor joist shorter to allow them to drop into their pockets and it would go. But the bottom of the center post would not drop into the stub tenon pocket.
The stub tenon could be trimmed so that the post would sit down on the sill and be supported.
But that would mean there will be a 1/2" gap between the vertical siding and the sill at the bottom.
I suppose this could be filled with a shim board.
But to me this sill should be replaced.

I most likely will cut a new sill.

I knew this timber had some problems as when I sawed it out on the mill, I noticed that it had a lot of stress in it. And it shifted while I was cutting one surface.

The sill is suppose to be 8x8. It is on this end but on the far end it is around 7 5/8" wide.

As it is 16' long, I most likely will cut it to four 4' pieces and use them for dunnage under a stack of timbers.

Sometimes you have to do this when you see it go wild and bend out of shape.

Jim Rogers
Whatever you do, have fun doing it!
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Offline Chilterns

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Re: How much bow is acceptable-2
« Reply #1 on: March 19, 2014, 05:46:06 am »
This is a very interesting conundrum.

A clue might lie in the hairy surface under the 4 inch tape mark. Reaction wood tends to result in a fuzy surface when cut and so this might provide a clue about the potential presence of tension or compression wood or in this case spiral grain. Following the line of surface cracking this appears to be a spiral grain log that might even have a degree of crook (read up in Hoadley).

The newly cut joist pockets have effectively cut through the wood fibres on one side of the sill and presumeably this has now resulted the release of internal stresses on one side of the beam causing the movement observed. Given that this beam was cut fairly recently I would suspect this problem is liable to get worse with the passage of time. It might be best to make a replacement sill but maybe also interesting to place the original sill aside and observe any additional movement that takes place over a few months and then report back so that carpenters will become more aware of the consequncies of using this type of timber.

Chilterns   

Offline Jim_Rogers

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Re: How much bow is acceptable-2
« Reply #2 on: March 19, 2014, 07:52:26 am »
I may just save it to show others.

I really have a hard time just taking a chain saw to it and cutting it up.

I think it will be a great learning experience.

Jim Rogers
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Offline giant splinter

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Re: How much bow is acceptable-2
« Reply #3 on: March 19, 2014, 11:43:50 am »
Jim,
I had a sill shift the same way yours has, mine was also boxed heart and 8X8, the only noticeable difference was the material (mine was red fir) I had given some thought to trying to place it on a couple short blocks with the crown up and an excavator bucket resting on it over the weekend to see if it would straighten out the curve .... but after realizing the joist pockets might work if i could switch ends out and roll the beam to "crown up" position, in the case shown in your photos this would take a 90° roll to the left (counter clockwise) and swapping the ends out 180° horizontal circle so that the joist pockets are facing the  correct way. then re cutting the stub tenon pockets in the proper position and plugging the three that are out of sight.
This might work for you in your case as the sill ends do not appear to have the final fit cut on the ends as yet. If it wont work, you have a new trick up your sleeve for future reference.
Jim ...... here is something that you may be interested in doing and its something that you already know about :D get some 80# test braided dacron fishing line and install it in your chalkline ............. you will be happy with the results, I could not resist "Tee-Hee" Sorry about that  ;D ;D
roll with it

Offline VictorH

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Re: How much bow is acceptable-2
« Reply #4 on: March 19, 2014, 07:49:30 pm »
Had this sill been off when you laid it out would you have still used it?  I'm assuming you are using square rule and with that you could have compensated for it.  Am I right or have I misunderstood how much you can compensate?

Victor
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Offline Satamax

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Re: How much bow is acceptable-2
« Reply #5 on: March 20, 2014, 06:22:35 am »
Jim, i might be cheap or crude, but, i would just push it back with the joists! Once all locked in place, it should all equilibrate. JMHO.
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Offline razor

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Re: How much bow is acceptable-2
« Reply #6 on: March 20, 2014, 08:34:13 am »
I'm with Satamax Jim. Too much work in it to turn it into dunnage. I would force it straight with the joists. A 16'er will bend nicely, especially with the pockets cut in it. The opposing sill may deflect somewhat but once the weight of the building is on it a couple of beetle blows should knock it all true.

Offline Jim_Rogers

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Re: How much bow is acceptable-2
« Reply #7 on: March 20, 2014, 09:12:02 am »
Had this sill been off when you laid it out would you have still used it? 

I was aware of the stress when I laid it out. I put the side that the stress changed on the inside as that side is a non-reference side. And any extra wood, or lack there of can go on that side.
As I mentioned one end was 8x8 the other end was 8x 7 5/8" and with the general frame rule that all joints are framed to 1/2" under the end where it was 7 5/8" means that the housing was just 1/8" instead of more, like 1/2".

The customer for this frame is not local to me. So I can't ask him to come over and inspect the timber and make a decision.
I want the frame to be a quality frame and therefore I may replace it.
Right now I can let it sit until we do a "fit up" workshop and test it to see if this sill would bend back into place and/or work.
I only have two small housing to cut to finish it. And these won't take much more time; even if I decide to not use this piece.

I hope that answers your question, Victor.

Jim Rogers
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Offline VictorH

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Re: How much bow is acceptable-2
« Reply #8 on: March 20, 2014, 10:44:00 am »
Yes I understand.  Especially knowing that the customer is off site.  I was getting a little worried about just how true my timbers needed to be for the worshop in May.  :D :D
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Offline shiver_me_timbers

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Re: How much bow is acceptable-2
« Reply #9 on: March 20, 2014, 11:52:46 am »
just out of curiosity Jim, what kind of lumber is that?

Offline Jim_Rogers

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Re: How much bow is acceptable-2
« Reply #10 on: March 20, 2014, 12:58:28 pm »
just out of curiosity Jim, what kind of lumber is that?

EWP (eastern white pine)

Jim Rogers

PS. it is usually rare that these logs have this kind of stress in them from my past experiences.
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Offline Mad Professor

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Re: How much bow is acceptable-2
« Reply #11 on: March 20, 2014, 07:02:18 pm »
How about opening up the mortice for the stub tenon to the chalk line, and when you cut the stub tenon cut it to fit the oversize mortice.  Wall will line up then but will have a little overhang in the middle of the bow.

Trim back the middle floor joists to account for the bow. or snap another chalk line and make the joist pockets line up

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Re: How much bow is acceptable-2
« Reply #12 on: March 20, 2014, 07:26:40 pm »
If this timber is for a customer frame, it would already be firewood for me. I don't believe in allowing any questionable work to be "out there" with my name on it. In my opinion, if you were really desperate to save it, the first thing to do would be to resaw the outside reference face. Then you could move the mortises and pockets to the new reference. In the case of the stub mortises, I would make some filler blocks so the posts were snug in the new mortise at raising. The outside reference face needs to be straight so that the siding lands on there nicely.

I see that the middle joist is a tying joist. You might be able to get away with pulling the end sills into compliance with ratchet straps and straightening it out. It might bow out the other sill. Ideally, you would want the other sill to have a matching inward bow. :D
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Offline Mad Professor

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Re: How much bow is acceptable-2
« Reply #13 on: March 21, 2014, 07:45:25 pm »
Before I ever timberframed I worked at a sawmill and learned to look at logs, tension (hardwoods) , and compression (softwoods) . 

That is where the stress is, and avoid leaners (trees), and line trees below 5' ( metal). 

Hard to see in the logs at the mill. but you know that when dropping them on your own (stress).  Growth lines give you a clue, sometimes.

Do your sawyers know this?

Still you will get warping boxed beams.  I bet all the hewers had it too.  But not enough axe time, for me, to really comment on that.

Drying has a great effect.  We put best boards and beams, stacked, stickered and covered, in the shade.  If you have a bander, band them.

Still that does not work for a long beam you can't find friends for (band too).

I have taken beams/boards and turned them, so they would dry/warp even.  Sometimes it helps or sometimes I'm lucky. Have a whole bunch of 2" pine and oak. 20" wide, pretty flat.

Beams are harder, as the limbs early on, and any lean have a great effect on the log. 

Back to Dave's perfect beam, if I am providing it; Why not mill a 10 X 10' , let it do it's thing, then trim to 8 X 8' ?   

Then it's mill rule, or close.

I still like a compass and snap line.  Work with it.

Still not sure why a fat stub tenon, on muddle post,  won't work on above sill?

Whole wall will be off the posts, put a shim or 5 of the boards that hide the sill, Wall will be fine.

Waste you time on bearing beams, not on a sill that is not really awful.

My 2 CENTS





Offline razor

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Re: How much bow is acceptable-2
« Reply #14 on: March 22, 2014, 09:49:53 am »
Coincidently I came across this bowed piece yesterday. It's an 8x10 x 24' with a bow of 3/4" mid beam. It's ultimate destination is the red post in the frame drawing.
I mulled it over for some time before deciding to go ahead with using it. The reasons for that are for one, I simply do not have a replacement that I can source in a reasonable time frame. I didn't saw it myself. Secondly, I am fairly confident that once in place, the summer beam that butts against it, along with being firmly secured at the principal rafter and sill, will straighten out nicely. At least that's what I keep telling myself.
The material removed at the tie with spline and summer beam area (shown) will help with the bend.
Basically it boils down to cost and logistics. That beam is expensive. Cutting it up simply isn't an option. I could re-saw it into an 8x8 but I have no need for one in this frame.
I'll stack it straight in the middle of the pile until raising day also. With luck it may relax itself straight. We shall see

  

  

  

  

Offline S.Hyland

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Re: How much bow is acceptable-2
« Reply #15 on: March 22, 2014, 10:59:42 am »
Razor, I'll bet that timber can be told where to go! It looks like it's going to be pretty locked in once it goes into place. I would use it.
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