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Stressed poplar

Started by Slab Slicer, January 30, 2013, 08:47:08 PM

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Slab Slicer

Started a milling job a few days ago. I'm doing some timbers for a customer who is supplying the logs. They are all yellow (tulip) poplar, and they have the most stress that I have seen yet. I'm following tips I learned hear to avoid stress, or at least relieve it from logs, but this stuff is bowing nearly 2" by the time I reach the end of a 13' log. They appear to be straight when I load them on the mill, and are very clear, but the stress is unbelievable. Dia. range from 10" to 20" approximately. I could use some help with this one. I want to get this customer the best timbers I can. I'm milling 3x12's, 3x8's, 6x6's, and 4x4's. If you need more info, let me know. I've had to stop milling, as the weather has turn ugly around here, and I'm milling on site. I'll be back to milling in a couple of days, so I'd like to go back to this job with some ideas of how to turn out better timbers. Any help would be greatly appreciated.
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Chuck

Okrafarmer

I took a TP log that had been sitting around for a year or more and milled it up recently, just to use for blocks to dry lumber on. It sure did go to bowing and springing this way and that. I was not amused. I guess some of them are just that way. A lot of other TP logs are fine. I think, in my limited experience, it seems that the smaller diameter logs tend to move more than the larger ones when you mill them, and that may be something that is true with almost any species. But yes, it can be most frustrating sometimes. Pecan does it a lot too.
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Slab Slicer

These logs have been down for about 4 months or so. Not sure if that will make a difference or not. I guess my assumptions of being one of the "softer" hardwoods, it would be pretty straight forward milling. Boy was I wrong. I've only cut 7 logs out of the 75 or so that are there, so I have opportunity to work with it, and try to get them straight.
2016 LT35HDG25, Kubota L2501 w/ FEL, Kubota BX1500 w/FEL and custom skidding rig, Stihl MS 500i, Stihl MS362-25", Stihl MS250-20", Stihl MS192-18",  2001 F250 SD 7.3, GMC Sierra Dually 6.0 gasser, Peaqua 16" 10K trailer, Sur-Trac 12' Dump Trailer 10K
Chuck

Okrafarmer

Well, if you have 75 of them, you can try some different strategies until you find it working better. I have better luck when I'm milling 4/4 lumber out of TP, compared to thicker stuff like beams. In that case I can keep flipping it every time if need be.
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

Operating a 2020 Woodmizer LT35 hydraulic for Upcountry Sawmill, Dacusville, SC

Now selling Logrite tools!

Writing fiction and nonfiction! Check my website.

Okrafarmer

Say, Slicer, remind me what type of mill you have. Do you have a swing mill? If you do, there is another strategy you can use that isn't available to band mills.
He that dwelleth in the secret place of the most High shall abide under the shadow of the Almighty. Psalm 91:1

Operating a 2020 Woodmizer LT35 hydraulic for Upcountry Sawmill, Dacusville, SC

Now selling Logrite tools!

Writing fiction and nonfiction! Check my website.

Slab Slicer

It's a WM LT 15 GO. I think the sawing of the thick beams has alot to do with it. No chance to adjust to relieve the stress, like you mentioned. I was watching another thread about using poplar for timber framing and such. I may have missed it, but I didn't see mention of the stress I'm experiencing.

I try to take equal amounts off the log, and center the pith in the cant. Then mill the beams. I just haven't found a way yet. Maybe thee isn't a way with logs of this size, but I'm not giving up yet.
2016 LT35HDG25, Kubota L2501 w/ FEL, Kubota BX1500 w/FEL and custom skidding rig, Stihl MS 500i, Stihl MS362-25", Stihl MS250-20", Stihl MS192-18",  2001 F250 SD 7.3, GMC Sierra Dually 6.0 gasser, Peaqua 16" 10K trailer, Sur-Trac 12' Dump Trailer 10K
Chuck

5quarter

Slab slicer...I imagine you've been rotating the cant after each cut and still getting some bow. You'l need to cut your timbers an inch or two larger and resaw them to size. depending on how they open up will determine how much oversized they'll need to be. Make sure when you resaw, you resaw all 4 sides, not just two. The less you take off the timber per cut, the less it will continue to move. Its alot more work, but you'll have straight timbers and customer for life, especially if he is aware of whats going on with his logs. Is the pith centered in the logs? If not, draw an imaginary line through the log end, bisecting it into the big half and the small half. cut all your timber from either of the halves but do not cut any timber that contains both halves. Keep us posted on your progress with the job.
What is this leisure time of which you speak?
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Slab Slicer

5quarter, the customer is doing the off bearing, and I pointed out the issue with the stress. It wasn't hard to miss it since it was soo bad. I'm turning these logs after each cut til the cant is squared up, then calculate what it will yeild, leaving the pith out of the timbers. If I notice any stress on the first cuts, I try to relieve it, but with little positive results. I can talk to the customer about oversizing the timbers, and resawing later. I assume they will be a bit more stabilized once they dry?
2016 LT35HDG25, Kubota L2501 w/ FEL, Kubota BX1500 w/FEL and custom skidding rig, Stihl MS 500i, Stihl MS362-25", Stihl MS250-20", Stihl MS192-18",  2001 F250 SD 7.3, GMC Sierra Dually 6.0 gasser, Peaqua 16" 10K trailer, Sur-Trac 12' Dump Trailer 10K
Chuck

5quarter

Slab slicer...sounds like your doing everything right. I would resaw them as I went whether he intends to use them right away or is going to sticker and let them dry, they are going to need to lay flat, so the bow is going to have to be cut out of them anyway. Do you know how they're going to be used? I've had several jobs like yours (except not as big) where I first had to cut oversize then resaw to the needed size. Hourly rate if you have to do it that way. Also, if you're boxing the heart to make you 4x4s and 6x6s, make sure that the pith is absolutely dead center on both ends or it will twist like a candy cane.
What is this leisure time of which you speak?
Blue Harbor Refinishing

hackberry jake

I have seen where people have used a small block of steel welded to the frame about 3/4" high for when you get the cant square you just drop your backstops all the way down and use the block as the backstop. Some of them have a little spike on them that keeps the center of the log from coming up on you while you're sawing. You might try that. Clamp pressure would likely be your friend as well.
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Qweaver

I've built most of my structures (a cabin and seven sheds) using mainly TP for framing and I've experienced a lot of bowing making 2" framing out of side wood.  I usually just put the bow up and call it good.  That's no help when trying to please a customer tho'.  Most of my posts and beams were made using the smallest log that I could and those stayed pretty darn straight.  Making straight 4x4s out of TP may be nearly impossible.  Drying in a weighted stack will help.  I often re-saw curved boards as needed after they are dry.  I don't know how that will affect strength tho'.
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DRB

Quote from: Slab Slicer on January 30, 2013, 10:47:43 PM
...... leaving the pith out of the timbers. If I notice any stress on the first cuts, I try to relieve it, but with little positive results. I can talk to the customer about oversizing the timbers, and resawing later. I assume they will be a bit more stabilized once they dry?

Sounds from this post like you are not leaving the center in the middle of the beam. If you try to get free of heart beams from such small logs they will bend. You need the center, the pith right in the middle of the beam for the best straightest beam.

okmulch

Me and my dad used to saw a lot of poplar. I would raise the cant up from the far end as he would enter with the mill and let it down slowly as he progressed with the saw head to the middle and then I would go around to the other end and start lifting it as he got to the far end. It is not perfect but it gets alot closer then letting it bow on its own.
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customsawyer

Keep in mind that most of us are talking about stress when cutting 1X and 2X material. When you are cutting 3X material and larger then it is that much harder to relieve stress. This is due to the thickness you are cutting. I would recommend that you talk the customer into taking some 1X material with the rest of it so you can relieve the stress as you saw.
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Slab Slicer

Quote from: 5quarter on January 30, 2013, 11:42:13 PM
Slab slicer...sounds like your doing everything right. I would resaw them as I went whether he intends to use them right away or is going to sticker and let them dry, they are going to need to lay flat, so the bow is going to have to be cut out of them anyway. Do you know how they're going to be used? I've had several jobs like yours (except not as big) where I first had to cut oversize then resaw to the needed size. Hourly rate if you have to do it that way. Also, if you're boxing the heart to make you 4x4s and 6x6s, make sure that the pith is absolutely dead center on both ends or it will twist like a candy cane.

All will be stickered, and stacked for drying. The 6x6's will be used for the posts, the 3x's will be used for beams, and the 4x4's used to brace at the corners. At least I think that's the plan. I'm not involved in the design for sure. That one is on the customer.

It sounds like boxing the heart for these thicker beams is the way to go. At least from what I'm reading here. That will leave alot of side wood, but at least they will be straight. He doesn't have much use for 1x material, but I could suggest he sell that to recoup some of his cost. I should be milling this job again this weekend. I'll talk things over with him about boxing the heart, and see how those beams turn out. If we have better results, we can avoid the resawing. If not, resawing will be in order.

The cut list was posted in another thread here on the forum, but just for reference, we're cutting:

6"x6"x12'  38 pcs
3"x12"x16'  12pcs
3"x12"x13'  4 pcs
4"x4"x13'   23pcs
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Chuck

Slab Slicer

Quote from: hackberry jake on January 30, 2013, 11:51:59 PM
I have seen where people have used a small block of steel welded to the frame about 3/4" high for when you get the cant square you just drop your backstops all the way down and use the block as the backstop. Some of them have a little spike on them that keeps the center of the log from coming up on you while you're sawing. You might try that. Clamp pressure would likely be your friend as well.

The LT15 has the little blocks you mentioned, but not the spikes to hold it down to the bed The manual clamp leaves little option for pressure, other than what I can give it. No hydros on this mill......yet.  :)
2016 LT35HDG25, Kubota L2501 w/ FEL, Kubota BX1500 w/FEL and custom skidding rig, Stihl MS 500i, Stihl MS362-25", Stihl MS250-20", Stihl MS192-18",  2001 F250 SD 7.3, GMC Sierra Dually 6.0 gasser, Peaqua 16" 10K trailer, Sur-Trac 12' Dump Trailer 10K
Chuck

slider

I feel your pain slab slicer,check out the stress on these logs .They were big straight fine trees but when they hit the ground the stress was obvious .And like yours they misbehaved.

 
al glenn

Slab Slicer

OUCH. That looks to be loaded with stress. If I was slicing 1x boards for roof decking, I wouldn't be so concerned, but this stuff is proving tough to work with
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Chuck

WoodenHead

I bought a 1000 bdft of Aspen (often called Poplar around here) back in September.  I sawed three logs about two weeks after they came home.  The remaining logs I still have.  I tried quarter sawing them because I had heard that they bend and twist.  And the very first cut for quarter sawing I would see at least 3 inches on 12' due to tension just as you describe.

Well this morning I thought I would clean up some of the remaining logs.  I didn't see any more than 1/8" of tension for any cut I made.  Couldn't believe it after all the fun I had with the other three logs.  I'm trying another one tomorrow to see what will happen.  Perhaps it was because it sat out for 6 months?  Perhaps it was because I'm sawing when it is 10 degrees F and the log is frozen?  Perhaps I finally found one that didn't have tension? 

Ianab

QuotePerhaps it was because it sat out for 6 months?

Yes that is possible. Some species of logs do tend to "de-stress" over time. Trick is to saw them then, and not leave them too long so the bugs / mushrooms / rot get to them.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

Slab Slicer

I'm not 100% sure how long these logs have been on the ground. I do know they were cut later in 2012. Maybe some time in october. The first milling took place last weekend, and we were just coming off a cold spell with temps in the teens for highs. That day it was around 30 though. Sonce then we had 65 degrees one day, with lots of rain, and now were down into the 20's for highs. I'll be back at it Sunday, and Monday. I'll post on the results after then. If there is any other info, I'd be glad to hear it from the long time mill guys out there.
2016 LT35HDG25, Kubota L2501 w/ FEL, Kubota BX1500 w/FEL and custom skidding rig, Stihl MS 500i, Stihl MS362-25", Stihl MS250-20", Stihl MS192-18",  2001 F250 SD 7.3, GMC Sierra Dually 6.0 gasser, Peaqua 16" 10K trailer, Sur-Trac 12' Dump Trailer 10K
Chuck

mikeb1079

QuoteSounds from this post like you are not leaving the center in the middle of the beam. If you try to get free of heart beams from such small logs they will bend. You need the center, the pith right in the middle of the beam for the best straightest beam.


this sounds like the key to me.  getting those bigger timbers out of smaller logs w/o pith seems to be at the heart ( :)) of the problem.  i know your customer doesn't want 1x material but he may be fine with it if he sees straighter beams. 
that's why you must play di drum...to blow the big guys mind!
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Slab Slicer

That's my plan on the next trip there Mike. I agree with the customer being pleased with the straight beams, even with the 1x boards. I can't see building this thing with bowed support. Unless he's looking for it to fall in on him, or at the very least, being a real PITA to build. Luckily, I didn't get that far into the job just yet. I know I'll be much happier giving him a high quality product to use, and I'm sure he will be also.  :)
2016 LT35HDG25, Kubota L2501 w/ FEL, Kubota BX1500 w/FEL and custom skidding rig, Stihl MS 500i, Stihl MS362-25", Stihl MS250-20", Stihl MS192-18",  2001 F250 SD 7.3, GMC Sierra Dually 6.0 gasser, Peaqua 16" 10K trailer, Sur-Trac 12' Dump Trailer 10K
Chuck

Slab Slicer

Went back on Monday since I had the day off from my regular, boring factory job, and the weather was lousy over the weekend. Went to cutting some more of the 6x6's, using the suggestions posted here, and keeping the pith in the center. More turning, and calculating, but they were straight as could be  :) . Even some of the logs with a touch of sweep were turning out nice. When the customer came home from work, he was thrilled. When I started milling, and had the issues, he told me not to worry, but I explained that building with this stuff would be a PITA, not to mention, not very structurally sound in my book. He must have reconcidered, and liked what he was seeing with these most recently milled 6x's. As for the 1x boards... he's actually found a use for them, and is happy to have them.

Thanks guys, for all the helpful info. I feel alot better about the work I'm turning out.  ;D ;D  Finally snapped a couple of picks of the set-up, and the waiting logs for the mill.

Nice sized log on the mill.



 

What's left of the 1st whack of poplar.


 

And yet another whack still waiting


 

2016 LT35HDG25, Kubota L2501 w/ FEL, Kubota BX1500 w/FEL and custom skidding rig, Stihl MS 500i, Stihl MS362-25", Stihl MS250-20", Stihl MS192-18",  2001 F250 SD 7.3, GMC Sierra Dually 6.0 gasser, Peaqua 16" 10K trailer, Sur-Trac 12' Dump Trailer 10K
Chuck

mikeb1079

QuoteMore turning, and calculating, but they were straight as could be   . Even some of the logs with a touch of sweep were turning out nice. When the customer came home from work, he was thrilled

woo hoo!  now we do the happy dance!   8) 8)

good onya for stickin to it.  sounds like it paid off!  as frustrating as problems like that can be it's an even greater feeling when you fix em.   :laugh:
that's why you must play di drum...to blow the big guys mind!
homebuilt 16hp mill
99 wm superhydraulic w/42hp kubota

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