Stressed poplar

[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.

[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.

[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.

[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.

[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.

[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.

[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.

[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?

[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.

[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.

[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'.

[DRB]

...... 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.

[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.

[Slab Slicer]

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

[Slab Slicer]

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. 

[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.

 

[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

[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]

Perhaps 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

[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.

[mikeb1079]

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.

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. 

[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. 

[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


 

[mikeb1079]

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

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:

[Slab Slicer]

It was definitely a good feeling to be turning out some quality for the customer, and that he appreciated my extra effort to get the job done right. Now all I need is some good weather, and a bit more time, and this job will be in the books. Not much time to do any onsite milling after work in the winter. Not enough daylight left, so it's weekends for now until the daylight hours get later. Should be milling almost every day then. 

[5quarter]

I'm so glad to hear that the job is running better for you! Going the extra mile to produce quality products is what separates the men from the boys. And happy customers will always tell their friends.  ;)

[customsawyer]

Glad it is working out.

[Slab Slicer]

Looks like the push for quality has paid off. Another neighbor stopped in, and has some nice red oak he wants milled into 1x boards for flooring. Random width is what he wants, and has someone to finish them into flooring. The trees are down, and bucked to length. He just wants to wait for warmer weather to start the job. I hope the work continues coming in 

[fishpimp]

Think I may need ur  stress relieving tips..... Hahahahaah

  

 

[Slab Slicer]

Boy do those look familiar.  It looks like your cutting 2x4's, and having the same luck I did with the beams I was cutting. What size are the logs you're milling? Seems that small poplar will be stressed, and isn't much good for anything but large beams from the center, with 1x boards from the edge wood, or all 1x boards. Not sure if you'll have much luck getting those 2x4's to mill straight.

I have 3 or 4 large poplar butt logs, about 24" dia. I'm anxious to see how they mill up.  ???

[beenthere]

Finding any difference in stress between the upper logs in a ypoplar compared to the lower and butt logs?

[Slab Slicer]

Not much difference in what I've been sawing. The largest butts so far are about 18", maybe 20" dia. Any large slice to the edge wood, and the stress shows it's ugly face. I have to take a little off each side, and try to yeild as many 1x boards as I can, then do the final cuts for the beams. Any thick slice off one side, and things start curling like Shirley Temples hair.  :D

[Mountain State Farm]

I had a good poplar day yesterday, cut 86 2"x6"x12' out of four logs, only one blade and 10 or so that had any bow, (lotsa flipping  smiley_flipping). I stacked all of them on edge and loaded 30 cinderblocks on top.  Should hold em down.

@Fishpimp, have a few extra blocks to hold those rocking chairs down. 

[Slab Slicer]

I'm wondering if...Stacked, stickered, and weighted properly, will poplar relax once dry, and be straight, or will they just speing back after they are pulled out of the stack.  ??? ???

[fishpimp]

Started big job today. Large prime poplar logs.
These trees have so much stress in them. It's frustrating. Customer wanting 2x material. All material is 14' , 16' 19.5'

I've flipped . I've turned ...split the pith... Dodged

  

  

   the pith.
These biggins are makin my blood pressure spike!
Anyone got any input.
Looks like I'm gonna have to take the glock 45 tomoro!

[Slab Slicer]

I'm looking for an answer on this one. Since what I was cutting was larger beams, I could center the pith in them, and make a straight beam. Not sure about this situation. It was mentioned earlier in this thread about cutting everything ovesized, and resawing after the pieces have dried.

[GeneWengert-WoodDoc]

I had a graduate student that looked at these growth stresses in drying using different kiln schedules including over 212 F.  The drying basically had no major effect on warp or straightening.

The study also looked a sawing 8/4 flitches, unedged and drying them and then ripping dimension, mostly 2x6.  The idea of this came from Bob Maeglin at the US Forest Products Lab.  It was called SDR...saw, dry, rip.  it worked well and is easy to do.  He used it for softwoods and hardwoods.

[Banjo picker]

Must be something in the water with all these people wanting structural popular...I just cut 80   22 ft .  2x6's ....and now have to cut 80  18' 2x10's ...I dread it...the 2x6's were bad enough...The logs looked fairly decent...Banjo

[losttheplot]

You could try cutting the cant with the pith in the center ?

[Magicman]

You do have to keep turning the cant as you remove boards, often after each board.  I would never split the pith as shown in the last picture.  That is a sure recipe for crook, but you found that out already.   :-\

[Slab Slicer]

I agree with MM. If you take too many boards from one side, what is left of the log will lift right off the mill. Saw, Turn, saw, turn, saw, turn.....was the order of the day.

[5quarter]

   Gene...that's exactly how I cut alot of my 2x material. first, it is nice to be able to cut the widths I need when I need it, but it also gives me the opportunity to resaw after it is dry. This method almost always gives me nice straight lumber.
   Just to be clear, when you're rotating the cant to relieve stress, always flip 180° from the previous cut and try never to take more from one side than the other. also, if you want to turn your cant 90° and begin taking boards, I usually make a skim cut, flip 180°, take another skim cut and then start taking boards, alternating 180° after each cut. alot of turning, but each board will have well balanced grain and be as straight and the log can give. The bad news is that once you've done all of that, then you'll be full of stress... >:(

[GeneWengert-WoodDoc]

In most other countries when dealing with growth stresses, they use two saws in one headrig...often a twin band or a Skragg...to make sure they cut equally off of both sides.  Due to the low level of growth stresses in most NA species, we seldom do that, except in some softwood mills, especially syp.

[customsawyer]

Splitting the pith like you did in the pics will cause lots of stress.

[Okrafarmer]

Splitting the pith like you did in the pics will cause lots of stress.

I'm also a member of the APSL. Having tried pith-splitting out of curiosity, I now don't recommend it for anything except making rocking chair rockers.

[fishpimp]

Ok so do what with the pith. Saw around . Firewood, toothpicks, stack sticks?
Lumber is 19.5' long.  Diameter of trees averaging 30" . Pith is 10 to 12" diamter.
Pith smith. Poplar is for 1x stuff. No more framing on this job.

[beenthere]

Don't think the pith is 10-12 inches diam. Heartwood maybe, and pith-associated wood. But the pith is the center ring of the tree.
Think the thought here is to have that center ring be centered in the wood piece sawn out in the center.

[Banjo picker]

I don't think most of us refer to the pith as being that large...May be and inch or so...could be I need to learn more....Here is my next victum its 18' + but I had 3 teeth pulled yesterday and I think i'll have to wait....

  ...beenthere beat me to it....

[losttheplot]

Take boards alternately, from each side of the log, until you have a cant that is your target width and as tall as possible.
The center of the log should be in the center of the cant.

Take boards from the cant rotating it 180* if you see any signs of stress.

If the log is big enough make three cants, however the outside cants may move or need a trim cut.