Releving tension in soft woods.

losttheplot · July 25, 2011, 07:48:01 PM

Hello.
I live on a small island so I take what ever logs I can get, usually Doug fir.
Lots of them have tension in them, although the sweep mostly comes out when they are bucked.

I am cutting 1 x 8 boards on a Norwood 13hp band mill.

I am trying to get straight boards so I am following the advice in the forum extras, however they are still moving as I cut them.

Any advice on my cutting technique would be welcomed.

First I lay it on the bunks and level the heart end for end.
The wide part of the log is parallel to the bunks.
any sweep is horizontal.

Then I measure up 4 inches from the heart, plus 1 and 1/8 inch if I can get a flitch.

Flip it 180 degrees and set the cut at 8 inches plus 1 and 1/8th for any flitches.

That leaves me with an 8 inch flitch.

That I flip 90 degrees.

Then I level the heart and cut off the wane and maybe a flitch, this is where I would be cutting off the hump or the ears if the log is bowed..
This is where the stress is showing up.

The first board or two often have more sap wood on one side than the other, this is hard for me to avoid.
They move towards the sap wood.
Once I get into the heart wood there is 1/8 to a 1/4 of an inch movement over 12ft

The closer I get to the heart the less the boards move as I cut them, I am rotating the cant as I cut, but it is not lifting from the bunks.

I can live with the amount they are moving, but I am worried they will move more as they dry.

Thanks.

carykong · July 25, 2011, 08:24:03 PM

What are the boards going to be used for?

Magicman · July 25, 2011, 08:32:42 PM

In my opinion, your sawing technique is correct. At least that is essentially the way that I would saw them. I am not surprised that you detect some movement as you saw and stress is relieved. That stress is in the log and you have to release it.

You may loose some lumber as it dries, but not much and not nearly what you would if you were not opening and sawing the log correctly. Don't worry.

redbeard · July 25, 2011, 08:53:07 PM

Hello losttheplot looks like you have it figured out. If you flat saw the tight grain sap wood down to where it looks like your boxing the heart it can relieve some of the compression. I call those windtrim logs. You probably have a fair amount of wind like we do on whidbey island. Nice pics of your set up.

rbarshaw · July 25, 2011, 09:08:30 PM

The only thing I can suggest, is if it is going to be a problem, cut them wider than needed, then when they dry, trim them again. Probably not what you want to hear, but it may be the only solution.

Tom · July 25, 2011, 09:14:45 PM

You can relieve the stress but you won't make it go away altogether. One thing you can do to help is not make such a deep slab cut. That slab you show here might make a 1x6 if you take the time to do it and the extra cut will let you see where the log is going to go. This is especially important when sizing the width of the cant.

Many stressed logs require turning after sawing each board. The thinner the board, the less it moves. If you are cutting 2x, or more, material, everything contains a lot of stress.

If your board is moving, then the cant is moving also, in the opposite direction. It pays to look under the cant on a band mill to see if the cant has daylight developing under it. If it does, You might benefit from turning it.

The more frequently the cant is turned, the less out-of-whack each board will be. The movement might be on the ends or in the middle.

You are doing a fine job and have the idea down pretty good. Just remember that the log is a living thing. No matter what you do, you are not going to be able to saw it as if it were a piece of plastic. It has a mind of its own. That's why saw milling is an art.

Rbarshaw has a the answer for those boards and cants that move a whole lot. Sometimes your only salvation is being able to come back later and edge the dried lumber into a straight piece. That might require that the board be cut 1 or 2 inches "fat" in the beginning. It's just hard to second guess that kind of thing.

redbeard · July 25, 2011, 09:43:44 PM

Have these logs been down a long time? Sometimes when they are windfall logs that have been down in the woods for a few years can be hard on blades. Doug fir is the most exspensive to saw for me. But I love the strength and beauty of the boards.

Larry · July 25, 2011, 09:54:35 PM

Quote from: losttheplot on July 25, 2011, 07:48:01 PM

From that off center heart I would be thinking the tree was a heavy leaner or a split tree. Since I've never seen a DF maybe I'm wrong. No matter which way it gets sawed it will move a lot due to the tension.

I would saw nearly the same as ltp while keeping the above in mind.

Chuck White · July 25, 2011, 10:10:55 PM

Seems like you are sawing just like most of us would!

I think your only recourse would be (as mentioned) to saw them at 8" and maybe check them later and some of them may need to be trimmed to 6".

You'd lose a little lumber, but you would have good boards.

The bottom line would be for you to figure out what the boards would be used for.

Remember, those boards are called "rough lumber".

kderby · July 25, 2011, 10:39:38 PM

Looks normal compared to the fir I mill. Trees are living and variable things even as they are turned to lumber. I also suggest going a bit wider and re-sawing after dry. I often put dry lumber on the mill and zip an inch off each side. I sell a lot of board and batt. The batts are often recovered from dry six and eight inch wide lumber that I mill down to three or four inch batts. That give me somewhere to send the narrow lumber and the customer gets clean/uniform/straight battens.

I agree with Mr.White. We are talking about "rough" lumber. For the price of the logs, you can lose and inch and gain a better edge.

kderby

Brucer · July 26, 2011, 12:41:28 AM

I saw mainly D. Fir timbers and I set up the log the same way you do. The only difference is that I stop when I get to the rectangular cant -- that's what I'm selling.

I've very rarely had a slab or a flitch go sideways like that (but I see it a lot on WRC). Where I do see a lot of movement is when I saw FOHC timbers. As soon as I cut out the center the timber on top curls up at the ends. The one on the bottom pops up in the center when I release the clamp.

Usually the customer can handle the slight bow on a FOHC timber. In special cases such as long newel posts, I cut out my FOHC cants about 1/2" to 3/4" thicker then the final size. Then I saw the two curved sides straight. I hardly ever see any additional movement when resawing them.

I imagine the same principle would apply to your boards. Cut them a little wide, then resaw them to the final size while they are still on the mill.

bandmiller2 · July 26, 2011, 08:04:52 AM

Lost plot,your doing everything right sometimes its just the logs nature,remember we just cut it we don't create it.If I needed straight dimension stuff I'd cut cants and set them aside for a wile to have their little hissy fits then recut.Frank C.

CalebL · July 26, 2011, 03:09:33 PM

Quote from: bandmiller2 on July 26, 2011, 08:04:52 AM
Lost plot,your doing everything right sometimes its just the logs nature,remember we just cut it we don't create it.If I needed straight dimension stuff I'd cut cants and set them aside for a wile to have their little hissy fits then recut.Frank C.

Great response. If the wood I use would only do what I want it to do, I would be one hell of a woodworker/sawyer. I have built furniture from from slabs that haven't moved in years and I make one rip on them and bam, they start twisting and bending like a roller coaster.

west penn · July 26, 2011, 05:17:05 PM

You could also make your cant 9+ inches wide then saw your boards then turn your boards from that log "hump up" , trim straight then flip and cut the other side to 8 inches. A little more time but makes straight lumber and relieves most of the stress

customsawyer · July 26, 2011, 08:52:51 PM

If the log is big enough some times you can put the hump or horns at a 45 degree angle and see if that helps.

losttheplot · July 26, 2011, 11:14:57 PM

Thanks everyone, for all the great tips and encouragement.
I have only had the mill for a couple of months.
I have made lots of mistakes.
And I think I have some of the finest looking firewood on the island

however I could not imagine trying to use the mill without resources such as this one.

The boards are going to be used for siding, on the outside of a small timber/stick framed shop I am building.Also for ship lap cladding on the inside walls and ceiling, as well as rustic flooring.

I am also sawing 1x6 along with the 1x8's. I will trim any bad 1x8's down to 6's and any wobbly 6's down to 4's to use for strapping.
I am guilty of not getting the most out of the logs that I could.
I get discouraged when I try get get an extra board and end up cutting bark.
The trees have only been down for a couple of weeks, however they are still pretty hard on the little mills bands.

I tried cutting 2x4's today but I could not think of a good way to cut a cant, with out splitting it through the heart. I think I am going to buy what I need for 2x4's from the store.

I am going to try cutting some of the remaining logs into timbers as large as I can get and then store them for a while.

Hopefully some of them will stay pretty straight.
There are twice as many again, down the bank out of sight.
Its a lot of work with just a log arch and a pick up, but its much faster than the Alaskan I have been using for the last few years.

Besides I think I have cut enough 1 by for now.

In fact I have so much my shop is full and I have not even built the walls yet !
Its hard to stop cutting once you get going..........just one more.... ;)

I think I have the saw dust disease.

I am not sure why all the trees are crooked here.

We have lots of hills, but the ones growing on the flatter parts are mostly crooked also.

I am trying to do the best I can with what I have, one neighbor told be they were not worth sawing, because of the off center heart.
I can only assume he does not frequent the Forestry forum ;)

Brucer · July 27, 2011, 01:19:20 AM

Quote from: losttheplot on July 26, 2011, 11:14:57 PM
I am not sure why all the trees are crooked here.

Because they're Douglas Firs :D :D.

losttheplot · July 27, 2011, 01:46:02 AM

Quote from: Brucer on July 27, 2011, 01:19:20 AM
Quote from: losttheplot on July 26, 2011, 11:14:57 PM
I am not sure why all the trees are crooked here.

Because they're Douglas Firs :D :D.

Thanks for clearing that up. :D :D

Ianab · July 27, 2011, 04:18:15 AM

QuoteI am trying to do the best I can with what I have, one neighbor told be they were not worth sawing, because of the off center heart.

Not worth sawing is different to "not perfect for sawing". Sometimes we just have to work with what we have....

If they are moving 1/2" over the log length I wouldn't be overly concerned, and maybe cut them a bit oversize if the log allows to let you rip them straight after they dry.

For the 4X2s. As you cut the cant down, like in this picture...

Go down till you have a 4" thick cant with the heart centred. Then stand that up and cut it into 4x2s. The grain should be evenly balanced. most of the movement would be bowing towards the heart, which you can reduce by putting weight on the drying stack.

You might get a few rejects, but I bet most of them will be usable.

My mill works differently, and cuts dimensioned boards from the top down, no flipping the cant etc. You know when you have tension in a log when you are cutting a 4x2, and the free end of the board is 4" off the log as you finish the cut :D But even then, get them on the bottom of the stack, weight them flat, and let them dry. Probably still come out straighter than the bought stuff..

Ian

Larry · July 27, 2011, 07:12:47 AM

It's interesting hearing you guys make fun of douglas fir. It doesn't move near as much as our plantation grown syp.

Magicman · July 27, 2011, 07:44:24 AM

There are many ways to saw 2X4's. Here is the method that I use.

Split the cant into 4's centering the pith.

And then stand them up and saw the 2's.

Ianab · July 27, 2011, 08:35:43 AM

But if you have tension in the log, then the 4x2s at the corners are the most likely to misbehave.

The ones in the middle vertical section should be more stable, and at least be partly controlled by the drying stack. Hence my suggestion of cutting the 1" siding, where you can balance the tension, and then the 4x2s from the final piece, again with the tension balanced.

If a board is bowing, you can usually do something, but if it's twisting, warping AND bowing all at the same time.... not so good.

Ian

losttheplot · July 27, 2011, 12:34:34 PM

Quote from: Magicman on July 27, 2011, 07:44:24 AM
There are many ways to saw 2X4's. Here is the method that I use.

Split the cant into 4's centering the pith.

And then stand them up and saw the 2's.

That's what I would LIKE to do.

What would you do If the log was only big enough to get an 8 x 8 cant?

Tom · July 27, 2011, 12:50:48 PM

Cut 2x8's off of each side. Stand the 4x8 up and cut 2x4's from it. then stand the two 2x8's up and cut/split them into 2x4's.

It's a production (found money) kind of operation to saw in multiples like this, especially if you are alone. But you also should keep in mind that you are sawing blind. You don't know what the boards are looking like inside of the cant. If you cut and remove boards and flitches as you go, to be resawed later, you might change your mind about how to saw the next board because of spike knots, rot, or other flaws.

So, knowing the techniques doesn't mean that you should make it a habit of following them every time.

This "Reading a Log" is the important art of Sawing. Knowing where you are going is a lot more important than knowing where you've been.

LeeB · July 27, 2011, 01:30:20 PM

When cutting off center hearts, the wood will tend to bow toward the side closest to the bark. Depending on what you want to do with the wood, a little bow is much easyer to deal with than side crook. Tom posted some picks on here once a pony time about sawing this kind of log and recovering as much as possible, least I think he did.