Just started chainsaw milling today some white oak. Was trying to cut 2 inch slabs. I have the Granberg EZ rails for my first cut. Unfortunately as I was cutting the first piece it starts to rise in the air where I've cut. I.e. it bows up behind me and throws off the entire reference making the cut slope down! Any thought on this. Anyone else have this happen?.....I guess maybe have someone hold it down behind me?
It's stress in the wood, same thing happens with a band mill. Basically a product of how the tree compensated while it grew for the effect gravity had on it. By cutting that board you have released the tension which was holding it together which is why it is rising on you. Not sure what options exist with a CSM given your need for the reference line.
Just thinking out loud... Perhaps runners along the side of the log(unattached to the log) could be used for problematic logs. Adds a lot of infrastructure, and kind of takes away the main benefit of Alaskan mills though.
Someone holding it or a wedge to hold kerf dimension and ratchet strap at the end will do it. You dove into the deep end of the pool, white oak will reach around and pick your nose sometimes :D.
Grab some new logs unless that's not an option. Stress should always be ignored , on and off the mill(s).
Quote from: OffGrid973 on July 29, 2019, 05:19:44 PM
Grab some new logs unless that's not an option. Stress should always be ignored , on and off the mill(s).
This seems like a good idea. I'd be afraid the problem with trying to find a workable solution allowing you to saw up this log is that the lumber is likely to only get worse as it dries.
You could try another cut. Maybe you've removed most of the stress with that first slab (or flip the log and try from another side). It's pretty easy to do this with a band mill but probably no so much for the chainsaw mill. Putting the log in the firewood pile might be the best choice, especially if it's got obvious signs of stress (off center pith, bow, twist).
Alan
Well thanks for all the responses. I'll have to try the strap hold down next time if it happens again. Next log is a yellow pine so I'm hoping that doesn't happen.
On a slightly similar topic (I'm learning as I go here) how do I determine what depth to set on my first cut one end compared to the other. The smaller end id just figure on cutting in about 1.5 to 2 inches to get the slab set up. But the way the rails work I could vary this depth at the other end.....measure same distance from the pith? Thanks.
There you go, I usually set up the same distance from the heart at each end. That white oak might make a better post or beam, centering the heart and stress in a larger timber, but if the lumber is for raised beds or a use where straight is only relative it might be fine if it bows.
I've slabbed very heavily chainsaw milling white oak for beams, then cut down and resaw that banana slab straight into boards. I've used another mill for recovering wood from those slabs but a CSM would work. The stress is largely relieved when that slab comes off.
So your first cut is the flitch(outside of the log)? It could be that the stress is in the drier outside of the log. You next cut may not do that, especially if you are slabbing 8/4 or more. The inside will be more wet and may not have stress.
As far as how far to go in for the flitch.... I do set my first cut the same distance from the center of the pith on each end of the log. Also, if I'm slabbing, I'll make plan to center capture the pith in the center slab. Then measure up half the thickness of that slab and mark, then measure up a full slab thickness plus kerf width, then mark that. Then continue marking like that. Make sure your slab thickness includes the amount you plan to take off when flattening. I'd say at least 3/8". If you think the slab is going to warp or move more than normal, add more.
Thanks folks. Very helpful. I'm set up for the pine but will have to do it tomorrow .
I think beenthere posted this article first years ago. It is a good description of growth stress.
LINK (https://www.fs.fed.us/ne/newtown_square/publications/technical_reports/pdfs/2004/316papers/Cassens1GTR316.pdf)