(https://forestryforum.com/gallery/albums/userpics/13036/IMG_0790.JPG?easyrotate_cache=1591994247)
(https://forestryforum.com/gallery/albums/userpics/13036/IMG_0792.JPG?easyrotate_cache=1591994246)
and will it dry straight?
It is 16 ft long, 13" on the small end and 14" on big end and has centered piths and a 2" bow. Customer needs a 4 x 10 beam.
If I cut the 10" dimension vertically as the log now lies the arc of the pith will be contained in the 10" width. However, I am not sure I will have 10" width after I remove the "hump and horns" to expose a 4" thickness on both sides. But containing the arc in 10" the beam would be more stable than containing it in 4". Is that correct?
If I cut the 10" dimension horizontally the arc of the pith will be contained in the 4" width which would make the beam more prone to bend. Does my reasoning make sense? or should I go to lunch? ;D
Your thinking is correct but if the bark is falling off the log it probably isn't a beam strengthwise.
Bark was removed during loading by an excavator. Log is oozing sap because it was harvested ~2 days ago.
I wood saw it to the largest cant you can saw, store it undercover for 6 months to a year where air can circulate around it well. Put it back on the mill after and saw to the requested dimensions. If cut to dimension green it will definitely twist and bow.
Leon
A good indication will be when you start to saw it. If she is full of stress then the boards will begin to lift off of the cant as you saw. If they stay dead flat then I would say there is a very good chance the beam will be fine. If the cant itself pulls down or up from the mill bed as you saw then there is a very good chance the beam will bow hard. I would try to get that beam from that log and watch the boards and cant movement to determine if the plan stayed the same or the lumber becomes destined for another project, sometimes that's all you can do.
As you saw also look for the boards to move left or right off the edge of the cant.
What is it for? If it needs to be true and pretty when dry the the above is good advice. Cut it over size and let it dry.
If it for a barn just cut it. I am not sure that the curve will have stress. Leaning trees have stress.
As above you will know when you make the first cuts.
I cut the hump first then flip it and cut the horns, then size it up for the best yield.
The closer the pith stays centered the more stable the beam in my limited experience.
The anatomical reaction to a lean in a softwood is to produce compression wood on the underside of the lean. The "weave" of the cell walls is laid down on a bias rather than being lengthwise and the cell walls are heavily saturated with lignin, the cement that makes wood stiff. Compression wood is stiffer than normal because of that higher lignin content but is less strong in bending because the fibers that reinforce that cement are running at an angle to the load. I've used it for a scaffold plank before, it is awesome stiff but then breaks unpredictably before it has given much warning by bowing. As the moisture leaves the cell wall that reaction wood shrinks more lengthwise than normal, again because the fibers are at an angle to the length of the log. Hopefully that makes sense.
When I'm sawing I keep my eye out. If I see a lot of compression wood that is an indication the log probably is not a good choice for a heavily loaded beam. I'm not seeing a problem in the end but it is something to keep an eye on as the log opens up. I think I have a pic of heavy compression wood, it has a dull, peanut butter appearance.
There we go, the center stripe is wicked compression wood, I hope I chopped that up for blocking.
(https://forestryforum.com/gallery/albums/userpics/10017/compwood2.jpg?easyrotate_cache=1192055667)
This is an end shot, this tree would have been leaning right. There are several bands of compression wood right of heart.
(https://forestryforum.com/gallery/albums/userpics/10017/compwdop.jpg?easyrotate_cache=1192055667)
All that technical mumbo jumbo aside, I sawed a not heavily bowed pine earlier in the week that was free of compression wood, the slope of grain was not severe and I got what I think will be a fine 8x10 out of it. It is on the stack drying which will be the real tell. If it goes haywire it'll get cut up for blocking.
There was not much room to spare but I sawed the 4 x 10 with minimal wane. The boards sawn from the cant remained in place with no discernable movement - no left, right, up and down movement. Because of the 2" bow in the log I could not center the pith and get the 4 x 10 but I sawed it anyway. The first pic shows the pith in the log end and two 2by boards; the next pic shows the cathedral grain (accentuated by the red rope) and the arc of the pith in the log. The face pith is about 3" from the edge and the arc extends to about 3" from the middle of the beam on the opposite side. Shouldn't that cause crook? I'll see what happens. After 2 hours there is no crook but about 1/2" of bow; The cathedral grain in the 4" face is centered as expected. (Sorry for the upside down pic)
(https://forestryforum.com/gallery/albums/userpics/13036/IMG_0798.JPG?easyrotate_cache=1592068230)
(https://forestryforum.com/gallery/albums/userpics/13036/IMG_0799.JPG?easyrotate_cache=1592068232)
(https://forestryforum.com/gallery/albums/userpics/13036/IMG_0803.JPG?easyrotate_cache=1592068234)
My bet is that will do fine. Good job.
Wow! That's the best news I've had all day.
Pretensioned beams should demand a premium.
When you say beam, I take it as referring to a horizontal member. You often want your best wood for beams. Preferably straight grain, symmetric, without defects in critical places like the middle and lower or upper portions. Generally you'd want to start with the straightest logs you can. I like to use live edge timbers, so I might decide to cut the sides off that to get the 4" dimension and leave the upper and lower live edges. Provided no significant defects it might be a bit stronger in bending due to the extra fibers and that you haven't cut them off which would create discontinuous fibers. In some places you can do the live edge thing.
No matter what, you want to mill with symmetry to reduce movement. so standing up like you originally showed would be the way to do it for the tall axis.
I didn't see you say what this was to be used for?
Ultimately I'd make sure the customers requirements are clear. and if they need 4 sides sawn and straight grain, you might want to find a different log.
The logs were from a customer/friend who is building his house. When I saw the logs he brought I alerted him that the logs should be straight and that many of the 13 or so pines he delivered had small bows (e.g. 2-3"). He needs three 4 x 10s and five 3 x 10s which I assume will be horizontally installed. He wants 4 sides milled and the logs delivered are what I have to work with. Hopefully, with 13 to choose from I can fill the bill, and maybe mill extras for him to choose from. Will anyone hazard a guess as to what the beam shown will look like in 2 years? I would really like to advise him as to what to expect so he can make contingency plans.
If there was no twist, and it didn't look like there was in the first pics, then it will tend to crown up if installed bow up, the way it was sitting on the mill in your first pics. The load will tend to hold it flat, so in a perfect world life is good. The warning might be that it might lift in the middle a bit. I see no compression wood, the knots I see grade out to high #1 or Select Structural grade, the slope of grain appears to be less than 1" in 10 which is the cutoff for #1, #2 is 1 in 8, SS is 1 in 12. Allowable crook in 16' is 1/2" in #1 and SS, 5/8" in #2. I'm not seeing all or all faces though.
The 1/2"of bow I reported has not from the beam, it was from the trailer. I'm using the customer's trailer that has an arch in the middle of about 3/4". I stretched a string over both sides of the beam and got less than 1/8". Nice. I'll continue sawing this week if the rain allows.