Question
I have three sycamore logs that I was thinking of sawing into 8x8 beams for a cabin I'm building. After reading about big sycamore logs I thought I'd ask if anyone who is familiar with sawing sycamore thought they would stay straight.
Forum Responses
(Sawing and Drying Forum)
From contributor T:
Sycamore would not be your first choice, but if you are dead set on it, make sure you let them air dry several months to gauge which ones are going to move more than you can tolerate. Sycamore is notorious for movement. Quarter sawing lessens movement but increases waste. In a timber application like this, if your trees are large enough, you can cut the timbers out of the tree like a diamond pattern FOHC (free of heart center) so that essentially you have mostly rift sawn, versus two quarter faces and two flat faces. I think they might move less being mostly rift but I have never tried it or heard of it.
If they are not large enough to get pith-free timbers, you want to box the hearts (center the pith on each end of the timbers, then take what else the log will give you for framing lumber etc). I would not place sycamore timbers in tension especially if they have the pith, unless you know how to accurately grade the timbers and understand the realistic limits of where you can, and cannot put them into service.
If you cannot get an accurate assessment of their load tolerances it’s better to use them in post and beam construction as posts where they will see only compression, as opposed to using them for beams. Sycamore makes excellent framing lumber once it is dry and kept dry. Timbers should be no different as long as you don't ask more than they can deliver. Certainly don't put them into service green, because one or more may move so much as to cause a failure.
Your application sounds fairly vanilla so as long as they don't have a lot of twist (an obvious spiral pattern parallel to the grain), large knots, deep bark inclusions, heart rot (even a little then don't use them), or crotch wood through the timber you should be okay. If you see what appears to be a "small crack" anywhere but there are ants coming out then don't use that timber either.
Let them air dry for 6-8 weeks or so and if they don't look like the keel of a ship then dress them and put them in service. Ideally you want them to 20% or less but they won't be there for several years. Also get a builder with experience with using timbers if you have any pause about your ability to judge what is a sound timber.
Every time you take some boards it will relieve stress and the beams will release it by moving to equalize the stress. The beams will continue to move to some degree for years. All you are trying to do is avoid putting one in service that's going to go nuts. That's why you want to stretch this drying out as long as you can. A maverick timber will show itself in the first few months and sometimes sooner.
Many sawyers like to allow the stress to be relieved naturally in the log, and I believe that's why contributor L suggested to leave them that way. I spalt sycamore all the time, but if I was going to use them for timber framing or post and beam, I would make cants with them right away and sticker and start the drying process. Not saying my idea is better than contributor L's, it's just personal preference.
