Friday, December 08, 2006

Hoisting the Beams

After eating a big breakfast, we started moving the beams down to the tree site. It took three trips with the tractor, one trip for each 16 foot beam, and one trip for the two cross beams.

In order to get the 16 foot beams up into the tree, we installed a lag bolt 3 or 4 feet above where we expected the permanent eyebolts would be screwed into the tree. We attached a pulley to each of these upper lag bolts, and then tied a rope to each end of the beam.

The plan was to pull up one end of the beam, tie it off, then pull up the other end. Luckily my brother-in-law Jason showed up, giving us a much needed extra set of hands. This was definitely a three person job, and we could have used a fourth.

One of us did most of the pulling, one guided the beam past the scaffolding and other obstacles, and the third took up the slack in the rope, wrapping it around another tree so that rope couldn't accidentally slip out.

After getting each end of a beam up to an appropriate height, Dad climbed either the scaffolding or a ladder to tie that end of the beam off. We used a lot of rope in the process, and often had two or three methods of holding each end of the beam up.

This was a lot of work, luckily our support crew showed up with some good mexican food that gave us a boost.

After getting the main beams up, we temporarily bolted some 14 foot 2" X 8"s across the trunks, so that we could rest the beams on them. We did this so we could later move the main beams around a bit to bolt the platform together. It was at this point that we realized just how much a tree moves around in the wind. I could understand how a statically bolted multi-trunk structure could tear itself apart relatively quickly.

We were running out of daylight, so we made sure we had everything roped off well, and quit for the day. We hoped that the tempoary sub-frame would survive the night. If it didn't, nothing would fall, but it might mean a lot of re-work for us in the morning.

It was another successful day, and it was starting to look like we were actually building something up in the tree.

Sunday, December 03, 2006

Beam Building

The next step was to start building the 16 foot beams. We ripped 4 strips of plywood to sandwhich with the 2" X 10"'s. We debated on whether the seam in the plywood should be in the center of the beam, or out toward the end. We decided it was safer in the middle, since otherwise it'd end up where the suspension points where, which already was going to be a weak point. We intentionally undersized it a bit, we didn't want it to form a ridge on the beam that would make laying the floor difficult.

We then clamped the four pieces together, and ran carriage bolts through the beam to hold it all together. Next, we used the outer plate of the suspension brackets as a template to drill holes through the beam. We wanted to get as much done on the ground, in the shop, as possible. Trying to do this kind of work up in the tree sounded nearly impossible.

It took a solid day of work to build up the two beams this way, and get the hardware mounted to them properly. We estimated that each beam was well in excess of 200 pounds, possibly as high as 300 pounds with all the hardware on them.

It took a few more hours to build the two connecting beams. We used two 2" X 10"s again, but this time without the plywood in between. In hindsight, I wish we had put the plywood in there due to the stresses on these beams caused by the suspension points.

We then bolted the whole thing together, and checked for squareness. The angle brackets appeared to keep everything square, it measured square on first try.

We labeled all the sides so that we could match everything up correctly when we were in the tree. We disassembled the platform, and tried to mentally prepare ourselves for the next big task, actually getting it up in the tree!