Adventures in steam bending - boom gallows
Posted: Thu Dec 22, 2022 5:22 pm
I know the manual says the gallows is optional, but that is followed by a list of reasons to have it. I agree. However, it seems a bit clunky to me, but the Pocketship is meant to built with a pretty small set of tools, so the design makes sense. Since I've been experimenting with steam bending, it occurred to me a 'hoop' gallows might be nice. I decided to make a semicircle, with straight legs at the ends, out of 1" x 4" white oak. I've been having decent success lately with steam bending (see my posts elsewhere), so I felt pretty confident. I built a form and planed the air-dried oak and eased the edges. In my first attempt I steamed the wood inside a corrugated drainage tube with some insulation added around it. This isn't an extreme bend but I thought it best to add a compression strap on the outer side, which I made out of 4" galvanized flashing and some aluminum angle. It started off well but my ratchet strap jammed up and I lost precious time. I didn't get the bend all the way in until after a half hour out of the steamer - not good. I also noticed part way into the bend that a section near the apex was not conforming to the mold; probably due to a weak spot in the wood, though I did not see any flaws. I pulled that in with clamps and let the thing sit overnight. ( Note: it seems most ‘professionals’ use a thicker strap. Although I’m confident my strap had sufficient tensile strength to keep the outer side from expanding, perhaps a thicker strap would help the wood conform to the mold. ) Next day, sure enough, I had about 9" spring back on each leg. I decided to re-steam it (though I've seen conflicting opinions on that). This time I decided to use the plastic bag method popularized by Lou Sauzedde on his totalboat YouTube channel. The nice thing about this method is you bring the wood up to steam but leave it in the bag and continue steaming as you bend it around the mold. I let it steam a good hour after the temperature inside the bag was up to 100 degrees C throughout. The process took an entire water fill of my Earlex steamer. This worked well:
I had very little spring back - an inch or so, but when I removed the board, I found a crack where I had the bulge from the first bend:
Anyway, I decided to mount it to see how it looked. I realize it's about 5" to 9" too high from what I have read, but you can get the idea. The picture makes it looked a bit bowed out but the verticals are straight.
Obviously I'll need to add a seat for the boom and mast to sit in.
I'm curious to see if I'm missing something doing it this way. Will I bang my head into the curved part, or is there any other possible problem?
I do have a second piece of oak, and may try again to make a nicer piece. After all it's winter and I have time on my hands....
I had very little spring back - an inch or so, but when I removed the board, I found a crack where I had the bulge from the first bend:
Anyway, I decided to mount it to see how it looked. I realize it's about 5" to 9" too high from what I have read, but you can get the idea. The picture makes it looked a bit bowed out but the verticals are straight.
Obviously I'll need to add a seat for the boom and mast to sit in.
I'm curious to see if I'm missing something doing it this way. Will I bang my head into the curved part, or is there any other possible problem?
I do have a second piece of oak, and may try again to make a nicer piece. After all it's winter and I have time on my hands....