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Hot Glue and Canoe
Mar. 5th, 2011 04:58 pmSo...
I don't remember if I mentioned it, but a while back I came across this page explaining how to use hot glue instead of staples, clamps, or fishing line to secure planks to the forms while the carpenters glue holding the strips to each other dried.
I was a little dubious; despite the assurances that it worked, the method struck me as running the horrible risk of gluing the forms permanently to the inside of the hull. However, staples leave holes in the strips that the epoxy fills and makes watertight while simultaneously making sure they will be visible forever. Clamps don't do a good job of securing the hull to the forms, so that the hull comes out with some distortions. Fishing line is kind of slow. Perhaps hot glue would be a way around these disadvantages.
So I shelled out 20$ to get a pound of the special sticks of hot glue, and a cheap hot glue gun. They came on Thursday. I had to go to Maryville to cut planks, so I stuffed the box in my pack in case Martin wanted to try it out. Thursday and Friday were busy and it didn't happen. Today I spent the morning mining Arkonor in Eve (long story) then went to get back to fixing the forms to the strongback. Looking at the dozens of screws in the forms already up, screws necessary to secure the fishing line if I went with that method again, it occurred to me that it would be smart to test the hot-glue method now, rather than put more screws in to hold fishing line, only to take the screws out again if I decided to use hot glue.
So I cut a bunch of short strips, put a piece of scrap plywood in the vise, figured out how to work the hot glue gun (first tool I've bought in a long time that didn't have any instructions) and started gluing up. White glue between the strips, a bloop of hot glue on the edge of the plywood, stick the strips onto the plywood, add a couple of beads of hot glue across the top of the strip-strip joint, count sixty seconds, and release.
It works. I glued up six or so strips, then tried a few glued to two scraps of plywood, so I could have the strips meet the plywood at an angle rather than in a T. This is because at the bow and stern of the boat the strips will meet the plywood forms at an angle, and I needed to be sure the hot glue would still hold (white glue, for instance, wouldn't hold worth a damn here because there's no surface-surface contact to speak of.)
And it works at an angle too. I left everything to cure 30 minutes (so the white glue between the strips would cure), then undid the vise, put the strips in the vise, and whapped the plywood with a mallet to see if the hot glue would indeed fail under sheer stress, and it obligingly does. I was afraid the hot glue would rip chunks out of the strips when it came away, but it takes only a few small splinters. It's slightly worse than duct tape, but only slightly, and I don't think it will be an issue, because all the divots will be on the inside of the boat, where they won't affect the shape that touches the water.
Upshot: I will be trying hot glue with this boat. Plywood form edges get no duct tape. I will have to be careful not to put too much white glue between strips; I don't want the boat gluing itself to the forms with white glue, as this does not have the obliging failure characteristics of hot glue. I took the screws out of the faces of the forms, since I won't be using fishing line and they would just get in the way. Putting the rest of the stations on the strongback should go faster without having to do the extra screws.
Martin says I'm his R&D department.
I don't remember if I mentioned it, but a while back I came across this page explaining how to use hot glue instead of staples, clamps, or fishing line to secure planks to the forms while the carpenters glue holding the strips to each other dried.
I was a little dubious; despite the assurances that it worked, the method struck me as running the horrible risk of gluing the forms permanently to the inside of the hull. However, staples leave holes in the strips that the epoxy fills and makes watertight while simultaneously making sure they will be visible forever. Clamps don't do a good job of securing the hull to the forms, so that the hull comes out with some distortions. Fishing line is kind of slow. Perhaps hot glue would be a way around these disadvantages.
So I shelled out 20$ to get a pound of the special sticks of hot glue, and a cheap hot glue gun. They came on Thursday. I had to go to Maryville to cut planks, so I stuffed the box in my pack in case Martin wanted to try it out. Thursday and Friday were busy and it didn't happen. Today I spent the morning mining Arkonor in Eve (long story) then went to get back to fixing the forms to the strongback. Looking at the dozens of screws in the forms already up, screws necessary to secure the fishing line if I went with that method again, it occurred to me that it would be smart to test the hot-glue method now, rather than put more screws in to hold fishing line, only to take the screws out again if I decided to use hot glue.
So I cut a bunch of short strips, put a piece of scrap plywood in the vise, figured out how to work the hot glue gun (first tool I've bought in a long time that didn't have any instructions) and started gluing up. White glue between the strips, a bloop of hot glue on the edge of the plywood, stick the strips onto the plywood, add a couple of beads of hot glue across the top of the strip-strip joint, count sixty seconds, and release.
It works. I glued up six or so strips, then tried a few glued to two scraps of plywood, so I could have the strips meet the plywood at an angle rather than in a T. This is because at the bow and stern of the boat the strips will meet the plywood forms at an angle, and I needed to be sure the hot glue would still hold (white glue, for instance, wouldn't hold worth a damn here because there's no surface-surface contact to speak of.)
And it works at an angle too. I left everything to cure 30 minutes (so the white glue between the strips would cure), then undid the vise, put the strips in the vise, and whapped the plywood with a mallet to see if the hot glue would indeed fail under sheer stress, and it obligingly does. I was afraid the hot glue would rip chunks out of the strips when it came away, but it takes only a few small splinters. It's slightly worse than duct tape, but only slightly, and I don't think it will be an issue, because all the divots will be on the inside of the boat, where they won't affect the shape that touches the water.
Upshot: I will be trying hot glue with this boat. Plywood form edges get no duct tape. I will have to be careful not to put too much white glue between strips; I don't want the boat gluing itself to the forms with white glue, as this does not have the obliging failure characteristics of hot glue. I took the screws out of the faces of the forms, since I won't be using fishing line and they would just get in the way. Putting the rest of the stations on the strongback should go faster without having to do the extra screws.
Martin says I'm his R&D department.
