I started building a cedar strip canoe and things were going swimmingly with good progress. I built the hull, fibreglass/epoxied the outside and took the hull off of the mold. Then... life happened. I had to move four times, got flooded out of one house, became a parent, etc., etc. The project inadvertently stalled for four years.

Picking it up again, I'm getting ready to glass the inside of the hull and install the gunwales and trim. But, I'm finding that the sides of the hull have curled slightly inwards making the boat narrower than its design.

What is a safe way to open it back up again without risk of cracking the hull? Should I steam it for a few hours and slowly bend it back so that the station molds again fit? Install temporary braces that can be slowly expanded? Other options?

  • I don't think you're going to get lucky and find anyone here who'll be able to give you on-point help on this, there just aren't enough members (much less active members, there's only a core group of maybe a dozen people who regularly post Answers here now with 5 or 6 doing all the heavy lifting). You'd be better off asking this on one of the large, active, woodworking forums. Oh and despite how this sounds, welcome to StackExchange! – Graphus Sep 27 '20 at 8:15
  • Now my reservations about you getting an on-point Answer aside, wood at length is surprisingly flexible. I'd be surprised if you couldn't spread this back out to the original width. Problem is there's no confidence it would retain that shape, because once wood has naturally assumed a form through drying a particular way (like when a board warps) it's notorious for wanted to return to that shape, at least to some degree, if remedial action is taken. But because of the specifics here (especially the fibreglassing) I think you could do with a person with relevant experience giving input. – Graphus Sep 27 '20 at 8:22
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    How curled in are you? A little extra curl above the waterline isn't going to make any difference in how the boat handles. It might even be a benefit, in that you've got a bit more paddle clearance. And to help with the actual question, I think the thwarts (yoke?) will push the gunwales a little bit. – Aloysius Defenestrate Sep 27 '20 at 21:47
  • It's curled enough that I have been concerned about whether there would be enough space to fit the seats in the ends. That's not quantified, but suffice it to say that in my unending stream of problems on this project, this was the first problem that I felt the need to reach out to a broader range of people on. – Rookie boat builder Sep 30 '20 at 22:23

I'm finding that the sides of the hull have curled slightly inwards making the boat narrower than its design

Sounds like your cedar strips dried out some over the years, and the wood shrank more on the inside than outside because the epoxy and fiberglass prevented movement on the outside. Heating the wood with steam will make it more amenable to bending back into place, and if you can put it back on the form or otherwise brace it so that it keeps its shape, that might work. But because of the heat involved, steaming can also dry wood out, so it might exacerbate the problem.

If the sides haven't curled too much (you did say "slightly"), it might be better to just accept it as it is. Canoes have varying degrees of inward curvature, or "tumblehome", so you could just glass the inside, fit the gunwales, and declare victory.

  • Yeah, I think that you hit the nail on the head. With the years of drying and the additional (late stage) fairing/sanding on the inside, it's shrunk the wood on the inside more than the out. There was some tumblehome in the design already, so the additional curling is what flagged my concern (seeming to make it more tumblehome than acceptable). – Rookie boat builder Sep 30 '20 at 22:17
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    I was able to put the station molds back into the boat, slightly toward the center (so that they fit) and then slowly move them toward the ends a few inches at a time over the course of a week. The hull gave, and didn't crack. The forms are back in place and I'm good to go. Thanks for everyone's thoughts and advice. – Rookie boat builder Nov 6 '20 at 19:34

The fiberglas is not going to respond to steam. I think you will need to put braces from side to side to open the shell. I don't know why it should be done slowly. I had a 90 year Oldtown canoe with cedar planks and elm bows ; 90 years , mostly in the weather and I could not see any movement . Maybe something else cause your movement.

  • The movement was probably caused by the fiberglass sealing the outside of the wood to protect it from moisture, while the bare inside was free to absorb whatever over 4 years. This different absorption rates were probably the root of the problem. – FreeMan Sep 28 '20 at 17:30

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