Saturday, April 11, 2015
Canoe Building: Bending the Stems
A few thoughts about stems. For some reason, I had it in my mind that bending and laminating/gluing the pieces together was one step. Wrong! There are two distinct stages to it. Stage one is steaming and bending the strips and clamping them to the mold/form to allow the strips to dry into shape. Stage two is gluing/epoxying them together so that they actually form the stem.
Since there are two stems for each canoe, I actually had to repeat the steaming/bending/clamping steps another time since I don't have enough clamps to do both at once. This isn't a bad thing. When you're steaming the stems, it's going to be easiest for you if you steam them one set at a time. 2" conduit only holds one set of stems at a time, and the pipe I had actually started to bend due to the heat of the steam.
Raka Inc. Two gallons were epoxy, one gallon was hardener. This should be enough for my canoe. I debated about using epoxy for the stems vs a wood glue such as Titebond 3. Ultimately, I decided to use the epoxy since it is completely waterproof and would be more solid than the Titebond. Not much epoxy is needed. The Raka epoxy is a 2:1 ratio of epoxy to hardener, so I mixed up 50 mL of epoxy with 25 mL of hardener, stirred quickly and thoroughly for a few minutes, then started to liberally apply it to the strips of wood. One strip, slather on the epoxy, put on another strip, "butter it up" with more epoxy, then add the 3rd strip to complete the inner stem. I put packing tape on top of the 3rd strip before I started so that I'd know not to add epoxy to it. I put on another strip, epoxy, strip, epoxy, strip. Then I clamped them together firmly, but not too hard. Too much pressure squeezes all of the epoxy out and leaves the stem weak. I also added a few clamps sideways to make sure the strips were aligned with each other. That's another thing- when you clamp the strips that have been steamed, they don't require tight alignment, but when you epoxy them together, you want them to be as precise and square as you can reasonably get them.
One more note- I used blue "painters tape" to line my form/mold when I laminated and glued my stems. It wasn't a bad mistake, but using clear "packing tape" would be much better. The epoxy slightly penetrates the painters tape and makes it difficult to remove, but packing tape is impervious to the epoxy. I'll be using packing tape to line my forms when I actually begin stripping and building the canoe.