Well, I recently launched into building an ultrlight canoe
http://gaboats.com "snowshoe 18". After cutting 3/8"x3/8" stringers, I'm finding this is closer to basket weaving than boat building 8) Anyways, cut out the strips, but they are so thin that any knots at all caused a break in that spot, not a huge issue, the plans said I would probably have to scarf them, I've just never done it before. The plans say 10:1 ratio, so with 3/8" wood, that's about a 3" overlap. I think I get how to cut the angles. I am working with thickened epoxy that came with kit as a glue. with pieces that small, and epoxy, should I just sqeeze the pices together, and then set them down to dry? I'm thinking they are so small, any clamping would be too much pressure. Hoping for lots of advice, maybe I should have just killed an old growth tree....
No need to kill old growth trees for canoes. Save them fer the big boats
With thickened epoxy, 2" spring clamps provide plenty of pressure, and the silica/wood flour/whatever else thickener will keep enough gap for the epoxy to make a good joint. For the scarf joints I do, I use a 8:1 ratio. To cut the angles, I use a miter saw and a 90 deg block against the fence. I don't recall the angle I used, but I think it was 5 or 6 degrees. I also had a special miter box set up at one time, but found the miter saw faster and more accurate. And I have no patience.
Just my .02 worth :wink:
Brit
Is it the cutting of the scarf joint itself or the joining of the two pieces with epoxy.
If the latter, I've used a little jig that keeps them aligned side to side while overlapped. I then drilled a pair of small holes for brads to go thru both layers of the overlap. Laid the pair on a piece of plastic wrap with the epoxy on the joint, wrapped one layer over the top and tapped the small brads inplace after coating the brads with vaseline.
This way they strips are in alignment, the brads keep them aligned while the epoxy sets and can just be pulled out easily with a pair of pliars when the epoxy has cured. The plastic wrap keeps the epoxy contained so it doesn't get on another surface and get stuck.
As far as cutting the scarf joint, I generally use a plane for thin stock with a number of the pieces set into a tapered jig and then cut a bunch of them at one time. I clamp down the bunch with them tightly held to the jig. The jig is just two tapered wedges attached to a base that allows for the strips to be held flush together.
The plane is run down the edges of the strips on an angle with the edges of the jig being the bearing surface for the sole of the plane.
Harder to describe than actually doing it.
That is just one approach that works for me. Others will have good suggestions as well most likely.
Good luck!
8:1 scarf ratios should be the lowest used and reserved for larger gluing surfaces, like wide pieces of plywood or dimensional lumber. The smaller the part needing a scarf, the longer the scarf ratio should be. 10:1 and 12:1 are very common on stringers, because they are small in dimension usually. The location of the scarf is also important. It should be across the bend, not with the bend. This way the loading, from bending will not work against the joint, trying to open it.
A lot of folks pin the scarf with brads or drywall screws. I usually rig a "U" shaped box, that is slightly wider then the assembled scarf, then dry assemble the joint, using a tapered wedge to hold it together, which is driven against one of the sides of the box, squishing the joint closed. I then mark the box and stock with a few pencil lines so it can be reassembled in the same position. You can use a couple of pieces of scrap wood instead of the box, just screw them down on the table with a small gap that can accept the wedge.
I use clear polyethylene plastic (cheap painter drop cloth stuff) inside the jig, to keep the goo from sticking to anything. I also use a set of clamps to hold the two pieces directly on the lines I made during the dry run. Butter things up, assemble, align the marks, clamp the two pieces so they can't slide past each other then lightly tap in the wedge, until you have good squeeze out all around, clean up the oozed out goo with a putty knife, then let it sit.