Stiffening up!

Yay! Back in the boat building game :).  So progress has been slow, but now I'm back on my feet I've picked things up again.  I'm now almost to the point where the boat can become a 3 dimensional thing so it's getting exciting, but let me back up and tell you whats been going on.

Having cut the boards to shape -initially with the circular saw, but I found this not to be too precise, despite what the books tell me.  The circular saw I have is probably a bit meaty for this bit, as you're supposed to be able to cut fair curves with a shallow setting of a small saw, but I was nervous and just stayed a few mm outside of the lines.  I suppose this was good because I found it takes almost no time at all to bring this right up to the pencil mark using my trusty block plane.  Taking a full 5mm off the plywood took me about 20 mins for the full length of the boat which, using the plane, can be controlled really accurately so highly recommended!

With the boards fully cut, the next job was to move on to the sheer clamps.  Sheer clamps are the name for the stiffening applied to the top edge of the side panels (in other words, they are inside the kayak, but on the joint between side and deck).  These are made of 1inch x 3/4 inch lumber.   (An aside here - you'll notice I've used imperial and metric measurements in the same article - deal with it, I'm British and we're seriously confused about our units - I use miles, feet/inches for height, grams for pasta and small distances in millimetres :).

Like the plywood, I needed to make the sheer clamps almost 16ft, and I was given 10ft lengths - time for the scarf joint to come out again!  In plywood, by far the easiest way to make this joint is to stack the wood into a ramp and plane it with a bench plane.  In lumber, you could do this, but it'd be hard work.  I decided to use my circular saw (Actually, I was going to use my table saw, but then I realised it was propping up the bench that I've been using to build the kayak, so durrr).

Scarf joints in lumber need to be 8:1  (12:1 if you're going to be making something critical like a mast or spar).  In other words, for 1inch lumber, this needed to be a 12 inch long diagonal cut.  First, I found 2 pieces of wood that I could use to make up a jig - 1 was the same height as my lumber, so that I could rest the wood next of it, both pieces being on top of the other part of the jig.  (I did have a photo of this, but I can't find it - will put it up if I do).  The idea was basically that the circular saw would sit flat on top of my piece of wood, cutting through the lumber next to it.

This worked ok, but I found that simply holding the 10ft long piece of wood was not a good idea when cutting - firstly because I don't like having too many things to do when playing with circular saws, but also because the wood tending to move slightly during the cut and thus shorten the length of the cut, messing up the angles.

The solution was to butt up a sacrificial piece of wood on the other side of the lumber, such that it was sandwiched in place and could not move.  The only thing to watch is where your nails are going so you don't send the saw through them.  Anyway, with this modification, everything cut much better.  A small application of epoxy and some time, and voila!  sheer clamps.

The next job was to then attach them to the side panels.  Fortunately I read the book at this point, and it helped remind me that by doing this, I was choosing which panels would become the outside of the boat.  Make mistakes slowly!  Anyway, I selected the best sides and after applying parcel tape to the top edge to prevent any stray epoxy getting on the wrong side, I set up for gluing.

This is the first part of the build which really calls for clamps.  I have about 14 spring clamps, 4 g-clamps and 2 bar clamps, which was just about enough.  G-clamps and bar-clamps are better because they noticeably apply more force, but the spring clamps are cheaper and easy to put on when the wood is sliding about on epoxy.  I've also heard you can make your own clamps by using pvc piping if you need more.

I was pleased with my epoxying, as much because I guessed the quantity of epoxy bang on - 1 full pump of resin, 1 full pump of hardener plus about 4 spoons of silica micro balloons was fine.  The sheer clamps need to stick up about 1/4 inch proud of the panel (so they can be planed at an angle later) so I marked that all the way along in pencil, and then used a brush to paint the epoxy onto the panel inside the lines.  After that, it was simply a clamping up job.  This was really nice, as I did it again 2 days later for the other side of the boat!

My next task is to drill holes along the (correct!) edge of the lower panels ready for wiring them together.  I also need to do the same for the upper panels (the ones with the sheer clamps on).  The bit after that is really exciting - I get to assemble the boat!  This is odd because stitch-and-glue boat building means that you get to do this whole bit in an hour or so, after which the boat is fully 3D, flat panels no more!  Due to limited space, this'll probably mean reconfiguring the garage again so the kayak can sit on the trestles, but at least I'll get my table saw back!