Wednesday, August 28, 2013

Filling and Sanding

Well it's been some time since my last update. I have been working, but truthfully - it's not very interesting. Or photogenic. But that is set to change soon, so I thought I'd set the stage.

Rough surface left by wood flour mixture.
I began the summer putting fillets along each of the plank edges. I used a wood flour mix in the epoxy to make a make a structural adhesive, but thick enough (peanut butter consistency, or "non-sagging" as the System Three folks say) to hold its shape. I used one of my yellow squeegees to scoop some into the corner between the planks, and then used the corner to make a nice, even, concave fillet.

You can see the result to the left. The wood flour and epoxy mixture leaves a surface that is rather rough.  I went back over it with a fairing compound.  This I made by adding "phenolic micro-balloons to the epoxy.  These, I guess, are tiny hollow spheres.  The resulting mixture sands more easily than the epoxy alone.  It doesn't keep the epoxy from running, though, so I also added a little silica thickener, which does sort of the same job as wood flour, but leaves a smoother surface.

Smoother surface left by fairing compound.
After that, it's been a matter of sanding everything smooth.  Finding all the scratches and dings in the plywood.  Filling and sanding.  Looking more closely at the scarf joints.  Filling and sanding.  Looking for all the screw holes.  Filling and sanding. 

I made a long sanding block from a 24" sanding belt and some scrap wood.  I used sandpaper over the rounded edge of a foam block to get into the concave fillets, and a metal sanding block with a thick felt pad, which I inherited from my grandfather, to sand the rounded edges of the planking. 

I made a frustrating discovery in the course of all this.   The sheerstrakes make a bit of a hard turn at station 3.  You may recall I had some difficulty getting everything aligned when I first glued the scarfs on the sheerstrake.  I had to cut it apart and do it again.  I tried, for the first time, gluing the joint on the boat, hoping that would keep everything in place.  It did do that.

Tools of the trade.

I had been using the station moulds as a reference for marking the scarf joints, and so all the joints fall right on a mould.  Apperently, the thinner wood in the scarf bends more easily.  In any case, the resulting join makes a sharper bend at that point.  It's not terrible.  It's not too noticeable when you just look at it.  But you can definitely feel my long sanding block rock back and forth across it.  I think when it's painted it will be easy to spot.  Hopefully I can coax it back into a fair curve when I install the interior framing along the sheer. 
See, it's not too bad.  Maybe no one will notice...

I cleaned up the ends of the planking at the stem and stern with my power plane.  Boy was that satisfying.  For once I followed my own advice and went ever so slowly.  The power plane also helped me plane the garboards down along the keelson.  I measured out where the keel will widen from 2 1/2" to 4" for the lead ballast, and planed a wider flat spot there.  Once I get the hull glassed, it will be all ready to receive the keel - the next big step in this project.