zondag 15 februari 2009

Working on rudder + centerboard

I put on the second coat on the hull las friday. I think it looks good enough, although the coat has some dust in the paint on some spots. Most of the hull wil barely be visible anyway once the hull is upright and complete with the floats. The visible parts (stern & bow) look pretty good.
When painting the first coat I made a big mistake trying to mix all the paint in one go and mixed way too much. This time I mixed some paint, painted the bottom of the hull and one hullside first (weighing the amount of paint needed for both parts of the hull) and then I knew exactly how much more extra paint I needed to mix for the last hullside. It's pretty obvious this is the way to do it. It's a shame I had to screw up the first time.

Before turning the hull for the last time I'm going to put some wax on and put the centerboard in. Below are the parts for the centerboard: sheave assembly (plexiglass + tuffnol sheaves), alu cover plate for control line exit, a bumper-stop for the centerboard made of a piece of PVC-tube filled with putty, and a cap to cover the pivot-pin made of cutting board (HDPE). I bought an antique Unimat SL lathe to experiment a bit, and the recess in the pivot pin cap was the first practical thing I made on the lathe.
Here's a picture of the control-lines and the sheave assembly. The top of the plexiglass spacers is level with the cover of the centerboardcase, so the lines will be retained. The bumper-stop is visible below the sheaves. Earlier on I couldn't decide how to finish the interior of the centerboard case, but now I had to make a decision. Searching the internet I found people telling it's absolutely NOT necessary to use anti-fouling in a centerboard case, and people telling exactly the opposite.
To be sure I put coppercoat on the centerboard and the case interior, and regretted a lot I didn't decide earlier about the finish and paint the case before assembly. It was a terrible job to get the coppercoat properly inside the case.
Although I will keep the boat on the trailer for now, it's nice to know that when I decide to put it in the water permanently I only have to antifoul the hull and don't have to worry about the centerboard and the centerboard-case.

According to the plans a washer should be welded at the end of the centerboard pivot pin and this should be screwed to the doubler. This seems to me a bit difficult solution (for instance: washer should be welded perfectly square) and my idea is it is easier and more leak-proof to retain the pin by screwing a cap over it.
The cap is a bit small. I'm going to make a bigger version.

The control line for the centerboard is continuous. The camcleat will be bolted to the side of the cockpitseat.

The rudder + case is almost ready. I used nylon m6-threaded rod instead of alu bolts to retain the block at the back of the ruddercase. Put stainless bolts on the nylon rod, just for the 'bling'.
Going to try to make my own PETP bushes on the lathe, not to save time or money but because I want to make as much parts as possible myself.

The tiller (next to the rudder) will be made of a spare handle for a spade, bought at the hardware store for 6 euro (6 US dollar). I got this tip from the F-boat forum. The tiller will possibly be the cheapest part on the boat.

maandag 9 februari 2009

First coat on hull

Primed hull is sanded wet till grit 400 (except for the bottom: grit 220).
When working with your face so close to the hull you keep on finding small spots & holes after every sanding/cleaning. I found it difficult to stop correcting but in the end decided enough was enough.

Then I put the first layer of paint on. I use 2-pack paint, roll it out and tip off with a brush. Before painting I use a tack-rag to wipe off the last dust and I mopped the floor to keep it a bit damp to trap as much dust as possible.
I used about 850 mg to cover the whole boat, much less than I thought I needed. Had to trow away a lot of mixed paint - downside of the two-pack. It has to stand for at least 30 minutes after mixing, so it's not possible to mix some extra in the middle of the paint job as you have to keep on painting wet in wet, else you''ll see an overlap in the paint job.

On the bottom there are still some sanding marks because I didn't sand it as thoroughly as the sides. The sides are not bad at all for an absolute beginner like me. Had a (very) few runs and a few visible brushing strokes and a few spots that show a very slight orange-peel-effect because I didn't sand down the rolled-on primer far enough.

Below a picture to show the gloss after one coat. By the time I'm writing this the whole hull is dull again, because I decided to wet sand out the last imperfections with grid 400 before putting on the final coat. I didn't have much dust in the paint. When painting the rudder I had more problems with dust and rubbish, but in hindsight that rubbish was probably trapped in the brush I used on that paint job. This time I cleaned the brush just before painting.
I also put the second coat on the rudder after sanding 400 grit. The hull will have the same finish after the second coat.
I was not very happy reading earlier this day a comment on Grant's blog, saying it's important the trailing edge of the rudder is no more than 2 mm thick. If I remember right my rudder's trailing edge is about 3,5 - 4 mm (4 layers C+layer in middle+ not very compact laminate).
If I'm going to try to correct this on my rudder, I'll have to do the paint job all over (+ primer). I'm tempted to leave it for now, and first try the rudder as it is.