Post XLII -- Another BIG SAND, and the Start of the Finish

I'm happy to say I'm getting down to the last few items before this boat is ready for paint. The last few sessions have been short and sporadic, but I've been taking advantage of the off-schedule to get done little jobs. First among these jobs was sanding the scuppers. Knowing that I'd be covering them in epoxy + varnish, I rough-sanded them with 100 grit. It was a bit painstaking doing 12 scuppers on each side, but they look much better for it, and are not so apt to catch fingers or cut hands.

Figure 206: Un-sanded scuppers

Figure 207: Scuppers post-sanding

The last and most nagging finish item was the bow. At this point, I realize there's very little I can do to make it look beautiful. The best I can hope for is a competent-looking repair job. I scarphed the gunwales back to the forward-most screws and made some short pieces to carry out to the cutwater. These short pieces were glued-and-screwed in place, and actually look half decent now that I've blended them to the rest of the gunwale by sanding. I don't have a pic right now but will try to remember to update the blog down the road. 

Figure 208: Gunwales cut back to receive new extensions

Figure 209: Extensions in place. This has been sanded since and looks decent.

In a longer weekend session I started the final BIG SAND of the boat. I had to smooth up the interior in preparation for paint & varnish. I'm going to paint below the decks for better waterproofness and varnish above. This went a bit quicker than the outside, but was still utterly painstaking. I'm glad it's done. I switched to 80 grit on the inside -- 60 grit was a bit too aggressive and I didn't want to go through the FG cloth by accident. Yet another instance where I'm glad I bought the RO sander that hooks to the shopvac. This would be a hellish job if I didn't have a dust removal machine operating the whole time. 

Figure 210: Sanding in progress. 

And finally came the interesting part -- the bottom coat. It's always more fun adding stuff to the boat than removing stuff (especially removing stuff with sandpaper, ugh)

The bottom coat is epoxy mixed with the WEST 423 graphite additive. The graphite is a solid lubricant that is supposed to protect the hull when it takes a hit. When I strike a pointy rock, the idea is that the graphite coating will help the boat slide off the rock, turning what could be a penetrating blow into a glancing blow. Not sure how this will all play out in practice, but I read lots of endorsements for the use of graphite additive as a bottom coat and decided to try it out. It was going to be painted anyway, so there's no harm in it.

Before starting to apply the bottom coat, I taped off the water line. The graphite (based on a test patch) does not thicken the epoxy very much and it *will* drip before curing. Taping off saves a lot of work cleaning up drips.

Figure 211: Waterline all taped up

The graphite-epoxy mixture (3/4 tbsp in 5 pumps of epoxy/hardener) paints on easy -- just like straight epoxy. I works best to brush from dry into wet areas, with a medium load of epoxy on the bristles.  

Figure 212: Closeup of the finish with tape still on

Just before final cure -- maybe 60min after application, depending on room temperature, is when the tape should come off. Remove it just after the epoxy tacks up (and stops running), but before it hardens appreciably. I stuck the tape down real good before starting, but I still had some seepage of epoxy underneath. The resulting line has some "hairs" for sure, but will be hidden by the paint before long.

The result wasn't perfectly symmetric. Not sure if this was my crappy attempt at marking a waterline, or some asymmetry in the hull. I don't much care at this point -- you almost never evaluate both sides of a waterline this way, except when it's under a builder's self-deprecating scrutiny in the workshop!

Figure 213: Closeup of the finish with tape removed -- note the "hairy" line left behind

Figure 214: And an overhead view showing the slight asymmetry. Oh well.

The very last thing to do before paint was to fix up my mistakes from sanding. Places where I got a bit overzealous, I ended up penetrating the cloth layer. You can see it in Figure 215, just above the gunwale. Nothing too bad, but I didn't want to leave anything to chance. I took unthickened epoxy and painted over any that the weave was showing. These areas will receive a final scuff sanding before I apply the paint. Yay...more sanding!

Figure 215: Slight penetration of the FG cloth near the gunwale. This will be sealed up

Figure 216: The hull, showing areas I painted over. These will be sanded later

Finally, I took the opportunity to put a nice round on the underside of the outer gunwales before I paint. I figure it's a good idea to get this out of the way so I don't have to worry about accidentally scuffing the new paintjob later on.  That's all for now. Next up is the paint job -- stay tuned to learn the EXCITING COLOUR that I picked!!!

No comments:

Post a Comment