Welcome to my blog!
I will be using this space as a journal, to keep you up to date on projects in hand, and for comments on building techniques, tools, materials, design considerations – just about anything that comes to mind in the course of a day’s work. I work alone, with plenty of time for musing, and I suspect that, like Cassius, I think too much. Perhaps this will be a good outlet for some of that excess cerebration. I hope you find it interesting.
If you have visited the news page of my web site, you will know that I have two projects under way at present. The photos show where they are now. The Grace Eileen, a 30 ft light displacement cruising sailboat, is well along, and I’ve been hoping for a launch next summer. However there is still a lot to do, most of it very expensive (spars, rigging, sails, hardware) – we’ll see. The 12 ft peapod awaits interior varnish and seats and a sailing rig – at least I can promise a spring launch for her.
Some of my time over the past couple of weeks had gone into applying epoxy resin to the peapod, and sanding it. I use a product called ClearCoat, from System Three Resins, for sealing wood surfaces before finishing with paint or varnish. It’s a bit pricey, but I like it for two reasons. One is that it’s thin enough that you can apply it with a brush more easily than regular resin. Although it is quite thin, it’s still thicker than varnish, and you might think that you could put on quite a thick coat without it running. No way! It will run and sag like crazy on vertical or sloping surfaces, so you need to brush it out into as thin a coat as you can. (On a horizontal surface you can put on a thick coat, and it will self-level to give a smooth, glossy surface.) I use cheap 2” bristle brushes to apply it in situations where a roller won’t work. These brushes shed bristles, so that first time you use one you have to keep picking them out of the resin. However, they are easily cleaned in acetone or denatured alcohol, and after the first use there is always some epoxy left near the ferrule, which glues the bristles in, so that on subsequent usage, they no longer come out. You can re-use the brushes many times before they become completely gummed up. (You can reuse the acetone or alcohol, too. The solidified epoxy settles out, and you can decant the clean epoxy for several cycles of use before it too gets too thick to work properly.)
The other reason I like ClearCoat is that it sands more easily than regular resin. You probably know that sanding epoxy is a bear. Even ClearCoat needs time to completely cure before sanding, or it will gum up your sandpaper in no time. I like to give it at least three days – more, this time of year, when my shop gets cold overnight. You don’t need to sand the first coat if you recoat within two or three days – there is no amine blush to prevent good adhesion of the second coat. I sand the second coat with 80 or 120 grit sandpaper. A random orbital sander works well.
I also use a cabinet scraper as part of this process. Even with the epoxy brushed well out, there are always some sags, and other slight unevenness in the surface. It takes a lot of sanding to smooth these out, but a cabinet scraper takes off the high spots very quickly and easily. I also use a triangular scraper like the one in the photo, to get into corners and tight spots. It also works well on the interior of the hull, where the cabinet scraper is harder to use. These don’t seem to be easy to find – if you know of a source, I would like to be able to pass it on.
Incidentally, I have seen people make a mistake in sanding epoxy. They want a smooth surface, and to get it they sand too much, removing almost all the epoxy. The trick is to build up to a smooth surface, not sand down to one. Repeated coats of epoxy, then paint or varnish, with sanding between coats, will build up the coating on the low spots, until you have a smooth surface.
I am sure that you know that the first coat of epoxy should be applied with the temperature falling. Why? Because there is always some air entrapped in the wood fibers. If the temperature is rising, this air will expand, and bubble out through the curing epoxy. You can easily remove the bubbles with a scraper or sandpaper, but this leaves tiny holes in the coating, through which moisture can enter. A second coat covers them, of course, but it’s best to avoid them. If the temperature is falling, the epoxy is drawn into the wood. The late Robb White based his whole boatbuilding technique on using this effect to draw epoxy into joints and glue his boats together.
That’s all for now. Next time I will have more about cabinet scrapers, and how to sharpen them, and more about Robb.