Saturday, February 10, 2007

Coating All Lower Hull Panels




The forecast for the weekend was for cold, but sunny weather, so I drove back down to my main building site where the shed is located and spread out all the lower hull panels I had cut a couple of weeks ago and prepared them for the first coating of epoxy. Based on my past boatbuilding experiences, I expected this to take quite awhile, and at first planned to only coat the panels for the port hull, which I plan to build first. But thanks to Thomas Nielsen's amazing window squeegee epoxy spreading technique (http://tiki26.blogspot.com/), I found it easy to coat all the panels for the first hull in less than half an hour, so I went ahead and did the starboard hull as well.

This method is much faster than applying epoxy with a disposable brush, as I often do, or even with a foam roller. Basically, you just pour the mixed epoxy around on the hull panel in a figure-8 pattern, or swirls or whatever, estimating approximately how much you need to wet out the entire surface. Then you pull it around all over the dry areas with the rubber window squeegee, (I used a small, handheld model bought in the grocery section of Wal-Mart). After spreading it out as much as possible, you then go back over it with a foam roller, smoothing the coating and further wetting out any dry areas to ensure a consistant, even coating. It's fast, doesn't waste epoxy, and makes it easy to apply the thin coats needed as sealer coats on all the parts before assembly. Thanks Thomas!

Okoume plywood can be really beautiful when coated with epoxy, as can be seen in the above photos where it is gleaming in the sunlight. I used it before to build two Pygmy kayaks, the Coho and the Arctic Tern designs. These kayaks were finished bright inside and out. I still have the Arctic Tern, my favorite of the two, and it still looks great, turning heads wherever I go with it. I plan to enjoy the natural beauty of the wood grain in the interior of the Tiki 26, finishing it clear with epoxy and then a U.V. inhibiting marine varnish. When building a wooden boat that you intend to finish bright inside, care must be taken to sand away or erase such marks as layout and lofting lines, numbers, labels, notes and other things you may have written on the bare wood parts. On the hull panels, bulkhead station lines will be needed to correctly position the bulkheads, but these lines will be hidden by the bulkheads themselves and then the fillets. Another consideration for finishing the interior bright is the filler material you use in the epoxy to make the fillets. I prefer to use a mixture of wood flour and silica for all my fillet making, as it is strong, looks good in a natural finished boat, and is relatively cheap. For this project I'm using pine flour, which makes a very nice, light tan colored fillet that blends well with the color of Okoume.

These hull panels were still a bit tacky at sundown today, and the temperature will probably fall to near freezing, but with more sunshine expected tomorrow, they should be completely cured by mid-day. I won't try to sand and second coat them right away. Epoxy sands much better after it's had a few days to cure, and besides, there are other parts I can work on, like the upper hull side panels.

4 comments:

Kim Whitmyre said...

You are making way, Scott! Excellent. As the Chinese say, perseverance furthers!

I scraped my rubrails of their flaking varnish last week, and painted them! No bright exterior wood will be left before long: too much maintenance. The bright interior is a good idea though, as others have pointed out: makes it much easier to inspect the hull over the life of the boat.

Scott B. Williams said...

Thanks Kim.

You're right about the maintenance of exterior brightwork. I don't plan to have any. Like you in Southern California, we have too much sun here for too much of the year to keep brightwork looking good. If I were building some kind of classic monohull, that might be different, but to me these Tiki catamarans look great with everything painted.

The bright interior will be easier to inspect, and as Glenn has pointed out, it's good for morale to see natural wood down below when you're far out at sea surrounded by water.

tsunamichaser said...

Hi Scott,

The plywood looks great once coated doesn't it! I hadn't thought about the inspection opportunity of clear finish. That's a plus. I don't plan to do anything further beyond the epoxy below the bunks. I looked at my interior the other day thinking about a clear coat. I have pencil lines and some notes too. As I'm not building a yacht I may finish it with a satin varnish and enjoy being to see the sweat I put into building. SystemThree makes a sprayable waterborne clearcoat that I may try,

Thomas

Scott B. Williams said...

Thomas,

I wouldn't worry about the marks that are already there. They probably will be hardly visible anyway, especially after the boat is fitted out. I plan to make lots of hanging canvas pockets, net bags, etc. for my interior, so a lot of interior surfaces will be covered anyway.

I got into the habit of getting rid of marks on wood panels when building my open boat design, the Mississippi Backwoods Drifter for paying customers. On a small open boat like that, any such marks would be visible and be a detraction.