Thursday, December 2, 2010

Quality Plywood & Epoxy Encapsulation

I am a believer in epoxy encapsulation of wood; I wasn't always. Encapsulation entails coating the wood with multiple coats of epoxy, saturating the wood surface and building up a moisture-barrier. The moisture barrier is key for bilges and underbodies as it keeps water out of a laminate and maintains a more constant wood moisture content in timbers. Wood movement and ingress of water is what often gives wooden boats a bad name: high maintenance. Encapsulating forms a stable base for varnish and paint. We tell customers to expect a 10 year life for their paint. After 10 years of normal use they may need to do a fresh coat. That is as good as any fiberglass boat maintenance.

What convinced us of the merits of epoxy encapsulation was a visit to my friend Steven's house. He has a faering he built with his son that shows the effects of different plywoods and of epoxy coating wood.

Plywood and Epoxy Encapsulation

You can see three panels in this Faering. The darker plank is Joubert Sapele faced Okoume (varnished), the middle strake is Okoume by Joubert, and the lower plank in the photo is Shelman Okoume. All planks are finished with a Behr spar varnish.

Plywood and Epoxy Encapsulation

This is the same boat closer up to one of the tanktops. It is Joubert Okoume. The neighboring plank is Shelman Okoume. Both were varnished the same. The tank top is more degraded and molded than the plank. The tank top along the edge of the plank is perfectly clear. This strip was inadvertently epoxy coated when the squeeze out from the glue joint was spread during the clean up process. The same thing happened in the next photo: can you see where the epoxy is?

Plywood and Epoxy Encapsulation

The results? It is clear that the epoxy coated areas of plywood are making the plywood much more durable and holding up much, much better. The sheer strake is probably holding up better because it is higher in the boat and receives less foot traffic and a lower angle of sunlight upon it. The middle strake and tank tops get more direct sunlight. But the different brands of plywood may have to do with the difference between planks made of Joubert vs Shelman. It is too bad Shelman went out of business. Clearly, Sapele holds up great and Steven made a good decision putting it in as the garboard. With that said, I have also seen Sapele planked boats flake and shed paint after many years and these were boats that were not epoxy coats.

The moral of the story: epoxy encapsulation is a good thing.

Plywood and Epoxy Encapsulation


7 comments:

  1. I'm with you on this one, Clint and like you I was a skeptic. I go one further these days and coat my planks as soon as they're cut to stabilize the moisture content in case the moisture exposure during build time is higher than the more controlled storage humidity. Some people leave the lap edge raw, if it's clinker built but I don't worry about that and still have good success by sanding well before reapplying glue. Lots of other little tricks in that bag, but I won't bore you today.

    doryman

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  2. That's what I was taught, but it is really useful to see it demonstrated. Thanks for that.

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  3. I've built the chester yawl from the CLC kit and, like I assume for all of their boats, was instructed to give the Okume ply a coat or two of un-thickened epoxy, later varnished for UV protection.

    Elsewhere, I am fascinated by the pics of the beautiful finnish rowboat you have on your site & say you will soon provide plans for.. but there is no other information about them. Would really be interested in hearing about them, their design, open water stability & touring characteristics in general. That plumb bow and full length waterline are striking - along the lines of modern yacht design. Assume makes for a fast boat, but curious what you think about them otherwise.

    thanks & cheers,

    peter

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  4. The Finnish rowboat is an astoundingly fast, lightweight boat descended from the Finnish churchboats. It is LOA 19, 20, and 22' and can be done fixed seat single/double or sliding seat single/double.

    The epoxy coating is easier to know with precut parts. It can be done on the bench before construction begins.

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  5. Thanks for the reply.
    Perhaps its possible to design them as either/or for fixed seat & then an easy drop in for a sliding seat like a piantedosi ... anyway, looking to sink my building teeth into something longer and faster. i'm definitely the novice in the group, but 19' seem like a lot of boat for a single? How would you estimate their open water characteristics... would you row her in something like the Blackburn?

    cheers,
    peter

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  6. Peter, Give me a shout by phone or email. More room to reply. 19' would be for a strong, experienced rower. It would be a winner in the Blackburn. I have other rowboats as well, Drake, and two St Lawrence River Skiffs in the works. The 18' Annie has won the Blackburn and might be a better boat for you.

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  7. And, yes, all these boats can take a drop in unit.

    Clint

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Thanks for reading and please comments away!