Transom lamination

[davidpm]

I tried laminating some 1/8" by 1" mahagony to a piece of Okume plywood as a sample. It looks great. What I want to do however is use that technique to laminate the transom and oil the wood so it looks the same as the gunnels, dagger board etc.

Doing this I'm breaking a major rule. The rule is that all wood is completly encapsulated in epoxy. This boat will be on deck most of the time, not in the water much.

What are my chances of this working if I keep it oiled up really well?

[wkisting]

David,

I'm no expert on this, but I've been considering doing something similar with my CS20's transom (laminating on thin strips of mahogany). I like the epoxy-and-varnish look, so in my case, the wood would be encapsulated, but as I was talking it over with a few folks (not on this forum), they did mention in passing that it is "not wise" to permanently epoxy on strips that would only be oiled. I believe the reasoning had something to do with the fact that, if the oil were not very meticulously maintained, you could end up with water-penetrated wood that is hard to remove or replace (i.e., not bedded in a removable compound).

Could you epoxy and varnish the wood on the transom instead? Or is it a case of having to match oiled wood elsewhere on the boat?

If you do epoxy on wood in strips (rather than one whole piece that covers the entire transom), you would need to find a way to fill the spaces between strips; otherwise, I suspect you would get moisture penetration between the strips that could be a real problem, and even if you "pre-oiled" the faces between strips, I'm not sure how you could re-oil them over time to maintain them carefully unless you left bristle-sized gaps between them.

Just a few thoughts. Other, more experienced/knowledgeable folks will surely chime in.

[davidpm]

In my test panel the strips got epoxy on the edges mostly but yes it it a little tricky.

If you do epoxy on wood in strips (rather than one whole piece that covers the entire transom), you would need to find a way to fill the spaces between strips; otherwise, I suspect you would get moisture penetration between the strips that could be a real problem, and even if you "pre-oiled" the faces between strips, I'm not sure how you could re-oil them over time to maintain them carefully unless you left bristle-sized gaps between them.

Just a few thoughts. Other, more experienced/knowledgeable folks will surely chime in.

[Garry]

You can do it. Go ahead and get epoxy all over the edges, remove the excess before it gets too hard, and plan on sanding the surface down as needed. And if you ever need to remove it, just belt sand the whole mess down to the plywood surface.

One caution - be careful about the idea that your boat will stay on deck most of the time. You are locking yourself into a maintenance problem. If you anchor somewhere for two weeks or two months, are you really going to haul the dinghy out every night? That may be your intention but it may end up being a pain in the neck.

I ended up towingthe dinghy everywhere except on long offshore trips.

Also, plan on a cruising dinghy getting banged up at the dinghy dock, on the beach, or  against a barnacled piling. It will be a working dinghy that will need to sustain wear and tear.

[PeterP]

Ignoring the fact that most so called oils have some kind of stain in them- here is one possibility for you to consider : To get the natural look of wood do varnish over epoxy. What gives varnish away is the wet look or shine factor. So to get around that hand rub the last couple of coats on with a lint free wad. Version of the French polish if you like. You get the benefits of epoxy encapsulation, UV protection of varnish, depth without the artificial shine. PeterP

[wkisting]

Peter, that's a great idea... you don't happen to have a picture of what the finished results look like, do you? Like David, I'm considering some bright trim on my CS20 and would be interested in knocking down the shine a bit if it can still be epoxy encapsulated.

[davidpm]

So what are you suggesting. Paint, epoxy then varnish.

You can do it. Go ahead and get epoxy all over the edges, remove the excess before it gets too hard, and plan on sanding the surface down as needed. And if you ever need to remove it, just belt sand the whole mess down to the plywood surface.

One caution - be careful about the idea that your boat will stay on deck most of the time. You are locking yourself into a maintenance problem. If you anchor somewhere for two weeks or two months, are you really going to haul the dinghy out every night? That may be your intention but it may end up being a pain in the neck.

I ended up towingthe dinghy everywhere except on long offshore trips.

Also, plan on a cruising dinghy getting banged up at the dinghy dock, on the beach, or  against a barnacled piling. It will be a working dinghy that will need to sustain wear and tear.

[Garry]

How do you plan to use the dinghy, as a cruising tender? What is important to you, looks, convenience? Where do you plan to sail? How much will you be away from the dock?

I can't usggest anything without some more info. From my experience, I want a good solid working dinghy that will take some knocks with little maintenance. Therefore, I would want a simple but tough paint job. But that may not be your solution.

[Hirilonde]

How do you plan to use the dinghy, as a cruising tender? What is important to you, looks, convenience? Where do you plan to sail? How much will you be away from the dock?

Important questions.  I don't see how anyone can answer detailing questions, even for themselves, without answers to these and possibly other questions first.  I love bright work, but have none on my dinghy.  It is a work boat, a tool for cruising, but that's me, and based on my answers to such questions.

[davidpm]

How do you plan to use the dinghy, as a cruising tender? What is important to you, looks, convenience? Where do you plan to sail? How much will you be away from the dock?

I'm building a SD10N. I live in Connecticut so we have a short sailing season. My friend just bought a 30' Catalina, and we take the boat out as often as we can during the week for really short after work sails. On week ends we may take a run out to Block Island or LI. I suspect that the SD will be used very little.

Special weekends when we have the time to actually go somewhere will be the main usage.

He has a daughter about 10 who maybe we can get interrested in sailing if she has access to a little boat. But most likely she will use it twice and that will be it.

Mostly I'm using the spindrift as a way to learn as much as possible about boat building. I'm leaning towards epoxy, varnish for transom, gunnels, dagger board, rudder, tiller and boom. LPU for plywood.

So yes this is to some extent a show off boat.

[PAR]

Oil coatings are not particularly effective at resisting moisture penetration. In fact, the only thing worse at preventing moisture vapor from getting into the wood is leaving it raw. Even the fanciest oils, which may have drying agents included, will only offer about 25% resistance, which isn't much, especially compared to a good varnish which is over 70% resistant or shellac which is over 80%. Good marine epoxy (total encapsulation of course) has 97 to 99% (depending on formulation) moisture vapor resistance.

The second issue with oil finishes is they need to be renewed often. In your area, you may be able to get away with twice a year, but honesty, if it sees daily sun shine, then three or more times a year is more likely. It's easy enough to apply, but does require more attention.

Lastly is the movement you can expect if glued down to a reasonably stable substrate (plywood) with epoxy. As the wood dries out and loses it's oil, it will gain moisture, swelling the fibers, straining the seams and joints. You'll likely have seam creeping in short order and something has to give, which will probably appear as cracks and checks along the grain lines closest to the glued seams.

If you do glue these little planks down, use a polyurethane or polysulfide. These will permit the movement and not try to restrain the planking, as moisture content varies.

[Tom Lathrop]

PAR is absolutely correct about the moisture/stability issue.  Whether that applies to laminations as thin as 1/8" is unclear.  When glued to a stable substrate with epoxy, 1/8" laminations will have a hard time moving very much.  Otherwise, normal plywood face plies would be in peril.  I agree that a waterproof coating will protect the surface of the nice lamination much better than an oil and be much easier to maintain.

Some like an oil finish, but a nice varnish finish, whether over an epoxy base or not, may show a beautiful depth of grain to better advantage. 

Given enough time, sun exposure and a few missed maintenance refinishes with the oil, the mahogany will probably start to craze and crack and look scuzzy.  Some oil finishes contain more solids than others and will protect the wood better but none are in the same league with a varnish or varnish over epoxy finish.

Basically, I agree with PAR.

[Oyster]

In lieu of the related matters of maintainance when using oils, I actually have had incredible success with first building up a lot of mahogany with high gloss varnish and then recoat the topcoat using satin MinWax poly or Helmsman satin or even their semi gloss. I use the satin on my sailboat and have not had to revarnish it after about 15 months. It gets plenty of salt on it and the sun hits the bow area constantly since it sticks out from under the 20 foot cover. My solid 8/4 bowsprit is also done that way and still going strong.

[davidpm]

OK so I'll nix the Penofin finish and go for varnish. I just bought the Brightwork book by Wittman.

So the only question left is I should epoxy first then varnish or start with the varnish.

What are the pros and cons.

Based on the post above epoxy is better at keeping out moisture.

[wkisting]

David,

I would definitely epoxy first, then varnish on top of that. It will produce the most durable finish, as the epoxy is much harder than the varnish and better at "waterproofing" in that regard. The varnish is needed to protect the epoxy from UV damage, which can cause the epoxy to become yellow and brittle if not protected.

I doubt you meant to suggest it, but just to be clear: certainly you would NOT want to "start" with the varnish and then epoxy over it!