Barrier coat or Epoxy for coating bare wood hull

[ajay73]

Scubaseas, I called LBI and they said that using vinyl ester with CSM would work good. They had no reservation with that suggestion.

[ajay73]

An update as to using Interprotect 2000E. I called Jamestown Distributors and asked them if using 2000E would be OK as a coating. The person I talked to said don't do it. That they had bad experience with that approach. So I called Interlux tech support and their response was that it would be better than epoxy because of their platelet technology. Not surprising that Interlux would say it's OK and recommended. They're in business to sell stuff. I'm surprised at the response from JD. I sure would have thought it would be OK. I mean it is epoxy after all.

[ajay73]

Ken Fry, since I'm sensitized to epoxy I've use a few gallons of vinyl ester in deck repairs on my Catalina 27 and the product works just fine. No failures, no health problems( I do use a respirator). From everything I read it's better than poly ester but not a good as epoxy. And it is good a preventing water absorption. My experience is that it adheres to plywood pretty good. And my reading says it has decent flexural strength. Boat flex but enough to break a vinyl ester bond? My experience is that it is not much different than working with poly ester.

[LakeSuperior]

Originally Posted by Ken Fry

...

Personally, if I were building a small lapstrake dinghy, and were not concerned about weight, I'd do it as a traditional wooden boat.

https://www.clcboats.com/forum/5/thread/14408.html

I second this suggestion and would use traditional materials like eastern white or western red cedar. Strong, lightweight, and very rot resistant.

I would then simply paint it using Sherwin Williams industrial alkyd enamel tinted to whatever color on the exterior and varnish the interior.

For your use case this is all you would need.

[ajay73]

I stopped to see a guy whose building a 24 foot lapstrake sailboat. We talked about what I was doing and we came to the conclusion that just several coats of a top quality varnish inside and out would work for the boat. May be the best approach.

[LittleWing77]

Originally Posted by Jim Cate

Have you succeeded in doing this? And if so, how did you avoid voids at the roots of the strake joints?

That's what I was thinking, too, Jim. I'm not a fan of lapstrake construction in the first place (sorry Ajay, no disrespect meant), but then I was trying to envision the hypothetical lay-up and I couldn't see a way of not having voids.

So Jim, I have the same question as you.

LittleWing77

[LittleWing77]

Originally Posted by Ken Fry

Jim, Jim, Jim. I could have the inside of that properly glassed (to be finished bright) in less than two years of full time effort... if I hired a helper... and didn't take time to eat. No big deal. Of course I am insane, which is a huge help.

No, Ken, you're a prissy, sensitive twit. You said so yourself.

Of course, that means you're right at home on this Forum!

LittleWing77

[LittleWing77]

Originally Posted by ajay73

...we came to the conclusion that just several coats of a top quality varnish inside and out would work for the boat. May be the best approach.

YES

[Ken Fry]

Originally Posted by ajay73

I stopped to see a guy whose building a 24 foot lapstrake sailboat. We talked about what I was doing and we came to the conclusion that just several coats of a top quality varnish inside and out would work for the boat. May be the best approach.

Perfect! I hope you have fun with your new boat.

[Ken Fry]

Originally Posted by LittleWing77

That's what I was thinking, too, Jim. I'm not a fan of lapstrake construction in the first place (sorry Ajay, no disrespect meant), but then I was trying to envision the hypothetical lay-up and I couldn't see a way of not having voids.

So Jim, I have the same question as you.

LittleWing77

I didn't use to like lapstrake, but do now. It's partly the old-fart/old-methods match. If the intent is to cover the inside in cloth, then frameless construction makes things feasible. With any framing, ribs, etc, it becomes pretty insurmountable.

So you make some temporary molds. Then each plank is rounded over before putting it in place. The the filets are put in so that the filet curve and the round overs are tangent and form s curves together. Put the cloth in dry and on the bias, and get it fitted well (i.e., about perfectly) before wetting it. The wetting must proceed in one direction without any gaps -- I think it would be nearly impossible to have two people working. Then wet it using mainly a brush or roller, (so you are not puling on the cloth) and wait to squeegy til the resin is getting a little thicker. Curse frequently. Resist the temptation to fill the weave with the first epoxy coat. The glass should be clear, with no little white spots, but the weave should be visible and evenly so. With the epoxy partly cured but still green, then roll on a filler coat or two or three. 6 planks per side is my limit, and I prefer fewer, partly because I like the look better, and partly because its easier.

The cool thing is that the laps lock in the quasi compound shape, so the boat is stiff without any internal pieces (the eggshell principal). That is unlike a simple stich and glue pirogue or skiff, which have decidedly adjustable rocker, etc until you add thwarts, etc. (It is also unlike some old lapstrake runabouts, where the macro compounding effect disappears in the aft 2/3 of the boat.)

The rowboat in the picture is 67 lbs -- very light for a 17 foot rowboat. I did a similar sort of thing with a kayou, which at 12 feet was 19 lbs. (Metallic blue on the outside, bright okume inside.) The kayou was glassed everywhere on the outside, but only on the central 1/3 inside, where it could be subject to abrasion.

Below the waterline I ditch the laps, in the interest of lower wetted surface.

[LittleWing77]

Originally Posted by Ken Fry

....frameless construction makes things feasible. With any framing, ribs, etc, it becomes pretty insurmountable.

I forgot that about lapstrake (no frames).

I've only done some amateur carvel-planking projects as part of some wooden boat-building courses I took, so I guess not only do I have a bias; I have a blind spot.

Thanks for the cool explanation, Ken. I can visualize it now.

Warmly,
LittleWing77

[Cadence]

Originally Posted by LittleWing77

That's what I was thinking, too, Jim. I'm not a fan of lapstrake construction in the first place (sorry Ajay, no disrespect meant), but then I was trying to envision the hypothetical lay-up and I couldn't see a way of not having voids.

So Jim, I have the same question as you.

LittleWing77

Having the boat up side down might help. Gravity and laying up , in essence overhead, is damn near impossible.

[Ken Fry]

Originally Posted by Cadence

Having the boat up side down might help. Gravity and laying up , in essence overhead, is damn near impossible.

Yes, it's essential, sort of: The inside is done with the boat right side up. The outside with the boat upside down.

The outside is much easier: at least tension on the cloth tends to put it tighter to the wood, whereas on the inside, it the opposite. Even so, the outside is not entirely easy-peasy, because any tension will cause voids at the laps. Roughly, I'd say the inside is twice as hard as the outside, even with gravity helping in each case.

Far easier, and something that some people do, is to cover the planks with glass on both sides first. (Seems like cheating to me) Then you either leave the filets (in and out) bare, or tape them with bias cut cloth. On the outside, you can tape and the scrape and fill get things smooth. But on the inside, you'd have to paint, if you did that.

I am probably a sissy, but in superlight construction, I don't like to leave the fillets uncovered. Much of the strength of structures like these comes from the surface: two 1/4" pieces of ply, butted with epoxy goop in between and then covered in six oz cloth in and out test as well in flex as a well-done 8:1 scarf. Without the cloth, a joint like that breaks right at the interface between wood and epoxy with pretty low forces. Bolger or Payson did some testing, if I recall.

When I have had to put cloth on something overhead (usually because of some planning screwup on my part) wetting the wood... then and waiting an hour or so, saturating and squeegying the cloth on polyethylene, and then trying to roll the cloth on with a foam paint roller has worked maybe up to a couple square feet at a time, or maybe 15 feet of tape. Again, it is a task that goes better with a certain amount of cursing. Once the cloth is in place, some of the same forces that geckos use to walk on ceilings come into play.

[Scubaseas]

You can buy veil mat which is 0.1 oz and lays down easily. You can also readily buy 3.5 oz cloth which also will easily follow your contours.

[Ken Fry]

Originally Posted by LittleWing77

I forgot that about lapstrake (no frames).

Traditionally, lapstrake boats are framed, but usually don't have stringers. (Now, there are all sorts of variations from no framing at all to some, to a lot.) Traditionally, the frames went in after the planks were riveted together. The process seems backwards, and like torture, but if you go into it knowing that it will take some time, I suppose it could be fun.



My process might have been stolen partly from Tom Hill and partly from the CLC people... although I don't really like the "Stitchlap" (CLC) process, on principal. It probably works fine, but I'd rather not remove material right at the laps, which serve a stringer function, and are a potential hinge point. This is all gut feel, without any really serous thought behind it. Their method is almost certainly just fine, and certainly makes things easier, because the planks almost snap into position. (I my construction, a tiny difference in overlap from one side to the other can make a boat decidedly crooked.

Oh, and THIS JUST IN!! I believe my wherry is 57 lb, not 67. (I think... when I have nothing else to do and have the shop space, I'll weigh it again.) I remember comparing it to an Annapolis Wherry (one of the CLC boats that's quite similar) and being happy that it was lighter. (The AW is 65 lb) .