Refinishing coamings--the fine points

[mcqmga]

Guys- Sorr y - Just read greenlake's suggestions on repairing screw holes with "epoxy and wax thread" thread !
!@@#$%^&&*9!!
Bob

[GreenLake]

Just to mention that, I got that suggestion from K.C. who got it from...

[K.C. Walker]

… West System, from one of their many publications.

[tc53]

Hi again. I've gotten the bench seats, thwarts, and coamings all stripped, and I am in the process of sanding in preparation for refinishing. In going the epoxy envelope route, I will probably go with System Three, as it is available within 90 minutes of my rather remote location (MAS is six hours away, near SF). GreenLake, you mentioned using one quart of resin, along with the required hardener, was a little more than enough to do your coamings and thwarts. But with the addtion of my two bench seats, I would assume I will need more. Do you think two quarts will suffice?

Unfortunately, one of my bench seats split completely down its length during the stripping/sanding process. It is a clean, bevel-type split that fits back together perfectly, so I plan to epoxy both pieces together before I do the finish sanding and refinishing.

Getting back to my previous question about how the "shelves" the outboard and aft edges of my bench seats rest on are mounted on wall of the side floatation tanks (just through the FG, or that and into a wood backing or carlin of some sort), I am uploading some pictures:

Side Floatation Tank A

Side Floatation Tank A.jpg (41.1 KiB) Viewed 20154 times

Side Floatation Tank B

Side Floatation Tank B.jpg (46.9 KiB) Viewed 20154 times

Side Floatation Tank C

Side Floatation Tank C.jpg (46.38 KiB) Viewed 20154 times

I am not sure how any sort of backing carlin could have been installed during manufacture in this tank, so I am thinking the mounting screws just go through the FG wall, but I would welcome any insights/advice about this. Several of the original brass screws have sheared and I want to make sure these "shelves" are solid before reinstalling the seats.

Thanks!

[GreenLake]

On coverage: the official word is in Appendix A of this document: http://www.systemthree.com/reslibrary/literature/STR_Epoxy_Catalog_web.pdf.

For the process of coating wood, see this overview: http://www.systemthree.com/reslibrary/literature/Outdoor_wood_finishing.pdf and for a more detailed brochure covering fiberglass lamination, see: http://www.systemthree.com/reslibrary/literature/The_Epoxy_Book.pdf (Except for the fact that SystemThree epoxy products are available pre-formulated (that is you can get thickened and putty like epoxies for gluing, filleting and fairing as separate products and don't need to mix your own) you might also look into the West System documentation, they have some great instructions.

[K.C. Walker]

There is no problem with shipping epoxy. I live close to four different distributors of marine epoxy and I still get it shipped in.

[GreenLake]

What K.C. says about shipping, fwiw SystemThree is on your side of the country, and they ship direct... but I get it that sometimes you'd like to go have a look at things in a store first.

On whether there is any wood backing the screws. My money is on yes. It's not that hard for a builder to glue a strip of wood in the right position before enclosing the tank. The fiberglass really doesn't do a good job of directly holding screws (other than for non structural trim pieces). I don't know what the proper name for such a strip would be, because unlike the carlins (wood pieced behind the coamings placed at the edge of the cockpit opening, these strips aren't part of traditional wooden hull layout. For example, I don't know if they'd be called stringers if they aren't part of the outer hull.

If you take off the wooden strips shown in your top image you should be able to probe the holes and verify whether they have a backing piece behind them. (If you hear a "thunk" when you pull the last screw, it's time for inspection ports -- I do think that they would have glued in any backing strips). Actually, fitting some large diameter 8" if you can fit that much, otherwise 6", would be something I'd recommend anyway. You would be able to view the condition inside the tanks and fill them with soda bottles, pool noodles etc. which act as backup in case the tanks spring a leak. Should your tanks have foam, it would be a good idea to remove. If it's not waterlogged already, it will be when there's the smallest leak.

Also, in your top picture, if there's a carlin behind the coamings you should be able to probe that easily and also get an idea about how firm the wood is -- a few posts above we were discussing how to restore these with epoxy. With inspection ports you'd be able to make sure that neither carlins or backing strips have been attacked by dry rot -- on my boat, there's at least one crumbly section, so the next time the coamings come off I may be looking at replacing some of all of them.

[tc53]

Thank, K.C. and Greenlake, for the very helpful responses. I am driving down to Redding, CA (about an hour away) on Monday anyway, and there is a System Three distributor there, so I will probably pick up the epoxy then. As I recall from the earlier posts to this topic, it should be Clear Coat, correct? Along with the appropriate hardener. I am assuming I can use it (along with a little filler to thicken it) as well for the gluing and rejoining I need to do.

Greenlake, I think the inspection ports are a great idea. Thanks for the suggestion! The transom and bow compartments both have a lot of foam pieces (still nice and dry, thankfully), so I would not be surprised if the side tanks do as well.

I am sure I will need more advice as I proceed with this restoration (still planning to repaint the cockpit and underside of cabin top), so I will be posting more questions. Thanks again.

[GreenLake]

For "casual" gluing, that plan should work well. Clear Coat is a bit thinner than SilveTip (which is the laminating epoxy for that brand) so that it can be applied more easily and evenly for coating. Therefore, it might need a bit more filler to bulk it up, but the result should still be plenty strong. I think you are unlikely to have a situation in this project where you really need to optimize your choice of epoxy for holding strength. And yes, why not use a little of what you have already.

On the other hand, epoxy lifetimes being generous, I always like to have some GelMagic in the caulk-gun cartridge around the house. I regularly find small things to fix for which epoxy is the best glue. If that is your experience, you'll appreciate the no-muss, no-fuss application via the self-mixing tip (you'll need one tip for each job).

Over the years, more than half the GelMagic I've used probably has ended up somewhere else than on my boat. The only thing is that the storage temperature should not be less than room temperature (70F) so not something to keep in the garage.

[tc53]

Thanks, Greenlake. The GelMagic is tempting (and yes, it would be handy to have it around). One description (Amazon) said it cures to a "tough opaque white solid." I could not find that spec on the System Three site though. I would not want this "opaque white solid" showing through what I hope will be my beautifully refinished mahogany seats and coamings. Depending on how my coverage calculations go (assuming I'll have some extra anyway), I may just go with the thickened Clear Coat this time around for the glueing, crack repairs, and screw hole restorations.

[GreenLake]

I don't see where they get the description as a "white solid". When I read "white solid" I'm thinking "MarineTex" or similar products, but they appear to have actual white pigments mixed in. That's not the case for GelMagic.

It's very slightly amber in my recollection (pale honey) and opaque in a milky kind of way. Definitely still translucent. But I doubt that it would show very visibly if you had a narrow glue joint viewed edge-on, and not at all in cases, for example, where you had a bit of overspill around the glue joint that you wiped off (leaving a very thin layer).

To make any gaping joint blend in more, you'd might experiment with mixing the epoxy (whichever you end up using as glue) with a bit of sawdust (sanding dust) from the same wood. In any case, if you are going to work to exacting standards, you are best off making a small test piece to verify that you got the process down.

To give you an idea, I found a messy sample I had lying around and took a picture. In the top half, you can see a raised ridge, that one does look very strongly milky as the light hits it. In the bottom half (you may have to scroll) you can see a gaping joint, part of it is filled, and part of it is only partially filled. The effect in one case a bit like tapioca, in the other you can see a bit of the amber coloring surviving. (Image is magnified at least 200%).

Over the entire surface there's a thin, but still substantial film of GelMagic of varying thickness, and you can see it's hard to impossible to tell it's there in the picture. It's just not opaque enough to show up in very thin to medium thin layers -- once you add some layer of ClearCoat and whatever varnish you are using, I predict any accidental thin layer of GelMagic will be invisible.

GelMagic on soft wood. Magnified. For scale note the wood grain.

DSC08302-crop_1024.jpg (92.54 KiB) Viewed 20137 times

[JPM01100]

Hi ,
I'm trying to find out the dimensions for the mahogany coamings on the DS 1. I find nothing online, but in a Daysailor.org Forum I reasd that you might be willing to post the dimensions or a template for the coamings.
Might you know where I can get the info needed to build DS 1 coamings?

Fair Winds,

Loose Lucy

[GreenLake]

For the floorboards there are patterns that people have been sharing. For the coamings, there seems to be less data out there, but I recall seeing that someone mentioned he could get some measurements. My suggestion is to locate that post in the Wood coamings pattern thred and send the poster a PM to get their attention. Otherwise you'll need to take your chances that the same person also follows this thread.

I can't help out, unfortunately; boat is offsite at the moment.

[tc53]

Okay, with all of the coamings, thwarts, and bench seats now stripped, repaired (broken transom coaming and split bench seat) and carefully sanded (and with a very sore shoulder!), I am ready to begin finishing. After reading up on the epoxy encapsulation method on this forum and on the System Three site, I plan to encapsulate two coats of System Three Clear Coat followed by two coats of WR-LPU. In both cases, will two coats be enough?

Greenlake, with your "nail bed" method for the coamings, did you apply one coat at a time to each side, flipping back to front, then back to front again? Or just complete the required coats on one side before flipping to the front (exposed) side?

Am I correct in assuming that with the Clear Coat applied first I do not need to use the primer before applying the WR-LPU?

With both the Clear Coat and the WR-LPU, the System Three literature says no sanding is necessary between coats (as long as they are applied within the specified time limits). Has this been your experience? The literature also says WR-LPU may be thinned up to 20-30% with clean water. Is some thinning advisable?

Thanks.

[GreenLake]

I would go three coats for the epoxy and four coats on the LPU. (No primer needed for the LPU over epoxy). You really don't want to be miserly with the number of coats.

The point of the 'nail bed' is to be able to do both sides in one pass and have just a few pin-point dimples on the back side of the parts where they rest on the nails during curing/drying. Those are easily sanded flat later.

As long as epoxy is in the so called "green" stage, the spec will tell you how long that lasts at each temperature, the new layer of epoxy will form a chemical bond with the preceding one. That's why you don't need to sand. As epoxy does not evaporate anything while curing you can add new coats while the epoxy hasn't finished curing.

For the LPU, there's an initial brief phase where the solvent (water) evaporates, followed by a long period of curing to final hardness. So give your parts a good week before using them hard. But you can recoat much sooner.

Need for thinning depends on the temp and humidity. When you do the epoxy, give a single (generous) coat on a piece of plywood. Then, while waiting for the second and third layer to cure on the real parts, play around with the LPU on that sample piece. You want the LPU not too runny, but you want brush marks to level. A sample will let you try different degrees of thinning, and you can figure out whether your brushing technique works.

Be sure to get high quality synthetic brushes.

For the coamings I brushed on the LPU. On the hull, I used the roll and tip method, but I think that's overkill for the smaller parts. I did not have problems with visible brush strokes.