Epoxy Tricks

[PAR]

The "cross hatch thingie" is referencing an earlier post, about long boarding the hull to find high and low spots. This previously described technique will create a cross hatched pattern of scratches on the hull.

 

Some try to fill divots, screw heads and other dings in one shot. I've never had reliable success with this method and have stopped trying, preferring to just hit them twice. I use the smash and go method. I smash a wad of thickened goo into a hole, intentionally trying to leave the surrounding surface free of goo. It'll shrink slightly when dry, at which point I come back and top it off with a light fairing compound, which will easily sand, without tearing into surrounding material. Of course, I try to do a lot of ding, holes and divots at the same time.

[PAR]

I've probably touched on this before, but just sitting down from a raw wood coating session, I thought I'd repeat. You can save a bit of trouble if you coat solid or plywood the way I have for some time. Simply, I pour straight, unthickened epoxy in a small puddle, in the middle of a panel or boat part. I spread this out easily, with a plastic applicator or squeegee and let it sit for a few minutes, soaking in. Then I come back, with a putty knife or stiff plastic applicator and holding it at a very acute angle to the surface, I mash the epoxy down, hard and in with long sweeping strokes. I drag excess around to other, still dry areas. I go with the grain, systematically covering the area I first spread it out, then again, pressing hard perpendicular to the grain. After all of this, the key part of the technique, I scrape the whole area I just applied goo, usually moving this to yet another dry area, so it can soak in.

 

The result of this technique, produces not a shinny surface, but a dull and/or satiny finish. Because no pools of epoxy are left on the surface, there's nothing for escaping air to "out gas" though, so no bubbles, pin holes, etc. Since it's been mashed into the surface, all the pores are sealed and any porous grain is too. This makes the next coats go on predictably, as you're prepping a uniform surface, instead of patches of more or less pooled goo and semi dry spots.

 

This technique is only appropriate on raw wood and doesn't work on previously sealed surfaces. There are two real keys to this technique, the mashing thing I mentioned and the let it soak for a few minutes thing. If you don't let it soak, you'll probably have dry spots, which isn't unusual on some wood species, but if you let it soak for a few minutes (5 will work), then even the most thirsty species will drink their fill and subsequent mashings, with and against the grain, will insure it's got goo to suck on.

 

FWIW . . .

[Fishman38]

Makes sense to me, certainly on horizontal and near horizontal surfaces.  Maybe a little trickier on vertical/near vertical but still do-able?

 

 

I'm in the long-boarding phase on my Ocracoke 20.  Having a little difficulty figuring out a technique for LB' ing the sharply curved surfaces, especially the concave ones such as up under the bow.  I'm sure it's going to require a different size, shape and  flexibility of the only one I've made so far which is 3x22x 1/4 inches.  Any suggestions?

[PAR]

It's all about angles, board size and it's flexibility. By changing angles and having a board flexible enough, you'll get it, but concave surfaces are naturally more difficult.

[Fishman38]

OK thanks Paul.  Just wanted to be sure I'm not overlooking an easy solution.

[PAR]

The easy solution is to say "screw it" and spray truck bed liner all over her.

[Ken_Potts]

Hmm...  If I use mold release and spray the bed liner thick enough I'll be able to pop it off the "mold" and have a plastic boat.

[Fishman38]

............uhh..what colors do pickup bed liners come in?

[Hirilonde]

............uhh..what colors do pickup bed liners come in?

Probably the same choices as the original Model T Fords, any color you like as long as it is black.

[PAR]

It depends on the type of truck bed liner you select, but there are tintable versions.

[Fishman38]

After the glass fabric is down and covered with a couple more coats of (unthickened) epoxy once the stuff is cured I have a sort of orange peel finish, which makes it next to impossible to sand to a level finish.  I use a roller, get a lot of bubbles, tip with a roller to remove the bubbles and still get the orange peel effect.  Is there anything I can do to prevent this?  The stuff doesn't seem to be "self leveling" as I had supposed

[PAR]

What speed hardener and what was the ambient temperature during the cure? Epoxy will self level, but you do have to have enough time and low enough viscosity for this to occur. To remove stipple or orange peel, you need to long board, though you can get a lot of it with careful DA work.

[Howard]

Fishman:

 

I got a lot of orange peel / fish eyes on the Spindrift. For that I used Raka, and when I inquired with them, the response was my surface was likely contaminated. Was told it could be a variety of things.......anything from propane space heaters (with oily fumes from spent propane floating in the air to settle on my surface.........that was their suggestion....not mine............to any type of oil or silicone contaminate. Wax would also do that, as in wax from amine blush. What I took from that was if you are going to do a hot on hot coating, it had best be from a non-blushing epoxy. If there is any blush at all, best to rinse with water between coats, give it a light scuff sand and build up with successive light coats. Also, if you do have blush, you must rinse. If you simply try to sand the amine blush off, you only grind it in. Rinse first, then scuff sand. As much as anything, the scuff sand knocks down the slick surface and reduces surface tension so the epoxy will flow out evenly. Usually, if you coat within 24 hours, you will likely still get a chemical bond as well as a mechanical bond from the light sanding scratches.

 

So, not sure what epoxy you are using, but check and double check for amine blush. If you run a soap and water clean and dry finger over the surface, and in reflected light, you can see a smear or smudge on your surface left from dragging your finger over the surface, you likely have some blush.

[Fishman38]

I'm using B&B epoxy (2:1), slow, which someone in an earlier post here says does not blush.  I can see no evidence of blush.  Yesterday I wiped down a section with a water wet sponge, no soap, and could see no evidence on the sponge nor on the surface that anything was being removed.  any contamination would just about have to be dust (there's always dust in the air here).  The shop is heated but with piped in hot water, no petroleum.  I have a can or two of diesel oil and such in there not necessarily tightly closed but the stuff is not very volatile.  

 

Temperature could be a problem.  I haven't watched it very closely and it could be in the low sixties F but don't think it's ever been below sixty when it was applied, but maybe afterward while still curing.

 

Another post above I think said to use water to remove blush, no mention of soap.  But if the stuff is waxy, it would seem soap or some type of solvent would be necessary.   BTW I have used denatured alcohol when wiping down to remove dust.

 

Anyway the problem now is mostly how to remove the dimples, so I guess it's back to the long board.  PAR, what is "DA work"? 

 

One more thing could be that I need to be more careful of contamination during the mixing process.  I use the same old aluminum cook pot to mix the larger batches.

[Fishman38]

Different question: I never see any mention of gelcoat on this forum.  Is there a place for gelcoat in the fiberglass over plywood build? 

[PAR]

A "DA" is a duel action sander, usually orbital.

 

The use of solvent to remove contaminates isn't a good idea, as they can leave a residue behind. This is why water with a mild soap wash is recommended for amine blush. Most home builders should consider always washing cured epoxy, simply because their building environment isn't secure enough to insure a contaminate free coating. Amine blush is water soluble, though a touch of dishwashing liquid helps. If you wash with a Scotch Brite pad, you can kill two birds with the same technique.

 

Gel coat is typically a polyester formulation, which doesn't stick well to wood or epoxy. This said, there are now epoxy comparable gel coats, that could be used, but their cost is significant.

[Howard]

The gelcoat most of us are familiar with is the white surface coat of a fiberglass boat. Helps to visualize the build process. When a glass boat goes into production, the builder first has to build a "plug", which is not much different than the plywood boats we build. They go to almost the same amount of trouble, except the interiors are not finished. After numerous wax coats, they will then "splash" a set of molds off the plug. Basically, covering the plug with a heavy fiberglass coating. Once the molds are pulled off the plugs, the plugs are often cutup and tossed in a dumpster. The molds are then polished with as many as 20 or more hand rubbed coats of special mold wax. To build the boat, you simply layup the glass schedule inside the molds. You wax the molds first so the layed up hull will be easy to pop free of the molds. It comes out perfect, with no sanding!!!! Most glass boats consist of three or more such molds......the hull, the interior pan and topsides decking. The hull is set, the interior pan is set into place and the cabin deck set on top and it is all bolted together. All that is left then is to finish it out.

 

First coat (more like first 2 or 3 coats) sprayed into the molds when laying up a hull is the gelcoat. Next is mat, then a variety of layers of glass cloth, mat, roving, etc. until the boat is done. Some will then spray a final finish coat of gelcoat which will become the boat's interior coating. Gelcoat is a polyester resin product (uses the same accelerator / hardener), which is compatible with the polyester or vinylester resins they build glass boats out of. They go to the trouble of building the molds so they can crank out numerous identical boats in short manner of time. If we wanted to build hundreds of boats identical to ours, we could do the same thing (with royalties to the designer, of course).

 

But since we are doing mostly one-of builds, we essentially build the same type of plug,then make a boat out of it by glassing it over and finishing the interior and fitting it out ourselves. In our world, paint systems replace gelcoat both on the interior and exterior.

[Fishman38]

Thank you very much Howard!  Really!  The reason I asked that question, a neighbor of mine, who has been buying, restoring, selling boats for years and has family connections to local boat stores, stopped by and seemed puzzled when I had no plans to finish mine with gelcoat, but with paint.  So I was concerned that maybe I was making a mistake by finishing with paint.  Which is also a type of epoxy if I understand it correctly.......

 

One more question: One of the selling points for fiberglass boats has always been low maintenance, meaning no re-painting.  How does paint vs gelcoat compare in that regard?  For that matter, is gelcoat an optional alternative for our builds?  Just curious, since I've already spent big bucks for paint. 

[Fishman38]

PAR, I didn't notice your reply until I had already posted the above.  And you basically answered my last question in the above.  Thanks to you also!

 

It so happens that I used a mild water/dishwater soap solution to wash my boat today.  I've also used an industrial version of scotchbrite for scuffing the surface but didn't think to use it for doing the scrubbing..............duh.......

 

Further, one of the concerns I had for sanding was the risk of getting too deep and into the glass fibers.  I got a little more aggressive with the sanding today and was able to cut through at least 95% of the fisheyes, dimples whatever without getting into the glass.  Which tells me that the orange peel effect was not as pronounced as it was on the first coat and if I'm careful about contamination and temperature the problem may go away.  For now I think scotchbrite will take care of the rest. 

 

DA, dual action.  again  duh........  I use a palm type random orbital and also a random orbital polisher with a 9" (about) custom cut piece of 80 grit adhered to the pad with a spray adhesive, which works very well.

[Alex]

One of my friends is an industrial chemist and he develops resins for fiberglass swimming pools, water pipes and many other things. He can make epoxy, polyester and vinyl ester for any environmental conditions. He said to me why don't I finish off my boat with a gel coat? I asked him if I could and he said no problem. He can easily whip me up a batch for my next boat and apply it with a roller for a much thicker and more abrasive protection than paint. Being a wooden boat, he doesn't think it would cause any problems at all. When I get to that stage I will report to you all about the findings.