On the Mark: Repair and refinish

Continued...

This photo shows the deck at the front edge of the rear cockpit. It shows both the scratching of the varnish and the small blisters in the fiberglass which will be fixed later.

Our experience may be a bit worse than that of others, as we do not have a boat house or other shelter for the boat and it is left in the water all summer long (Late May - September). It sometimes gets pulled for cleaning. Over the winter it is covered completely and left outdoors. There does not seem to be any significant winter sun related damage. The damage seems to be primarily UV related as the transom, which faces west, and the tumble home of the sides were the worst affected areas. The top, which is covered much of the time, did not show a lot of UV damage, but was highly scratched in the ares where we climb over and get in and out of the boat. The area by the windshield which suffers no traffic still looked great.

This photo shows the fine blister pattern of varnish that is left below water level for an extended period of time. In this case it is at the waterline.

Causes of damage to the varnish

• UV damage
• Water damage - The water line is just a bit too low. The areas that stay submerged blister badly over the summer and will peel off large areas as the finish dries out. This was also experienced in the bilge. After pulling the boat out to dry for a couple of weeks, large sheets of varnish popped free. The bilge had looked fine all summer.
• Acid damage? The boat gets wiped down with vinegar and CLR (acid based stain remover) to remove the water spots and waterline grunge. Maybe the use of acid contributed to the early finish failure. The lake water around here is extremely hard due to the limestone in the area.
• Gasoline - The area around the filler and vent lost their gloss early.
• Poor surface prep - Shame on me. When I recoated, I did not sand to full scratch to preserve as much thickness as possible. I also sanded very lightly around the vinyl letters to avoid scratching them. Under some of the crazed areas, there was nice glossy varnish in several spots.

This photo shows the crazing pattern and underlying shiny varnish. This is on the side, near the transom in an area of high UV exposure.

Assess and plan the repairs

It appeared that the only way to fix this correctly was to strip and refinish. Based on the research I had done, there was no assurance that the new finish (Imron 2 part polyurethane) would be completely compatible with the varnish. It seemed that the only way to assure myself that there would be a perfect finish and no surprises was to completely strip the varnish. I did not want to do all of the prep, apply a couple of hundred dollars of finish and have wrinkles or blisters in the end.

It was also a good time to repair some damage to the fiberglass. There were some spots where the boat had hit the dock, pontoon boats, gotten hit by anchors, etc. While a light hit may not be seen or result in a slight dent, a hard enough hit results in the fiberglass separating slightly from the wood. This results in a cloudy spot or a hazy outline if it only starts to separate. The repair of this damage will be covered in another article.

There were also small areas on the deck and around the cockpits where there were tiny blisters in the pattern of the fiberglass weave. Where the glass fibers crossed, there were these tiny blister patterns. These had first appeared after leaving the boat covered in the sun in the parking lot of a boat dealer for a week (in for engine work/consulting). Of course, that week was very hot, sunny and still. This, coupled with the dark green cover, must have raised the temperature enough to damage the epoxy in a few areas. I also contacted Gougeon tech support and they said that this small blister pattern can also happen when doing dry fiberglass application if you squeegee it out too hard, leading to a glue starved joint in the fibers.

Other work to be done this spring

As pointed out in the previous two articles, the swim platform and wakeboard pylon were to be added. The cut vinyl letters for the boat numbers and "Wow" would need to come off and be replaced after refinishing. The refinishing also included dent and ding repair as well as fixing the tiny blisters that had formed at the cross weave points in a few areas.

Stripping

Lest you think that given the surface damage to the varnish, the spar varnish would be easy to strip with almost any stripper, that was definitely not the case. I tried several strippers that I had around from furniture projects and they did not do the job, barely softening the varnish if at all. Then I read the stripping section in Bob Flexner's book and went looking for a stripper with high methylene chloride content. I settled on Zip Strip Sprayable stripper. This worked very well. It stayed in place and softened the varnish. It does eat sprayer mechanisms. I went through a number of them.

Stripping is a messy, toxic process. The Methylene Chloride metabolizes in your bloodstream, creating Carbon Monoxide! When stripping, goggles, eye protection, heavy chemical resistant gloves (vinyl and nitrile last only minutes), a respirator, and skin protection are required. Use fresh cartridges in your face mask, or this is a great time to try out that new forced air respirator that you will need when applying the new finish.

Stripping Technique

Spray a roughly 2x3 foot section. Let it sit for about 5-10 minutes and spray on more stripper. At the time of the second coat, also apply the first coat for the next section.You are going for an even COMPLETE coating of stripper. Any bare spots will really mess up your scraping technique. After 15-20 minutes total, scrape off the softened varnish. Use cabinet scrapers. Razor blade type scrapers can dig in and can cut through the fiberglass. With the cabinet scraper, you can remove long strips of varnish. Make overlapping passes. There is a texture change when you go from the varnish to the epoxy. The epoxy will give more of a "clean scraping sound". The scrapings from the varnish will be yellow in color. Epoxy scrapings will be nearly white.

This photo shows the final stages of the initial scraping. The yellowed/creamy color scrapings are the last of the varnish. The pure white shavings are some of the underlying epoxy.

With proper scraping technique, the surface is nearly clean with minimal goo left behind. Be sure to wipe off any residue. Remnants will cause discoloration and softening of the epoxy. Methylene chloride WILL soften epoxy. It just softens varnish much faster. If you apply too much stripper, you can end up softening both the varnish and the epoxy. If you do soften the epoxy, it will be slightly cloudy. Scrape it down a bit and mark it with tape for later. You will need to go back and apply more epoxy to rebuild the finish thickness in that area.

Cleaning and epoxy prep

Once the boat is stripped, wash the hull with detergent several times to remove the stripper residue and wax. The wax is added to the stripper by the manufacturer to slow the solvent evaporation. A final pass with solvent (MEK) won't hurt.

Now is the time to sand out any remaining scratches or glossy spots. The entire hull must be uniformly dull prior to recoating. The epoxy will only have a mechanical bond. The reason to sand after cleaning is to make sure that no wax or other residue is forced into the scratches.

Recoating with epoxy

Roll on and tip off the epoxy, just as you did when building initially. I applied two coats, waiting for the first one to set up to a hard gel (but not yet fully cured). This results in an optimum chemical bond between the coats and avoids intermediate washing and sanding. If you do not wait long enough between coats, you will end up with a terrible case of "orange peel" texture in the finish and have to remove more of the epoxy that desired.

Once the epoxy has cured overnight, scrape the surface smooth. When I originally built, I sanded the surface. It is amazing how much more quickly the scraping works to provide a smooth surface. The photos below, show the transom getting scraped. Basically, three complete passes were required to remove all of the ripples, sags, etc. This is sooooo much faster and smoother / flatter than sanding. I really wish I had thought of scraping when I initially built the boat.

This photo shows the first pass of scraping. Note the triangular sag in the upper left corner. My roll and tip technique still leaves something to be desired at times. I am sure that some of you do not suffer from these imperfections. The other ripples and general orange peel type surface show readily under the first scraping pass.

This is the second pass. You can see that the scraped surface is more uniform and the scrapings / shavings are larger.

Third pass and ready for sanding. No hints of the major surface imperfections are left. The surface has a nice fine finish, ready for 150-220 grit sandpaper. Once again we are going for a "full scratch" sanding of the entire surface. The finish coat is to be very high gloss which will show any bumps, dents or ripples.

Next month: Other repairs, dents and dings

We are very pleased to have Mark sharing his expertise with his fellow boat builders. If you would like to comment on this article to Mark, he can be reached at "builders at bronkalla.com". Replace the at with @. (Just trying to dodge a few spammers). See Mark's great web site for information about his Riviera project.

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