BLISTER REPAIR

Upon removing Hullabaloo from the water for the 1st season, I discovered a rash of blistering. With too many projects already on the list for the 2008 winter season, I quickly decided to temporarily ignore the problem and deal with it the following winter season. Well, we're now here and it's time to tackle the problem.

Hullabaloo came out of the water on October 13 and made its way into storage. Knowing I was planning on taking on the blistering this season, I decided to go with indoor storage so that work could occur over the winter months. Luckily I was able to get inside. Pier Milwaukee is limited on indoor storage, but they managed to squeeze me in.

The boat is tented in within the building and I installed a simple exhaust system to keep the dust out of the rest of the building for the duration of the work.

After doing some research, I decided to remove the bottom paint and gelcoat using a sandblasting process. The bottom paint is VC-17. After beginning the process, I discovered that there was also an older paint system below the VC-17, but I do not know what the paint system is. It does not appear as though there was ever a barrier coat applied, so I obviously did not need to worry about removing a barrier coat system.

The blasting media that I have used is Starblast. West Systems recommends Black Beauty but after talking with a local contractor who has done this type of work, they felt Black Beauty was a relatively aggressive media for this application. They recommended Starblast. The other item that I found in doing research on the type of media is that you do not want to select a media that will fracture upon hitting the blasting surface as the fractures can become embedded into your final product.

The VC-17 paint came off almost effortlessly. The bottom paint below the VC-17 took a bit more effort to remove. I figured out towards the end of the process that it is important to have a fresh nozzle in the sandblaster. The nozzle I was using was worn. I replaced the nozzle with a new 5/32 nozzle towards the end of the paint removal process and was surprised at the difference it made.

Once the bottom paint was removed, it was on to the gelcoat. There are basically two options for opening up the blisters. When there are a manageable amount of blisters, they can be individually drilled out using a countersink bit. In my case, there were literally thousands of blisters over the entire hull. This meant either countless hours of grinding each blister out (and hoping I did not miss any) or removing the entire gelcoat to open up the blisters. I have chosen the option of removing the entire gelcoat below the waterline.

My initial thought was to sandblast the gelcoat off. I realized quickly that this is not as easy as it sounds. The gelcoat is a rather dense material whereas the fiberglass below the gelcoat is much softer. The gelcoat takes a considerable amount of time to sandblast through and, once through, it is almost impossible to not gouge into the fiberglass layer, leaving an extremely rough surface.

I've disussed options with a few guys at the yard for removing the gelcoat. Most everyone seems to agree that sanding is probably the best option. I've decided to use a pneumatic board sander. I experimented a bit tonight using 80 grit paper. It seems to take quite a bit of time to work throught the gelcoat with this grit. I'm going to attempt tomorrow to us a 36 grit to get through the majority of the gelcoat and then finish off with an 80 grit. More to follow after tomorrow....