Sailboat bottom restoration | Part 1: Sanding

Sailboat bottom restoration | Part 1: Sanding

Warning: This blog post is about DIY boat refit. Perhaps in the near future we will be back in the water, which might mean sailing stories from the eternal Ionian archipelago. In the meanwhile, we find ourselves up on the hard, in the pequliarly immobile sailboat, where the refit continues. So hang in there, if sanding and coating a boat’s hull is not exactly your thing – something else is coming! But if you’re into DIY on a boat, by all means keep reading. Just to make sure, though – this is not meant as a how-to for anyone contemplating on a similar project, it’s just our own experience of doing it. Feel free to ask more, if you’re interested!

Last time I wrote about the surprise our boat Aina had in store for us. We had planned a quick stay at the boatyard to replace the seacocks and the adjacent plumbing, but alas, that sort of thing is just never going to happen with us and this boat. Something more pressing was discovered the moment Aina was up on dry land.

Our boat’s bottom has been osmosis treated over a decade ago. The original 1980’s gelcoat was not completely waterproof, and who knows what kind of waters this middle-aged lady has sailed and anchored in during her life, and what her voluptuous but undeniably old-timey figure has been through. We don’t know much about her past, except that she bravely crossed the Atlantic from New York to Finland and then spent a decade very quietly in the Finnish archipelago, before ending up with us. What kind of adventures did she have on the other side of the Atlantic? Chartering in the Caribbean? Sailing around Long Island with an American family? Who knows. What we do know is that her hull has been through a major refit at some point. The gelcoat has been peeled off completely under the waterline, leaving only naked fibreglass.

Fibreglass as such is not a waterproof material, so it always needs a waterproof layer on top – nowadays usually epoxy. After it was peeled, our boat’s hull was coated with epoxy, but the coat was much too thin, maybe just one layer or two. We didn’t really have to think too hard about what to do next, the decision was pretty clear: we would sand off all the paint layers back to fibreglass, and re-coat the hull, this time with enough epoxy. And because using professional labour wasn’t really within our budget, we would do the job with our own pretty little hands.

The first thing was to get a proper sanding machine – our otherwise comprehensive selection of power tools didn’t include a heavy-duty sander. We found Bosch GEX 150 at a Greek online shop, and equipped it with a big heap of sanding paper. As an additional sander, we used the polishing machine with a sanding disc, as it proved to be easier in the more delicate places where the Bosch was a tad too fierce. It sure could get the paint off!

So, let’s get started! Working in a sweaty overall is not the most comfortable thing you can do on a hot summer day in Greece. The motorized whole face mask completes the style! But it also brings fresh air for you to breath, so it actually turned out to be very nice.

Some observations from a first time boat hull sander:
1. The disposable overall always rips first at the crotch
2. The paint dust is hardest to remove from inside your ears
3. The glassfibre dust penetrates all protective clothing and makes you itch like crazy!
4. You can actually notice your biceps growing in just two weeks!

Some more useful observations:
1. Sanding a boat is hard physical work. If you’re not used to that sort of thing, don’t overestimate your abilities and think you can pull around-the-clock shifts. It’s more realistic to sand 4-5 hours a day, and perhaps use the rest of the time for some lighter work. Try to change positions often.
2. Start from the most difficult and ergonomically challenging places in the morning, when you’re still feeling strong and fresh. As you get weaker and your lumbago gets worse, move on to easier places. The sides of the keel are generally easy, the hardest parts are the nearly horizontal areas under the hull.
3. Replace the sanding paper as soon as it doesn’t seem to sand anymore
4. Keep yourself hydrated!

As more and more surface was revealed, we got more and more anxious – what surprises would be lurking under there? How much damage, moisture, wet blisters? We were amazed not having found anything alarming by the time we had finished sanding the first half of the boat. There were three blisters, each about the size of a golf ball, but they were all very superficial. Once ground open, they dried immediately. Everywhere small pinholes were seeping a tiny amount of brown liquid as soon as the sander revealed them – the phthallic acid of hydrolyzed polyester resin – but there was no damage in the hull. Only a few old blister repairs were revealed. Every night after sanding we would wash the hull with fresh water to remove all dust and seeping acid, and once the sanding was done we pressure washed the whole hull. When it was dry, the moisture was measured with a moisture meter, and the boat was dry! The only place where there was still a little moisture was at the aft end of the keel. As the boat was sitting on its keel, it would be the last place we could paint anyway, so it would have time to dry a little longer.

A seeping blister was opened and ground down to healthy fiberglass (outside the light circle around the blister)…
… then it was filled and fared smooth.

The whole sanding project took about two weeks. We had some breaks, however, because we had friends in the area we wanted to spend some time with. A couple of boats from our winter marina kept visiting the anchorages outside Nidri and Vlicho, and every now and then we would join their crews at some nice taverna, skipping the next day’s early morning shift. Some spare time was also happily spent building the toilets and plumbing.

For the duration of our boatyard projects we rented a small car, that quickly proved a necessity. The boatyard is situated within a nice bike ride from both Nidri and Vlicho, but for the hardware store, chandlery, paint, plumbing and wood shops we have to visit Lefkada frequently, and that’s 15 km away. The early summer has been very quiet in this normally very touristy area because of the coronavirus, so we could get an old Fiat Punto for a very reasonable price.

During the refit we are living aboard – where else would we go? It can be a little more complicated living on the hard, as many of the systems might not work properly. For example, the toilet uses sea water to flush, and our fridge and freezer are water cooled and therefore don’t work out of the water. But we had bought a composting head – it was not yet installed, but has worked very well as a temporary facility, so we’re looking forward to replacing one of our heads with it permanently. To store cold food, we moved all of it to the better insulated freezer, and keep buying a new bag of ice cubes every day, and that keeps it cool enough.

Mostly we’ve been cooking our own food at the boatyard – often in the barbecue on the aft deck, because the gas stove brings too much warmth indoors. On the busiest days we eat out, however, and there’s no shortage of good, reasonably priced restaurants in the area. Hot weather brings its own difficulties, as there’s no cooling effect from the surrounding sea water. Part of our home is normally under the waterline, and that has a significant effect on the temperature indoors.

Finally the boat has been sanded – the worst part is over! Next we will start painting on the epoxy layers. More about that next time!

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