Wednesday, 27 June 2012

My poxy hulls

Some small blisters on the topsides have led me to learn a lot more about my hulls.

I'd sanded the topsides, expecting simply to add another couple of coats of paint, but noticed some small blisters. Normally, a sign of osmosis, but I wasn't worried about that because I'd already removed all the antifoul from the underwater parts of the hulls, and they are in fine condition. Half a dozen blisters in total I should think. Moisture meter readings fine. And a bit of sanding below the antifoul suggested that the layer of paint on top of the gel coat was probably epoxy barrier coat. I did my best to leave this as intact as possible. I intend to add a few more layers of epoxy under the water line, and then add Copper Coat.

So I wasn't wasn't worried about the small blisters on the topsides. I just sanded them out. But then they started weeping some brown ooze.

You can see brown patches around the holes in the paint. Well, I had to investigate further:

So here's some paint scraped away.Under the white gloss, there's a blue undercoat I can't identify, but it may be an epoxy high build coating. The brown stuff I suspect is car body filler. Wherever I found pox in the topcoat I found body filler underneath. This theory was shaken a little when I found the blue paint under some pox in one section of the hull, but after a little sanding, I found filler under the blue paint. I was curious that the only places on the hulls where there was no pox at all, was under the saloon. I wondered whether the heat of the sun on the hulls had something to do with it, but I now realise that those areas were never filled - just painted over.

If I ever wanted a coating on the topsides that was durable, I'd have to remove all the body filler. I'd have to strip away all the paint. After spending days scraping away the antifoul, this wasn't a pleasant prospect, so I went home to do a little googling.

A steamer used for removing wallpaper proved to be the tool I needed. I wish I had tried it on the antifoul. 15 seconds steaming is all the is needed for the paint to peel away in strips, not damaging the substrate underneath at all. Of course that high temperature could damage the fibreglass if I left the steamer on for longer, but 15 seconds is enough to peel the paint, leaving the hull underneath just a bit warm. 

I've now removed all the paint from a hull and a bit - it will all be done in a couple of days. And the filler is easy to sand away.

My hulls were constructed in this way - the underwater sections were made in a mould up to the level where the hulls flare, 2-6 inches above the water line. The hulls above that level have been made by bending on flat panels. These panels have no gel coat on, and sanding through the paint and filler (being very careful not to sand below that into the glass) shows the laminate underneath to be really excellent. No air bubbles at all. No dry glass fibres. It seems to have been an excellent layup, and very fair. Naturally, where the panels have been joined, there needs to be some filling and fairing, and some of it has been done with epoxy fillers:

The white area on the left I believe to be epoxy-based filler. Unfortunately, this has been applied leaving small air bubbles, which has probably caused some solvent entrapment in the paint applied on top. On the right is some more body filler! What a shame the builder switched to using this stuff! According to my moisture meter, the body filler is dry, but it feels damps, and some of it is fairly soft. I think it has absorbed solvent from the paint applied on top - it doesn't smell of styrene.

In 2-3 days, all the paint and body filler will be gone. The hulls look terrible, but what I am left with is excellent. I intend to replace some of the body filler with epoxy-based filler where it really needs it, but I have no intention of filling and fairing forever. A fellow with a cat in the yard spent two months filling and fairing, and his boat does look brilliant. But I want to go sailing. I'll fill and sand enough to give a really good surface to be painted over, but I won't be applying filler to large areas in an attempt to take out some of the waviness of the hull. It's only slightly wavy, only enough that a boat-builder or surveyor would notice. I'm more interested in the durability of the work I'm putting into the boat than trying to make the boat look flawlessly fair. Life's too short for that.

I'll make the topsides smooth and fairly fair, add 2-3 coats of epoxy primer, and then some International Brightside - that's what I'm stripping off at the moment, and I think it would have been fine if I've originally painted it on a good sound surface.

Monday, 25 June 2012

Important little details

I'm spending most of my time filling and sanding, and most of the rest of my time sanding and filling. I spent nearly £300 on a fancy Makita sander, and wore it out in a fortnight. Fortunately, it was replaced under warranty. The break gave me a chance to rest my arms and attend to some small but important jobs.

This is the aluminium beam at the front of the boat. I've hacked away some of the material that was bonding it into the hull. It was partly solid polyester resin, with some glass/resin on top. It didn't work as a seal. Water was able to penetrate along the beam and reach the plywood bulkheads inside the boat that support the beam. The ply has softened to the extent that I have had to remove it all, and will replace it soon. Not a big job, but it is essential that that plywood is intact. I'll replace the polyester around the beam with epoxy, but since I doubt even epoxy would seal the beam due to differences in the rate of expansion/contraction with temperature change between the beam and the hull, I'll also add a thick layer of Sikaflex round the join. The Sikaflex is flexible enough to accommodate the differences.

This guttering around the inside of the forward hatches allows the hatches to be flush with the deck, which is a nice tidy setup, that allows any green water to quickly go over the side of the deck rather than piling up against an upstanding hatch edge. But still some water managed to find its way into the hatch, so I've raised the edges of the guttering with epoxy and glass, and then sanded it down bit by bit until the hatch is once again flush with the deck, but there is only a very small gap between the bottom of the hatch and the top of the guttering. Only a small amount of water can now get past the edge of the hatch , and the size of the guttering and drains ensures it will drain away before the next wave sends more water over the deck. This job took quite a lot of time and effort - it involved going into the hatch, pulling the lid over and marking where the edge of the guttering needed sanding down, then trying the hatch lid on again, then more going inside, marking etc. 

There may be times when water is frequently sprayed over the deck. If even a little of it gets inside, it would accumulate and the forward section of the boat would lose buoyancy.... anyway, this fix should solve that issue.

Here's a wooden mini-keel I added a couple of years ago so enable the boat to sit on a beach without damage from stones. There was a problem with the hull flexing a little at the aft end of the mini-keel if the slope of the beach made the boat sit heavier at the the aft end. So I supported the boat by putting some big blocks under the hull beneath the bulkheads that are attached to the main beams and removed the supports that were under the mini-keel. I appreciated the fact that the boat is light enough that I was able to do with with just wooden blocks, wedges and a lump hammer. Once the weight of the boat was taken off the mini-keel, I epoxied a plywood framework inside the hull to strengthen it:

Now, back to the sanding....

Sunday, 3 June 2012

Boat dismantling

Lot of work to do, so it's reassuring to have a neighbour in the boat yard with a big catamaran and even more work to do:

This is a 39' Catana, with the gel coat stripped away and the hull drying out before re-coating with gel coat. It will be drying for several months in the shed before it's ready for the new gel coat.

Fortunately, my hulls are fine. Only the decks have leaked, but the damage is quite a bit less extensive than I'd expected. Still, there there are holes in the gel coat on the coachroof that can only be dealt with properly under cover, and I have a piece of plywood to replace on one of the bows - the plywood is meant to provide the strength for a big cleat which will take a lot of strain anchoring, mooring or riding to a sea anchor, so that needs to be reliable. I'll replace that next week.

An extra job I hadn't anticipated is the removal and re-installation of all the windows. I did this recently, but on close inspection, it was clear that a couple of the windows were no longer bonded well to the coachroof - so they all had to come off as losing a window at sea could be catastrophic. I'd followed the instructions here for fitting windows without using bolts, but the paint I used on the windows failed. I'll try again, but without priming paint on the windows this time, having the Sikaflex directly in contact with the coachroof. The 3M double-sided tape was disappointing too - it was ridiculously easy to remove from the windows. It was supposed to provide much of the bonding strength. I'll use bits of it again, but only enough to hold the windows in place while the Sikaflex cures. I'll protect the Sikaflex from UV with some paint on the outside of the windows, round the edge.

Oh well, with windows out I can use grinding and sanding machinery more easily.

Since replacing the toilet, holding tank, valves and through-hull fittings with a simple composting toilet, I've got the bug for removing anything more complex or less reliable than it needs to be.

This corroded lock for the stern locker won't be replaced. All locks corrode, unless you pay a lot of money for them. And a fancy lock might suggest something worth stealing behind them. I'll fill the holes, and attach a rope to the inside of the locker lid which extends through the bulkhead into a cupboard in the bedroom. To lock the lockers, just pull the rope tight and press it into a jam cleat. Nothing can go wrong with that! And would-be thieves won't know where to start to open the locker.

Here's a water filler top that won't be replaced either. The new pipework I installed on the boat doesn't fit this, so I left it disconnected while I tried to think of a neat way to make the connection. But the rubber seal on this fitting needs replacing too, which is a hassle to find or to make. Without a decent seal, drinking water can easily be contaminated with sea water. And the screws into the deck leak water into the deck. Solution? Get rid of it! The pipe that leads to the water tank leads to the stern locker. This fitting is in the deck of the stern locker. If I just get rid of it, and leave the pipe loose in the locker, I'll have no screw holes in the deck to leak, no seals to maintain, and no chance of sea-water getting in. Filling the tank means just lifting the end of the filler pipe out of the locker and putting the hose in. Which is no more inconvenient than getting the winch handle to unlock this fitting. Of course I'll have to tie the end of the pipe up under the deck to prevent my water syphoning out, and stick a cork in it for good measure.

A weak point of the Autohelm steering system is the plug/socket arrangement to connect the actuator to the power supply and data feed. When I bought my Autohelm, I didn't wait for this fitting to leak and corrode - I chopped it off immediately and replaced it with some highly recommended gear!

But you can see it is beginning to corrode, and I had to fiddle about with it to get it to work on my trip up the river. So this has to go too. This is also screwed into the deck above a stern locker. That stern locker has a ventilation pipe close to this fitting - I'll use a plug and socket system that isn't screwed into the deck. I can pass the lead with the socket on through the pipe when I want to connect up the Autohelm. The connection can be shoved back down the pipe where it will mostly be protected from water. And when not in use, the lead can be left in the ventilated locker, where it is very dry due to the continuous ventilation I've built in.

Let's see how much further I can minimise boat maintenance during this refurbishment!