There comes a time in every boat’s life when its bottom needs scraping.
There can be a number of reasons for this:
- The antifoul may have built up into layers over the years leaving a very uneven surface. This can affect the hull speed.
- The antifouling might even be falling off in clumps exposing the epoxy or the gelcoat underneath. I once looked at a boat for sale which was suffering from this. At the time I didn’t quite know quite what to make of it. I do now; it means at least £2,000 off the asking price.
- You might just want to be letting the hull dry out. You might have some osmosis that needs treating.
- You might want to change the type of antifoul you are using and the change requires removing all previous antifoul.
Or, it might be a combination of these.
That was the situation in my case. The antifoul on ‘Petrel’ my Westerly Storm 33 was uneven and layered and although I’m not a racer or a speed merchant (though I love the whooshing sound when I pass other boats), I was continually dissatisfied with the state of the hull when it was ashore. Funny that, no human sees your boat bottom when it’s in the water and comments ‘nice bottom’. But I was always aware that mine wasn’t.
I decided to strip my Storm’s bottom in order to Coppercoat the hull and save the annual labour of rubbing it down and re-antifouling each year. I knew stripping the hull would be hard work and laborious. However, but there were several big wins as it would enable me to:
Remove the old uneven antifoul
Apply fresh epoxy and then Coppercoat (which is epoxy based) would protect the hull
Save the work and cost of annual re-anti fouling as well
And (I hope) make Petrel more attractive should I want to sell her.
What You Are Stripping?
This article is written from mostly first-hand experience. It deals with GRP boats. Wood, metal and aluminium may involve some of the same issues, but may differ in some respects. I have no expertise in those areas, so more research would be required. But as you know Westerlys are all GRP, so why would you want to do that?
So, your Westerly hull will obviously be GRP with a smooth gel coat covering the raw material underneath. The underwater hull is essentially the same as the upper parts of the boat and may be either gel coated or, for improved resistance to osmosis, epoxy coated.
When planning to strip your hull, you first need to decide how far you are going to go. Are you taking it back to the gelcoat, i.e. stripping the anti-foul and the epoxy. Or are you just removing the anti-foul and taking it back to the epoxy?
Stripping Options
There are several ways of stripping the anti-foul off your hull. They broadly break down into the industrial, the chemical and the manual.
Industrial
The industrial involves the least labour and is the most expensive. It involves paying a contractor to blast the hull which strips the anti-foul (and possibly the old epoxy). The blasting is with sand or soda or salt.
Chemical
The chemical involves painting a caustic solution onto your hull, in some cases covering it with plastic film, leaving it for 24 hours and then power washing it off or scraping it off. You can buy a commercial version of the solution or make it yourself using wallpaper paste and caustic soda.
Manual
The manual method involves scraping the anti-foul off by hand and, if you want to remove all the anti-foul, then sanding the residue off. This is the hardest but the cheapest method. The scraping can be done with a variety of tools. Some people have used a power scraper like a Bosch GOP 30-28 multi-tool or an equivalent. I used a Proscraper attached to a vacuum cleaner, in my case a Henry. Other people recommend a Bahco 665 Carbide Edged Paint Scraper. There are also other similar tools available.
If you are just trying to get a smooth hull which you are then going to re-antifoul then you just need to scrape the old antifoul off to get a smooth surface. You will be left with some antifoul residue, but it will be pretty flat.
But if you want to Coppercoat your hull you will need to sand off all the antifoul residue. Scraping will only get you so far. The same is probably true for the chemical method. To get all the antifoul off, you will need an orbital sander. I used A Wolf orbital sander. But there are lots to choose from. You will also need a lot of sanding discs mostly of 80 grit but possibly some 60 grit and possibly some 120 grit too.
The Impact of Location
I am assuming you will be out of the water (don’t try any of this whilst you are still afloat) and probably at a boatyard of some sort. Before you decide on one of the above methods, it is very important that you talk to your boatyard. They will have rules and quite probably be able to provide valuable advice. You also need to negotiate how to work round what is propping your boat up when you do this work. Some boatyards, including mine, no longer allow hull blasting; it throws up too much dirt and dust, even when the boat is sheeted off with plastic. So that may not be an option, especially where boats are packed tight together as they often are.
Whichever method you use will create mess and dust. Your boatyard may insist on protective measures. My Westerly Storm sits in a cradle which I rent from the yard. The yard required a single large plastic groundsheet underneath the cradle. As I hadn’t talked to them prior to the boat coming out of the water, that required an extra boat lift to fit the groundsheet, which was an extra cost.
Method and Time
Whichever method you use will affect the time it takes. You can probably get your boat shotblasted in a day or two. The Chemical and Manual methods will take quite a lot longer. Two people could probably scrape a 30 foot hull in a week. But that will be hard work and you will need to be fit to do it. I decided to take my time (I also had other commitments). I started on 8th March and didn’t finish until early May. That was doing 2 – 3 four to five hour sessions per week. I used the scraping method and I did most of the work on my own. I had other work on and was away for at least a week and on some occasions, I was delayed by the weather. It was hard work and even if I had been able to do it full time, I am not sure my muscles would have approved. The time it took me obviously cost extra in boatyard costs. But stripping your hull is a project for the long term.
The time it takes will also depend on your hull shape. Most Westerlies are similar with rounded hulls and fairly flat bottoms. A Contessa 32 was also being hand stripped in the same yard as I was doing Petrel. That has a completely different hull profile – more of a wine glass shape. If hand or chemical stripping, your hull shape has an impact on how you approach this as different hull shapes require different postures.
Managing the project
I decided to break the project down into phases largely determined by areas of the boat. I started with the starboard side and stripped from the waterline to the end of the hull curvature and from close to the stern to the bow. I then did the same for the port side. I then did the underside, the keel and finally the big flat bottom section at the stern.
Each time I went to strip a bit of the hull, I would choose an area to do. I would look at it and think, ‘I’m never going to do all that today’. But usually after about 30-40 minutes I’d find I was a half to a third of the way to my destination and that would spur me on. I found taking it in small chunks was psychologically the best approach. Each day I worked on the hull I felt I was making progress. The pictures tell the story.
Having done the scraper stripping, I would then go back with the orbital sander and remove all the traces of antifoul, so I was left with a grey/green epoxy coating and a beautifully smooth surface. Occasionally I would accidentally go further and strip the epoxy so I was left with white gel coat. So long as it’s small areas of gel coat that’s not a problem, unless you intend to take off all the epoxy. But there are cost implications in doing so as I will explain further on.
Keel and Flat Bottom
There were two areas I was not particularly looking forward to; the keel where you have to get down on hands and knees and secondly, the portion from the stern end of the keel to the stern which on the Storm is beamy and flat. I envisaged having to spend hours crouched in awkward positions and was not looking forward to that at all.
The keel was as I expected. I highly recommend using some foam rubber to protect your knees – or even gardening knee pads. I think part of the keel was the last area to be stripped as it was indeed awkward and fiddly. I decided not to attempt the bottom of the keel at all, but apply normal antifoul just prior to lift in.
The large flat stern underside proved to be far less a problem than I envisaged thanks to a bright idea. ‘I wonder,’ I thought ‘whether a deckchair would help?’. So I brought one down and found that sitting in a fairly ordinary deckchair put me at just the right height to strip and sand the flat area of the hull in relative comfort. Holding the sander up could be quite hard work. But one wasn’t having to crouch. And I could take it in small bite-sized stages from a seated position and could do quite an area before having to move the deckchair. It was actually quite comfortable, something I never expected.
Hints and Tips
As I had some chemical stripper called ‘Strippit’ I thought I would try it in case it saved time and effort. I must confess I didn’t cover it with cling film as they recommend and I scraped it off rather than power washed it off. It was easier to scrape. Personally, I didn’t like it. I found it far harder to see what you had covered and to get back to the epoxy than scraping and Strippit it was messy. It may well have been more effective had I followed the instructions to the letter. But to do so you’re going to need an awful lot of cling film, which is not stuff I like either.
WOA Magazine Spring 2015
I used the Proscraper attached to a Henry vacuum and a Bahco 665. I found the Proscraper got the first layers of antifoul off – it does obviously depend on how many layers of antifoul you have on your hull. Where there was some layered antifoul left, the Bahco was good at getting rid of
those and then the orbital sander could easily deal with the residue. If I didn’t use the Bahco then I found myself going through more sanding discs than was necessary.
Both the Proscraper and the Bahco have very sharp ends on their blades. It is quite easy to dig into the gel coat and leave nasty nicks that you really need to fill before re-coating. Some people angle grind the ends of their scrapers to prevent this. It’s not a bad idea. I had quite a lot of nicks after sanding to fill to get a completely smooth bottom. And after Coppercoating I could see some nicks and grooves I had missed. They can be hard to see. I marked them with blue masking tape before filling them.
When first using the orbital sander, I found that the discs didn’t seem to last that long and had a habit of flying off. The discs are hook and loop ones that stick to the sander. Then it occurred to me to adjust the variable speed so the sander wasn’t spinning quite so fast. Problem solved and the discs – which are about 20p each – stayed in place much longer.
When stripping your boat bottom, you will inevitably also be stripping several metal areas, some large, like the keel and some very small, like the through- hull outlets or skegs. If there is any sign of rust, you first need to grind that back and cure it and then treat it with metal primer before applying Epoxy paint. Even if there is no rust you will need to apply metal primer to areas like strainers and through hull outlets before applying the Epoxy paint.
Mess and the Vacuum
Antifoul paint is nasty stuff and dried antifoul almost worse. The advantages of the Proscraper attached to a vacuum cleaner is that it sucks much of the mess away from the boat. But make sure you have a good quality vacuum cleaner and plenty of new vacuum bags. I filled about 5 Henry bags and there was still residue under the boat that I had to sweep and hoover up. I bought a Henry specifically for the stripping purpose. It was great, but needed a lot of washing out before I sold it on. On a couple of days I had some help and needed a second vacuum. I used a spare cheap vacuum I had and the antifoul clogged it up and destroyed it. Use a good quality powerful vacuum that can be easily cleaned.
Recoating the Hull
I was advised that if you strip back to the bare gelcoat you will need to recoat with at least 5 coats of marine Epoxy paint. However, if you strip back to the epoxy paint, i.e. just remove the antifoul – and you will inevitably take some epoxy paint off in the stripping process – you only need to recoat with two coats of Epoxy paint. When I was buying epoxy paint it was £85 – £90 for 2.5 litres which would just about do my hull. As prices have risen since I did this work, five coats of Epoxy might now cost around £500 – £600. So you can see the benefits of only having to apply two coats. Marine Epoxy Paint comes in two colours, green and grey. You apply it in alternative colours so you know how many coats you have applied.
Before applying the Epoxy paint, you need to wipe the hull down with Acetone to remove as much dust as possible. This doesn’t take anything like as long as it sounds. I found it took about 15 to 20 minutes to wipe down the whole hull. And it doesn’t need a lot of Acetone either.
A litre was more than enough. You are then ready to apply the Epoxy paint. Once you have re-epoxied and it has cured – c 1 – 2 days – you can then antifoul with whatever system you choose to use.
Cradle Supports
Out of the water, my boat is supported by a cradle with four cradle ‘pads’ plus about six wooden chocks and wedges. My boatyard were happy for me to remove the chocks and wedges whilst stripping, re-Epoxying and coppercoating. The cradle pads and the untreated patches behind them required a different approach, especially as I was coppercoating. The most sensible method was to re-epoxy and coppercoat the entire boat, then get the boat repositioned in the cradle. That left me four completed untreated patches. I was able to scrape and sand these, then re- epoxy them and then apply the four coats of coppercoat required. This took a couple of days, principally to let the Epoxy paint cure. Once completed although it was possible to see where the patches were, the coppercoat cured perfectly. It is important to keep a bit of Epoxy paint and coppercoat back for any cradle patches you have to treat.
Equipment and re-coating costs
Owing to all sorts of global changes, prices have risen and have risen since I stripped my hull just six months ago. Hence, the prices should be considered to be indicative only but they do give a sense of the respective costs. They are based on a 33 foot Westerly Storm. Those good with maths will be able to find hull dimensions on sailboatdata.com and work out an approximate cost per m2 for their own Westerly.
Soda Blasting
Blasting back to gel coat ………………………………………………………£700 – £800
Epoxy Paint 5 x 2.5 litres………………………………………………………£500 – £625
Anti foul x 2 coats ………………………………………………………………………….£200
Total cost…………………………………………………………………………..about £1,600
Chemical
Strippit – 3m2 coverage per 5 litres………………………………………………..c £345
Or Owatrol 4m2 coverage per 1 litre……………………………………………….c £180
Plus cling film
Epoxy Paint 5 x 2.5 litres………………………………………………………£500 – £625
Anti foul x 2 coats……………………………………………………………………………£200
Total………………………………………………………..about £1,005 (Owatrol version)
Manual
Pro Scraper……………………………………………………………………………………..£35
BahcoScraper………………………………………………………………………………….£27
OrbitalSander…………………………………………………………………………………..£35
2ND Hand Henry………………………………………………………………………………..£70
Vacuum Bags………………………………………………………………………………….£10
100 sanding discs…………………………………………………………………………….£20
Epoxy Paint 2 x 2.5 litres…………………………………………………………………£200
Antifoul x 2 coats……………………………………………………………………………£200
Deep Heat Muscle Rub…………………………………………………………………….£10
Total…………………………………………………………………………………….about £607
WOA Magazine Spring 2015
I got a Boat Show deal for about £800 for the Copperecoat. I also employed an expert to apply the Coppercoat as it is possible to get it wrong. Application should cost about £400.
The Coppercoat should last 8 – 10 years. My annual antifoul costs were in the region of £200 per annum and rising. You do the maths!
Conclusion
I am looking forward to seeing Petrel out of the water this winter, especially to see how the Coppercoat is working. And you never know, I might even get the occasional comment – ‘nice bottom!’.
Scraping By Hand: What You Need
- Groundsheet
- Scraper(s)
- Vacuum cleaner and bags
- Orbital sander
- Sandpaper – lots!
- Acetone
- Epoxy
- GRP filler
- Ladder
- Bench
- Deckchair
- Patience
- Time
- Energy
What will make the time pass faster?
Music or audio books on a mobile phone or MP3 player.