Hi All,
Quite a while ago now I posted that my Cav 28 had many small blisters on her hull, all between 5 cent and 20 cent piece size.
Shes not been out of the water for 4 years and I had to have her out last week for an Insurance Survey.
It seems to be the opinion of the surveyor and the local fibreglass guy who had a look that the vast majority of the blisters are in the paint layers and not in the fibreglass itself. And they have not got any worse or any more numerous in all this time. So I'm going to have her out and do the job as well as I can in a few weeks. I intend to remove all the old antifoul which is very thick and re primer and paint the hull once any deeper blisters have been fixed.
The surveyor poked about in a few of the blisters with his screwdriver and got down to a red primer layer with out too much trouble, see photos.
I have a couple of scrapers and have bought some different and bigger ones to see how they go but I am hoping someone on here will have some experience of this they can share with me?
I'm wondering about using a belt or orbital sander or perhaps a grinder/polisher with a flexi head?
And what would be best for cleaning up the keel which was covered in barnacles?
Any advice much appreciated, thanks.

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Cockpit said..
Hi All,
Quite a while ago now I posted that my Cav 28 had many small blisters on her hull, all between 5 cent and 20 cent piece size.
Shes not been out of the water for 4 years and I had to have her out last week for an Insurance Survey.
It seems to be the opinion of the surveyor and the local fibreglass guy who had a look that the vast majority of the blisters are in the paint layers and not in the fibreglass itself. And they have not got any worse or any more numerous in all this time. So I'm going to have her out and do the job as well as I can in a few weeks. I intend to remove all the old antifoul which is very thick and re primer and paint the hull once any deeper blisters have been fixed.
The surveyor poked about in a few of the blisters with his screwdriver and got down to a red primer layer with out too much trouble, see photos.
I have a couple of scrapers and have bought some different and bigger ones to see how they go but I am hoping someone on here will have some experience of this they can share with me?
I'm wondering about using a belt or orbital sander or perhaps a grinder/polisher with a flexi head?
And what would be best for cleaning up the keel which was covered in barnacles?
Any advice much appreciated, thanks.

Most yards won't like you grinding or sanding without elaborate tarps and dust mitigation arrangements. Where are you planning on hauling out?

As Jules said, few (if any) yard will allow dry sanding or grinding of antifoul.

The yard I go to said they will probably allow me to wet sand thick antifoul using an air powered sander driven by a hired air compressor.

I've been dry sanding using a 150mm Festool "ROTEX" random orbital sander with a Festool dust extractor. It was an expensive tool, but the yards I have antifouled at have been happy once they knew what I was using. It took me 2 full days to completely remove 10 years of Alex No 5 anti foul on a 40' yacht. Might take double that to remove the paint as well depending on how soft it is, but there could be just as much time re-fairing if you are taking a lot of material off.


A

just scrape it off.
You cant sand it effectively timewise if its so thick.
I've actually found it easier to scrape straight back to the hull if it is thicker, as it often tends to come off in chips.
Get a good long handle scraper with replaceable blades, facemask up, bang in the earbuds and off you go.
Cav 28 is better than H28, believe me.

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crustysailor said..
just scrape it off.
You cant sand it effectively timewise if its so thick.
I've actually found it easier to scrape straight back to the hull if it is thicker, as it often tends to come off in chips.
Get a good long handle scraper with replaceable blades, facemask up, bang in the earbuds and off you go.
Cav 28 is better than H28, believe me.

Yes, that was my intention thanks. I am hoping someone will say they've done it and used x or y scraper and which was the easiest way they found.
I'm on the Sunny Coast in Qld and I had heard about the sanding restrictions but the boat builders and repairers must have to sand at some point.?

I would apply a thick coat of the special antifoul paint stripper prior to scraping.

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Cockpit said...... x or y scraper and which was the easiest way they found.
.... I had heard about the sanding restrictions but the boat builders and repairers must have to sand at some point.?

I normally get the yard to do the haul-out and one hour of them doing the water blasting and scraping. That does most of the work.

Ask at the yard you will go to, what they use, or what the tradesmen there use. For manual paint scrapers, a new sharp edge is essential. I have just bought a couple of scrapers at Bunnings in different widths, 50mm, 100mm, etc
for $5 to $10 dollars. If you've got lots of scraping to do, and especially smoothing out the surface, an orbital sander will be good too. Either a flapper disc on an angle grinder (might be too vigorous for f/glass, but OK for steel), or an air-driven one or a 12 volt orbital sander might be OK.
And some 80 and 40 grit sand paper with one of those boards to attach the 1/3 sheet.
On the day you might change which tools you are using. Your arms might get tired, so you change to an orbital sander, or maybe some wet sanding and scraping will be sufficient. At least you have an array of tools to use and experiment with, so less need to go back to a shop on the day.

Cockpit,
I used a Bahco scraper, 90 deg head, worked well. I dont think there is a fast and easy way to remove antifoul manually.
Please make sure you cover up well, plenty of PPE. There's some evil **** in that antifoul
Mike

Ahh the magic surveyors screw driver. I was fascinated by this highly technical piece of equipment for years. It can be used at one end to determine the difference between osmosis and a bad paint job with some poking and scrapping. The other end can determine the state of any material with a few taps.
Normally leaves more damage than before and you have to do a repair now.
Since I learnt there is no magic a long time ago. I now stop the magic screw driver and call the insurance company and say you have sent a man with a screw driver to assess this vessel. Are you serious! Will you cover any cost of damage he causes. What are your terms for damage caused during an assessment.
No guarantees they will insure you again though!

Hydrochloric acid for the barnacles, if the yard will allow it. I am in France and it still seems crazy the stuff they do/allow.

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Magpiemike said..
Cockpit,
I used a Bahco scraper, 90 deg head, worked well. I dont think there is a fast and easy way to remove antifoul manually.
Please make sure you cover up well, plenty of PPE. There's some evil **** in that antifoul
Mike

Do you mean this one? There is the same one without the extra handle and one with a triangle blade. I had looked at these but can only find the one without the handle. I'm guessing you pull more than push with these so the extra handle will be beneficial?

yes, thats the only one i've found that works well.
The blades are reversiable, get a spare set while you are there.
Just knock the blade corners off on the bench grinder first, it will stop you doing a seriously deep gouge.
It wont take that long really once you get into it, plus you end up arms and shoulders like Arnie.

Got this today also as I already had batteries for other drills etc. I'm interested to see how it goes, might save some muscle work. Has the scraper as shown plus small detail sander.

I've used this scraper to good success when stripping back my keel and rudder recently: www.bunnings.com.au/uni-pro-63mm-carbon-steel-four-edge-scraper_p1674121

It's handy that it has four edges on each replaceable blade. The two handed setup is great - it allows you to push down on the blade with one hand and drag it along with the other. Sharp blades and pressure are essential to take the antifoul off in big chips, rather than fine powder. You might also want to grind the corners off each blade so as not to gouge the fibreglass hull.

Before starting on this job might I suggest a 6 month stint in the gym to build up your shoulders and back - :-)

The bahco type are the goods & not only for antifoul. For the upsidedownis longer handles for the big runs might be a bonus, a concreter's pointed trowel is a handy tool for hacking & poking ( keeps ya knuckles away from the action) & a long handle square post hole shovel is good for shifting major growth
if you spend as much time as possible with a serious pressure washer it will save a lot of scraping, but a big pressure washer is no duck walk either, it's good to have a tag team
It's sort of ok to burn & scrap it from steel & wood but glass reinforced glass it's possibly best to leave the blow torch at home

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Microbe said..
I've used this scraper to good success when stripping back my keel and rudder recently: www.bunnings.com.au/uni-pro-63mm-carbon-steel-four-edge-scraper_p1674121

It's handy that it has four edges on each replaceable blade. The two handed setup is great - it allows you to push down on the blade with one hand and drag it along with the other. Sharp blades and pressure are essential to take the antifoul off in big chips, rather than fine powder. You might also want to grind the corners off each blade so as not to gouge the fibreglass hull.

Before starting on this job might I suggest a 6 month stint in the gym to build up your shoulders and back - :-)

Saw that today in Bunnings so might give it a go if you reckon it works. My collection of scraping tools is getting larger by the day.
It took me a good 30 mins solid scraping with a metre long steel scraper the yard lent me to get the barnacles off. Mainly the keel which was thick with them so I've already got a start on the gym work.
cheers

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cammd said..
I would apply a thick coat of the special antifoul paint stripper prior to scraping.

I had looked at that also but will try the scraping method first before I go to any chemicals. Thanks though.

As woko said a high power pressure washer may save you a lot of time. Maybe worth paying for. Not your house hold pressure washer.
Technique will help. Move your body, don't just scape with your arms. Almost lock your arms and use your body if that makes sense. You will have to reach sometimes. Even a plank on a couple of blocks of wood so you can scrape at chest height more than shoulder or above shoulder helps.
I think the Bahco scrapers are worth the money. Again they will save you time in the long run.
Or make your own out of planer blades.

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My mates boat just went back in the water today.

Previously when we've gone on the hard stand we've been lifted out by crane and tide and wind dependent. But issues have shut them down so we had to go to a marina hard stand.

So paint scrapers work really well and Tarquin has a great selection of his own but I find it hard to believe that France let's you use a corrosive acid!

"Most yards won't like you grinding or sanding without elaborate tarps and dust mitigation arrangement "

This was oh I need to sand the paint off a couple of small areas to glass. Ok it's a 20 knot day no one painting so tarp cover on and 125mm sander out for 10 minutes max, but still felt a naughty school boy.

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crustysailor said..
yes, thats the only one i've found that works well.
The blades are reversiable, get a spare set while you are there.
Just knock the blade corners off on the bench grinder first, it will stop you doing a seriously deep gouge.
It wont take that long really once you get into it, plus you end up arms and shoulders like Arnie.

Got the Bahco scraper today as in the photo and some spare blades but noticed that all the blades have a v slight convex curve to them. Did yours have them as I would have thought that dead straight was best.?

no, mine were always dead straight, and on the replacements also.
Sydney tools were an agent, and stocked the blades.

Totally unrelated, but if anyone needs a new faceshield/grinder shield,
Bolle Sphere: $45
www.totaltools.com.au/108308-bolle-high-impact-sphere-head-gear-clear-visor-1652501?gclid=CjwKCAiA0JKfBhBIEiwAPhZXD99TNc6w81HJXwyHcE2wd29r5JM-SWT-DEaicY91SGxOUIys5L5nPhoCG4gQAvD_BwE

but if you show them these on special, $29
www.vektools.com.au/bolle-sphere-grinding-safety-face-shield-1652501-covid.html?gclid=CjwKCAiA0JKfBhBIEiwAPhZXD6dddPpJRAx4A9C5IfCTygocE5brxP4KfS5A7nZPXM5do48CdN2wZhoCnRwQAvD_BwE

my local total tools happily pricematched $29 plus no shipping cost.
Useful for stopping the antifoul grit getting all in your facehair but still lightweight

There are 2 types. Flat smooth ones more for varnish and wood work where you want to leave a nice finish. Then the slightly curved ones that also have a slightly wavey edge. So I would say you have the right ones for antifoul. What you don't want to do is use the curved ones when scrapping varnish of wood!! I learnt the hard way.

Well these are what came with the scraper.


As can be seen there is a slight but definite convex curve. And the same on the spare blades I bought from Total Tools. They say it's to stop the blade digging in. But it seems to me that it will take more from the centre which is not what I want. Thoughts please?

it will be fine.
If anything, the slight curve will minimise the edges of the blade accidently gouging in.
Plus you mentioned the antifoul is thick, you will need as much help as possible. The centre of the blade will probably wear first anyhow, so it might be a good feature.


Were you planning to re barrier coat again after sanding?
Just Norglass shipshape or the like, to seal up any inevitable scrapes.
Next slipping season will be cruisy by comparison

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crustysailor said..
it will be fine.
If anything, the slight curve will minimise the edges of the blade accidently gouging in.
Plus you mentioned the antifoul is thick, you will need as much help as possible. The centre of the blade will probably wear first anyhow, so it might be a good feature.


Were you planning to re barrier coat again after sanding?
Just Norglass shipshape or the like, to seal up any inevitable scrapes.
Next slipping season will be cruisy by comparison

Ok thanks, I will see how it goes. I've got around 10 different ones including the Ozito so hopefully a couple do the trick.
I'm not sure about the painting side as I've actually never antifouled before.I'll be talking to the expert in the Marina but any advice or info happily received.

An easier way for this job is to use a power planer. Oh no!!! Shock horror.
It works. You just need to set the planer for a shallow cut (say 1 mm) and not put too much pressure on it. Try it on the flatter areas of the hull first to get your technique right then graduate to the more curved parts. It obviously will not work on the concave areas.
I did it successfuly on anS&S 34 hull some years ago. The Ozito planer is still going strong.

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cisco said..
An easier way for this job is to use a power planer. Oh no!!! Shock horror.
It works. You just need to set the planer for a shallow cut (say 1 mm) and not put too much pressure on it. Try it on the flatter areas of the hull first to get your technique right then graduate to the more curved parts. It obviously will not work on the concave areas.
I did it successfuly on anS&S 34 hull some years ago. The Ozito planer is still going strong.

Thanks, I had thought of this and I do have a planer but was a bit concerned if it would do any damage. And I guess messy? Good to know you've done it successfully though so I might give it a try if the multi tool doesn't work.

Don't do it ! An electric plane will take the gelcoat without discrimination. If you've got an osmosis issue it's the way to go. But if you just want the old antifoul off blast the crap out of it with a big balls pressure washer & scratch around with that nice curved scraper you have, then some wet sanding to feather the bumps It would be wise after all that effort to use something to reseal the substrate and form a tie coat that is compatible with your antifoul

^^^.This.
Its not rocket science, just messy.
Have a crack, seal it, antifoul it, then go sailing. thats all.

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woko said..
Don't do it ! An electric plane will take the gelcoat without discrimination. If you've got an osmosis issue it's the way to go. But if you just want the old antifoul off blast the crap out of it with a big balls pressure washer & scratch around with that nice curved scraper you have, then some wet sanding to feather the bumps It would be wise after all that effort to use something to reseal the substrate and form a tie coat that is compatible with your antifoul

Second this, if you use a planer the odds are that you will regret it.