Barnacle damage or zebra muscles?

[PerfectPirate]

Definitely you can extend the barrier coat up over the bottom portion of the boot stripe. If I were tackling the job, my approach would be to sand the top one inch of the barrier coat that is on there, to remove the bottom paint, taper it down and provide some "tooth" for the new epoxy barrier coat to bond to, then roll layers of barrier coat overlapping that up to whatever new waterline you want to set.


In the original photos, your bottom paint looks like VC-17, which is a great favourite here on the Great Lakes. I have used it here for the past 40 years. However, it may not be the bottom paint that you want for salt water exposure. If you are going to use a different bottom paint, then you first need to remove the VC-17 because it is Teflon based and the only thing that will stick to it is more VC-17 (and of course some slime and barnacles). If that is the case, you will need to sand the bottom down with some 150- or 180-grit paper, using a random orbital sander. If you are already having to sand down the bottom for this reason, then it may make sense to seize the opportunity to apply a couple of additional coats of Interprotect. Otherwise, I would not bother with the rest of the bottom, unless you are actually seeing gelcoat problems elsewhere. I have redone bottoms on boats five times in my years of ownership and trust me, it isn't something that you want to do unless it's REALLY necessary. Of course, once I had done it properly, I never had to do it again on the same boat. Wear really good filter masks and attach a Shopvac with an ultra-fine filter to the sander if you decide to do the job.

The Contessa 32 is a beautiful boat, a classic well worth the investment of time and care. I remember touring 'Sean Ios' back in the eighties, a Contessa 32 which had completed a circumnavigation of the world. Even after all those sea miles, she still looked great and completely ready to do it again. If you haven't already, read John Kretschmer's book 'Cape Horn to Starboard', in which he tells the story of sailing a Contessa 32 all the way from England across and down the Atlantic and around Cape Horn.

[Avoegeli]

Originally Posted by PerfectPirate

Definitely you can extend the barrier coat up over the bottom portion of the boot stripe. If I were tackling the job, my approach would be to sand the top one inch of the barrier coat that is on there, to remove the bottom paint, taper it down and provide some "tooth" for the new epoxy barrier coat to bond to, then roll layers of barrier coat overlapping that up to whatever new waterline you want to set.


In the original photos, your bottom paint looks like VC-17, which is a great favourite here on the Great Lakes. I have used it here for the past 40 years. However, it may not be the bottom paint that you want for salt water exposure. If you are going to use a different bottom paint, then you first need to remove the VC-17 because it is Teflon based and the only thing that will stick to it is more VC-17 (and of course some slime and barnacles). If that is the case, you will need to sand the bottom down with some 150- or 180-grit paper, using a random orbital sander. If you are already having to sand down the bottom for this reason, then it may make sense to seize the opportunity to apply a couple of additional coats of Interprotect. Otherwise, I would not bother with the rest of the bottom, unless you are actually seeing gelcoat problems elsewhere. I have redone bottoms on boats five times in my years of ownership and trust me, it isn't something that you want to do unless it's REALLY necessary. Of course, once I had done it properly, I never had to do it again on the same boat. Wear really good filter masks and attach a Shopvac with an ultra-fine filter to the sander if you decide to do the job.

The Contessa 32 is a beautiful boat, a classic well worth the investment of time and care. I remember touring 'Sean Ios' back in the eighties, a Contessa 32 which had completed a circumnavigation of the world. Even after all those sea miles, she still looked great and completely ready to do it again. If you haven't already, read John Kretschmer's book 'Cape Horn to Starboard', in which he tells the story of sailing a Contessa 32 all the way from England across and down the Atlantic and around Cape Horn.

Funny you should mention John Kretschmer. He is the reason I discovered contessa 32. Big fan! Read all of his books.

10mm seems awfully thick. That's well over a 1/4"!! How is that even possible without a massive lip? I indeed am wearing VC17. New coat went on when I bought the boat. I purchased her in northern Michigan and sailed her home. I then went another season on the Hudson with that same bottom paint. Now I'm going to use sea hawk monterey for this upcoming season. I need to, like you said, get that vc 17 off of there. To what degree do I need to remove the VC17? So there is no trace of it at all? Since my boat is launching in a couple 3 weeks, I don't think I will address this mild osmosis until next season. When I can properly sand dry and repair damage. At which point I will add more layers of interprotect 2000. And that will be that. Right, there is no reason to apply barrier coat over osmosis?

[PerfectPirate]

Okay, some metric confusion here. One mil is not a millimetre, it is engineering speak for 1/1000th of an inch. So a ten-mil thickness ends up being 1/100th of an inch, rather than 3/8 of an inch. You should expect to gain about two mil of thickness with each dry coat of Interprotect. A more reliable measure is to use Interlux's guidelines for how many gallons of Interprotect should be applied. Because the shape of my hull, like yours, creates somewhat more bottom surface than the typical cruiser/racer, or round-bottomed modern European boat, I treated my Ontario 32 as if it were a 36-foot sailboat by Interlux guidelines, which can be found in their guide for "The Prevention and Repair of Gelcoat Blistering" at:
https://www.international-yachtpaint...tect-guide.pdf

The Sea Hawk Monterey looks to be a nice paint to live with. However, if you are planning on sanding down the bottom, it will be far easier to do this with only the VC-17 paint on it. This is because VC-17 goes on in a hard layer which is only microns (millionths of an inch) thick. The liquid contents in the can are mostly a solvent which acts as a carrier for the Teflon and copper powder. You can literally watch it dry in minutes and you pour it into the roller tray in very small quantities, especially in warmer weather. So it sands off very quickly and easily, even with a relatively fine grit sandpaper. If you are going to be recoating with more Interprotect, or with the Monterey, then I would use an 80-grit paper to provide tooth for the next layer to grip. The Monterey, however, will go on in a semi-hard layer with a thickness somewhat greater than Interprotect. This will be considerably more work to sand off than straight VC-17.

You are at a moment of decision. Your pictures show that a good portion of your VC-17 has already worn away. Everywhere that you are seeing light grey, you are already down to the Interprotect. If you want the Monterey to stick to your bottom, then you need to sand off the rest of the VC-17, otherwise the new bottom paint will simply slough off any area which still has a coating of VC-17. If you are already sanding off the VC-17, then it simply makes sense to fix your osmosis and apply more Interprotect now, before putting on the Monterey. Fixing the osmosis divots does not take that much time and, if the weather is moderately warm, you can roll three coats of Interprotect over your entire bottom in a long day of labour. I had a fortunate weather window back in early November and rolled on nine coats in four days, by myself, alternating layers of grey and white Interprotect to guarantee that I was achieving full coverage with each layer. As I mentioned before, that required five gallons from a bare hull, but you already have a decent layer on most of your bottom. You could easily do four coats per day on your boot stripe area and then maybe two more coats over the entire bottom. That would probably require two gallons of Interprotect and two or three days for application. If I were in your shoes, this would be my preferred approach, even if it meant delaying launch by a few days. If it is absolutely not possible for you to do this before this year's launch, then I would contemplate simply applying another layer of VC-17, since that will be easier to remove after haulout.

[Avoegeli]

Originally Posted by PerfectPirate

Okay, some metric confusion here. One mil is not a millimetre, it is engineering speak for 1/1000th of an inch. So a ten-mil thickness ends up being 1/100th of an inch, rather than 3/8 of an inch. You should expect to gain about two mil of thickness with each dry coat of Interprotect. A more reliable measure is to use Interlux's guidelines for how many gallons of Interprotect should be applied. Because the shape of my hull, like yours, creates somewhat more bottom surface than the typical cruiser/racer, or round-bottomed modern European boat, I treated my Ontario 32 as if it were a 36-foot sailboat by Interlux guidelines, which can be found in their guide for "The Prevention and Repair of Gelcoat Blistering" at:
https://www.international-yachtpaint...tect-guide.pdf

The Sea Hawk Monterey looks to be a nice paint to live with. However, if you are planning on sanding down the bottom, it will be far easier to do this with only the VC-17 paint on it. This is because VC-17 goes on in a hard layer which is only microns (millionths of an inch) thick. The liquid contents in the can are mostly a solvent which acts as a carrier for the Teflon and copper powder. You can literally watch it dry in minutes and you pour it into the roller tray in very small quantities, especially in warmer weather. So it sands off very quickly and easily, even with a relatively fine grit sandpaper. If you are going to be recoating with more Interprotect, or with the Monterey, then I would use an 80-grit paper to provide tooth for the next layer to grip. The Monterey, however, will go on in a semi-hard layer with a thickness somewhat greater than Interprotect. This will be considerably more work to sand off than straight VC-17.

You are at a moment of decision. Your pictures show that a good portion of your VC-17 has already worn away. Everywhere that you are seeing light grey, you are already down to the Interprotect. If you want the Monterey to stick to your bottom, then you need to sand off the rest of the VC-17, otherwise the new bottom paint will simply slough off any area which still has a coating of VC-17. If you are already sanding off the VC-17, then it simply makes sense to fix your osmosis and apply more Interprotect now, before putting on the Monterey. Fixing the osmosis divots does not take that much time and, if the weather is moderately warm, you can roll three coats of Interprotect over your entire bottom in a long day of labour. I had a fortunate weather window back in early November and rolled on nine coats in four days, by myself, alternating layers of grey and white Interprotect to guarantee that I was achieving full coverage with each layer. As I mentioned before, that required five gallons from a bare hull, but you already have a decent layer on most of your bottom. You could easily do four coats per day on your boot stripe area and then maybe two more coats over the entire bottom. That would probably require two gallons of Interprotect and two or three days for application. If I were in your shoes, this would be my preferred approach, even if it meant delaying launch by a few days. If it is absolutely not possible for you to do this before this year's launch, then I would contemplate simply applying another layer of VC-17, since that will be easier to remove after haulout.

Well that makes a lot more sense on the mil thickness. I feel stupid now🤔. The interprotect you see is because I've already began sanding and wiping down with acetone. There was barely any visible after hauling out for winter. I was removing VC17 in prep for Monterey. I think I'd like to try and get this done before launch. So my next question is do I grind out the signs of osmosis and forgo any drying out period since I don't have that kind of time. And so I just grind and fill with thickened epoxy and prep for interprotect 2000.? I'd rather do the work instead of wasting any money on anymore VC17. Will I need peel ply or pva or gel coat on top of the repair area so epoxy cures? Or will it be ready to accept interprotect since it's epoxy also? My plan would be to cover original boot stripe with barrier coat. My boats keel is also sitting on a plank of wood which obviously prohibits me from getting to bottom of keel. Also jack stands blocking is keeping me from 4 squares on hull. I'm not sure about your boat yard but there is no way I'm gonna get into the lift for any length of time to complete those areas. If I'm lucky I'll be last in sling for the day and I can touch up bottom paint in those spots before morning launch.

[garyfdl]

Originally Posted by Avoegeli

do I grind out the signs of osmosis and forgo any drying out period

There's a site called "Epoxy Products" https://epoxyproducts.com/ run by a guy named Paul Oman. IIRC he has product that can be applied to wet surfaces, and then be painted over. He is also a wealth of knowledge, and will get back to you if you email or call. I've used his 'stuff' for years off and on. As good as West (IMO) and not nearly as expensive.

[Avoegeli]

Am I supposed to remove the VC17 completely so there is no trace it was ever on there? Seems like I'd be removing a bunch of interprotect in that process.

[fstbttms]

Originally Posted by Avoegeli

Am I supposed to remove the VC17 completely so there is no trace it was ever on there?

VC17 is not compatible with whatever non-teflon paint you intend to use. So unless you want your new paint to fail, you remove all traces of the old.

[Avoegeli]

Originally Posted by fstbttms

VC17 is not compatible with whatever non-teflon paint you intend to use. So unless you want your new paint to fail, you remove all traces of the old.

Is there a secret to a more efficient approach? I am using 80 grit and it takes a lot of time and effort to get to no trace at all. Should I be concerned about wearing away the inter protect or removing too much of it? Is it a combination of solvent and sanding?

[fstbttms]

Originally Posted by Avoegeli

Is there a secret to a more efficient approach? I am using 80 grit and it takes a lot of time and effort to get to no trace at all. Should I be concerned about wearing away the inter protect or removing too much of it? Is it a combination of solvent and sanding?

You're asking the wrong guy. This kind of work is why they invented money- so you can pay somebody else to do it

[garyfdl]

Originally Posted by Avoegeli

Am I supposed to remove the VC17 completely so there is no trace it was ever on there? Seems like I'd be removing a bunch of interprotect in that process.

Yes.

https://sailingmagazine.net/article-...e-bottom-.html

[PerfectPirate]

Originally Posted by fstbttms

You're asking the wrong guy. This kind of work is why they invented money- so you can pay somebody else to do it

While there are some jobs that I leave to professionals with expertise in certain technical issues (like rebuilding an engine), I generally prefer to do my own work because nobody else will be as determined to 'get it right'. I also like to know exactly what has been done to my boat and how it was done. Professionals have to worry about the fact that time is money, either in terms of lost income or increasing charges to the customer. Generally, this means that they cannot afford to be perfectionists.


The original owner of my boat was a Scots engineer who did not cut corners and hung on to the boat until he was 91 years old. However, in his old age he had to hire people to do labour-intensive work for him. So, when the bottom had to be done, he hired 'professionals'. They sand- or soda-blasted the bottom to get rid of old paint, but did not bother to sand off the remaining traces that were left behind. The owner wanted four gallons of Interprotect applied, but only one gallon was actually put on, at least as far as I could determine. At most two gallons, but I really don't think so, based on a lot of experience in sanding and coating bottoms. The net result is that when I bought the boat, some fifteen or more years later, I had to sand everything off, including the Interprotect, and start over. Thanks to Covid issues, this burned up a couple of seasons.

When I bought the boat everything looked good and I was happy to have a hull that had already been barrier-coated and protected with Interprotect, a product I had learned to have faith in. However, after the deal was closed and some really warm weather arrived, a host of little bubbles appeared on the bottom, revealing the inadequacy of the initial application of Interprotect. So I like to do work myself and be sure that it is done properly.

[PerfectPirate]

Originally Posted by Avoegeli

Is there a secret to a more efficient approach? I am using 80 grit and it takes a lot of time and effort to get to no trace at all. Should I be concerned about wearing away the inter protect or removing too much of it? Is it a combination of solvent and sanding?

Your pictures show the typical "eggshell" finish of Interprotect which has been rolled on and not subsequently sanded smooth. I always sand mine smooth (180- or 220-grit) because, doofus that I am, I'm a racer and I want my bottom to be as slick as possible. VC-17 goes on in such a thin layer that it does not add any texture at all, unlike ablative paints. For this reason, I always add a couple of extra coats of Interprotect, to give me some room for sanding.

In your case, you need to take it down to a uniform, light-grey finish that is only Interprotect, with none of the dark grey VC-17 visible. This will in fact remove a bit of thickness from your barrier coat, which is why I recommended putting on at least another two coats after you have sanded off the VC-17. In your original pictures, there appears to be a clearly defined 'ridge' at the top of the barrier coat. To me this indicates that whoever applied the original barrier coat did not cheap out and actually built it up to an adequate thickness. Of course, people who go to the extent of buying a Contessa 32 usually tend to be very thorough in other aspects of equipping and maintaining their boat. So you have some room to work with, especially if you add a couple of fresh coats. Once the bulk of the VC-17 is off, try removing the remnants with 120- or 150-grit sanding discs. Less aggressive, so less removal of material. I also use a triangular sanding pad on a multi-tool for dealing with the tighter spaces and sharper curves.

[gulfislandfred]

A less expensive and extremely effective barrier coat is industrial coal tar epoxy. It is used to coat mild steel that will be immersed in salt water. Often used as a barrier coat on cast iron keels.
I get mine from an International Paints dealer. Under $100 Canadian a gallon.
I think one of the yacht paint brands has a tar/epoxy paint at yacht prices.

[Avoegeli]

Progress so far. The plan is to remove dark paint and get down to original red boot stripe. Fair and sand any osmosis damage above the current barrier coat. Which is a very small area. Negligible. Then I'm taking 3 gallons of interprotect 2000e and raising the water line to top edge of original boot stripe. See what happens when you pick at the scabs? More work!

[Franziska]

Little suggestion, get different colors for the barrier coat layers. That way you can ensure that you don't miss a spot.

Ideally note the colors and materials you used for future reference. When you work on the hull few years down the line, it's handy to know things like ".. the red barrier coat is the last layer before fiberglass.." or similar.

It's also good to keep track on what antifouling you used.

Last not least, document where the original waterline was in relation to the new one.