Hull bottom renovation project

Maintenance and refit discussion
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Hull bottom renovation project

Postby Antti_DD » Mon Feb 03, 2014 9:45 pm

During the previous winter (2012/2013) we did a full bottom paint renovation project. Right after the lift out in September, Dolphin Dance was stripped naked from the old layers of antifouling and epoxy barrier coating. Then she was let to dry over the winter for six months before painting new layers of epoxy coating and antifouling in the spring.

The reason for this fairly large project was, that I noticed after the first season, that the antifouling and epoxy coating was missing at few places in the bow section, and shiny white gelcoat was clearly visible. It seemed that the gelcoat was not sanded before applying the original epoxy coating, which was perhaps the reason, why the epoxy did not stick well to the gelcoat. I could reveal more gelcoat by scraping the bottom paint around those areas. However, the epoxy barrier coat appeared to be mostly very sticky, so removing all the bottom paint with hand scraping method would have been very difficult and time consuming. Furthermore, it was very difficult to tell what was what in the bottom, since there were multiple layers of old antifouling paint and telling the difference to the epoxy barrier coat proved to be difficult. Thus, the only option to gain peace of mind was to get rid of all the old bottom paint and apply new layers of epoxy and antifouling in the spring.

The old bottom paint was removed by soda blasting method, where normal baking (or cooking) soda is sprayed against the surface using compressed air. Soda blasting was chosen as it is more gentle to the gelcoat than sand blasting. To my surprise, the bottom paint appeared to be mostly very sticky, so the guys from the soda blasting company had to change to glass bead at some places to improve the efficiency of blasting. They commented later on that it was the most difficult job, that they had done. So in case of Dolphin Dance, the bottom paint appeared to be not very uniform, as it was mostly very sticky, but flaking easily off at some places in the bow and keel.

Soda blasting.jpg
Soda blasting
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DD stripped naked.jpg
Stripped naked
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The blasting also revealed some tiny pin holes in the gelcoat at couple of places. These were probably formed by air bubbles between the resin and gelcoat, when the hull was built. They were not of course a very nice thing to find, since that is where the moisture can start to collect, if it manages to penetrate the epoxy coating. Fortunately, the moisture meter did not show elevated readings on those areas. The small holes were filled in the spring, so in this sense, the boat is now in better condition, than when it left the yard some 20+ years ago.

Pin holes.jpg
Small pin holes in the gelcoat
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The job was finished by coating the underwater hull with five layers of Teknos Inerta 5 epoxy primer and two layers of Hempel Hard Racing (black) antifouling. Also the antifouling waterline was rised about two centimeters as the white stripe near the waterline was coated with white Hard Racing. Especially as the epoxy coating requires a lot of paint, I decided to opt for a less expensice paint manufacturer, and used Teknos Inerta, which is a Finnish alternative to Hempel's Light primer for example.

It would interesting to hear about your methods/experiences on osmosis protection? I have understood that in addition to normal antifouling/epoxy treatment, copper coating is another method for treating underwater hull. However, I have never heard about that kind of treatment used in Finland, so there might be even some environmental regulations against that, not sure about this though.

Ready for the new season.jpg
Ready for the launch
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Antti Laine, Forum Administrator
HR 29 # 483 "Dolphin Dance"
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Re: Hull bottom renovation project

Postby Chris » Wed Feb 05, 2014 7:37 pm

Unless a hull is scraped back from time to time, antifoul will obviously build up. Also if the priming layer was not carried out in ideal conditions it can lead to flaking and so what you were faced with Antti, is only too common and probably going to happen sooner or later. Fortunately, when I bought Impulse, the previous owner had just had her hull completely renovated and Coppercoated.

I am the one now benefitting from his actions as I don't need to antifoul each season. The coating is a copper powder in a water-based epoxy and in the right conditions can be applied by DIY. I am going to be recoating the rudder as I have ended up stripping it all off and will probably include a resumé of the application in the rudder posting.

So far it has performed well. Comparing the waterline with other boats in the marina, towards the end of the season, I would say coppercoat appears better but this is hardly a scientific study, just my observation. It is a permanent coating and not self-eroding like conventional antifouling so I would have thought there are no environmental issues. There is plenty of literature and info on how it actually works at

http://coppercoat.com/

One drawback though, but not really the fault of Coppercoat, it doesn't like being dipped in mud. The first season I had Impulse, the berth I was in was in need of dredging. At LWS the keel nestled into the mud. I just thought this mildly inconvenient as there were only a couple of occasions I had to wiggle my way through the mud to get into my berth.

When she was lifted at the end of the season I was horrified at the amount of marine growth about 500mm from the bottom of the keel. I contacted Coppercoat who explained that whilst the boat may have only been in the mud for a short time, the muddy coating had rendered the Coppercoat ineffective.

That winter I had to lightly abrade the surface where it had been dipping in the mud with fine wet and dry paper to revitalise the copper. Needless to say I requested another berth where I didn't touch the bottom. No problems since. So I would happily recommend it as a long-term antifouling.
Last edited by Chris on Thu Feb 06, 2014 7:51 am, edited 1 time in total.

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Re: Hull bottom renovation project

Postby Martijn » Wed Feb 05, 2014 9:51 pm

Super you dedicated a topic to this subject Antti and I think it's interesting to learn about the different treatments our fellow HR29-ners applied on the bottom. I was a very surprised by the fact DD had these air pockets since the hull was manufactured under Lloyds supervision. Obviousely not the full process in being controlled which in a way also makes sence. BTW I have checked with the Lloyds register (and also HR) if they still have kept a hull certificate since the one belonging to QUINT got lost switching owners. Both replied negative and said that certificates dating from that era are no longer kept in file. Do any of you still have the document referring to the hull number.

The hull bottom of Quint was treated as following; First three layers of International epoxy TAR were put over the hulls sanded gel coat. The last one being color white so wear of the anti fouwling top layer could be well observed. Secondly two layers of VC 17m were applied. VC17m is thin copper based anti fouwling with Teflon PTFE. The thin nature of the system ensures that the hull will not grow due to accumulation of thick layers like other more traditional products. The super slick surface and copper ensure nothing sticks to it. When pressure cleaning the hull recently not a single organic residue could be found left on the hull. Every year two cans of 750 ml are sufficient to cover it with two layers.

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Re: Hull bottom renovation project

Postby Antti_DD » Thu Feb 06, 2014 1:48 pm

Chris, I did some googling about the Coppercoat, and found out that the company promises 10+ years without need to antifoul. If it can really deliver what it promises, I think that the initial investment is paid back many times during those years. Does the epoxy resin carrier within Coppercoat mean, that you don't need to have any epoxy barrier coating in addition to the copper coat so it is basically applied directly on the gelcoat?

Martijn, how was the old bottom paint removed in the case of QUINT? About the Lloyds certificate, DD has the certificate and also the partly hand-written document of the inspection done prior to the delivery. I think that the idea behind the Lloyds certificate and supervision is also that they 'guarantee' for example that certain conditions in the hull lay-up process are met, but obviously, they cannot follow the whole production of every boat from point zero to finish. Furthermore, these boats (especially compared to today's mass production boats) are mostly handmade so there is always room for human error, even in case of a quality manufacturer.

Speaking of the air bubbles/pinholes in the gelcoat, it was interesting to read about similar findings in this HR 46 refit project: http://reginasailing.com/fixing-the-hull/
Leon (previously also an HR29 sailor) writes about fixing the hull:
We got two surprises.The first was that the gelcoat of Regina Laska appeared not to have had not been sanded or otherwise treated before adding the epoxy when she was originally built. Therefore, the gelcoat was still so smooth that large patches of epoxy came loose during the iceblasting.


He also found some tiny holes from the gelcoat after the iceblasting:
Despite the ice being very gentle with the hull, it shot through the the thin gelcoat and left thousands of tiny holes in the hull. The sight was not uncommon by the experienced members of the team, since other brands have the same problem with some hulls. It is very good that it is discovered, since how it can be treated correctly by filling all the hulls, which is a tremendous work.


Maybe you have already read about this massive refit project from the Yachting World magazine. They basically changed everything in that boat, built in 1997, and made it almost a brand new. The refit cost was over €300,000, but they calculated that they saved perhaps over €400,000 compared to buying a new boat with similar equipment. I think that Leon's story gives motivation for all of us, who are maintaining an old boat. When the basic construction and design is sound and strong, you can give a new life to the boat, even if she would be neglected as was the case with this HR 46.

You can read the whole story from here:
http://reginasailing.com/press/YW2013_8.pdf
http://reginasailing.com/press/YW_Sept_2013.pdf
Antti Laine, Forum Administrator
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Re: Hull bottom renovation project

Postby Chris » Thu Feb 06, 2014 6:33 pm

Antti, when I spoke to Coppercoat about the best way to remove the coppercoat from the rudder (a regrettable but necessary task), during the conversation they did say that some people do put on an epoxy prior to Coppercoat but it is unnecessary. I have to say that it was incredible difficult to remove which would indicate it is in itself a very hardwearing and protective epoxy coating as well as being an effective antifoul. So your financial calculations look even more worthy of consideration.

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Re: Hull bottom renovation project

Postby Martijn » Sun Feb 09, 2014 9:47 pm

Antti, the bottom of QUINT was treated four years ago and was done by a specialist before I bought the boat, this was one of the insentives for bying it. Therefore I do not know how the previous coating layers were removed. The job was done well since it is not showing any problems so far. The coppercoat I use is very thin and every year one application is sufficient for a whole season. This system is not accumulating thick layers so the hull does not 'grow', the surface stays slick and free from organic attack.

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Re: Hull bottom renovation project

Postby Mallemuk » Sat Oct 21, 2017 5:33 pm

I am in the process of "thinking about" scraping off the old layers of old anti fowling paint.... a project that I have thought about for years. Now I have second thoughts about the big project. Is it really necessary?
The previous owner had the hull pressure hosed five years ago by a company to remove a lot of old layers of paint but they didn't apply any extra primer. According to the company it wasn't necessary with more primer and they removed most layers of old anti fowling.
To day I scraped off paint from the rudder to test the status of the primer layers and I found it very difficult to tell the difference between primer and old anti fowling. Very easily I scraped straight into the gelcoat. At this point I was a bit surprised as I thought the old layers of primer would be stronger and more sturdy.
After removing most antifouling and primer on the rudder's port side I decided to stop and evaluate the project. There are no signs of osmosis, the anti fowling is not peeling and the hull looks fine. My point is: if it works don't fix it.

Any good advice from the forum?

Kind Regards,
John

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Re: Hull bottom renovation project

Postby Mallemuk » Mon Nov 13, 2017 6:54 pm

I decided to get a sandblasting company to remove the old layers of anti fowling; the idea of spending the next many weekends scraping off old paint by hand didn't' appeal to me.
Mallemuk is now back in her boat shed and I am ready for the next step of using polyester filler for the many pin holes and minor damages to the gelcoat after the sandblasting. Then I shall paint the hull with epoxy primer.
The sandblasting hasn't removed all the old primer and I am wondering how the the new two- component epoxy primer will react on the old primer used by Hallberg Rassy back in 1986 -if it turns out to be a one- component primer. If have tried to wipe a bit of thinner on a cloth on to the hull and some red paint (primer)does appear on the cloth. But does that mean that it is a one- component primer?!
Does any of you guys have any idea of which primer Hallberg Rassy would have used back then, one-or two component primer? ( I did ask them but they didn't have the answer) And how does a two component primer react on an old one- component primer?
Finally it is my plan to give the hull Coppercoating - I would be glad to hear any advice on the matter. Is it worth the effort and cost?

Kind Regards,
John

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Re: Hull bottom renovation project

Postby Chris » Mon Nov 13, 2017 7:23 pm

Hi John,

I have a Coppercoat on Impulse and have would recommend it if you want to stop carrying out the arduous task of removing and reapplying conventional antifoul each season.

Antifoul is horrible stuff in many ways and quite honestly I cannot understand why anybody still uses it.

Coppercoat once applied correctly is stable, protective, long lasting and works.

You may have to do a couple of pressure washes during the sailing season if you don't use the boat regularly (once a week).

I am unable to offer any advice with regards to your primer issues but suffice to say it would be best to get back to the original gelcoat. I would contact Coppercoat for their advice they are very helpful. Coppercoat is an epoxy in itself and offers much better protection than polyester resin as well as being an effective antifoul.

All the best

Chris

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Re: Hull bottom renovation project

Postby Mallemuk » Mon May 07, 2018 8:11 pm

Hi

I finally finished the Coppercoat treatment of the hull and I 'll have the boat launched in a few days. It will be interesting to see how Coppercoat reacts compared to conventional antifouling
After sandblasting of the hull I sanded away the remains of old primer - just to be on the safe side. Then I used an epoxy filler to fix minor scratches and pinholes in the hull - and then applied 3 coats of epoxy primer and finally 4 coats of Coppercoat. The project has kept me busy for a period of time but it has also been an interesting process. We have had a cold spring and it was difficult to get the desired temperature of minimum 12 degrees until recently. Having the boat in a boatshed made it the job a lot easier and since last week we have been blessed with nice weather making the job possible. With the help of two friends I applied the 4 coats of coppercoat wet-in-wet in one day.Then the epoxy had to cure for 5-7 days and after that a light sanding with sandpaper 240 and finally a rub down with a Scotchbrite pad.
It will be interesting to see what the hull looks at the end of the season.

Kind regards,
John, Mallemuk

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