To grind or not to grind?

[if1038]

Hello! Sorry for my English)) This spring I bought IF 1038, 1972 in Goteborg. Now I lifted it after the trip and inspected the hull. It looks perfect, but I dont know, what have I do now? Is I need to grind old antifouling to gelcoat, or it could be better to leave the boat till the spring without any manipulations? In general, I meant to paint underwater part of the hull with the epoxy compound (or primer). But reading the forum, now I'm not sure with my next steps. Is anyone could to help me to decide, what I could do in nearest time? The IF is staying under open skies, and I not having a hygrometer to test laminate. Launching is planned to the May 2019, and then IF will be sailed in a cold and strongly salted water of Arctic Ocean.

[johan swe-1870]

Congrats to the boat and welcome to the forum!

If the underwater parts look fine and smooth and has no blisters I think you can leave it. Just paint new antifouling. But if the primer is still the original Polygrund (often dark red) and there are many years of antifouling on top perhaps you have better remove everything and start all over.

Your trip makes me curious: which whay did you get the boat from Gothenburg to Russia? And where is it now?

[if1038]

Oh, thanks)) Yes, it is really looking fine. And the old "Polyground" is still laying there - is I need to grind it off too? I planned to use any "hard" antifouling, which could to work for 2-3 seasons. In fact, in those waters, where I'll sailing, the fouling is very weak. And there I won't have an able to make a good repairs in next few years.

My trip were not been extroordinary)) I just sailed around Sweeden via the sea, then i went to Alands from Stokholm archipelago, and sailed to Viborg, Russia along Finland. I dont been hurry, and all this taken a 3 months. Now my IF is wintering near Viborg in Sovetskiy (Johanness) village. Next year I will go to the Barents and Kara sea via Belomorkanal channel - I was sailed this marschroot earler. But now, with so perfect boat, I believe, what I could to go more eastern, then earlier.

[if1038]

Oh! I brought home a rudder for the experiments It have 6 layers of paint:
light-blue layer with soft mechanical consistence;
deep-blue layer - soft;
black layer - hard,
thin light-blue layer again, with undefined mechanical cosistence;
polygrund.

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Maybe, it will be enough just to scrap off only 2 upper blue layers? Have you any ideas about the type of a hard black paint?

[johan swe-1870]

That's an impressive tour you have made already!

I am no expert on these things. But I think that the original red Polygrund primer is only a primer, i.e. it is not watertight enough. So when sailing in salt water you risk some water penetrating the glassfibre laminate and that can lead to osmosis blisters. The best cure is to remove the old antifouling and put on epoxi primer and new antifouling.

When I removed my old paint, I manually scraped off all antifouling with a paint scraper. Then I sanded the old primer to even out the marks from the paint scraper, which removed most of the Polygrund primer also. Finally I washed thorougly and let the boat dry outside all winter. In the spring I sanded a little again and then I painted epoxi in several layers, 3-4 layers I think, and finally some layers of antifouling. Be aware that it can't be too cold when working with epoxi!

It all depends on how you think the boat is now, and If you have the time to do the work.

I am sure others will add their points of view on the subject.

[if1038]

You will be laugh, but I find the best tool to fast and safe scraping upper layer... This is the most ordinary axe, used like a scraper.

5 minutes, and the rudder is ready to grinding. I found a couple of blisters under the paints, but I think, what this is not critical. Moreover - this is rudder, which always keeping wet, with water inside! I drilled the holes, recommended here.

In the end I think to leave the black paint as is, because it is very hard to grind off, and it staying very well on a grund. Also, I suggested to use an industrial vinyl-epoxy antifouling. But I still feeling doubts about barrier layer on a probable-wet laminate.

Yes, I have a lot of time - this is primary target for this winter to prepare the boat. By the way, I always thought, that in salt water polyester laminate lives much longer, than in fresh water.

And after tomorrow I'll go to the boat. With the axe

[if1038]

I'm started. Today I was scraped all the left board and I wasnt found there any osmosis or blisting. It's great!

I think, that "black paint" was exactly that "barrier layer". It have a perfect adhesion to the gelcoat, and it very hard to scrap. In short, I mean, that is not nessesary to totally remove it - just do matte, then cover with the epoxy.

I can't attach photos. If you intersted, you can look its here: https://vk.com/album240938277_256580246

[if1038]

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[johan swe-1870]

I think you are doing well! If the black paint sits that hard, then leave it.

From the pictures I think you have made the right decision to renew the boat underwater painting.

Have you tried a paint scraper with a new, good and sharp blade? I think you will be surprised of how much easier it is with the rigth tool. I think I used 6 blades when I did mine, and it was worth it.

[if1038]

Hello again!

Spring is coming, and I started to grind. In 8 hours total, I grinded off a half of boat. Later I'll grind a right half, and will waiting about a month.

The technology of covering I see as follows:
When the constant positive temperatures will established, I will wait for a few Sunny days. Then I'll grounding IF's bottom with a pure epoxy. After about 12hrs, I'll overcoat first layer with mixture of epoxy and aerosil (tixotropic additve, which helpes to make more thick layer). Then, after another 12hrs I'll cover this with the most common and xx ground - for further layer of antifouling.


Sadly, I have no photos less than 800px.

https://pp.userapi.com/c850428/v8504288 ... SZ2UzE.jpg

https://pp.userapi.com/c855232/v8552328 ... j1l45A.jpg

[johan swe-1870]

Well done!

The forum software should scale down your images automativally if they are too big. Doesn't that work?

[if1038]

Oh yes! It working!)))

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My wife posing

By the way, my brother proposed me to cover the bottom with the polyurea. His firm is engaging in the application of such coatings. In the past I has such experience - I was coated my another boat with polyurea. However, in that time I failed my work, due to technology disruption. Now, the work would make a real specialist with industrial equipment. Hmmm... I thought hard.

[if1038]

So, I grinded hull quickly for a few days and leaved to stay it naked during April. A dry and sunny weather is staying, and this qute perfect! Now is time to a final preparing for a painting Also, I want to lift a waterline for a few centimeters up.

After a couple weeks I'll buy about 20kg of epoxy resin and some primer in the sales office of chemical factory, and then could to paint the bottom.

[johan swe-1870]

That looks good! I think it is clean enough for the epoxy painting. Those last old Polygrund primer rests wont have to be removed.

Follow the instructions for the epoxi resin. Wait for some days with good weather, so that you can paint the layers with the proposed settling time between. If you wait too long after one layer, you probably will have to sand before putting the next one on.

[if1038]

That looks good! I think it is clean enough for the epoxy painting. Those last old Polygrund primer rests wont have to be removed.

Follow the instructions for the epoxi resin. Wait for some days with good weather, so that you can paint the layers with the proposed settling time between. If you wait too long after one layer, you probably will have to sand before putting the next one on.

I planning to paint the layers without a sanding: it just necessary to put next layer bofore a full hardeneng of previous - with about 10hrs periods. I worked a lot with materials of this firm in a past and got some expirience with it. And factory technologist recommend me a same scheme. In this fact, I'll wait a more warm weather in May with positive temperatures at nights, to live and work in a boat.