Question about hull coating

[Bill G]

I had the bottom paint soda-blasted off of the hull of my 1986 Vancouver 32 (built by Northshore Yachts in England) "Rincewind" last week and it exposed a bottom coating that my boatyard (in Maryland, USA) has not seen before. Can anyone give me some insight into what this is? (I have attached some pictures.) I am going to need to decide how to proceed from here. Do I need to completely strip off this coating? Or can I use an epoxy fairing compound to smooth out the bottom? Any advice? Also, I have water in my rudder. I would appreciate advice from anyone who has dried out and resealed a Vancouver rudder. (Lots of work ahead for me!)
https://plus.google.com/photos/11427...KzMgqj-jdub9QE

[minaret]

The pics are before blasting right? Got any post blasting pics?

[oceannavigator]

It *looks* like a bunch of anti fouling paint over raw fiberglass. What more can you mention about the texture?

Certainly, you have to get down to bare glass to use an epoxy fairing mix.

[Cheechako]

Assuming the rudder is a foam filled one. open a big window with a skil saw on one side. Save the panel. Gouge out all the old waterlogged foam. Let it dry out well and inspect any welds where the tabbing is attached to the shaft. Core a couple holes on the top end and replace the window and glass it in place. Taper the perimter of the window as well as the ruder to glass it back together. Then fill the rudder with your choice of material.. something like epoxy or casting resin with a lightweight mix in it.
It's really not a bad job, you just have to go right at it and get it done. That's a big rudder!
Those pics are pre soda blast I hope? It appears like I see some glass directly below the paint. If those pics are after blasting... you got screwed.

[Bill G]

Thanks for the input so far: The pictures that I posted are post-soda blasting. The blasting took off layers of red bottom paint. The yard is saying that this coating is harder than gel coat. Below the blue coating is bare fiberglass.

[minaret]

Originally Posted by Bill G

Thanks for the input so far: The pictures that I posted are post-soda blasting. The blasting took off layers of red bottom paint. The yard is saying that this coating is harder than gel coat. Below the blue coating is bare fiberglass.

Grind that stuff off. I see a solid day or two of work here, for an experienced pro. Don't let that yard take you for a ride. Then barrier coat and bottom paint, after ensuring the hull is dry.

[HappyMdRSailor]

Originally Posted by minaret

Grind that stuff off. I see a solid day or two of work here, for an experienced pro. Don't let that yard take you for a ride. Then barrier coat and bottom paint, after ensuring the hull is dry.

*** Hommmmmm.....***

Resident Resin Head has spoken.... Proceedeth with the task which you bear....



(edit: and you're lucky you didn't have to trek your sorry butt to Nepal for that wisdom)

[Suijin]

Not sure what the stuff is, but it's clear that the rest of it needs to come off and you need to fair the bottom and barrier coat. Like Minaret said a couple of days with a grinder with the appropriate grit should give you a surface you can work with. The fairing work, depending on how the bottom ends up, is going to take longer than grinding all that off. There is no way in hell I would just try and fair over that stuff...not only will it take you longer than if you take it all off, but it's just asking for trouble down the road. Do it right the first time and you'll sleep better at night.

I'm with Cheech on the rudder repair approach. Make sure you give it a good long time to dry, and don't bother with moisture meters. You have enough metal in that rudder that getting an accurate reading is going to be pretty hit or miss.

[delmarrey]

I'm with minaret. There's nothing out there that would be used on a boat bottoms that would be harder then gelcoat. To me it looks like a spray-on gelcoat that has delaminated.
Power sand it down to bare FG and barrier coat it. Then a light hand sanding and bottom paint.

Depending on the core material of the rudder will warrant its repair. If foam cored it needs to have some drain holes at the very bottom and you need to find where the water got in.

If it's a wood core and how wet it is will determine how to proceed. Drill a couple holes at the very bottom edge and see what material comes out on the drill bit, and let us know. I would guess its wood cored from its design.

[Nicholson58]

This looks like friable anti-foul bottom paint over partly blistered gel coat. Whatever, it is not the gel coat and you probably need to remove it.

I have a few pictures here on CF. Look for rudder rebuild, hull blisters, & big blisters. Yours looks reminiscent of ours.

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Ours started with a black tar anti-foul that had to be stripped with scrapers. Blaster would not touch it. After scraping, you can see in the photos the blue bottom paint below the black as well as the white gel coat. The blue was easily removed by blasting as this stuff had the consistency of hard chalk.

After blasting there were small gel blisters exposed and opened about 1 per square inch. We Diligently opened every blister with a carbide burr on a 20,000 rpm tool. I used a 1/4" drive panel cutter, (tiny router). Every hole was faired out to good gel and then back filled with thickened epoxy.

There were also several deep GRP blisters up to about a foot in diameter and 3/8" deep. These were ground out until solid hull was encountered. You should first drill a tiny drain hole in these blisters to relieve the pressure or you might get it in your face. We found these blisters as lump-shadows as the sun threw shadows in different directions. Repair is easy if you are comfortable with epoxy & glass. Pre-cut patches to fit of increasing size. Mix the epoxy and dip the glass starting with the smallest. Apply to the prepared divot in progressively larger size. I find a throw-away paint brush helpful. Cover over the patch with polyethylene film and then apply force to compress the patch and force out excess resin. I used timbering and heavy weights.

We used a right angle grinder with 40 grit carbide 9" diameter wheel. One day, 58 foot hull, sore arms.

Use an epoxy based barrier coat to finish. We applied 6 coats of Interprotect 2000E

On the rudder, If the skin is viable (ours was not), the window and clean-out is great. I suggest the filler to use is US Composites 635 THIN resin with 3M glass microballoons as filler. This is syntactic foam, 3000 psi compressive strength and totally waterproof forever. This resin is NO Blush, very slow cure so no heat and also about 1/3 the cost of WE$T. I use this and no other for nearly all repairs. http://www.uscomposites.com/ Shipping is non-hazardous.

[mitiempo]

Originally Posted by Nicholson58

Pre-cut patches to fit of increasing size. Mix the epoxy and dip the glass starting with the smallest. Apply to the prepared divot in progressively larger size.

I agree except for this. The largest piece of glass should be put on first, working to the smallest. This way the sanding needed before fairing will not remove any of the piece that gives the most strength.

[Cheechako]

I'm just not seeing anthing (yet) to indicate filling and fairing is required...? By the time that is all ground off you will know. But there's nothing that says a bottom has to be smooth as a spanked baby's butt. any small things will smooth a lot from a couple coats of epoxy resin.

[David M]

Do the acetone test. If acetone dissolves it, it is probably anti-fouling paint. If acetone does not dissolve it, it is either gel coat or an epoxy barrier coat.

Do not guess at what it is and risk your coatings not being compatible.

[Nicholson58]

close ups downloaded sure looked like the standard old-fashioned bottom paint we use on the Great Lakes & pips of gel missing. Refer to my photos close up. Its too bad the blaster didn't strip it clean.

I've never worried about the biggest layer first as our hull is 1-1/2 inch thick & solid. Do make sure you fully wet every part of the hull and all of the patch. Dry glass is long-term death. Also, I would never use any resine but epoxy

note the blue bottom paint. This used to be the only cheap paint and covered 4 of 5 boats.

[delmarrey]

Originally Posted by David M

Do the acetone test. If acetone dissolves it, it is probably anti-fouling paint. If acetone does not dissolve it, it is either gel coat or an epoxy barrier coat.

Do not guess at what it is and risk your coatings not being compatible.

A rag soaked with MEK will devolve epoxy slowly. Acetone evaporates too fast.