boat bottom repair advice needed

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anaisdog

pictures are at https://www.dropbox.com/sh/e2obli3c7mv27di/AAA8aKllYMzmQg2HPNoo0-A9a?dl=0, one example at https://www.dropbox.com/sh/e2obli3c7mv27di/AAA8aKllYMzmQg2HPNoo0-A9a?dl=0&preview=P1040413.jpg

i have a blistered boat bottom, none look severe but i'm looking for what to do, videos for advice, etc... for how to fix it.  as far as i can tell, i'm to dremel or "hard sand" out the blisters, put on west 410, sand again, put on interleux 2000, sand, vc17.  i just want to confirm these are compatible products and i'm just looking for some how tos before i make a bad situation worse.

thanks

becki kain
Hull #99, c34, 1986, Detroit Yacht Club

britinusa

To my very inexperienced eye (but I'm pulling our boat this December for a butt paint job), they look like poorly applied bottom paint rather than blisters.

Paul
Paul & Peggy
1987 C34 Tall Rig Fin Keel - Hull # 463

See you out on the water

Engine:M25XP

anaisdog

Hull #99, c34, 1986, Detroit Yacht Club

mark_53

I don't see blisters but you appear to be missing the anode on the strut.  That may have been the cause of the pitting.  Blisters are best seen when you first haul the boat.

KWKloeber

#4
becki

looks like blistering (examples P21, P25, P17, P40) but certainly not extensive and none severe.  Very typical - pea size, not dime or quarter size.  If blisters they should shrink back on the hard and then reappear when whetted again (next haul.)  Nothing critical (as in boat threatening.)  To verify, pop a couple of the zits with a sharp pocket knife - they should oooze water if a blister, or will be hard or flake off if the cause is paint/prep.

The other areas are more of an issue to me than the slight blistering.  Looks like underneath might not have been prepared, something foreign on the there when applying the VC, coat too heavy, or maybe temperature/humidity?  The larger peeling areas you might carefully peel off and see if you can tell if there's anything incompatible left underneath them, just to satisfy yourself/identify why. 

As far your paint sequence below, you have VC but what's your barrier coat?  Make sure they are compatible and barrier overcoat is compatible. (Interlux website has a chart of compatible paints, or call them or your supplier.)

Some of the areas (many) appear to be old (P7) where the VC was applied over what had already peeled, was missing, and not repaired and faired/feathered out.  The same might be true of some of the crazing.  Nothing I see is going to hurt the boat from floating and sailing -- I have seen A LOT worse on floating graveyard boats that are still on the water after 30 years.

The deep cracking above the strut -- (where it has been sanded?) looks to extend into the substrate below?  Is that fiberglass showing below VC or is it barrier coat that appears to have cracks with VC remaining in them?

Is your garboard plug leaking rusty water?

If you don't already, get yourself a GOOD DA sander with a vacuum attachment if you are doing repairs yourself.

k
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

scgunner

     Becki,

         I wish my bottom looked as good as yours when I pulled it last July. I repaired around 475 blisters which is not unusual for my boat, I've done the bottom 7 times. I usually drill and fill, then sand and prime, followed by two to three coats of bottom paint.
         You've got a few options here; the best is a barrier coat but you're talking some serious $$$, next if your planning on racing you'll want to make the hull as smooth as possible(lots of fairing and sanding), lastly if you're just going to sail or cruise then I'd just chip, sand, fill, and fair the bad spots, prime and paint.
         Mark is right you need a zinc on your strut, I'm amazed your boat has made it 30+ years without one. It's easy just drill a hole the size of the zinc bolt dead center right through the strut.
Kevin Quistberg                                                 Top Gun 1987 Mk 1 Hull #273

KWKloeber

Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Noah

Becki- just for an FYI- if a wet spot is a true osmotic blister, (caused by water penetrating the gelcoat) when you pop them, the water that drains out will smell like styrene/vinegar. Some of your spots could just be just water trapped under cracked faring and flaking bottom paint. I would leave most of the small circled spots (probably true blisters) alone. When/if they get bigger, grind, rinse, dry, then  fair/fill, paint. Deeper ones may even need glass cloth patching.

Most of your issues look like poor fairing and paint application, (either applied over dirt, over incompatable sub paint, poor drytime, or applied to thick??? —causing bad adhesion/bonding/cracking issues. Just a guess without being able to poke at in person. All fixable by just working on/patching those areas.
1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig

anaisdog

the shaft was replaced when i first bought the boat, 6 years ago, and i'm wondering if the anode was just forgotten by the repair person.  i just sent him a note.
Hull #99, c34, 1986, Detroit Yacht Club

tommyt

Looks more like fairing or layers of bottom paint. What is the history on th boat? I ask because it looks like VC17 now, but was it something else prior and over laid wit VC. I see you are in Detroit. Freshwater, VC makes sense, but there is no way it would be as thick an application to show that much pitting.Freshwater also explains the sacrificial.
Tom Mallery, C34 #1697, 2004 MKII, Splash Dance

KWKloeber

#10
Becki I forgot to add re: a sander.  You  May already know this, but you can save a lot of time and sandpaper if you towel the VC off with acetone and sand just  what's underneath that.

Even if your shaft was replaced, there doesn't seem to be any sign that there was anything on the strut.  Of course you realize you don't want zinc in the Great Lakes.
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Noah

OK Ken, what anode does Becki need, if any? I am a saltwater sailor, not freshwater, but I believe Becki might benefit by a magnesium anode on her strut?
1990 hull #1014, San Diego, CA,  Fin Keel,
Standard Rig

KWKloeber

#12
Correctamundo mon ami

http://www.defender.com/html/zincs_info.html

It must be true, I read it on the Internet
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

tommyt

And the reason for the magnesium anode is???
Tom Mallery, C34 #1697, 2004 MKII, Splash Dance

KWKloeber

Quote from: tommyt on October 21, 2017, 05:58:38 PM
And the reason for the magnesium anode is???

Read the web link, but in short freshwater being less conductive you need a less noble metal anode than zinc or aluminum (for brackish).
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain