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 Catalina/Capri 25/250 Sailor's Forums
 General Sailing Forum
 Bottom Gelcoat		  New Topic  Topic Locked
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Harbourmaster
Deckhand

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Canada
4 Posts
Initially Posted - 02/10/2007 :  15:20:46  Show Profile
Hello.
I have recently had the bottom of my boat Soda Blasted to remove all of the "Bottom Kote" paint off and have discovered a bunch of small little pin bumbs in the white finish...I have opened these and they are dry and a nice clean blue surface under them..I am curious what is the gelcoat...Is it the Blue or the white surface?...I am starting to think that the white surface is a barrier coat that was not applied right and I have a good blue gelcoat...If this is the case then I can probably sand down the white and paint on a new barrier coat then onto the VC17...
Anyhelp would be great
Corey K
1982 C25 TallRig Fin
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John Russell
Master Marine Consultant

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USA
3444 Posts
Response Posted - 02/10/2007 :  15:47:31  Show Profile
Not sure, but I think the white surface is the gelcoat but the blue has me wondering. In any event, it sounds like you're describing gelcoat blisters. Do a search on this website for blisters. (As well as a general Google search) You'll find a lot of discussion about them. Some will say they MUST be repaired and others will say they're not such an awful problem.
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Nautiduck
Master Marine Consultant

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USA
3704 Posts
Response Posted - 02/10/2007 :  17:57:35  Show Profile
Perhaps the yard that did the soda blast could take a look. I have not heard of blue gelcoat. Perhaps they didn't get all the paint layers off.
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Harbourmaster
Deckhand

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Canada
4 Posts
Response Posted - 02/10/2007 :  18:22:57  Show Profile
Thanks,
Iam going to take some pics when I go to the boat next...I contracted the sodablaster myself so there is no yard crew to ask....However a couple topics below on the "bottom stripping" thread Aceguy mentions that he was hoping to see a blue gelcoat which would match what I am seeing....
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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts
Response Posted - 02/10/2007 :  19:09:31  Show Profile  Visit Frank Hopper's Homepage
What color is you hull?
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Harbourmaster
Deckhand

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Canada
4 Posts
Response Posted - 02/10/2007 :  22:00:29  Show Profile
It is a white hull
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Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts
Response Posted - 02/11/2007 :  07:49:20  Show Profile  Visit Frank Hopper's Homepage
Then you do not have blue gelcoat under your bottom paint. The mat resin under the gelcoat often has a blue color and it would be a disaster to remove all of your gelcoat.
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Leon Sisson
Master Marine Consultant

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USA
1893 Posts
Response Posted - 02/11/2007 :  10:57:43  Show Profile  Visit Leon Sisson's Homepage
Corey,

The surface where the soada blasting stopped is your gelcoat. I don't know the technical name for the darker color, but I think I know why it's there. Does the dark color match your original bootstripe and cove trim? Mine does. If a solid layup fiberglass boat is built with a light color gelcoat, the hull comes out of the mold translucent. Sales people don't like trying to explain to potential buyers that the hull is plenty strong enough, even as the buyers are experimenting to verify they can see the outline of a hand pressed against the outside of the hull from inside the boat. So the factory shoots a coat of very dark gelcoat in the mold after the light gelcoat. Sometimes this is only done in the areas where the potential buyer is likely to be able to do the hand shadow experiment on the sales lot.

Does the dark color you're seeing match your original bootstripe and cove trim? Mine does. Those stripes are created by applying masking tape inside the empty mold before shooting the light outer gelcoat. The tape is then pulled while the first (outer most) color is still wet, and the dark trim color is shot next, before the mat is laid. While doing some repairs below the waterline, I found a layer of something red buried in the layup. (My trim is chocolate.) Now maybe it's some sort of exotic barrier coat. Or maybe the factory got a close out deal on red gelcoat about the time my hull was laid up, and they were shooting the cheapest dark color they had laying around as a light barrier down below the waterline where it didn't have to match anything, it just needed to prevent the 'glass bottom boat' effect until the first coat of bottom paint was applied.

In my C-25, if I remove the access covers below the stbd coaming in the quarterberth, I see lots of sunlight through the sides of the coamings. (I've considered remaking those covers in frosted plexiglass to let some light into the quarterberth.)

I remember removing worn out cheap carpeting glued to the topsides in the V-berth of a customer's boat. From inside the boat through the exposed hull layup, I could see the dancing patterns of sunlight reflecting off ripples on the water. My boss said to be sure to apply a coat or two of dark paint before painting the V-berth ceiling a light color as the customer had asked.

-- Leon Sisson
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Nautiduck
Master Marine Consultant

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USA
3704 Posts
Response Posted - 02/11/2007 :  13:22:18  Show Profile
I think Frank and Leon nailed it. The white is the gelcoat. Do not sand it off. Just sand the little bump spots flat and then I think you can do the barier coats if you are so inclined. The fact that the bumps are tiny and dry is a very good sign. My guess is that it is simply cosmetic. The fact that your 25 year old hull does not have blisters also means you could probably skip the barrier coats, just put some epoxy on the little bump areas that you sand smooth.

I had the same thing Leon did in my C22. If I removed certain drawers I could just about see through the hull! Still plenty strong but translucent.
Edited by - Nautiduck on 02/11/2007 13:47:32
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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.