Why was there lack of adhesion with my gel coat repair?

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Author Topic:   Why was there lack of adhesion with my gel coat repair?

ShrimpBurrito posted 11-07-2002 03:33 PM ET (US)
I patched a few small (1/2") fiberglass-depth holes on the very bottom of my 15' SS a few months ago using Spectrum's Whaler-matched gel coat repair kit. Much to my surprise, when I just looked at the spots again, the patch is gone! The boat was out of the water for a few weeks before patching, and I then ground out the spot with a Dremel. The entire patch disappeared all the way down to the ground out hole. The spots do go right over one of the keel rollers.
Any idea why the patch didn't adhere?
jameso posted 11-07-2002 03:44 PM ET (US)
Shrimp boy,
This is the way I do, can't say it's right but works for me.
After grinding a bit fill hole with two part,let cure a couple of days then sand and apply gel coat.
Hope this works, gel coat is not really for patching holes plus the Spectrum stuff is finicky as hell concerning mixing ratios and I find it really brittle.
Jim Armstrong
Jimm posted 11-07-2002 03:48 PM ET (US)
Shrimp, give Spetrum a call, their tech dept. should be able to help.
www.spectrumcolor.com/
kingfish posted 11-07-2002 04:53 PM ET (US)
ShrimpBurrito-
I'm not sure what you meant by, "fiberglass depth", but my experience is that gelcoat starts to get a little iffy much beyond 1/8"
in depth when you're patching. If the depth is less than that, make sure the substrate is warm and dry after having been sanded for adhesion and flushed with acetone. And of course as Jimm suggested, contact Spectrum if you're stumped. I would think a properly prepared and executed Spectrum paste patch would hold up over keel rollers.
If the depth is more than 1/8", try a West Systems patch kit, mixing filler in to a consistency between mayonnaise and peanut butter then dremel and sand just below flush when cured *then* gelcoat. Agreeing with jameso-
ShrimpBurrito posted 11-07-2002 05:36 PM ET (US)
Thanks for all the suggestions. By fiberglass-depth hole, I mean that the entire ~1/16" layer of gelcoat is gone and I can see the fiberglass. There is no glass damage, so we're talking about a very shallow patch.
I called Spectrum, and the only thing they could think of was that I added too much catalyst. Apparently, this would cause the patch to shrink. I made a few batches to do all the touch-ups, but all the other gel coat I added is doing just fine.
I guess I'll just try again.
DJS posted 11-11-2002 01:16 PM ET (US)
ShrimpBurrito,
A question that comes to mind is, did you correct the problem that originally caused the gel coat to come loose from the fiberglass? You mentioned something about a keel roller, is it functioning properly? I don't know what batch size you were mixing up, but for small amounts of gel coat paste it may only require a few drops of the catalyst.
Hope this helps.
David
Taylor posted 11-11-2002 01:34 PM ET (US)
One thing that is important is to make sure the hole is clean before you put in the patch. Oils from your fingers and tools can interfere with the bond. For instance, I think its pretty natural to blow into the hole after you grind to clear the dust. That can't be good.
I have one word for you. Acetone.
ShrimpBurrito posted 11-11-2002 04:23 PM ET (US)
DJS & Taylor - The keel roller appears to be in fine shape. I was only making very small batches, like 1/4-1/2 oz., and thus, only adding a few drops of catalyst like you said. But I may have overdid it on the catalyst the first time. I wiped the areas down with acetone, so excess catalyst is really the only thing I can possibly see as the problem -- aside from a bad batch of gel coat. And since Spectrum never heard of this problem, I doubt that's the case.
Seabrook posted 11-12-2002 02:13 PM ET (US)
If it is on the keel of the boat and is not that noticable, use Marine Tex. Sand the area lightly with 400 grit wet/dry sand paper, clean with acetone, then I clean with alcohol to make sure there is no residue from the acetone, then apply Marine Tex. Marine Tex is very strong and should work. If you want it to better match your gel coat, you can use the same colorants that come with the gel coat repair kits.
jimh posted 11-13-2002 08:34 AM ET (US)
Scrub the repair area with soap and water, too. Some stuff comes off with old fashioned soap and water that would otherwise be left in place with acetone or alcohol.
David Jenkins posted 11-13-2002 01:21 PM ET (US)
Taylor, that sounds like a line from the unmade movie, The Graduate, part II :)
If Marine Tex is used to fill cracks, can it be topcoated with gelcoat?

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Author	Topic: Why was there lack of adhesion with my gel coat repair?
ShrimpBurrito	posted 11-07-2002 03:33 PM ET (US) I patched a few small (1/2") fiberglass-depth holes on the very bottom of my 15' SS a few months ago using Spectrum's Whaler-matched gel coat repair kit. Much to my surprise, when I just looked at the spots again, the patch is gone! The boat was out of the water for a few weeks before patching, and I then ground out the spot with a Dremel. The entire patch disappeared all the way down to the ground out hole. The spots do go right over one of the keel rollers. Any idea why the patch didn't adhere?
jameso	posted 11-07-2002 03:44 PM ET (US) Shrimp boy, This is the way I do, can't say it's right but works for me. After grinding a bit fill hole with two part,let cure a couple of days then sand and apply gel coat. Hope this works, gel coat is not really for patching holes plus the Spectrum stuff is finicky as hell concerning mixing ratios and I find it really brittle. Jim Armstrong
Jimm	posted 11-07-2002 03:48 PM ET (US) Shrimp, give Spetrum a call, their tech dept. should be able to help. www.spectrumcolor.com/
kingfish	posted 11-07-2002 04:53 PM ET (US) ShrimpBurrito- I'm not sure what you meant by, "fiberglass depth", but my experience is that gelcoat starts to get a little iffy much beyond 1/8" in depth when you're patching. If the depth is less than that, make sure the substrate is warm and dry after having been sanded for adhesion and flushed with acetone. And of course as Jimm suggested, contact Spectrum if you're stumped. I would think a properly prepared and executed Spectrum paste patch would hold up over keel rollers. If the depth is more than 1/8", try a West Systems patch kit, mixing filler in to a consistency between mayonnaise and peanut butter then dremel and sand just below flush when cured then gelcoat. Agreeing with jameso-
ShrimpBurrito	posted 11-07-2002 05:36 PM ET (US) Thanks for all the suggestions. By fiberglass-depth hole, I mean that the entire ~1/16" layer of gelcoat is gone and I can see the fiberglass. There is no glass damage, so we're talking about a very shallow patch. I called Spectrum, and the only thing they could think of was that I added too much catalyst. Apparently, this would cause the patch to shrink. I made a few batches to do all the touch-ups, but all the other gel coat I added is doing just fine. I guess I'll just try again.
DJS	posted 11-11-2002 01:16 PM ET (US) ShrimpBurrito, A question that comes to mind is, did you correct the problem that originally caused the gel coat to come loose from the fiberglass? You mentioned something about a keel roller, is it functioning properly? I don't know what batch size you were mixing up, but for small amounts of gel coat paste it may only require a few drops of the catalyst. Hope this helps. David
Taylor	posted 11-11-2002 01:34 PM ET (US) One thing that is important is to make sure the hole is clean before you put in the patch. Oils from your fingers and tools can interfere with the bond. For instance, I think its pretty natural to blow into the hole after you grind to clear the dust. That can't be good. I have one word for you. Acetone.
ShrimpBurrito	posted 11-11-2002 04:23 PM ET (US) DJS & Taylor - The keel roller appears to be in fine shape. I was only making very small batches, like 1/4-1/2 oz., and thus, only adding a few drops of catalyst like you said. But I may have overdid it on the catalyst the first time. I wiped the areas down with acetone, so excess catalyst is really the only thing I can possibly see as the problem -- aside from a bad batch of gel coat. And since Spectrum never heard of this problem, I doubt that's the case.
Seabrook	posted 11-12-2002 02:13 PM ET (US) If it is on the keel of the boat and is not that noticable, use Marine Tex. Sand the area lightly with 400 grit wet/dry sand paper, clean with acetone, then I clean with alcohol to make sure there is no residue from the acetone, then apply Marine Tex. Marine Tex is very strong and should work. If you want it to better match your gel coat, you can use the same colorants that come with the gel coat repair kits.
jimh	posted 11-13-2002 08:34 AM ET (US) Scrub the repair area with soap and water, too. Some stuff comes off with old fashioned soap and water that would otherwise be left in place with acetone or alcohol.
David Jenkins	posted 11-13-2002 01:21 PM ET (US) Taylor, that sounds like a line from the unmade movie, The Graduate, part II :) If Marine Tex is used to fill cracks, can it be topcoated with gelcoat?