• Announcements

    • Zapata

      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  

Recommended Posts

I was told to use Polyurethane adhesive/sealant(colored) to fix hairline crack / crazing on fiberglass surface. I believe it works but is it quite right way?

How do you fix crazing?

Share this post


Link to post
Share on other sites

I had a cape dory 22 ....cape dory line was known for gelcoat crazing...it's difficult to get rid of....on my nonskid I would put on a fresh coat of interdeck and that would keep it covered up for a couple of yrs then redo....I believe it's more cosmetic than anything...it does keep coming back ....

Share this post


Link to post
Share on other sites

1) sand the gelcoat off and repaint with PU.

2) stiffen the structure with extra laminate and re-gelcoat

 

Those are really the only ways to fix it permanently. The substrate is more flexible than the coating, so the coating is cracking. You need to make the coating more flexible or the substrate stiffer.

 

I'm assuming this is happening in corners etc. If happening all over then it is probably just the gel coat getting old and shrinking off.

Share this post


Link to post
Share on other sites

1) sand the gelcoat off and repaint with PU.

2) stiffen the structure with extra laminate and re-gelcoat

 

Those are really the only ways to fix it permanently. The substrate is more flexible than the coating, so the coating is cracking. You need to make the coating more flexible or the substrate stiffer.

 

I'm assuming this is happening in corners etc. If happening all over then it is probably just the gel coat getting old and shrinking off.

Thank you,

How about the hairline over fiberglass? Is it good using same way, sanding surface and repainted over?

Share this post


Link to post
Share on other sites

1) sand the gelcoat off and repaint with PU.

2) stiffen the structure with extra laminate and re-gelcoat

 

Those are really the only ways to fix it permanently. The substrate is more flexible than the coating, so the coating is cracking. You need to make the coating more flexible or the substrate stiffer.

 

I'm assuming this is happening in corners etc. If happening all over then it is probably just the gel coat old and shrinking off.

+1. The problem with GRP hulls is the gelcoat is more brittle than the laminate beneath it? So when the hull flex's tue laminate can mobe cause its got a fibre structure to support it but the gelcoat is just coloured poyester resin with no structure and as such just cracks.

Share this post


Link to post
Share on other sites

 

1) sand the gelcoat off and repaint with PU.

2) stiffen the structure with extra laminate and re-gelcoat

 

Those are really the only ways to fix it permanently. The substrate is more flexible than the coating, so the coating is cracking. You need to make the coating more flexible or the substrate stiffer.

 

I'm assuming this is happening in corners etc. If happening all over then it is probably just the gel coat getting old and shrinking off.

Thank you,

How about the hairline over fiberglass? Is it good using same way, sanding surface and repainted over?

 

 

sanding surface yes, but all the way to glass.just roughing up the gel coat will transmit the cracks.

Share this post


Link to post
Share on other sites

If gelcoat is spider crazing in areas that don't appear to flex much, it is probably just failing due to age. Gelcoat is brittle, and gets more brittle with age. I'm not sure if this is UV exposure or drying out, but I have seen many cases of a broad expanse of gelcoat, all spider crazed, with a small section in the middle covered in say vinyl lettering or a painted on name. Under the vinyl/paint it looks like new. If it is spider crazing, you can have success sanding it down until the crazing is removed, which may not be all the way to the laminate. Then repaint with PU, which sticks much better, is much more flexible, and stops the deterioration of the gel coat. If you go all the way to the laminate then there is significant expense/labor in repriming and refairing.

 

It would be helpful to see a picture.

 

If it is just a few cracks, the usual remedy is to reef them out wider (Dremel etc.), fill with gel coat patching stuff, sand smooth. You have to reef them wider or the patch will not stay stuck. It is usually very difficult to make this look good, because you are trying to match an old faded color with new unfaded color, which is going to fade at a different rate. But it might look better than the cracks for awhile.

Share this post


Link to post
Share on other sites

The first pic looks like damage caused from flexing.

Yes, i am thinking same,,

Share this post


Link to post
Share on other sites

I think the first pic looks like scratches, not cracking. Someone ran into your boat. Scratches will have a V shaped cross section while cracks should be tight (until pieces fall out). Look very closely at it, with an eye loupe if possible. If someone hit it, there may also be stress cracking in the area.

 

The second one looks like the gel coat is shrinking off the surface. Maybe it was applied extra thick there. In that area, you could sand down and paint or re-gel coat.

Share this post


Link to post
Share on other sites

Lightly tap the crazing area in the second picture. My money is that there's a void between the gel coat and glass in the area. A rather sharp corner like that it's pretty common that the guys laying up the hull didn't manage to get the glass into the bend.

 

That or DDW's theory of too thick gel coat application that has shrank.

Share this post


Link to post
Share on other sites

The first picture, where is that on the hull, at the bottom of the transom? If it is I'd think the cracks are right along the inside taped edge of the hull and deck are bonded together. Some additional reinforcement should be layed up inside as part of the repair.

 

The second picture, could very well be from thick gel coat.

Remember you're looking at it from upside down as to how the part was made. That that toe rail was a trough on the mold, very easy to overspray that area when applying the gel coat.

Overall an easy gelcoat repair.

Share this post


Link to post
Share on other sites

The first picture, those cracks came up sudden, like an over night. I did not have any idea what's happened.

I understood now for the second picture.

Thank you, all!

Share this post


Link to post
Share on other sites

Is that first pic your stern overhang?

 

Is it possible someone - or something, like a floating dock - got under there and the boat slammed down on it?

 

Have a look at the hull underneath and see if there's any evidence of something hitting it.

Share this post


Link to post
Share on other sites

Is that first pic your stern overhang?

 

Is it possible someone - or something, like a floating dock - got under there and the boat slammed down on it?

 

Have a look at the hull underneath and see if there's any evidence of something hitting it.

Thanks, I started thinking that way, will check out.

Share this post


Link to post
Share on other sites

I had a cape dory 22 ....cape dory line was known for gelcoat crazing...it's difficult to get rid of....on my nonskid I would put on a fresh coat of interdeck and that would keep it covered up for a couple of yrs then redo....I believe it's more cosmetic than anything...it does keep coming back ....

+1. Still, there are ways to fill, wipe and let cure using epoxy. Depends. comment 12 and 13 seem logical also. I did not own the boat, but acquaintance did and I crew when racing. He was constantly fiddling with finish, especially inside the cuddy, which I would have done up every couple years, as it appeared.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now