Hairline cracks in gelcoat-Need to fix?

Discussion in 'Sunfish Talk' started by Randy Ricchi, May 27, 2009.

  1. Randy Ricchi

    Randy Ricchi New Member

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    I just bought a 1973 sunfish. The deck and hull are nice and firm, but there are clusters of hairline cracks here and there on the deck, probably from something banging against it. I'm not sure about the hull yet, have to wash it to see how it looks. It does look and feel sound, although on the sides there are some areas where the gel is a little rough.

    If there are hairline cracks in the hull, do these HAVE to be repaired? I'll be taking the boat out of the water after each use, and storing inside. I was always under the impression (from fiberglass kayak experience) that hairline cracks didn't really pose a problem.

    If they really need to be fixed to keep the boat from absorbing water, can I just sand the whole thing and roll a layer of epoxy over everything? I built a cedar strip kayak so I have glass and epoxy experience, but I don't have gelcoat experience. I also have epoxy on hand. I figure for the hull, if I have to do something about hairline cracks it would be a simple matter for me to just sand the whole hull, roll a layer of epoxy over the whole thing, and after that cures I'd just paint it with a high quality white paint. Does anyone see problems with that approach?

    I'll probably just leave the deck as it is. The hairline cracks aren't that easy to see, and after washing the deck with softscrub cleanser, it looks pretty good.

    One other thing, I took the coaming (splashguard) off to repair a crack in it. It looks like each of the screw holes has a drywall anchor in it. Were these boats built with these in them, or is it more likely someone had screws tear out and didn't know about sealing the holes with epoxy and then re-drilling (or maybe they found the backer blocks were rotted :eek:)

    My plan is to get these anchors out of there (drilling if I have to) and then epoxying the holes and re-drilling them. Hopefully, the wood backer blocks are solid.

    Thanks for any help you can provide.
  2. minifish

    minifish New Member

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    I don't know about the cowling since I have a minifish (little sister of the sunfish). But for the cracks-

    You can take a screw driver and widen them by gouging it, then filling it with gel coat (or they make a gel paste good for this). If you have a dremel, it'll be much easier. Just get the sanding/grinding tool that comes to a point and trace them. Get to the bottom of the crack then fill it (as long as fiberglass isn't damaged).
  3. Randy Ricchi

    Randy Ricchi New Member

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    Thanks. I've been reading about that, but I'm wondering if my idea would work because it seems to me it would be a lot less work, plus I already have the epoxy.
  4. minifish

    minifish New Member

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    I'm not sure epoxy will get into those cracks to seal them. :confused:
  5. Wavedancer

    Wavedancer Upside down? Staff Member

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    When the boat isn't leaking, there's no need to repair hairline cracks. Therefore, do a leak test first and foremost. If OK, go sailing :).

    I will leave the splashguard issue to more knowledgeable others. I had a 1979 fish and the splashguard/cowling was riveted in; not sure about a 1973 boat. I am also not sure if the rivets were backed up.
  6. Randy Ricchi

    Randy Ricchi New Member

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    Thanks. I know that epoxy sticks very well to gelcoat if it's been sanded first. My thinking is if I roll a coat of epoxy on it would give me a thin, unbroken barrier across the entire hull. It wouldn't matter if it actually penetrated the hairline cracks. That's my theory, anyway. Since I have no experience with gelcoat I figured I'd ask here before attempting it.

    Good to hear about the hairline cracks not necessarily needing to be fixed. Very good to hear.
    I haven't weighed the hull yet. Seems kind of heavy, but I don't know what 130 pounds should feel like. I'm used to 40# kayaks. I'm betting it's heavier than it should be. I don't think I could lift it completely off the ground by myself. Lifting one end doesn't seem too bad.
    I'll try the bathroom scale thing as soon as I get somebody over to help me lift it down off the sawhorses I have it on.
  7. papayamon2

    papayamon2 Member

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    I'll chime in on the hairline cracks to say "no worries"--they're simply a fact of life as fiberglass boats age. As long as there is no structural damage to the fiberglass itself (which should be noticeable when pressing hard), you've got nothing to worry about. Go sailing and enjoy the time saved! As for the epoxy, anytime you paint or coat a hull, you do two things: 1) add weight, and 2) create an ongoing maintenance need. I'd rather be on the water!

    Kevin
  8. Zeppo

    Zeppo Member

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    I would do as Minifish suggests, if you ignore these fine cracks you risk letting water into the laminate, this will eventually give you a larger project to focus on instead of sailing. "A stitch in time saves nine"
  9. Webfoot

    Webfoot New Member

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    The fasteners should be Bronze machine anchors cinched in at the factory. If they are the originals, leave them in. Since you can't screw directly into fiberglass, the other option is to install a deck port and use machine screws with washers and nuts. The screw holes will leak without anchors so you will have to use Marine Sealer around the splash guard.
  10. Randy Ricchi

    Randy Ricchi New Member

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    Webfoot,
    That would explain the machine screws I took out (the end of the screws were flat, like a bolt). There were also some wood screws as well. Every single hole has something plastic protruding from it. Some of them are flanged, some not. Different colors, too. The flanged ones look (viewed from the top, I haven't been able to get one out of the hole yet) exactly like drywall anchors like the kind you use if you want to hang a painting on a drywalled wall, but need to hang it where there isn't any stud.

    By bronzed machine anchors do you mean there are bronze blocks originally cemented under each screw hole, and the blocks had threads machined into them?
  11. Webfoot

    Webfoot New Member

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    The Bronze anchors were threaded dowels flanged at the top. They were inserted and look like they were cinched with a tool as the flange sat on top of the fiberglass and the cinched bulge was below the deck. I'm sure you have plastic drywall screws. You can go with pop-rivets but the end of the pop-rivet will need a washer inserted before riveting. That means a deck hatch is needed.
  12. minifish

    minifish New Member

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    It's less work to fix them than to epoxy the entire boat.
    It could be something to work on after the sailing season if you wish. I've learned that putting things off or doing a hasty repair always comes back around three fold. :eek:

    They make a scratch patch (by Evercoat) that is perfect for this that's roughly $10.
    You can widen the cracks and see if they go to into the fiberglass.
    If not, clean with acetone and follow the directions (IIRC, you wait 30 minutes after applying then squeegee). You should be able to scrape off or squeegee the repair to surface level and not have any finishing work to do.

    If it does go into the fiberglass, you've got some repair work you should be doing. If you catch it before being exposed to more water, you may save yourself a lot of work. You may even just need to put a little epoxy in there to prevent further damage and be done with it. Then put the scratch patch over it and go sailing worry free.
  13. Wayne

    Wayne Member Emeritus

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    Gelcoat (colored polyester resin) develops hairline surface cracks with age when left exposed without UV protection, something as simple as regular waxing. If the cracks are purely surface crazing you can leave them alone. Repair involves either widening each crack line in preparation for a new top layer or wet sanding down past the crevice to unweathered gelcoat.

    Widening is done because most topcoats (new gelcoat, primer for paint, epoxy overlay, fairing compound) won’t wick into the extremely thin cracks, they only bridge them. When only bridged the cracks reappear in a short period of time. Buffing, rubbing-out, or fine wet sanding (~600 grit) can polish out some levels of surface crazing. This approach also works to restore heavily oxidized gelcoat that is weathered beyond the capability of basic gelcoat restoration products.



    The other cause of gelcoat cracking is impact. This is usually evidenced by a concentric ring pattern ((( ))) as opposed to random criss-cross spider webbing. In this case the cracks need to be examined closely, even chipped away at, to see if they extend through the gelcoat’s 0.020” thickness to the structural fabric layers. If the gelcoat has broken through, the damaged area needs to be sanded down and a new gelcoat layer applied. You’ll be lucky if the gelcoat is all that’s damaged in this instance. Frequently sanding reveals damaged fiberglass that also needs some repair.



    Similar to transparent epoxy in application, but different enough you need to read up and practice a little to learn the differences in material behavior.



    I guess you could do that, I’ve never tried transparent epoxy as an undercoat. The same Interlux, Awlgrip, and the like polyurethanes favored for kayaks and canoes are preferred for Sunfish as well.



    The anchors were factory, at least the factory used anchors at one time, yours could be owner installed. Can’t say for sure which without a picture. The factory also put a vinyl gasket between the coaming and deck for a period. This often deteriorated into crumbles leaving the coaming loose or, as in my case, it turned into something resembling a layer of hardened plumber’s putty that required careful knife work to remove. Either way, a bead of marine caulk seals the coaming nicely nowadays.

    Your proposed approach is the typical repair method with one exception, there are no backing blocks here. Last I saw, the factory is just pop-riveting the coaming on with a caulk sealer. If you want a more secure attachment, install an inspection port for under deck access and pop-rivet the coaming using backing washers to better distribute any loading or thru-bolt with SS screws backed by washers and Nylock nuts.
  14. Randy Ricchi

    Randy Ricchi New Member

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    Thanks everyone, for all the useful information.
  15. 67stang

    67stang Member

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    ...on the coaming, I used aluminum rivet nuts to replace the old factory brass ones, no access hole needed, It was quick, easy and no messing with epoxy. If you are planning on rivets with back up washers, there are about 8 that are buried in foam blocks, so you would have to rely totaly on rivets alone. I don't believe there are any backer blocks for the coaming.

    Anyone's thoughts??

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