Grid separation....expoxy vs. resin

Discussion in 'Sailboats' started by Villainy, Oct 15, 2010.

  1. Villainy
    Joined: Oct 2010
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    Villainy New Member

    We have a newer sailboat and we went aground earlier this year and seems that our grid has separated from our hull. There has been no water leaks and we did not see any nicks on the keel or cracks in the hull at all. Since we are new owners we thought we could get some feedback from the community about which repair direction to take. One yard wants to use epoxy and one says they only use polyester resin. Is polyester resin the same as fiberglass? Which repair do you recommend? Thanks
     
  2. Paul B

    Paul B Previous Member

    Please be very careful about this. It might seem like a minor issue to someone with little experience, but that grid is what is holding your keel on. Without a good secondary bond between the grid and the hull you are in danger of a catastrophic failure.

    If a yard says they only work in polyester resin I would walk away pretty quickly.

    Don't settle for some cosmetic repair that looks like it has "stuck" the grid back to the hull. This is a job you might want to have a real professional look at. If the grid popped with little other visible damage it is possible the whole grid was not bonded correctly in the first place.
     
  3. Villainy
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    Villainy New Member

    Thanks paul. So are you saying that doing the grid with a poly resin is not good? We have had two different professionals say that they would repair it with poly resin which is what was used at the factory. Additionally, I understand the structural part of the topic but the keel is bolted on.

    If you are saying that resin is not good, can you elaborate as to why you feel that way?
     
  4. gggGuest
    Joined: Feb 2005
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    gggGuest ...

    Well basically the problem is that polyester resin is not a great adhesive, and for this repair job you want an adhesive.
     
  5. Paul Kotzebue

    Paul Kotzebue Previous Member

    And the grid is what transfers the load from the keel bolts to rest of the hull. If the grid fails you may lose the keel.
     
  6. mark775

    mark775 Guest

    You are getting all advice I agree with above (not that mine means that much!), in particular note this: "If the grid popped with little other visible damage it is possible the whole grid was not bonded correctly in the first place." It was stuck on in polyester the first time. The secondary bond (which is what this is - gluing two completely cured parts together with no chemical bond) of epoxy is stronger than the primary bond (the bond when laminating new) of polyester.
    Problem is with boats, production boatbuilders built a bunch of part A, stacked them in a corner under where the pigeons roost for a month or year while the orders are being filled or part B was being made, then dusted off part A, had some tortillas and rice in the convenient spot, then stuck them together. You have the opportunity to make it a better boat than it was new.
     
  7. Paul B

    Paul B Previous Member

    I would say the "professionals" who say the way to repair this damage is with polyester resin aren't what I would call "professional". Yes, your boat was probably built using that material. That does not mean it is the correct material for the repair.

    Your biggest problem right now is not knowing the extent of the issue. You can't see how much of the structure is bonded correctly. The 100% solution would be to remove the grid and re-bond the whole thing. Of course this would require the removal of the interior and possibly the deck and other structure as well.


    If the structural grid comes adrift the skin of the hull takes the load locally and can fail, dropping the keel off and leaving a nice big hole in the bottom of your boat. Someone lost their life due to this very problem in a failure that was very highly discussed on these forums in the recent past.


    Sad to say you are not in a good situation with this.
     
  8. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    As Paul states it can be just a tip of the iceberg.. but you don't know. Ask if there's any surveyor around who can ultrasound or something to find out what you are dealing with in the first place. Find out too (if possible) if the boat has been grounded or hit some uw object in the past. There could be some signs of this in the bottom or on the keel..
    Here's the keel thread Paul mentioned above http://www.boatdesign.net/forums/boat-design/keels-keels-again-10410.html You might want to take a look there before making any repairs or further sailing..
    BR Teddy
     
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  9. Villainy
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    Villainy New Member

    Thanks

    Thanks to everyone responding to my post. I posted after we had already had a survey done and were told that this is a minor issue and not structural. So possibly everyone was getting a much worse image than i meant. But as it is, I truly appreciate the advice. We have yet to make a decision as to which yard to go with for the repairs. Thanks again.
     
  10. mark775

    mark775 Guest

    Bear in mind that there are "societies" or "cooperations" that will give a surveyor a certificate to hang on his wall but there are no standardized qualfications. Anybody can be a surveyor. I don't know as much about the structure as the above posters but I wud venture that they cud know more than a random surveyor. Be careful on this one.
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    There is no "newer sailboat" that I can think of, where the grid is not a structural element of the design. This assumes the yacht was built in the last 15 years. Given this, I would seriously question the surveyor's suggestion that this isn't a structural issue.

    Epoxy is the much better choice for the repair. This isn't a debate, it's simply fact. Epoxy's adhesive qualities are far superior then polyester, which is why it's necessary for this repair.

    The grid could be reattached to the hull shell with polyester, but it would be an inferior bond, as this is about the most difficult thing to expect from a polyester mechanical bond and why your boat, though built from polyester was "cast" in a 24 hour period (chemical bond).

    All of these points have been born out by previous posters.

    Lastly, many shops don't work with epoxy because they're not set up for. They've been using polyester for years and epoxy is a wholly different animal that would require employee training, different solvents, different techniques, etc, so they just avoid it. This doesn't mean they couldn't successfully repair your grid with polyester, it just means they prefer to work in polyester.
     
  12. mark775

    mark775 Guest

    "This doesn't mean they couldn't successfully repair your grid with polyester, it just means they prefer to work in polyester." - Typo. I'm sure "epoxy" is what you intended.
     
  13. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    No, it's not a typo Mark. The grid could be successfully repaired, at least as well as it came from the factory, with polyester. In a repair, they'd need more material then the factory used, but the repair could be preformed with polyester.

    We are at a disadvantage as we don't have the year, make and model of the yacht. This would help if it is a systemic difficulty of the manufacture with this particular model or a design flaw, both of which could have been addressed with alternative methods, techniques, etc.

    This all said, epoxy is the way to go if you want to have a strong bond, without the weight and bond penalties that come with a polyester repair. The problem with the polyester repair is the shop preforming the repair, may not have the product understanding and they may make the same mistakes, that the manufacture did, what ever they were, if any at all.

    Remember it was grounded, which I suspect was a horrific event, which hasn't been discussed. I'd be looking at keel bolts and likely talking about a replacement yacht, for this total lose after a close inspection (my assumption). I think if the boat hit hard enough to shear the tabbing bonds, it did a hell of a lot more damage then this. Or, the manufacture had issue with grid tabbing (possibly other tabbing) on this model/year, etc. and this is the reason it's so badly damaged, in which case the whole yacht should been taken in question in regard to build quality.
     

  14. mark775

    mark775 Guest

    I understand now
     
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