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Gcat 5.7 Delamination  Bottom

  • I have some delamination on the deck of my Gcat 5.7, it starts in front of the rear cross beam and goes almost halfway to the mid crossbeam. Seems to only be on one side of the deck. The sections by the crossbeams seem stiff. I think a section that big is too much for injection method, any opinion on that? I am thinking of cutting off the top skin but don't want to bite off more that I can chew. I am guessing a pro repair will be about $1000 including paint and whatever else they do while they are at it. Considering I can get another Gcat for $2500, is $1000 really well spent? I know these are adult questions I should be answering myself



    Edited by jalex on Jul 21, 2018 - 10:50 AM.
  • There is no limit to the injection method. I have done 6' successfully. The only problem is about 200 holes to be drilled and injected. Buy 4 syringes from West Marine and divide it up into 2-3 sessions so that you don't tire. Be sure to do it in shade and early morning so 70-75 degrees. Have a roll of paper towels next to you & plenty of plastic gloves. What's the cost ? $50 bucks and your labor. Pete
  • It's possible you will not fix the problem by buying a new hull as this is a problem affecting many g-cats. I read here years ago that the glue used to bond the hull and deck goes brittle over the years, and the joint simply degrades. I have seen this first-hand on my old g-cat and on several replacement hulls that I purchased to remedy the problem. Even the good looking hulls (with only some delamination) could be easily pried apart with a hacksaw blade.

    A good repair is truly difficult. I completely removed the decks of my g-cat. The glue was so brittle, but removing it entirely to clean the joint was very difficult. You could inject west system to bond the cracked portions, but without removing the glue, new cracks will form over time.

    That said, you can probably treat this as a chronic problem that can be maintained by cleaning out areas of the joint with a hacksaw blade and filling in the void with west system. However, in my case this became a very upsetting approach because the simple act of cleaning it with a hacksaw blade caused the brittle glue to continue cracking, thereby extending the length of the delamination.



    Edited by traphappy on Jul 22, 2018 - 03:28 PM.
  • Not clear on your description of the delamination problem. The top of the deck in the area you mentioned is really thin and nothing there to delaminate. One of my 5'7s had a thin deck this area and the fix was easy but I had to cut an additional opening port to access the area. Turn the hull upside down, get some West system cloth and resin and it will be a messy job but inside the hull it doesn't matter. A lot of these old G-Cats have been sitting around for years with water in the hulls and that may contribute to the problem. I think what you are talking about is where you can see the hull to deck joint at the bottom of the rails. It is common to see some splitting at the back up bars possibly caused by over tightening the thru bolts. Anything more could truly be a problem and I agree with traphappy that you should clean it out and fill it first before you get drastic. My current 5.7 does not have this problem and it's for sale. Good luck!

    --
    Bill Townsend
    G-Cat 5.7
    Sarasota
    --
  • I have soft deck on one hull where the skipper would typically sit, in front of rear cross beam. I believe I have cored decks and the top skin has separated. If it’s not cored, what would cause the softness? I am concerned about the hull to deck joint as well, but I think it is unrelated to this issue. Just debating cutting out the bad section and replacing, doing injection, hiring a pro or buy a another boat
  • I'd drill holes into the foam core only. Dry out thoroughly over several weeks. Then inject West System. If still flexible you could take cardboard paper towel rolls, cut them in half length-wise and fiberglass them in for additional support. You'd have to put in a porthole for access. Behind the rear beam would be great, but, unfortunately, some 5.7s have a bulkhead located under the rear beam (some do not, construction varied) that would prevent access to where you are trying to reach. I bet given the convex curved surface, injection of West System would do the trick if things were really dried out well first. There is a bulkhead halfway between rear and forward beam as well.



    Edited by traphappy on Jul 22, 2018 - 05:48 PM.
  • Thank you, sounds good. If I can ever get it to dry out in this Florida Summer. I guess if it doesn’t take I can still hire a pro or buy a new boat
  • You're going to have to be very careful. My friend gave me a parts boat G-Cat 5.7 but the hulls are shot.... at one point someone has filled up the hulls with that expanding high density ( now waterlogged ) foam..... bet the hulls are 300# each. I've started cutting them into disposable cross sections and i can see clearly how it was constructed. The deck is extremely thin but does have a foam core. The outer fiberglass skin cant be thicker than 3 sheets of paper, 2mm core then another super thin inner skin.
    I've done the Hobie 16 delam fix many times so i'm curious how this project is going to work out icon_eek

    --
    Tim Grover
    1996 Hobie Miracle 20
    Two Hobie 14's
    1983 G-Cat Restored
    Memphis TN / North Mississippi
    --
  • The 5.7 that I mentioned before was not foam cored. I guess they had different construction methods depending on the year.

    --
    Bill Townsend
    G-Cat 5.7
    Sarasota
    --
  • shortyfoxThe 5.7 that I mentioned before was not foam cored. I guess they had different construction methods depending on the year.



    catmanFew things, The 5.0 is built differently than a 5.7. The drilling a hole idea may not work because the deck is solid glass and has two foam stringers that run the length of the deck. Depending on where you drill you may find foam or not. My experience with those decks are the foam that's in them will be full of water so there's no injecting them as a repair. They are not built like a Hobie so comparisons with them are out. Hans can't answer to any degree of certainty because the guys building his boats sometimes ad-libbed. I knew a guy that made a deck mold and changed both decks. That's probably not an option. Two ways to do this. Add glass to the top of the deck. A lot of work and you have to refinish the deck. Last option that I have done is cut a hole in the deck for a 6-inch port to get access. I made bulkheads that fit snug to the deck and hull. That gets glassed into the hull and deck and will make the decks good as new. You may need to add more than one considering the soft area is 30".

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