Advice for Keel repairs

Discussion in 'Boat Yard Basics' started by buddy, Apr 11, 2011.

  1. buddy

    buddy Let's go fishin!!

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    I have three places that are damaged on my keel that go all the way through. One at the front right where it starts to turn under. Second one in the middle below the livewell. And a third place at the rear near the drain plug.

    I have cut them out and sanded them down to a 12:1 taper. Next I am going to put a form on the inside, cardboard or pvc pipe or use a pool noodle to get the shape I need then start the repiar.

    I thought I would put the first layer as CSM, then follow up with biaxial cloth, CSM, biaxial cloth etc and build it out and make each patch progressively larger.

    I sanded down the gel coat over the entire length of the keel and I am going to use two layers of 4" biaxial cloth offset by 1".

    So what am I missing. I know there must be something else I need to do. I have done some fiberglass work before but not to this extent.

    The one question I have is the proverbial poly vs. epoxy. I am going to coat the entire bottom with truck bed liner so I was wondering of poly would work since it will be coated (I always heard that you must use epoxy below the water). But then why in the world if you need to use epoxy below the water line then why do boat manufacturers use poly?
     
  2. Brett

    Brett > PRO STAFF <

    Your procedure sounds much like I would do.
    Polyester over polyester will work fine, just has to be sealed over when complete.
    Polyester is a lot cheaper than epoxy and CSM is engineered for use with polyester.
    The binder in the mat dissolves in polyester resin, but not in epoxy.
    If you were to use epoxy, then CSM is not recommended.

    http://www.westsystem.com/ss/chopped-strand-mat-epoxy/
     

  3. buddy

    buddy Let's go fishin!!

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    What should I use as fairing to help smooth it out once done?
     
  4. DuckNut

    DuckNut Brandon, FL

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    If you use poly then get a marine bondo (NOT automotive). If you use epoxy get some filler such as cabosil.

    Cabosil makes sanding a real job - phenolic glass beads make sanding much more enjoyable.
     
  5. buddy

    buddy Let's go fishin!!

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    I'm guessing you mean something like 3m marine premium filler? That stuff is expensive!! Seems like I may need at least a quart?
     
  6. Brett

    Brett > PRO STAFF <

    Doesn't sound like big repairs. Over build the laminates at the repair sites
    then block sand to level, no fairing compound needed.
    60 grit on a small section of 2x4 will cut it down quick.
    It's the underside of the hull and is going to get chewed up again.

    No need to go for yacht finish... ;)
     
  7. buddy

    buddy Let's go fishin!!

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    you're right Brett. A yacht it aint. It'll be a pond, creek and river fishin' boat!! And thanks for the help from everyone. Now one more question.

    I want to stiffen up the floors and I know I can put down false floors, but I was wondering if I could just lay some biaxial tape down the keel on the inside and then a layer of mat out to the first ridge.

    I would like to add the false floors but I don't want to spend money on the marine plywood and epoxy resin to coat it. If I could get by with top quality plywood and poly resin I would do it. This boat won't see any water from chop or waves. Just from fish and If I get caught in the rain, maybe once a year.

    Which way should I go? Plywood and poly resin or just lay biaxial tape and then mat?
     
  8. DuckNut

    DuckNut Brandon, FL

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    On your second question there is no right answer, you need to decide what will be the best overall solution.

    Example: if you are going to haul this in the bed of your truck and drag it into a pond then "I" would not opt to put a heavy sheet of plywood on the floor. 

    The hull may seem to be on the flexible side but many small boats are designed that way.  They actually get strength integrity when they are on the water.  If you look up racing canoes you will find that they are so thin that you can see through them and if you stand in them on land your foot will break the hull.  However, when they are on the water they are quite strong.  They are built for a particular purpose and they achieve it well.

    Cloth will add some strength, mat will not unless used in conjunction with more cloth (adding more weight). If you have gel coat you would need to grind that down to remove it before you add the additional glass. It is a messy, nasty job.
     
  9. buddy

    buddy Let's go fishin!!

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    I am having a hard time finding biaxial tape locally. Should I order it or will cloth do the job? Also, I was planning on 6 oz biax tape instead of 12 oz. Which one 6 oz or 12 oz? I am running two strips down the keel offset by 1".
     
  10. DuckNut

    DuckNut Brandon, FL

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    If you put where you live in your signature then we might be able to assist with suppliers in your area.

    If you are going to continue to drive your boat onto land then go with the 12.
     
  11. buddy

    buddy Let's go fishin!!

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    Yep that makes since. Signature updated!!

    I never drive it on land just in the water ;).

    Typically when I off load it I then pull up to the bank and the nose barely sits on the edge of the bank 'til me and my son get in then the same thing when we come back in. If I can find the 12 oz. I'll probably use it but if not i"ll test the 6 oz and see how it performs for me.
     
  12. Brett

    Brett > PRO STAFF <

    6 oz will do the job, no problem, just takes twice as many layers.
    Build up to the thickness needed, let harden, sand smooth.
     
  13. buddy

    buddy Let's go fishin!!

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    Okay I ordered the 12 oz biaxial last night. Hoepfully it will be here in a couple of days. Just for funsies I called a fiberglass shop that was rewcommended by a supply house that sells autoboy repiar supply, Finishmaster.

    I aksed the fiberglass shop if they had any and they said, we don't use it, why don't you just use some mat. Thats what we do to make repairs on the bottom of boats.

    Not saying that it might not work, but that is not in agreement with everything else I have read and learned.
     
  14. buddy

    buddy Let's go fishin!!

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    This has probably been done before but I thought I would share anyway.

    I was wondering how to get the shape/profile of my keel to make the repairs. At first I bought a pool noodle and it looks like it would work just fine. Then I had an idea about using "flower foam". The green foam that you pute in a vase to hold the flowers!! This is the small pore kind that is easily shaped. There are two types like this, one that is meant to stay wet for live flowers and another that is meant for dry or fake flowers. The dry stuff is tougher than the one that is meant to be wet.

    ANyway I used a tablespoon to get close to the shape and then I took the bloakc and rubbed it in the keel on the inside of the boat. A minute later I have the exact profile! I'm gonna put some parchment paper over it then lay the fiberglass!!
     
  15. DuckNut

    DuckNut Brandon, FL

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    Not sure of what you just said. Did you fill the hole with foam crumbs?

    You want the cloth/epoxy to fill the hole and if you filled it with foam pieces then when you apply the epoxy it will stick to the foam and you have not gained much.

    One way to do it is to take a piece of plastic and lay it over the hole on the inside and cover it with something just to prevent the application from the outside from pushing all the way through. Then you make the repair to the outside and after that has kicked off you remove the plastic from the inside and finish the repair. After it is dry then you sand it down using a sanding block or a long board to get the profile.
     
  16. buddy

    buddy Let's go fishin!!

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    It all sounded just fine in my head. When I was typing the wife was talking!!

    What I was trying to say is that I was trying to get a backing for my fiberglass that had the same shape/profile of the keel. I was going to use a pool noodle on the inside but thought of this foam. The foam was "shaped" by rubbing it inside of the boat on the keel. This essentially "sanded" the foam down so it had the exact profile of the keel.

    Make sense now? I am going to cover it with parchment paper, tape it in place inside the boat then start laying the fiberglass up from the outside.

    If I didn't explain it clearly that time maybe I should just take pictures tomorrow and post them. I know sometimes the thoughts are clear in the old noodle but the translation between there and the fingers gets garbled sometimes!! :)
     
  17. DuckNut

    DuckNut Brandon, FL

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    Yea man you gotta tel the wife to give her jaws a break. Crystal clear now.
     
  18. buddy

    buddy Let's go fishin!!

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    I have viewed several videos on fiberglass repair and the one thing that is counter intuitive is that when patching a hole, you use a big patch first and then sequentially smaller patches. I would think you would start with a small patch and then get progressively larger.

    Why from large to small instead of small to large?
     
  19. Brett

    Brett > PRO STAFF <

    The hull around the hole is ground down from the edge of the hole
    tapering up to the surface of the undamaged hull.
    Fiberglass is laid back in to fill that hole, thinnest at the undamaged perimeter
    thickest over the hole itself.

    Green is the hull, hole sanded tapering back.
    red is the individual layers of 'glass filling in the hole.
     
  20. buddy

    buddy Let's go fishin!!

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    Thanks for the drawing. That is the way I undertand it should be done, btu my thoguth process is opposite of that. I thought thet smaller to larger would be better. On some sites it shows starting out smaller and working to larger. While the majority shows it like you have.

    Also, if I lay up 3-4 layers of poly, mat, biax etc. and then let it dry do I need to sand before applying anymore layers? I think the answer is yes but I am not 100% sure!!

    Buddy