Fiberglass bottom repair questions...

Discussion in 'Fiberglass and Composite Boat Building' started by Mhall, Jun 30, 2022.

  1. Mhall
    Joined: Jun 2008
    Posts: 14
    Likes: 1, Points: 3, Legacy Rep: 10
    Location: Leesburg, GA

    Mhall Junior Member

    I have a 1979 Berg Maverick 18.5 (kevlar) hull that I am in the process of rebuilding. The hull has a lot of small damage on the bottom and some cracking along the strakes. The strakes are made up of what looks like only the skin layer of CSM and some very hard foam then above that the hull was laid up with kevlar and more glass. The cracks on the strakes are not causing any structural issue nor allowing water into the hull. The issue with the strakes having been made with such thin glass is that it will be difficult to fix the damaged areas by feathering the edge for new glass being laid up. It looks like at a minimum I will need to lay up a layer of new glass over the entire strake blending it into the thicker glass of the hull. I may just lay up the whole bottom with new glass after I spot repair the strakes. I think the biggest question is do I need to remove all the gelcoat in areas where I am applying new glass? I will be using epoxy for all the repairs and still up in the air on what glass to use if either just going over each strake with new glass or the entire bottom. I want to do this right but removing every bit of the gelcoat on the bottom may be difficult on the strakes being the glass is so dang thin already. Overall the hull is very straight and no major issues at and I want to do these repairs well and correctly so any advice would be well received.
     
  2. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    There is no "correct " way to fix it.
    Some techniques wight be better in some ways but less in others.

    Gelcoat under glass is going to be a weaker than if it was removed.

    But it can be good enough.

    Removing it usually destroyed any fairness of the hull. Resulting in many many mant times more labor.

    Quick and easy is to simply fill the dings with fairing compound and then paint. But it will remain susceptible to further damage.

    Adding a layer of glass to the whole bottom is a lot of work and weight added. It will by impossible to get large sheets of fabric to drape over those strakes. This is why the were under glased by the factory.

    Wide strips of twill overlapping on the strakes might be just manageable.

    If you remove gelcoat
    USE A BELT SANDER !!!!
    nothing with a disk

    Good luck
     
  3. Mhall
    Joined: Jun 2008
    Posts: 14
    Likes: 1, Points: 3, Legacy Rep: 10
    Location: Leesburg, GA

    Mhall Junior Member

    Thanks for the reply. Yes I do have a nice belt sander and will try to keep it as true as possible. I also have a couple nice straight line sanders that do work well for cutting down faring with courser grit papers and it would be helpful in fixing this as well. So twill is what I would want to possibly use over the strakes? Any particular weight in mind?
     
  4. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    From the original construction, I assume light weightness was chosen over durability.

    You are adding both weight and durability.

    The thicker the cloth the more of each you will add.

    I would not enjoy forcing anything heavier than 8oz on to those strakes. You will probably have to round over the corners of those strikes and then add fairing after the glass to sharpen Tham back up.
     
  5. Mhall
    Joined: Jun 2008
    Posts: 14
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    Location: Leesburg, GA

    Mhall Junior Member

    This hull was built very light weight. I assume it was custom built for someone because Berg did not even offer a kevlar hull until 1983 yet this whole boat is kevlar and its a 1979. I can actually grab the back of the hull and I am almost able to lift it off the trailer so I know its light weight because I am not that dang strong. haha The 1983 Kevlar hull was stated to be 750lbs and I am not so sure but I bet this hull weighs way less than that.

    I was looking at some 6" E-glass 8oz Twill tape. I agree the strakes are still pretty sharp and it would be easier to take the edge off then add it back with the epoxy faring compound. I do not think this is going to be too terribly difficult to get things back in order. I think the key will be keeping things straight when doing the sanding and maybe i will not have to do as much faring as I expect once the repairs are done. I will be painting the bottom with Awlgrip but no bottom paint so I want to get this bottom nice and true like it should be. THe bottom paint that was on the hull sure hid a lot of the flaws which is why I bet it had bottom paint on it in the first place.

    Thanks for the info and suggestions so far.
     
  6. Blueknarr
    Joined: Aug 2017
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    Likes: 341, Points: 83
    Location: Colorado

    Blueknarr Senior Member

    My approach

    Fill voids in strakes with fairing and round corners to 1/4 inck diameter

    6oz twill from just past center to just past 1st strake. This will give double thickness on center

    Start next row of twill at inside corner of strake and bring it past the next strake. This will help keep the inside corners of the strakes sharp.

    Repeat until you reach the gunnel

    Add extra fairing to the outside corners of the strakes to sharpen them up.
    Fair to your heart's content.
    Prime and paint.
     
  7. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Forgive my crude drawing. 20220630_172847.jpg
     
    Mhall likes this.
  8. Mhall
    Joined: Jun 2008
    Posts: 14
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    Location: Leesburg, GA

    Mhall Junior Member

    That is exactly what I had in mind. Overlapping the layers to help them stay put. I know that if I just terminate close the strake there is a chance it will have issues but if I let it flow past then overlap like your drawing then it should all stay put...I do plan on using epoxy for all the hull repairs and the faring compound will be epoxy as well. I like sanding the epoxy faring more than polyester as it just seems to cut better for some reason. I will sure update as I progress...Thanks
     

  9. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Use a two roller technique , a long small diameter washer roller held in the inside corner and a shorter one to roll away from it both ways. Such laminations often become a bit resin rich, but whatever it takes to make it lay down.
    At only 18 feet, and super light, are multiple lift strakes in the bow even needed?
    Grinding them right off would remove a lot of the headache.
     
    ondarvr and Mhall like this.
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