Large Depressions in Hull

Discussion in 'Fiberglass and Composite Boat Building' started by SailingWithFriends, Jan 16, 2021.

  1. KeithO
    Joined: Jul 2019
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    Location: Michigan

    KeithO Senior Member

    Understand but I find it unlikely that the resulting heat gun job will turn out so perfect that no filling and painting is required. Thus in the end one is very likely to have to sand fill and paint regardless, although it may then just be a skim coat. Silicone heat pads controlled by a temperature controller as used by the guy on Athena (YOUTUBE) might be a safe way to do the heating of the skin, less risk of scorching something.
     
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    I have done it several times with good results. As far a being perfect, you would have to quantify the term.
     
  3. KeithO
    Joined: Jul 2019
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    Location: Michigan

    KeithO Senior Member

    The OP will be the decider of whats perfect. Hail damaged cars can lose a very substantial % of their value, even though the damage doesnt impact the use of the vehicle at all. People just tend to be very fussy over waviness and other irregularities in otherwise smooth or gently curved surfaces, even though it has minimal impact on the function of the item.
     
  4. gonzo
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    gonzo Senior Member

    Car bodies are usually made of steel. It deforms and stretches under impact which is different from a polyester/fiberglass laminate. Also, cars have a very shiny paint finish, while boat bottoms have flat finish antifouling. That is not a good comparison.
     
  5. KeithO
    Joined: Jul 2019
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    Location: Michigan

    KeithO Senior Member

    Larger boats, yes. But his trailered boat has no anti fouling and the bottom is pretty shiny....
     
  6. brendan gardam
    Joined: Feb 2020
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    Location: east gippsland australia

    brendan gardam Senior Member

    You need to get a sailboat trailer with keel support . The multi roller trailer is for powerboats only. I would sail it as . Rl24 is a very fast boat even with a few dimples.
     

  7. rxcomposite
    Joined: Jan 2005
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    Location: Philippines

    rxcomposite Senior Member

    There are times when the heat gun magic will not work. Fiberglass has a property called “creep”. The tendency of the resin to relax (become soft) and assume a new shape when subjected to heat and prolonged pressure. Unless post cured, the resin has some extra to fully post cure.

    Speaking of cars, this was a personal project which was put on hold and stored in a warehouse for more than a year. The laminate was made of high temperature mould resin and fiberglass. It was fully cured when it was stored but they put the tires on the roof and hood during storage. The roof lost its nice convex shape and the hood flared at the edges.

    To repair, the roof has to be filled in with the same resin loaded with microbaloons. Up to 3/8” in some areas. Then a thin layer of laminate was added effectively making it a cored laminate for stability. The roof itself is perimeter reinforced.

    The hood was placed back in the mold and clamped. The flared edges were shimmed to allow for springback and extra lamination was added. The hood was allowed to stay in the mold for a week and heat gun was used to ensure the laminate was fully cured. Taking a cue on how the steel hood was fabricated, the hood was perimeter reinforced. Used to be X framed only.

    Very little putty was used to correct for imperfections and the painted car seemed perfect. Note that the red car sits beside a big mold. This is because it was done in a boatbuilding yard and the guys who worked on the repair are the same guys building boats using the same materials. They know what they are doing.

    We did not have problem with the boats we build except for occasional lapses on shoring as the boats comes out one every week and most that it stayed on the cradle is a month. Heat gun cured most minor mishap. Yes, we do have a Barcoll hardness tester that we use all the time and an electric space heater that was never used.
     

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