Opportunity to remove hull-deck flange

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  • 03 Jan 2019 01:18
    Reply # 6980837 on 6980313
    Deleted user

    All  production fiberglass boats use some type of flange to locate and join the hull and deck together, and there are a lot of different methods for gluing and fastening the top and bottom parts together. On older fiberglass boats the hull and deck join can also be a source of problems.

    Your two biggest considerations will be the labour cost of removing the exterior flanges, and ensuring you retain the strength of the original join. The amount and type of fiberglass used on the inside of the join may need some specific design. Whether you use polyester, or epoxy resin is immaterial in terms of strength, and the difference in cost between the two types of resin will only be a tiny percentage of the overall cost of this modification. Another consideration is that the rubber over the joint I imagine serves as the belting to protect the hull from damage when alongside wharves etc, so you may need to replace the rubber with some type of timber fendering.

    So, in summary, how much would you really gain by the proposed modification compared to putting the money towards just getting the boat completed so you can go sailing?

    Just playing Devils Advocate here!

    Last modified: 03 Jan 2019 01:22 | Deleted user
  • 02 Jan 2019 23:27
    Reply # 6980634 on 6980313
    Scott Dufour wrote:"Why not just cut it off and glass?" he asked.  

    My head spins.  Is this structurally doable?  The interior is open, mostly, except in the few places I've already glassed in bulkheads to the hull and deck, making it stronger than originally designed anyway.  He'd glass the interior of the joint, cut off the flange on the exterior, and glass that, too.  

    On cold intellect, it makes sense that it will all be just as strong as originally designed, but...  it just seems crazy.  

    I sure would like that flange gone, though.

    Factory boats are about speed and training (as little training for the fastest result). The flange mean two pieces can be made in a mold where the guys who do nothing but lay glass in a mold... then the two pieces are joined by the guy that knows nothing but screws and nuts. The flange is a fast way to join the two halves but is prone to leak and the screws mean there are small points where the strain is concentrated. So rather than being "just as strong as originally designed" the fiber glassed over join would likely be both stronger and less likely to leak. This assumes the glassing is done correctly with old surfaces being ground off and roughened, all dust cleaned off and any gaps filled with filler. I guess I should add that by making the halves in molds the outside is prefinished and needs no painting after. If the halves were to be joined with FG, the area would need to be ground down, faired and painted. The painting especially would require a whole new room and trained people to do that.

    Because you are joining fiber glass to fiber glass, normal resin should be just fine. If there are any other materials involved, (wood for example) it may be better to use epoxy resin instead. However, epoxy tends to be a little more pricey and once you start using epoxy putting normal resin on top can melt the epoxy.

    My understanding, is that many people at least in the DIY world just use epoxy for all repairs because they know it will work with whatever they are repairing.

    Last modified: 02 Jan 2019 23:34 | Anonymous member
  • 02 Jan 2019 20:32
    Reply # 6980393 on 6980313

    Hi Scott,

    I am not the one for technical / structural advice.
    This is something just from the heart.... if you can do something to your boat, which does not adversely affect its seaworthiness, but really improves her looks, and the extra cost to get it done is negligible, I say : Go for it!

    Point in case - I never liked the long oval windows on my boat, so I had the opportunity during the rebuild to change them to more traditional small round port holes - end result is they look fantastic, and make an already good looking boat ever better looking. As I walk away from the dock I always just quietly say to myself "Oh yes, yes, yes, so glad I made that change" .

    My 2cents - I'll let the experts take over from here about the technical / construction point of view :-)


  • 02 Jan 2019 19:42
    Message # 6980313
    Deleted user

    I've been quiet on the forums lately because, well... life.

    But I recently had a conversation with the boat renovator who will be finishing out the  interior of Moon River for me.  He drove all the way down from Maine on his own dime to scope out the size of the project.  I've seen much of his work online, and it's great quality.

    Toward the end of the tour, I mentioned that there's just one thing that I really don't like about the boat - the outward flanged hull to deck joint.  It requires a really ugly rubber bumper which traps all sorts of grossness, and the joint itself is subject to dock rash.  

    "Why not just cut it off and glass?" he asked.  

    My head spins.  Is this structurally doable?  The interior is open, mostly, except in the few places I've already glassed in bulkheads to the hull and deck, making it stronger than originally designed anyway.  He'd glass the interior of the joint, cut off the flange on the exterior, and glass that, too.  

    On cold intellect, it makes sense that it will all be just as strong as originally designed, but...  it just seems crazy.  

    I sure would like that flange gone, though.

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