Fibreglass help needed

Discussion in 'Fiberglass and Composite Boat Building' started by RSD1, Oct 5, 2019.

  1. RSD1
    Joined: Oct 2019
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    Location: Melbourne, Australia

    RSD1 Junior Member

    If plan A doesn't work then we will be carefully looking at everything.

    There is certainly some metal overkill in the rails the tabs connecting the round top rail to the square box tube under them are 10mm aluminium - and everything else is built too strong too.

    That is made from 3mm aluminium - 1.5 would have sufficed

    It is designed for tieing fenders to - but again has been built far stronger than needed.
     
  2. RSD1
    Joined: Oct 2019
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    Location: Melbourne, Australia

    RSD1 Junior Member

    I only just bought the new one to suit what this boat was supposed to weigh :-(
     
  3. RSD1
    Joined: Oct 2019
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    Location: Melbourne, Australia

    RSD1 Junior Member

    Unfortunately towed weight and gross combined weight are limiting factors

    It wouldm, but having just bought a new truck I don't want to have to buy another new truck.

    It might help a little bit

    No bilge as such - the tank is between the hulls.

    Have to have two motors for commercial boat registration, has twin 60hp Suzukis on it - it would probably be expensive to trade them in on something else.

    It might save a bit. The anchors have ten metres of chain and then dyneema rope behind that.

    I'm going to calculate the weight of those - they would be very easy to get rid of with a grinder.

    Totally agree - damn boat has been built total overkill.
     
  4. fallguy
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    fallguy Senior Member

     
  5. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Yep, that seems the obvious answer. I think the only likely answer. Weights carried aboard, usually tend to climb higher than planned for.
     
  6. RSD1
    Joined: Oct 2019
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    Location: Melbourne, Australia

    RSD1 Junior Member

    OK PVC foam it is.

    CSM on the top would be good for walking grip as well I would think.

    We are going to save about 60kg by removing the existing bombproof swim platform at the rear and replacing it with a frame made from carbon/kevlar hybrid fabric and a mesh inner. Current one looks like it could be run over by a warship and survive.
     
  7. fallguy
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    fallguy Senior Member

    you could probably get buy with 1208 on the top and 1700 on the bottom or if you wanted less flex, something like a light triax on the bottom

    also, you don't need 8" centers unless you are driving a car there; you need to take all the centers to 16" minimums
     
  8. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    I suggest making a sample that is a few feet square. Drop an EMPTY scuba cylinder from chest height on it. Before committing to a whole deck.
     
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  9. fallguy
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    fallguy Senior Member

    Yup. Some testing is needed.
     
  10. RSD1
    Joined: Oct 2019
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    Location: Melbourne, Australia

    RSD1 Junior Member

    Indeed!

    Does anyone know of an adhesive or similar that we can use use to glue the fibreglass panels to the aluminium longitudinals? Would much prefer to do that than put fasteners through from the top if possible.
     
  11. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    3M 5200 sealant is good stuff and has strong adhesive properties - be aware though that it is Very Sticky, and gets everywhere.
    https://www.amazon.com/3M-5200-Adhesive-Sealant-cartridge/dp/B0000AY6AC/ref=sr_1_5

    It also comes in black and tan (as available on Amazon), and there is also a fast curing version.

    There is also Sikaflex 291 - https://www.amazon.com/Sika-Sikaflex-Adhesive-Sealant-Cartridge/dp/B01GPIXX5Y/ref=sr_1_15
    I presume that both 5200 and Sikaflex should be fairly easily obtainable in Australia?
     
  12. RSD1
    Joined: Oct 2019
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    Location: Melbourne, Australia

    RSD1 Junior Member

    Cheers Bajan,

    3M products are very hit and miss in Australia, but I just took a look at the Sika Australia website and it seems that 291 is readily available which is good news, I'm not sure where their distribution centre is these days as the last one burnt down a couple of years back - took them a week to finally get the fire out as all the chemicals keep reigniting.
     
  13. gonzo
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    gonzo Senior Member

    As a boatbuilder and diver, I think that a lightweight deck laminate is a really bad idea. Tanks get routinely dropped on deck, which will soon crush the core and delaminate the panels unless they are really heavy. A cored laminate that is as tough as a metal deck will likely be heavier. Your best bet is to sue the builder for his mistake.
     
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  14. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Despite my support for the fellas questions; I tend to agree with the general sentiment about the cored laminate eventually causing troubles.

    It might be wiser to drop the deck to 12mm ply.

    What will happen is impacts and subsequent use will cause delamination and you will end up injecting epoxy into the deck to repair it. Another option might be to have an area for that purpose where the deck is designed for more rigorous abuse.

    This is why I suggested he do some testing. If he drops a tank on the test panel from 3 feet; he might get real ill from a 12oz glass.

    Thanks for adding the comment. I don't know about a lawsuit, but the builder is sort of on the hook for the costs to make it right.
     

  15. RSD1
    Joined: Oct 2019
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    Location: Melbourne, Australia

    RSD1 Junior Member

    That's kind of what I'm thinking too Gonzo - in the materials forum you will see a new thread about 2mm tread plate - would appreciate your thoughts on that
     
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