Core for Deck Fittings

Discussion in 'Materials' started by packsail, Feb 27, 2012.

  1. packsail
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    packsail Junior Member

    Hi everyone. I'm building a 32 foot catamaran and we're ready to begin vacuum infusing the decks on our male mold. I have a question about core materials for deck fittings and need some help.

    Is there something other than wood that I can use in the place of the foam core for deck fittings? I'm worried that if I use wood and the fittings are not properly sealed, water could rot the core over time.

    Any suggestions?

    See Packsail on Facebook for pics of our progress.

    http://www.facebook.com/pages/Packsail/326000720760662
     
  2. Herman
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    Herman Senior Member

    If you seal the fittings properly, the next technician or owner that lifts a fitting, will not seal properly. This gives YOUR boats a bad name.

    Either convert to single skin in critical places that encounter high forces, or use a high density foam. A PVC foam is possible (and available at least up to 250 kg/m3) but PET foams are available as well, and are much cheaper.
    See Airex T90 series for PET, and C70 series for PVC.

    The choice between the 2 options (cored or non-cored) depends totally on the forces, the location, and the surrounding core.

    A third option can be using a couple of layers of Soric (www.lantor.nl) which wil also give a relatively high compression strength pad, which infuses easily.

    A fourth option is to laminate aluminium sheet into the boat, in which the technician can tap threads for mounting.
     
  3. packsail
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    packsail Junior Member

    Herman, thanks for the info. I may elect to go with a single skin, but reinforce with more than the required layers of 24 ounce biax glass and put a plate underneath.
     
  4. CatBuilder

    CatBuilder Previous Member

    Herman's advice is the best, but I figured I'd post what I did just for builders who may not be following the plans to perfection.

    Because I didn't know where my deck hardware would go, I used balsa for my entire deck (hulls are core cell).

    Balsa, properly removed around the through bolt holes and filled with thickened epoxy, with an additional backing plate, will hold any and all deck hardware. It has a very strong strength in compression compared to foam, but is only just a little heavier.

    Doing this, I am now able to locate my deck hardware the the end of the build rather than during the infusion process.

    It may work for some, which is why I put it out here.
     
  5. michael pierzga
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    michael pierzga Senior Member

    Herman...what does the laminate alloy plate layup schedule look like ?

    "A fourth option is to laminate aluminium sheet into the boat, in which the technician can tap threads for mounting.?


    The aluminum plate is surface prepped then set in high density epoxy bog , with skin on both sides ?
     
  6. Herman
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    Herman Senior Member

    Yes, basicly it is a core, made of aluminium. In general just slapped in some paste (polyester or epoxy) then the inner skin added. Sometimes you get lucky, and the builder even applies some extra glass (up and below).

    I am not too fond of this solution, but on many boats it seems to hold well. In theory you should prep the aluminium, but I hardly see anyone doing that.

    Catbuilder is right about the balsa route: you can mount about any fitting through a balsa core. But MAKE SURE water will not reach the core. Which can be a problem, later it the boats life. Normally the first owner is OK with it, but as the second or third owner arrives, the knowledge is gone, and people start drilling holes randomly in the deck, without sealing them.
     
  7. PAR
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    PAR Yacht Designer/Builder

    G-10 or a home made version will do just fine and not present any rot or other common issues.
     
  8. groper
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    groper Senior Member

    the foamed epoxy is another option...

    coosa board is another option...

    solid blocks of PVC or ABS plastics, cleaned, roughed up and primed with a gas torch prior to bonding is another option...

    there really are many substitutes that will not rot or suffer from water ingress...
     
  9. Steve W
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    Steve W Senior Member

    Coosa board is a very good solution as long as you know ahead of time the placement. The stuff does not absorb water (ive done my own testing)and is lighter than solid glass. I think G10 is a better solution for backing plates than aluminum. I agree with Cat re using balsa, there is nothing wrong with balsa other than the person using it, it is equally as good for hulls as long as the same precautions are taken. There is another board like coosa called Penske board but i have not used it so cant comment on it.
    Steve.
    Steve.
     
  10. Stumble
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    Stumble Senior Member

    In all the boats I have worked on there were only three core materials used. Balsa which can rot if not sealed, foam which 'rots' through hydrolic erosion if not sealed properly, and honeycomb which is a whole different problem.

    I prefer epoxy filled holes into whatever core I find, not just for sealing, but for compression strength. If I found G10, I guess I could leave it, but I would probably still epoxy seam the holes. It takes a few minutes agitating more, but not much, and that way I know that even if I am near the end of the G10, I won't have a migration issue with water no matter what happens.
     
  11. Steve W
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    Steve W Senior Member

    Aluminum is a poor choice for backing plates and an even poorer choice when used inside the laminate, if you tap threads into it you must use something like Tefgel on the threads to avoid corrosion and even when using clearance holes,nuts and washers you still get corrosion. Ive just seen too many corroded backing plates to consider it a viable material for this use. I like to use G10 and epoxy it in place to spread the load properly.
    Steve.
     
  12. upchurchmr
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    upchurchmr Senior Member

    G10, Balsa is a fools paradise. Come get the rotted out Tornado hulls in my back yard and you'll see the reason for my opinion. You can't tell when rot stops and then it just continues until that part of the deck is soft enough to move. Then it is really late.
     
  13. CatBuilder

    CatBuilder Previous Member

    Ah, too bad you didn't take care of the hulls and seal up the holes in the deck properly. :rolleyes:
     
  14. upchurchmr
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    upchurchmr Senior Member

    You make a lot of assumptions with that comment.
     

  15. CatBuilder

    CatBuilder Previous Member

    I know... I am just trying to make a point. Sorry. Going a little crazy building boats and talking air conditioners. Thanks for not taking me to the cleaners on that one. You could have. :D

    The point I was trying to make is that balsa is just fine if you take care of it and do the proper installs of hardware, a la Gougeon.
     
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