best material for a swim platform

Discussion in 'Materials' started by Charlyipad, Sep 22, 2015.

  1. Charlyipad
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    Charlyipad Senior Member

    needs to be as light as possible.

    I am thinking cedar slats lashed to an aluminum frame, but then they would absorb water.

    Also, this needs to be strong enough to support a dingy and crew.

    is trex strong enough?

    What does wharram use?

    what is everyone else using- ply sandwich w/ foam core?

    any "magic" materials out there?
     
  2. Ike
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    Ike Senior Member

    Teak is pretty common
     
  3. Charlyipad
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    Charlyipad Senior Member

    Sorry, Ike, I erased a good part of the orig post.

    this is for a 36 sailing cat. needs to be light as possible. and strong.

    I was looking online at composite decking. it looks interesting, but I don't know what it weighs, or how much more when wet.

    Has anyone used it?
     
  4. KnottyBuoyz
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    KnottyBuoyz Provocateur & Raconteur

    If it's the same stuff I'm thinking of I've used it on my porch decking. It's heavy and very flexible. I had to frame the sub structure at 12" instead of 16" or 24" that you'd normally find. I have seen it used on a swim platform on the back of an old Chris Craft Conny. I think they had 6 stainless brackets under it.
     
  5. rasorinc
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    rasorinc Senior Member

    Western Red Cedar is a very light wood, very durable to water and rot. however, I
    would give it a coating to seal it and to make it less slippery. It will be stronger if you use it in layers at least 2 and 3 would be better to get to your desired thickness. It weighs 23 pounds a CF and 1.92 pounds a board foot. Teak weighs 43 pounds a CF and 3.58 pounds a BF
     
    Last edited: Sep 22, 2015
  6. Charlyipad
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    Charlyipad Senior Member

    yeah I have noticed the sag factor on some of that composite decking. I never used it, but iirc, it is a mix of plastic and wood fiber, and it was already heavy before it gets wet. I was thinking of the engineered stuff with the internal webbing, and maybe wire mesh reinforcement. We have a plastic community dock where I live and the stuff has held up now for 20 years. I don't know what it is called, and I can't swipe a piece of it to test. I hate plastic. but I will use it if it makes sense.

    laminated cedar sounds like a good choice. I guess ill have to make some pieces and test it, to really find out. Not sure yet about the unsupported span length, but I probably will be a be to keep it under 16 inches. I am wondering though, if I laminate it, I might as well just pickle it with epoxy resin while Im at it, then have to paint ti to protect from uv etc. mucho trabajo. and adds weight too.

    I looked at wharrams site, but couldn't find a reference to what he uses.
     
  7. PAR
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    PAR Yacht Designer/Builder

    The composite decking generally isn't considered a structural element, so requires a lot of sub structure just to hold it up. This tends to be heavy. Cedar is an option, though I think too light, even if epoxy coated. A cored laminate is a way to go, and it's inert. Plywood, maybe over foam is an option, but not inert. Hardwoods or dense softwoods are the usual choices, with the usual issues. It really depends on what you want, cheap, strong and durable, inert, light and what combination of these things are important to you. I'm inclined to go inert, just so I don't have to worry about it again, but the cheap element goes out the window usually.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    How about expanded aluminium mesh over an aluminium frame.
     
  9. Charlyipad
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    Charlyipad Senior Member

    Online metals has that. Trouble is I don't have sense enough to tell what gauge to use, and still be rigid with, say, 16"x 16" unsupported sections. How long do you think it would hold up out there in the salt spray?
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    Salt spray won't worry it if it is the right alloy. I'd be a little concerned it might be a bit hard on the body, as in being like sitting on a cheese grater ! :eek: But it may be possible to take the edge off. You'd have to check the various gauges to get a feel for what won't deform under load.
     
  11. SaltOntheBrain
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    SaltOntheBrain Senior Member

    Coosa board's densest offering is 26lbs/cuft. Waterproof, tough, ugly. You'll have to paint and non-skid it, but it is light, strong, and waterproof.
     
  12. minno
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    minno Junior Member

    polycarbonate (not polyvinyl) roof panels with the square corrugation rather than round with 4mm ply on top.



    minno
     
  13. Charlyipad
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    Charlyipad Senior Member

  14. minno
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    minno Junior Member

    that might work, looks pretty light though, I was thinking of something similer to this stuff

    can't find what I had, it was a bit heavier with uniform square corrugations, I've seen it hold up under 4 feet of wet snow on top of stringers spaced at 3 feet apart, amazing stuff.

    it was held down with screws and washers, had to pre drill so it wouldn't crack.

    in your case I'd be inclined to put it on a light aluminum frame with aluminum rivets and then use small stove bolts to fasten the plywood on to the polycarbonate, that way you'd avoid corrosion from having different metals in contact with each other.

    minno
     

  15. groper
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    groper Senior Member

    All the commercial dive operators around here use aluminium as per Mr efficiency post. It holds up quite a long time, although when it's old and weathered it gets the usual aluminium powdery corrosion. Alot of the commercial aluminium boats are being painted with some kind of clear coat to prevent this weathered look. Might be just a poly urethane clear but I'm not sure...
     
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