Trampoline Material

Discussion in 'Multihulls' started by Fanie, Jul 18, 2008.

  1. Trevlyns
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    Trevlyns Senior Citizen/Member

    Awww rite boet, dis Ok
     
  2. Trevlyns
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    Trevlyns Senior Citizen/Member

    Hey Jeff! How come I always end up on the start of a new page and then everyone loses the context, gets mad, starts world war 3 (or is that 4)...
     
  3. Maciek188
    Joined: Jul 2005
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    Maciek188 Junior Member

    Tramp made by Sunrise Yacht Products on F39
     

    Attached Files:

    1 person likes this.
  4. tspeer
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    tspeer Senior Member

    Actually, high-modulus fiber makes economic sense for tramps. Compared to nylon, an ultra-high molecular weight polyethylene (UHMW) like Dyneema is five times the cost per pound as nylon. However, it is far stronger than nylon per pound and has many times the UV resistance. So over a long period, it is actually the less expensive alternative. And the high modulus makes it a joy to walk on - you don't sag down with every step the way you do with nylon.

    I don't think just rolling up a bunch of netting at the edges makes much sense. It's far more common to install a bolt rope. If the cells of the netting are oriented so they are square to the centerline of the boat, then the bolt rope can be lashed to the edge of the netting. I chose to orient the cells on the bias, and double the netting over the bolt rope, as shown here:
    [​IMG]
    The hem was secured with UHMW twine in two rows of running clove hitches. There was actually a lot less wasted net doing this, since the netting is woven such that it expands in the bias direction, and you have to cut off big corners to get a square orientation to the cells.
     
  5. Trevlyns
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    Trevlyns Senior Citizen/Member

    Fanie, pop down to Durbs, swim out and cut yourself some shark nets. We used to as kids and make bangles out of them. Very cool, but not too clever.:p
     
  6. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Hi everyone, thanks for the advice and pictures. I can get a capenta net with an 8mm hole in it which seems about like the thing I want. The nets with large holes could be less comfy to walk on... the other net they offered me has a 110mm hole, and is really heavy.. The lady said all us guys can sit on it :D and I didn't doubt it ;) I haven't had time to find out from the other suppliers though.
     
  7. Fanie
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    Fanie Fanie

    [QUOTE}Actually, high-modulus fiber makes economic sense for tramps. Compared to nylon, an ultra-high molecular weight polyethylene (UHMW) like Dyneema is five times the cost per pound as nylon. However, it is far stronger than nylon per pound and has many times the UV resistance. So over a long period, it is actually the less expensive alternative. And the high modulus makes it a joy to walk on - you don't sag down with every step the way you do with nylon. [/QUOTE]

    That is exactly the thing I'm looking out for Tom, thanks, it would be better value for money. I'm not a nylon fan. Aparently the polyethilene nets are also very strong and UV resistant. When I'm ready to buy I'll go and look at them to see what they actually look like and get an idea of their weight.

    That F39's net looks as neat as the price tag :D
     
  8. tspeer
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    Location: Port Gamble, Washington, USA

    tspeer Senior Member

    The downside is the new nets put a lot more stress on the attachment points. The old nets were secured to eystraps that had self-tapping screws into the fiberglass fairing on the beam, so they were only supported by the threads. I've just spent several boat-bucks and two months in the boat-yard having fiberglass flanges added to the beams that will take the loads to the beam in shear and be vastly stronger than the old attachments.

    Here's what a cross-section of one of the flanges looks like:
    [​IMG]

    The rounded bit is a fiberglass rod (batten material), with the carbon cloth wrapped around it. Holes are drilled between the rod and the flare for the beam to take the laces. The upper flange is almost aligned with the direction of pull, so most of the load will be taken in shear along the bonding surface. And the rod will help spread the load across the attachment points, not to mention being more robust to damage and friendly to people.
     
  9. Fanie
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    Fanie Fanie

    Hi Tom, thanks. I think one should impliment the povision for the trampolines from the start rather than as an afterthought as in your case... and I do see the duct tape you are going to use there :D I have a few pictures of a fourier being built with pictures of how they did it.
     
  10. tspeer
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    tspeer Senior Member

    Oh, yeah. The cost of this little sojourn in the boatyard has cost as much as a new mainsail! In general, the boat is very well built, but this is one area where they messed up.

    As for the tape, they use that green masking tape in the yard to mark work that has to be done. Can't miss it!
     
  11. boat fan
    Joined: Sep 2008
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    boat fan Senior Member


    " Haul in the mainsail guys , let`s get this baby moving so it buries the bows...
    We are going FISHING ! " :D
     

  12. BigCat
    Joined: Jan 2008
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    BigCat Junior Member

    Seat belt webbing

    I am going to make my own out of seat belt material-10,000 pound test per 2" strap. Why sew it at all when you can have an arrangement like that found on backpacks all around the edges? Just attach each piece to the boat at the ends and basket weave them-:eek:
     
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