Net attachment

Discussion in 'Multihulls' started by Charly, Feb 3, 2012.

  1. Charly
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    Charly Senior Member

    Hey guys,
    I just stumbled upon this old thread while searching for ideas on net attachment. I am currently building the front fairing for a Kurt Hughes 36 beachcat, and this sounds like a good way to go. I am not sure what is meant by unidirectional "tow" what is that? Has anyone done it this way?

    This post is copied from the old thread:

     
  2. ThomD
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    ThomD Senior Member

    As long as it doesn't chafe where it hangs down.

    Tow is sorta like floss, comes on a reel, and it tends to be flat and made up of a lot of small fibers, being uni it has great properties in line. Like the strands in a knit fabric without the stitching, or roving.

    http://www.aircraftspruce.com/catalog/cmpages/sstrand.php
     
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  3. Charly
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    Charly Senior Member

    Ah. I see. Thanks for that link ThomD.

    I was hoping to find a way to defer the actual layout of the tramp attachment points until after assembly of the hulls and crossbeams. If I merely glassed on a pvc pipe to the outside of the fairing, hull etc, I could go ahead and close the fairing up, without worring about interior access for backing plates, etc.
     
  4. cavalier mk2
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    cavalier mk2 Senior Member

    The thing is it is a skin load . I'm transitioning to the Searunner screw and washer approach which uses a s.s. screw with a wide washer at the attach points. Very simple and on a wood boat it carries the loads into a structural member. If installed using the Gougeon bonded hardware approach (oversize hole filled with thickened epoxy) it is even stronger and can work on a fiberglass boat too. The fasteners are an expense but remembering Rob James, strength here is essential. If you use Carbon tows you'll have more fatigue resistance.
     
  5. teamvmg
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    teamvmg Senior Member

    Best to use individual lashings to avoid chafe
     

    Attached Files:

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  6. cavalier mk2
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    cavalier mk2 Senior Member

    That is attractive but I'd like it better if it was a laminated strip with screws as well as epoxy/cloth holding it on. Of course then you'd want to epoxy in hole liners to take the wear.
     
  7. Charly
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    Charly Senior Member

    hi teamvmg,
    That looks nice, thanks for posting.

    Is that tube an all glass layup? Is it through fastened anywhere? What will be used inside the tube to take the lashings?
     
  8. AndrewK
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    AndrewK Senior Member

    Glased over electrical conduit has been around for a long time now. Have not seen any failures. Stainless steel or glas rod can be used to hold the lashing.
     
  9. catsketcher
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    catsketcher Senior Member

    Go the PVC

    I agree with Andrew about the PVC and glass. About one layer of 600db seems to be enough for a tramp. I have done this over wood and it's not really necessary and you get a better job by going just PVC. Indeed I like the idea so much on my newish cabin top I didn't even put in normal genoa tracks. I just put down some PVC and put some unis over it, drilled some holes in the cabin top, fed uni glass around the PVC and uni and underneath to a structural member and back around a few times. Then another layer of DB over the lot. It's a really light, cheap, strong, noiseless and leakproof method. For genoa tracks it takes a a bit longer to pull out the stainless rod and move the block but I have't done that since I got the position correct. (I don't furl my genoa -I only furl it)

    cheers

    Phil
     
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  10. cavalier mk2
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    cavalier mk2 Senior Member

    Very interesting, can there be much weight savings with the stainless rod? I'll keep the laminated versions because they add a little strength as well. My boat was built with teak strips to take the load which has done the job but they were mounted vertically which puts the load on the fasteners in shear so they are on our list to change over. I haven't had chafe problems with the lashing, it wears at the same rate as the netting I use so they are renewed together.
     
  11. catsketcher
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    catsketcher Senior Member

    It is lighter

    Gday Cav

    I reckon the rod is shorter than the combined length of all of the bolts. As for wearing out on nets. I used to go through nets really quickly - I use PVC pipe on the edges and lash to this. Kankamas nets are still great after 11 years. They are fishing nets and are coloured black.

    cheers

    Phil
     
  12. teamvmg
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    teamvmg Senior Member

    Charly
    You can use a PVC tube and glass it in with 3x the weight of the outer skin over the top. But because the PVC tube does not bond to or add any strength to the lay-up, if you use a tube made of the same material as the skin - you can use just 2x outer skin over the top
    Its a 20mm bore with 6mm fibreglass rod inside
    No through-core fittings/binders, but there an extra bit of Unidirectional glass where there is major foot traffic near the cockpit

    What's a s-c-r-e-w?
     

  13. cavalier mk2
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    cavalier mk2 Senior Member

    Those metal thingies are just for a small piece of net in back, if I did the whole thing searunner style it might be more metal. I use heavy fishnet and continous lashing with individual knots in case anything breaks, There is no chafe and the paths are on a slight diagonal which tensions the net very nicely. If I did nets that chafed my old seine boat captain would have put me in irons.
     
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