Net attachment

[Charly]

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:

Originally Posted by tspeer

One of the slickest ways I've seen of attaching the tramps to the hull is to glass in a PVC tube all along the hull or beam where you want to attach the net. Then cut/grind away a portion of the tube at intervals where you want the net to attach. A fiberglass rod is inserted down the tube to thread through the loops in the net, or to take the lacing from the net.

The glassing of the tube transfers all the load to the outer skin, of course. If you wanted to really nail it to the hull, you could drill all the way through above and below the tube, then run unidirectional tow through the holes from outside to inside and back out again to tie the tubes to the structure. Once the tow and holles are filled with resin, there would be no leaking into the boat or the core.

This method requires no hardware or fasteners, and is lightweight. Not to mention cheap. Looks good, too.

[ThomD]

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/catalo...es/sstrand.php

[Charly]

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.

[cavalier mk2]

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.

[teamvmg]

Best to use individual lashings to avoid chafe

[cavalier mk2]

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.

[Charly]

Originally Posted by teamvmg

Best to use individual lashings to avoid chafe

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?

[AndrewK]

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.

[catsketcher]

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

[cavalier mk2]

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.

[catsketcher]

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

[teamvmg]

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?

[cavalier mk2]

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.