Trampoline replacement.

[manisland]

I have a Lagoon 42, and the trampoline is made of string quite thin, exceptionally strong (ignoring errant whacks with machetes on coconuts), and uncomfortably stretchy/springy.
Whilst fun for children with little to do, it is unacceptably, well, trampoliny when walking upon it, especially so when banging into oncoming seas.


So being a handy guy, possessing an ancient degree in physics, and being armed with a sewing machine and a credit card, as well as being retired, I decided it would be great fun to make a new one.


So keeping in mind that opinions obey the first law of economics: Does anyone have data, or negative experience with going from a trampoline with 95% permeability, to 25%?
(My new design would have only 25% permeability.)


It suddenly came to me that an unusually unfriendly wave busting upwards on a now 25% permeable tramp might gain enough purchase to rip out some (all?) of the hooks the tramp is attached to.
Does that ever happen? Is that why the design is that way?


I looked on Sailrite of course, and some other sites, and they all offer material which is quite closed, and I have seen a lot of trampolines which are dense and not attached with exceptionally robust hooks/hangers, so I think it would be okay.


But I thought it wise to ask if anyone has any real life experience with disasters in this arena.
Thanks.

[ggray]

Not personally, but I've heard of problems even with more permeability than what you are contemplating.

Of course you could just stay at the dock and close to shore, and be fine.

[tkeithlu]

I think that for purposes of your use, netting would work better than cloth. I built a cargo net out of fishing net with a rope edge bound on with nylon twine. It's lasted 20 years, and colors my thinking on this. The rope edge seizes each segment of the net, so it distributes load much better than grommets in cloth would. Take a look at the netting on this site and see if it leads your mind in new directions. Good luck with it.

https://www.seattlefabrics.com/50-86...AaAi_FEALw_wcB

[manisland]

Sorry sorry....


I posted too quickly, and should have looked at what the experts have to say.


Here is the answer:
https://multihullnets.com/Product/tech/netOpenness.aspx

[tkeithlu]

You're not the first. Best wishes on a successful project.

I would not have imagined that there is that much technical information available on the mesh size of catamaran trampolines.

[ggray]

Sunrise made our tramps, they do good work.

The webbing w/ diagonal weave gave me pause at first, but I was converted. One continuous piece of webbing. No stitching, the weak point, but at the two ends.

I'd like to watch them weave it.

[Palarran]

This is what you get with 40% open in real heavy seas. Plus the $4k in fiberglass repair work.

[Kiwi Dave]

Hi all

I made new tramps for my cat from dyneema fishing net, dyneema peripheral rope and dyneema lacing. I expect them to last for ages.

See 9:00

https://www.youtube.com/watch?v=GPgYDihEJ5g&t=1sin

[arsenelupiga]

Originally Posted by manisland

Sorry sorry....


I posted too quickly, and should have looked at what the experts have to say.


Here is the answer:
https://multihullnets.com/Product/tech/netOpenness.aspx

i am not expert but have been in large angry seas. When you get that 10m freak wave directly in front of you without a warning, you want to be as buoyant as possible (not load bows too much, lagoons are good in that respect) and have net that let water thru very easily, else that extra 1/10 of a second that your bows are under water, may turn into tragedy. But as other said, if you do not plan sailing in black holes (lots of nasty weather) , you should be fine.

[fxykty]

Originally Posted by manisland

I have a Lagoon 42, and the trampoline is made of string quite thin, exceptionally strong (ignoring errant whacks with machetes on coconuts), and uncomfortably stretchy/springy.
Whilst fun for children with little to do, it is unacceptably, well, trampoliny when walking upon it, especially so when banging into oncoming seas.


So being a handy guy, possessing an ancient degree in physics, and being armed with a sewing machine and a credit card, as well as being retired, I decided it would be great fun to make a new one.


So keeping in mind that opinions obey the first law of economics: Does anyone have data, or negative experience with going from a trampoline with 95% permeability, to 25%?
(My new design would have only 25% permeability.)


It suddenly came to me that an unusually unfriendly wave busting upwards on a now 25% permeable tramp might gain enough purchase to rip out some (all?) of the hooks the tramp is attached to.
Does that ever happen? Is that why the design is that way?


I looked on Sailrite of course, and some other sites, and they all offer material which is quite closed, and I have seen a lot of trampolines which are dense and not attached with exceptionally robust hooks/hangers, so I think it would be okay.


But I thought it wise to ask if anyone has any real life experience with disasters in this arena.
Thanks.

Check with Lagoon, they should be able to tell you the minimum openness that your boat requires. Generally smaller trampoline areas can have less openness, but again, check the specs for your boat.

Note that it’s not just water passing through that’s the issue, though that can cause issues like with P’s cat earlier (wow, I’ve never seen something like that!), but air. Think about going on a beam reach or upwind in big seas and wind and the bows lift over a sea and all that wind gets under the trampolines. It could capsize you.

Nets at 70+ openness are completely comfortable as long as they are tensioned very tight. Polyester and Dyneema in dark colours will last years. Webbing nets should only be used on small areas and only if they meet the minimum openness of your boat. 25% may as well be solid - that just doesn’t seem safe.

[Tupaia]

If you want to lounge at anchor I have seen people use over sheets. A fabric sheet with bungees to hold it in place over the existing tramp. Unclip and fold it up before going to sea.

[chrisr]

this is the only stuff to use on your tramps

https://www.sergeferrari.com/product...-meshes-492-s2

cheers,

[Chotu]

Hmmm. I’m not sure why no one mentioned it yet, but the primary purpose of the net is to avoid pitch pole. It’s not really about water from the underside. It’s about water from the top, when you’ve dug your bows into a wave.

With plenty of open space in the net you can plow forward with the sterns in the air and the bows dug in deep. With a solid deck or closed trampoline, the deck catches in this close call situation and helps flip you over the rest of the way into a full pitch pole.

Best to keep the net as open as possible for safety

[fxykty]

Originally Posted by chrisr

this is the only stuff to use on your tramps

https://www.sergeferrari.com/product...-meshes-492-s2

cheers,

Only if your trampolines are very small - that’s a very low openness for that fabric. OK for a marina queen or heavy boat with small bow openings, but not medium to large trampolines.

[chrisr]

Originally Posted by fxykty

Only if your trampolines are very small - that’s a very low openness for that fabric. OK for a marina queen or heavy boat with small bow openings, but not medium to large trampolines.

we don't fit into either category and find it perfect...but we don't bury the bows that deep that often. prefer the security of this material, which is not going fail

anyway, each to his own

cheers,