DRAGONFLY Trimarans User Forum

The topic of DF trampoline mesh being too dense came up before, for example towards the end of this thread: http://www.dragonfly-trimarans.org/phpB ... php?p=2575

So I dug into some science and engineering papers, and the feeling that windward tramp is a significant destabilizing factor when heeling in gales is real. Specifically for DF35 at 45% heel (off a wave for example), the upward force perpendicular to the net (so the component that is directly contributing to the capsize moment) is 1ton at 60kt wind. It is 1.5ton in 100kt gusts. In terms of what this means, think of the equivalent weight placed on the leeward tramp, or half that weight on the leeward ama (equivalent to flooding the leeward ama with 143 gallons of water at 60kt wind). This force is decreased 12 times for a net where rope is 1/8th of the cell size.

So the project I am considering is buying this net http://www.net-sys.com/catamaran-netting.php , then having a canvas shop cut the existing stitching on the tramps I have and replacing the OEM mesh with this net. And use UV-resistant thread while doing this.

1. Has anyone done this?
2. What can go wrong?

Ivan,

The link is good, but you have to remove the comma at the end.

I agree the existing nets on mine give the same feeling when launching off a big wave, and I'd rather trade a bit of dry ride to achieve less unwanted lift!

If you do change the mats, make sure to keep the diagonal web strip.
This is engaged as the boat is in the early stages of unfolding.

Steve B.

Yes, and my concern is that this is not linear -- at 30kt, what most would consider strong winds, the load is about 36% compared to the 1 ton at 60kt. Maybe I am influenced by Vendee Globe starting tomorrow, but keep imaging finding myself offshore in a real storm, and still overcanvased, even with the sails down... And OEM tramps are not even dry to sleep on. The only concern is finding a shop that would do the work properly -- I imagine getting uniform tension on a net is harder than on the fine mesh material.

Sunrise specializes in multihull nets. They would have the experience to do it right. http://multihullnets.com/

Yes, their Dyneema 1" open net appears to use the same net as the Net-Sys supplier above. And Net-Sys apparently is not the manufacturer either -- http://www.fitecfishing.com/sizecomparisons.asp is.

Sunrise's standard pricing for Farrier 36 wing net using this material is $3,150. Farrier nets are more simple though, without the diagonal webbing strap, the two boltropes, etc. I was hoping to reuse the structural components of the OEM nets, the vinyl borders, etc, and just re-attach the more open net.

Nets of course are more point-loaded than the mesh on the stock trampolines, so they would need to go inside the vinyl borders with a perimeter rope that would distribute the load. I am still uncertain who can do this properly, given how hard nets are to work with when not under load. Maybe if we could get multiple orders we could convince folks at Sunrise to design something.

1" seems a little wide to walk on barefoot comfortably -- has anyone tried?

Force, whether drag or lift, is increased by velocity squared. It is not linear.

I have walked on the open mesh netting discussed and it is not bad bare foot though you can catch a toe in it. Further, I've found the OEM netting to have less give, and therefore, more secure feeling (granted comparing DF to Farrier tensions).