Looking at some A-class sites & pics, I can`t help notice many A-class boats trampolines do not quite extend to the deck of each hull. There seems to be a 100-150mm gap to the hull which is laced up to the track.
Anybody know why they do this ? The ony advantage to this I can see would be that it might let spray from inside the hull miss the trampoline - ie less drag ?
Disadvantage I can think of is that I`d stick my foot through the gaps and end up in a tangle.
Attached is a pic of what I`m on about.
Perhaps they just can`t afford a full-size tramp after spending all their cash on all the CF bits.
Just curious,
Steve

The tramps on many A's are based on the Tornado tramp. The tramp goes over the front crossbar and laces on both sides and the back. It's light and strong. It can handle center sheeting or on Tornado's the jib blocks are sometimes attached directly to the tramp.

Compared to a track type tramp, it will handle a lot higher loads and it can be tighten to the point it's a little scarey.

I like it because it's tight, reliable, easy to get on and off and the laces give me a place to put my foot.

It also gives air trapped under the trampoline another place to escape if the hull suddenly falls down (when hull flying), or a huge wave goes beneath you.

It also gives you something to push off of when you're "stepping out" to trapeze. Also, there's less wind resistance to push you over when the hull is way up in the air. Mine, however, is not easy to put on or take off.
Al

There is no track on the Marstrom T...just hooks embedded into the inner gunwales that the tramp laces to. From the pic of the A, looks liek that boat has a rod (glass?) inside the edge of the tramp that the laces wrap around. This is a better solution than the tramps I've seen on current Tornados...which lace to webbing straps on the tramp. These wear out frequently.

Tornado limits how much of a gap there is, while I believe the A is unlimited. Tornado also limits the tramp material to prevent people using wide open nets, as some guys tried in the past. Wonder why we don't see these on the A?

I guess the T's you have seen prefer to assemble/disassemble quickly, and face the extra maintenance replacing worn web-loops.
Many weekend warriors have tramps with glass-rods, like the ones on the A-cat pictured. Then you have to thread the lacing every time, and that takes some extra time (or leave the rods in the tramps, and have a really large trailer ). If you want to convert your tramp, it is a 20 minute job for a sailmaker, or you can do it with materials from sailrite and a domestic sewing machine.

Older T's had trampolines of sailcloth (80's), and the current cloth used is a big improvement (traps less wind).

Mike: Do you remember your source of information about larger masks in the cloth used for trampolines on the T? I think I remember a story about Mich Booth trying such a trampoline on Sydney harbour, but I'm not sure.. I always assumed it was the current material he introduced, and that it had become commonplace by now?

The older T's used a dacron weave matertial, and I'm pretty sure this is that same stuff that is still used now, only the threads are much thicker/flatter than previously used. I suspect this just gives better strength to allow for the higher loads they used to have when running central sheeting mainsheets and jib blocks on the tramp. No big advantages as to wind resistance for the actual cloth. The reduced windage of the current setup is from the lacing gaps on 3 edges.



I think you ment to state "larger mesh"? Yes, I recall a team was using a net type of tramp, with larger (~1") openings throughout to reduce weight and windage. This is why the rule was brought in.

The Nacra F18 and now the Nacra 20s share a very similar trampoline design now with fat rounded head bolts spaced slightly above the hull on which the trampoline is laced to. I really like it because, like someone said, it gives a great spot to push off from and it also gives a great handhold when you need it.

It's probably a development that came about because someone somewhere won a race with something like it. However, it does allow for a more cost effective and reliable method by which to attach the trampoline to the hull.

Regarding the picture attached to the first post, does anyone know what the fittings are on the rear beam that the trampoline is laced too. Where can yo get them?

Those beam fittings look like shaped delrin bolted to the beam. Could be easy to make with a lathe. Otherwise, just use the tried & tested method of riveting eyestraps to those same locations...worked great on older Tboats. Current T's use the same stainless hooks (found along the inner gunwales) on the rear beam. Two things that are different on the Marstrom T...the tramp laces to the front of the rear beam (I think this is an option on the Marstrom Tornado order form) and the hooks are not in a straight line...they get higher off the water towards the centerline of the beam...I suppose it helps raise the tramp up a bit...but the beam is still there to smack a wave!

I think the main reason for this setup are costs and weight. In case of the Tornado I suspect that Marstroms techniek of making the hulls in one go (not in halves) makes integral trampoline tracks by laminating in a carbon tube rather difficult if not impossible.

Personally I have the laminated in carbon tube integral track and due to a summer storm this year my boat was covered by 10 inches of wet sand with a gap below my trampoline. I calculated this to equal a 1000 to 1400 kg laying on my trampoline. My trampoline was fully stretched out and hung between the bulls in a big downward ard. Middle of tramp came some 8 inches below its normal level. It looked awfull and I was sure that I had to buy a new trampoline. More so because the trampoline wouldn't move back to its orginal state after I removed all the sand. It was like it had been 3D molded to this inversed dome shape. Luckily after a week of heat from the sun the trampoline black mesh polymner molecules remember their original stated when they were cast in the factory and the trampoline slowly moved back to its orginal size and flexibility.

Point of the story is however that the side tracks held the loads that were linked to holding some 1000 kg's or more of the ground. The loads on the tracks must have been much higher as a result of the amplifying effect of a tight trampoline. This together with the fact that tracked trampoline systems on the Taipan have withstood the loads of centre sheeting and jib sheeting for 15 years now convinces me that tracked systems can not be regarded weak or less strong by any standard.

This leaves weigth, cost and ease of production as the only possible reasons for one over the other. That and maybe the reason to let air out. However I see trapped air as a benefit as well. High pressure under the trampoline will lift the boat out of the water right ? Something we are all trying to do with canted boards and stuff. Must be a benefit then.

Wouter

The A2 has a mesh tramp with tubes on each side that are attached fore and aft, but not to the hulls (along the sides). Nobody complained after sailing in a good breeze at the North Americans- so it seems to work.