Articles, Catamaran Maintenance, Design and Construction

By Matthew Dunning

I had the occasion last summer to construct a deployable aft trampoline for my catamaran Boondock. Hang on a second, did I just say aft trampoline? Well, Boondock is a special case. I describe her as a Northwest interpretation of a Polynesian voyaging multihull. She is a 54′ open bridgedeck cat with central cockpit, a ketch rig, and an aft trampoline.

I load my dinghy onto Boondock’s aft tramp when underway so the tramp needed to be very abrasion resistant. The tramp also carries my kicker as well as my crew when tending the mizzen, relaxing out of the breeze, clambering aboard or playing fetch with the dog at anchor. So the trampoline had to be strong and comfortable. And with Boondock’s slender sterns, it needed to be an open weave to drain a pooping wave with ease. This is quite a list of functions to ask from a trampoline material. Thankfully, advances in fiber technology allowed me to replace Boondock’s old netting with a durable, strong, comfortable and deployable working trampoline.

Peter’s Marine up in Port Townsend welded up a rigid aluminum frame for the tramp and for the mesh I turned to the netting used on both America’s Cup boats.. Luckily their supplier, Net Systems (, manufactures and supplies the world’s fishing fleets with net from right here on Bainbridge Island. In addition to their usual clientele, Net Systems’ new Ultra Cross Silver ® netting is showing up on advanced multihulls around the globe including both BMW-Oracle and Alinghi. The big cat and tri use it with good reason when they need to span their 90′ beams. Ultra Cross is woven from Dyneema ® fibers – the strongest, lightest weight fibers ever made. And Dyneema ® happens to have very good UV and abrasion resistance properties. The strength of Net Systems’ Ultra Cross is incredible and the engineering is top-notch. Knots are eliminated, braids are balanced and filaments run continuously through the netting so that strength is maximized in every direction. Each 1/8th inch 4-strand twine has a breaking strength of approximately 862 lbs.


I toured the factory and the machines that knit the netting are fantastic to behold. They look vaguely like upright jet turbines spinning out 7/8ths inch open weave netting sheets 100 mesh count wide. 100 7/8ths mesh expands to cover an area about 10′ wide. Ultra Cross Silver can be ordered in a variety of lengths but always the 10′ widths. Larger sheets can be made bTrampoliney lashing two sheets with Dyneema ® twine.

Ultra Cross is very adaptable for multihull trampolines. On Boondock I gathered three mesh worth around the perimeter of my trampoline and lashed the mesh to the aluminum frame with Dyneema ® twine. I cut the Ultra Cross netting with a hot knife and used ½ inch Amsteel ® (line also made with Dyneema ® and with a breaking strength of over 20,000 lbs) to create the living hinge at the front of the trampoline and for the lifting lines led through stern cleats to the cockpit winches. In a normal static forward tramp installation the Ultra Cross would be lashed to a perimeter rope of Amsteel or to perimeter battens which would lash in turn to the hull and beam attachments.

The Ultra Cross is silver in color and tinges a bit gold over time as binding agents used in the weaving process are exposed to UV (I have been assured this is not a degradation of the fibers). The harmonious metallic color of the netting goes with almost any color scheme and looks very sharp. Ultra Cross has a waxy feel and conforms to people and objects kind of like a very tight hammock. I will often get up from a siesta on the aft tramp and see my imprint. Even with a very taught installation the qualities of the weave and low stretch materials seem to give it some memory. This cradling feels good against the skin for a 7/8″ weave. I think the absence of knots and the somewhat slippery texture contribute to a nice feel. Sunbathers might want to lay down a towel to prevent wafflemarks though.

I am very happy with Ultra Cross and have negotiated special pricing for clients of 5 Oceans Marine Group. If your trampolines are in need of renewal you can order 10′ x 5′, 10′ x 10′, 10′ x 15′ or 10′ x 20′ sheets of Ultra Cross Silver directly from Net Systems. Call 800-722-5568 and give them the code: MULTIHULLUC and you will receive a 20{87af57bf33b759b13edf1201e0aac8ff568782d54202a219d5fee60abad8e986} discount. Tell them Matthew sent you.

About the Author

Matthew brings fifteen years experience cruising multihulls on Puget Sound and points north to the TMC brokerage team. Along with his practical knowledge of multihull designs and seamanship, Matthew is a graduate of Dartmouth College with a degree in Geography. He has an intimate knowledge of the Northwest’s unique maritime geography that he describes as, “One of the world’s most beautiful, intricate, and extensive cruising grounds. The joys of which are advantageously and endlessly displayed to the owner of a cruising multihull.”