Trimaran Design
 
 

     Back in 1986-87, Chesapeake Catamaran was searching throughout Europe for production multihulls that might be marketable in the USA (something other than the Prouts and Catalacs of the time). We settled on two, the Fountain/Pajot cats from France, and the Dragonfly tri from Denmark. We imported a sample of each and embarked on a concentrated marketing campaign.

     The smaller trailerable Dragonfly tri was very well received. The product, along with our aggressive marketing, produced 2 deposits before the first boat ever arrived in the US! Subsequent exposure in the fall and spring shows resulted in another 10 deposits for this design. We had picked a winner! Regrettable the manufacture was totally unable to supply those boats. His European orders had increased dramatically, and he could not/did not physically expand his production capacity to meet our needs, nor those of his other new importer in Canada. I had predicted such a possibility during my original talks with the manufacturer, but was assured that this was not a problem should we receive orders. Nine months of negotiations still resulted in no boats for our market, nor even a hope for any. Our frustration and that of the Canadian gentleman grew exponentially.

     With half the deposits still on board, we set about the project to redesign the boat for the North American market. We incorporated numerous changes based on both our considerable past experiences with multihull craft, Brian Eilandís previous sailing design studies, and very importantly, the publicís feedback responses. We had often encouraged our manufactures to listen to their potential client, even while they tried to sell them their product. A number of our modifications in redesign were a direct result of listening to the public feedback gained at the numerous boat show exhibits and demonstration sails:

1) We lengthened the main hull by a foot to provide more buoyancy in the stern and cut some small drag experienced there; (the original boat subsequently did the same).

2) We eliminated the transom-hung rudder and designed an entirely new kick-up system to fit into a newly created slot in the stern extension. This allowed the hull to act as an end plate for the top of the rudder blade.

3) The amas were lengthened by 2.5 feet both to provide additional buoyancy in their tails when hard on the wind, and to allow for the aft crossbeam (aka) to be moved from bi-secting the cockpit, to a new location at the aft bulkhead of the cockpit; (this cockpit obstacle was one of the greatest concerns of potential buyers).

4) The aluminum crossbeams were changed from elliptical section tubes that passed thru fiberglass openings in the main hull, to round circular tubes where the AKA tubes would slide thru concentric tubes bonded into the main hull. This produced a stronger structure, and one that was less demanding of the owner in setting-up the boat properly. An added bonus was realized when we were able to hinge & hang the amas from the protracted extensions of the main hullís receptacle tubes during trailering, and during set-up and disassembly; (the original design required two people to detach the amas entirely and place them on a rack for trailering

5) The mainsheet traveler was moved from bisecting the cockpit, to a position atop the aft cockpit railing, and formed into a circular track which follows the new loose-footed mainsail.

6) The rig was totally redesigned in form and function. The sailplan area itself was increased in size and redistributed to balance the new retractable centerboard arrangement. The mainsail was a new shape, and its traditional boom at the bottom was eliminated. Correspondingly the sheeting angle of the mainsheet had to be correlated with the circular traveler track arrangement in combination with the absence of the normal outhaul force provided by a boom.

Often overlooked was the correct rotation function of the rotating mast. It is to be preferred that the mast rotate on its own into full rotation, rather than having to be manually induced into position. Then all thatís necessary is a simple rotation limiter that automatically stops and sets the mast at a preset rotation limit upon tacking. This was all accomplished by careful attention to 3 factors, separate, and in combination; a) the location of the center of rotation chosen for the mastís cross-section (determined by the design of the casting at the base of the mast), b) the design of the hound fixture with respect to the separate attachments of the shrouds and the forestay, and c) considerations given to the fact that a boomless mainsheet arrangement acts to pull the mast back out of rotation.

An entirely new mast extrusion shape was selected along with a 2-ft taller spar. This new shape was superior aerodynamically, as well as lighter in weight for handling during trailerable rigging.

The lower shroud attachment points were changed from a single location at the ama deck lip to an upside-down ĎYí arrangement with two points of attachment at the outer ends of the AKA beams (spread the load, and provided an athwartship mast stabilizer system during the raising and lowering operation).

7) A kick-up, pivoting centerboard was designed to replace the original daggerboard and trunk. It was unconventionally placed off the true centerline of the boat, and incorporated in a rectangular box that became a structural backbone of the boat. The off-center location was chosen to limit damage to the leading edge of the centerboard upon beaching & to keep gravel and sand out of the trunk. Eliminating the huge daggerboard trunk really opened up the relatively small interior of this boat.

     There were numerous other detail changes that were made, and a number of others in the planing stages. Wherever possible we retained the same looks of the original boat as it had always received admiring compliments, and we had invested a lot of marketing time and money already. We really felt that our new Firefly 26 had the potential to become the J-24 of multihulls, particularly with an initial strong marketing program through our 50+ beach catamaran dealers at the time (ref our archive letter to those dealers). The F-27 trailerable trimaran program was developing concurrently, and we felt their massive print advertising campaign could only help us as well; plus! we had a distribution/dealer program in place that they were not considering at that time.

     Unfortunately this was all not to be. Several financial hiccups and finally a partnership disillusionment killed the project. We had built six boats including the prototype. And they were all fun to sail!! A couple of photos are included below. For additional drawings, photos, etc., please visit the archives

 

 

 

Observations. After over 18 years involvement with the sailing and selling of trailerable multihulls including our Firefly tri and over a hundred Stiletto cats (23,27,& 30'), I would offer a few general observations.

     At a boat length of less than 30', I believe the trimaran configuration is the superior form for a small cruising multihull. I liken them to a small monohull with training wheels. Their accommodations are superior to those of the long slender spaces of a catamaran at this size. The wives were quick to point this out. Submerging the amas (training wheels) under sail provided an element of predictability as to when the vessel might be overpowered. And there's some security of being located in a central cockpit as opposed to crossing over a trampoline onto which one is setting.

     At 30 to 35 feet I would call it a draw. There are reasonable good designs of both at this size.

     Above 35' the catamaran type really starts to shine as a cruising design. The wing bridge deckhouse becomes usable space, and quiet a nice one at that. And the hulls are now large enough for nice staterooms that are separate and distinct from both each side, and the shared saloon area With all things considered, including building cost, it's tough to beat a cat at these larger sizes.

     Big ocean racing multihulls are a totally different breed. As we saw with the original Formula 40 boats, the tri's are taking over. Look at those fantastic 60 footers, and the many new developments with each new design. It will be interesting to see what designs might appear for the next unlimited RACE around the world. Personally, I'm still betting on a catamaran design for this RACE. But if I were looking for a big trimaran design, I'd be seeking out Nigel Irens or one of several French design teams.

 
 
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