Sailing the Catapult catamaran: the design



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   THE SAIL

Jon Montgomery designed the roundhead sail in 2005 (covering  Sail Nos: 500 - 520). It stays at 10sq m, with a straight leech, and batten-supported round head.

  It is more powerful than the previous rigs, and most racing helms trapeze by 20 knots of breeze

 With a 10 sqm sail, it can still be pushed hard in most winds (as Alex Montgomery demonstrates powering along at Bala, left)

The Catapult fleet can keep sailing up to the point where the Race Officer calls everyone back in, and will usually out-survive the other fleets

Several sail-makers have offered this rig:

  Sobstad: Kevlar Laminate, 3DL construction

  Dolphin: Polyester Pentax Laminate, Radial construction.
   Northrop: Maxx European Laminate, Cross Cut construction
   Hyde: Pentax laminate: radial.

 
(More information on sail options from John Peperell, see Home Page



  









   THE FRAME (Above) 
The basic structure of the boat is set up on a piece of ground chosen for flatness, allowing the two main beams and fore and aft cross beams to be quickly connected with two hand-tightened bolts at each corner.

  The trampoline is pulled along tracks on the inner face of the main beams, and tightened at the aft crossbeam when the frame is made up.
(Assembly and rigging details here )

 
THE SHROUDS (Above left)
Catapult's rig is simple with the two-piece mast supported by two shrouds and a forestay. The picture (left) shows the six-part tackle for each shroud, with the line running across the boat, allowing the mast to be tilted for easy capsize recovery (More)

HULL AND FOIL DESIGN

C
A
D
B

   A The Hypalon inflatable hulls are pulled into place along a track in the alloy main beams, and with their small diameter hold shape well after inflation (timed at one minute for each hull.) The hulls are very tough, sitting on stony beaches and tolerating being pulled across a beach. (The wilder fringes of the helmsmen have at times sailed the boat up onto the beach, not recommended.)

  The fine entry forward (see also below) give Catapult a dramatic low profile on the water, and a fine sense for the helmsman of the boat's speed, close to the water.

  B The main buoyancy is well aft, so that tacking is quick---with the helm’s weight moved aft before the tack, the bows lift, and can be swept through the tack, skimming the surface rather than braking the turn

  C The bow-boards are the solution to combining a very fine entry to the inflatable hulls with sufficient buoyancy in the bows. They slot snugly over the main beams as the final stage of pulling the deflated hulls along the tracks. 

(The rotational moulding process (turning a heated mould containing the plastic plugs) was unique to the Catapult design on introduction---the Association now owns the moulds.)

  
D and left: Twin daggerboard foils are inserted into “outrigger” channels, through a window in the trampoline. The foils are highly efficient, so wetted area and overall draft remain small (although there remains the option of raising the boards off-wind.) They have a “breakaway” ability if the boat grounds heavily, preventing damage.

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                                           More on Catapult's unique place in catamaran sailing in the UK:

                          Introducing Catapult         Rigging and Tuning          Sailing Catapult           Class Association