Twissel^TM Rig

Part of The Underway Gourmet by Suzy O'Keefe

During a recent SSS (Singlehanded Sailing Society) Trans Pac Seminar, there was some interest among short handed sailors (someone who sails their boat without a full compliment of crew) in a piece of equipment known as the "Twissel Rig"^TM. It performed well for me in the downwind sailing conditions of the South Pacific. This rig is a furling double headsail assembly that allows a vessel to carry sail downwind thru nearly 150 degrees without jibing and without handling poles. With the apparent wind at 105 degrees port through 105 degrees starboard only minor sheet adjustments are required for the headsails. Of course, you'll still need to deal with the mainsail though ;-) The designer/captain that gets the credit for developing the "Twissel" is Dr. Malcolm McLaren of the Royal Air Force Yacht Club, U.K.

Dr. McLaren was Fleet Commodore to the 20 month "Tradewinds Around-The-World Rally" (late 1995 to mid 1997). His 44' Moody Grenadier Ketch, Malmac was the primary test vessel for his "Twissel Rig" but several other yachts had these rigs on board as well. I must say that I heard a number of disparaging remarks about this experimental rig before I became a member of his crew (from Cairns 'round to Darwin), but having handled and flown it myself and having driven while the Twissel was deployed, I can say "It works, and works well!" Malcolm was comfortable flying it in even 35 knots. He had good control and the boat's downwind roll was minimal.

I'll give you my standard one liner description then try to give enough specifics so you'll have a clear picture... The Twissel Rig is a free-floating double pin assembly, two socket type poles, and two furling sails made on a single luff tape. The spring/pin assembly looks like a double-ended dildo! Sorry, but it does!

The rig is built from two furling sails sewn on a single luff tape, two poles, connected end-to-end with a large steel spring and the usual collection of guys and sheets. The two pin type connectors (for socket type poles) are joined together by a strong suspension type stainless steel spring. The fact that this apparatus is free floating... that's the key! The center of effort moves with the aft ends of the poles as they move port or starboard of the centerline. Where the individual poles would normally be connected to the mast, the Twissel simply floats on a topping lift and is held down via a down haul.

Poles should be of a length that does not allow them to touch the mast. You need clearance for the free-floating poles to pass in front of the mast when moving the stern of the boat through the eye of the wind.

The entire pin/spring assembly of the Twissel is about 20" long and the spring allows the connector pins to bend toward each other forming any angle between 180 and 0 degrees. This means that when the poles are connected, they spread open the double sails at any angle and fold together when the sails are furled. A ring near the end of each pin allows the poles to be manually pulled together and secured for storage. A short ring harness assembly provides an attachment point for the up and down hauls. The forward ends of the poles are attached to the clews of the sails. In the case of the inventor, he simply tied the poles to the clews and let the sheets run free through the jaws. That worked just fine. I also recommend a taming line to help secure the mast ends of the poles while deploying and un-deploying.

The two sails can be made on a wire luff or can simply be hanked onto the inner forestay and a mariner type furler tied to a bollard on deck (swivels top and bottom). There's no need to have a permanently attached foil/furler system for this rig.

When rigged and ready, the poles are attached to the pin apparatus, folded together with the forward ends resting against the furled sails, and tied to the clews. The up-haul and down-haul are connected to the ring harness on the Twissel and the rig is tamed to the mast via the taming line.

To fly the sails, adjust the up and down hauls so that the poles will fly approximately horizontal. Take the taming line off the mast so the poles float free. Head downwind and unfurl the sails. The spring in the "Twissel Rig" spreads the sails apart opening one to port and the other to starboard. With the wind coming from the starboard quarter, the aft end of the poles will swing off to starboard of the centerline. Moving the wind to the port quarter will swing the balance point to the opposite side.

Dr. McLaren made several modifications to pole length, spring size, etc. during the rally and like most good designers was content to live with the full scale model long enough to see what worked well and what didn't. I suggest anyone wishing to devise their own should do the same. Or, better yet, see if you can contact Dr. McLaren through the RAFYC. I'll bet that he's managed to get the spring/ pin apparatus into production by now!