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Thursday, July 18, 2013

Cat-Ketch if you can.


Tanton 45.

It has been a while since I have had a look at cat-ketch yachts and unstayed rigs.
The following is from a small brochure printed years ago and serves the base for the present study of a new 40' version incorporating what I have learnt about this type of cruising boats over a period of 35 years since the first O.G.VW. 37 and the Tanton 43 followed by the 45 appeared on the scene.
How did the cat ketch rig develop?
The rig was developed and utilized on various craft throughout the past 2000 years, and was particularly popular on the Chesapeake Bay and with Yankee fishermen seeking a means of sailing their work vessels single-handedly and efficiently. It proved its worth. Like the 5-speed auto transmission that does the job while reducing cost, weight and fuel consumption, the cat ketch did the job for those working sailors. The same holds true today. Cost, weight, and crew considerations, plus the increased desires of sailors to "try on their own" have contributed to a new, renewed I hope interest in the cat ketch rig.
What so different about the cat ketch?
First, there the amazing absence of clutter on deck. Consider all the headstays, shrouds, spreaders, turnbuckles and other rigging aboard most yachts. Consider the inventory of headsails and spinnakers to content with- not to mention the attendant sheets,blocks, running rigging,winches, travelers, tracks, etc. All are gone!
That is the first difference.
The second is ease of handling. Having eliminated the usual clutter, you now simply attach the halyard to the sail, hoist the sail and enjoy sailing. Coming about becomes a simple matter of putting the helm over. To return to the original tack, turn the wheel the opposite way. The sails are self-tending. Should you need to adjust one, there are but two sheets to consider. Dangerous crashing booms are gone. Foredeck work is eliminated. You seldom leave the cockpit. And in the event of a person overboard, retrieval is a simpler, single-handed maneuver.
The third is performance: nothing short of outstanding. But we will discuss that aspect further along.
What are the advantages of free standing spars versus stayed spars?
Stayed masts are supported by wire stays, each of which relies on fitting at each end to attach it to a tang or a turnbuckle, which in turn must be fastened to the mast or deck. The average 30' ocean cruiser has over 30 of these vital connecting points; and the failure of any one means the probable instant loss of the mast. To effectively support the mast the whole network of stays has to be pre-tensioned which creates an enormous downward compression load on the mast, with corresponding upward load on the ends and sides of the hull. This has created a whole modern generation of boats that are artificially strained before they ever meet the demands of wind and wave. You may recall, they used to put wires on airplanes wings. But that primitive approach was quickly discarded in the name of better safety and efficiency. Pilots simply could not trust their lives to an elaborate network of wires- the failure of any one of which meant the wing would fall off.
So aeronautical engineers developed the free standing wing as a simpler, safer solution. The free standing spar has evolved for exactly the same reasons-it is a simpler, safer solution because it is free to flex under load without high compression strains and without depending on a series of potential failure points. And it allows for new creativity in simple, safe and swift sail employment.
Free standing masts are engineered and developed to accept bending forces and torque, without worry about compression loads that no longer exist. They are then installed in a boat where the deck structure has been designed and built to become an integral connecting structure with the hull-similar to the fuselage of a modern aircraft. A mast's only purpose is to support a sail's luff. Modern engineering and material technology now provide this capability without wires, as is the case with airplanes wings. Why then must we continue to complicate our sailboat rigs or our sailing enjoyment?