Subject: Re: [harryproa] Re: mast bouyancy
From: "Chris Ostlind" <>
Date: 2/7/2006, 6:53 PM

OK, Mike... and everybody else who may have an opinion on this.
Located in the Files section is a folder titled End Plate Sail where I have put a collection of renderings of a concept device for preventing turtling, principally for multihulls. The idea here is pretty straight forward.
I'd been seeing a bunch of folks talking about adding foam panels up high on the sail to assist the sealed mast when capsized. It occurred to me that you could go all the way with this idea and just make the foam a specific shape to take advantage of an end plate effect at the head of the sail. If it were slotted to fit the sail chord up high on the head, it would help to contain the airflow that gets lost up there and contribute additional drive to the sail. I was going for the same, wingtip thing that you see on most modern airliners to enhance wing lift.
A matching form would be fit to the mast head as well so that the flow would be smooth and not abrupt. This piece, too, could be made to provide buoyancy at the far end of the mast righting lever if tipped over. The two pieces would not be attached, so the sail can be hoisted and/or reefed like normal and the endplate float would move with the sail.
I haven't done any aerodynamic calcs, so I don't know if the design would make more drag than it could save. It will, hopefully, provide two tasks at once and might be worth it. I know for sure that other floaty stuff up on the mast like Hobie Bob's are not making any additional power for their drag, so it might be a cool idea, especially for cruising boats that don't have big worries about total performance like a racer would. They cold pick-up some lost power from their sails and gain some peace of mind at the same time.
If anyone is an aeronautical engineer and can contribute to the design of the product, I'd be interested in hearing from you. There's bunch of prior art established and I have dropped the dime on the USPTO for the provisional patent thing, so I'd like to see where this could go... if anywhere.
So, have at it. Would it work?
Chris Ostlind
----- Original Message -----
From: Mike Crawford

<<what if a mast head flotation system could be built that actually enhanced the anti-capsize function while having a positive gain on aerodynamics? Would that get your interest?>>

  Well, only a fool would say "no" to that question.  :-)

  If I were to try to design such a system, I'd ponder the following:

    - Minimal impact in huge gusts.  If one were to get caught in a 60-knot squall (and the sails are reefed), the resistance of anything at the masthead could represent some additional heeling moment, as well as additional stress on the tops of those flexible masts.

    - Minimal heeling moment due to weight at the masthead.

    - Compatibility with the flexible unstayed masts.

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