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Conference unifix::sailing

Title:	SAILING
Notice:	Please read Note 2.* before participating in this conference
Moderator:	UNIFIX::BERENS

Created:	Wed Jul 01 1992
Last Modified:	Mon Jun 02 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2299
Total number of notes:	20724

1444.0. "Gadgets and Gizmos" by ECAD2::FINNERTY (Reach out and luff someone) Mon Feb 19 1990 16:08

                           
    I've been wondering about a few gadgets and gizmos.  Most are probably
    bad ideas for more than one reason, so go right and say so if that's
    the case.   Blame it on winter delerium, but here goes...
    
    
    Mast Airfoil
    
    	Imagine an airfoil-shaped flexible plastic sleeve which would
        fit loosely around the mast and would press against the main
        about 5 mast-thicknesses or so aft.  The hope is that this
        would reduce turbulence on the lee side of the mast, and not
        cost too much.
    
        It would fit loosely so that it could pivot and align itself
        in the direction of the sail.  It would also have to be flexible
        enough to accomodate the sail when the sail is furled.
    
        Cutouts could be made for the spreaders and light.  I don't
        see any satisfactory way of handling the spinnaker track (but
        I don't have one anyway).
    
    Ballast Tank
    
        Is there a fluid which   :
    
    		a)  provides a substantial amount of ballast,
    		b)  safe if spilled in an accident, and
    		c)  not exorbitantly expensive? (and doesn't require
     		    a major refit of the boat)        
    
        I've figured that if I added a second water tank, and rigged
        a valve system which would allow one tank to drain into the
        other (one on port, one on stbd), the most I could expect is
        to have the equivalent of one person sitting on the rail.
        OK, but not enough to get excited about. (b) and (c) are
        satisfied, though.
    
        If a cylindrical tank 21" by 7.5" diameter is filled with
        mercury (horrors!), this is equivalent to about 3 175lb crew
        sitting in the right place.  Downwind you couldn't get rid
        of the weight, and therefore would sail slower, but upwind it
        would be advantageous, at least for boats which otherwise
        would have low initial stability.  (a) is satisfied, but
        (b) is disastrous,  and (c) is very doubtful too.
    
        Are there any liquids which satisfy (a), (b), and (c)?  Is
        there a different method that's better?

T.R	Title	User	Personal Name	Date	Lines
1444.1	Sea-water ballast	AKOV13::DOUGAN		`Mon Feb 19 1990 16:56`	11
	re ballast tank: Eric Tabarly in one of his Pen Duiks, I think number 5, had a system of ballast tanks using sea-water. This is Ok for a reasonably large boat used on a cross-ocean voyage. He won the San Francisco - Japan single handed race in it. The problem is the energy and time used in pumping the stuff around. Not the sort of thing you would do when tacking every few minutes. The other very real problem is that you can only use this sort of thing in a relatively rule-less event. Most racing rules prohibit movable ballast. I guess you could use it in a cruiser, but then you would want to use that space for something else.
1444.2	pumping vs gravity	ECAD2::FINNERTY	Reach out and luff someone	`Mon Feb 19 1990 17:26`	12
	the idea I was working on was to allow the tank to drain from the windward side to the leeward side just prior to tacking, and let gravity do the work. not so great for large tanks, but I don't have any room for large tanks anyway. if the wind was strong enough that emptying to the leeward side prior to a tack became dangerous, then I suppose you'd have to equalize the tanks. /Jim
1444.3		MFGMEM::KEENAN	PAUL KEENAN DTN 297-7332	`Wed Feb 21 1990 08:52`	13
	Most of the Globe challenge and BOC boats use water ballast. They fill the tanks from a port at the leading edge of the keel. As long as the boat is moving at a reasonable speed, no pump is needed. As you mentioned, gravity is used to drain from the windward to leeward tank before a tack. More often, the boat is trimmed by bringing in more water from the keel port or dumping over the side. The current limit on tank size for the BOC is 10 degrees of heel with one tank filled (no sails up, calm water). Due to the loss of so many Globe challenge boats, the BOC is thinking about reducing the tank sizes. -Paul
1444.4	transat 6.50 ballasts	SUTRA::JAHAN	CocoJAH, on the way...	`Thu Feb 22 1990 04:28`	12
	Same thing for the "Voiles 6.50" class in France. These 6.5m length boats (little 22ft) are designed to race offshore singlehanded across the Atlantic, and apart from this length limit, all is free. 200 liters ballast are authorized. So, combined with a wide hull (2,80m) and a deep keel (1,80m), they can support a huge sail area, specially to downwind. The last "mini transat" winner (oct 89) had maintain an average speed of 6,5 knt in every kind of weather conditions. Anyway the good stability is strictly controlled heeled at 90 degrees with 30 kg in the head mast in the worst configuration. . Pierre .
1444.5	200 liters ~~ 50 gallons	ECADSR::FINNERTY	Reach out and luff someone	`Thu Feb 22 1990 10:33`	7
	I'd like to achieve the improved stability, but I don't see how to get, re .4, 200 liters of ballast without a major sacrifice of comfort below. Perhaps the wide beam of the Voiles 6.50 class make the space easier to find? /Jim