From: dwl@watson.ibm.com (David W. Levine)
Subject: Re: Tuff Luff and other headstay foils
Date: Wed, 18 Nov 1992 02:37:33 GMT
Reply-To: dwl@watson.ibm.com 
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM Thomas J. Watson Research Center

In article <1992Nov17.215451.3441@klaava.Helsinki.FI>,
tarkkone@klaava.Helsinki.FI (Lauri Tarkkonen) writes:
|> In <guido.722012392@sparc-3> guido@blink.att.com (Guido Bertocci) writes:
|> 
|> >tarkkone@klaava.Helsinki.FI (Lauri Tarkkonen) writes:
|> 
|> >>In <1992Nov13.185255.4694@ttinews.tti.com> scott@soldev.tti.com
(Scott Taylor) writes:
|> >>>I am afraid that you know not of what you speak. When sailing bare headed
|> >>>you lose both boat speed and pointing ability. On a large boat, where a 
|> >>>headsail change will take 3-5 minutes with hanks, you could easily lose
|> >>>30-40 boat lengths.
|> 
|> >I've crewed on a C&C 35 with hanks and it never took us that long to
|> >change head sails.  Our procedure involved undoing the lower hanks
|> >on the jib that is still up,  attaching the new jib in the space vacated
|> >by the current jib hanks.  When the new one was completely attached, the
|> >old one was "de-hanked" as it came down.  As soon as old one was completely
|> >off the new one was hoisted.  Hoisting a hanked sail is very fast.
|> >We were probably completely without headsail for only 15-20 seconds.
|> >While this boat was relatively low tech with a lousy handicap we
often beat 
|> >much faster boats by not screwing up boat handling and paying attention
|> >to tell tales and wind shifts.  We also ate real well since
|> >we made good food a priority :-). 
|> 
|> As I said, if you compare badly executed hank sail change to a well executed
|> foil change there is a real difference. Because people interested in winning
|> races invest more in practice as well as equipment Mr. Scot might be under
|> the false impression that there is a really big difference between the
|> two procedures, when the real difference was between the crews. :-).
|> Maybe I am not that stupid after all. ;-).
|> 
|> - Lauri Tarkkonen

I'm not trying to pick a fight, but that still doesn't add up. Consider all
other things being equal, we take two boats, have one do twin foil tack
change and the other a barehead. I don't know about you, but on most boats,
you can't hoist with the sail full, except in light air. So, let's assume the
headfoil folks lose two or three tenth of a knot while they have the extra
guy on the bow, but they go from full jib to full jib as they tack. We'll
assume that the guys with hanks have a sharp crew and they drop the old jib,
(With a few hanks off, the new jib hanked on under it) at helms a-lee, as the
boat starts to tack. 30 seconds for the old jib to come sliding down, (I
suspect
that's generous, but hey, we'll assume they guys are *good*) The boat's through
the eye of the wind and falling off on the new tack. The new jib starts on 
it's way up and both both start to accellerate. One about twice as fast as
the other as the hanked on jib is still being hauled up, We'll give these guys
about 30 seconds for the hoist (Again, these guys are good) At full hoist,
the jib trimmer and his tailer can start taking sheet tension, which
isn't going
to be all that easy in any breeze, as the moment the sail starts drawing at
all, the load is gonna be ugly, but again, good crew-work and we're in at
trim in 30 seconds. It's that minute there, between old jib down and new
one drawing fully that's gonna hurt you. If we assume that half of it
occurs between head to wind and when the sail could be drawing, you've still
got 30 seconds when the other boat's accelerating under a headsail and
you're not. My guess is that you're talking about over a knot of boatspeed
difference, for a period of at least 30 seconds. That's about 2 boat lengths. 
My guess is I've overstated the case in favor the hanked on jib, by the way,
it could easily be a minute of exposure, and if it is, then the differential
increases, since the other boat probably gets up to near targets before you
get to get your jib drawing. Now we could easily be talking 5 to 10 lengths,
which is all the sudden pretty real.  40 lengths, doesn't seem likely, unless
you're talking pretty sloppy crew work. Although... consider that for each
20 seconds that your opposition goes a knot faster than you do they gain
about a boatlength. That's side by side. If they're also outpointing you,
it gets that much worse. If it's two knots, it's a boatlength almost every
10 seconds. Those add up mighty quickly. (Assuming a 34 foot boat, to make
the numbers mildly pleasent) 

			- David

David W. Levine --  dwl@watson.ibm.com  -- IBM Thomas J. Watson Research Center
                   -- My Opinions, IBM's hardware. -- 
"Fanaticism consists in redoubling your efforts when you have forgotten your
aim" - George Santayana  
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