From: bowers@rigel.dfrf.nasa.gov (Al Bowers)
Subject: Re: 5 sailing questions
Organization: NASA Dryden, Edwards, Cal.
Date: Wed, 14 Oct 1992 18:40:13 GMT

In article <JAMESM.92Oct13164044@lunch.austin.ibm.com> jamesm@lunch.austin.ibm.com (James Miller) writes:

>sailing question 1

>I'm thinking of drilling out the holes in the aluminum shaft to accept
>a brass tube (with 1/4" I.D., to accept the stainless bolt, and say
>3/8" O.D.) of 1 5/16" length.  Then the aluminum need only contend
>with *smooth* brass and the easily replaceable brass can fight with
>the stainless bolt threads.  Does this sound OK?

Yes, this is a good idea.  But rather than using brass (and
introducing yet another dissimilar metal for galvanic corrosion
action) why not use some soft aluminum tubing to make your bushing?
Years ago (back when I was a foolish youth) we used to put bushings
into aluminum tubes for hang gliders.  You simply cut off a piece of
aluminum tube that protrudes about 1/4 inch.  To flare the end we used
a simple drill bit, and then flattened the end with a couple of well
placed hammer taps.

>sailing question 2

>I do not want to put a traveller across the middle of the cockpit, but
>one across the aft deck just forward of the transom wouldn't be so
>bad.  How much beneficial control of the main would be gained by
>replacing the block abaft the tiller with a travelling block while
>retaining the cockpit-centered block/cam cleat?

This would be a great improvement on what you currently have.  But, it
is expensive and it is more cumbersome (passing the tiller extension
back and forth when tacking).  If the improvment in sail control is
what you want, then do it.  Also, because you are avoiding the center
cockpit traveller, you will not get as wide a sheeting/traveller angle
as if it were center cockpit.

>sailing question 3

>The only literature I have on this so far is skimpy and a bit
>inconsistent, and I don't think I'll have the opportunity to
>apprentice to a racer (=8^) any time soon.  What's a good book to
>peruse to learn the basics of tuning a marconi rig?

The best book on the aerodynamics of sails has not yet been published
(Frank Bethwaite is _still_ working on it).  But in the interim, Wally
Ross' "Sail Power" is an older but good primer.  There are others of
more recent vintage.

>sailing question 4

>Is there a good place (e.g., a particular issue of
>_Sailing_) to get a description of the prepared surface of that 12 m
>America's Cup boat?

What you are refering to are "riblets".  These improve the skin
friction in a fully developed turbulent boundary layer (nearly all of
a sailboats wetted surface).  It is a new idea, and the results are
only marginally better than a good clean surface.  There are no
reports on the applications to sailboats as yet, but in the aircraft
industry try NASA Technical Memorandum 4387, Zuniga, Anderson and
Bertelrud, "Flight Test Results of Riblets at Supersonic Speeds" (the
bibliography has many older riblet reports referenced), June 1992.
Two of the authors happen to be in my aero group.

>sailing question 5

>Another fairly recent fad in hull designs from our Cup racing guys is
>the winged keel.  (Weren't some people here talking about having their
>cruisers retrofitted with these?)  It seems that this might actually
>do some good when sailing *off* the wind (ddw to a broad reach), but
>wouldn't it merely increase drag when sailing into the wind (beam
>reach to close-hauled), when the boat is heeled over?  If this is the
>tradeoff, how close is it?  Is there a good writeup on it anywhere?

Yes, wings assist on every point of sail, except dead downwind.  The
shape assists in the reduction of drag, and the shape also assists in
getting the lead down lower (making the boat less tender).  An
excellent reference for winged keels is: NLR MP 85048 U, J. W. Sloof,
"On Wings and Keels", National Aerospace Laboratory NLR, The
Netherlands (don't worry, it is in English), Sept 1985.

--
"But the fact that a 1938 touring bodied Alfa Romeo I once had is
worth $1 million sometimes bothers the hell out of me.  It's a
personal problem."                                     -Phil Hill
Al Bowers                                 bowers@rigel.dfrf.nasa.gov
Iaido   Takamine   Hobie   Rossignol   Alfa Romeo  Ducati (DOD #900)
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