[alberg30] PHRF QUESTION

[sunstone]

From: sunstone <sunstone at idirect.com>

Lee, et al:

The LP, the 90o measurement Guy spoke of is called the Luff
Perpendicular, the minimum straight line measurement from the clew to
the luff when the sail is on a floor laid flat with a moderate tension
enough to remove the wrinkles.

The actual length of the foot or leach is irrelevant to the measurement
as the clew line runs parallel to the luff and therefore a high cut 170%
will have a longer foot and shorter leach than a 170% deck sweeper
(which has a shorter foot but longer leach) yet both will have an LP
measurement of 17 FEET.   

And that's regular FEET not Canadian Feet, eh ;)

The choice then becomes whether one wants a deck sweeper which likely
has superior performance as the air does not have a chance to escape
from under the foot - the deck functioning as an end plate - but with
reduced visibility of things ahead to leeward.   Or the higher cut or
something in-between less vulnerable to a boarding sea and a reduced
blind spot.

Amusingly Luff length is not measured so maximizing this is important
and a big performance enhancer.

The person who mentioned the California PHRF of 228, I assume that is
the Spinnaker rating as that is the base rating and the NFS Main and Jib
rating is added to the base rating after any penalties are applied.  If
this is the case then it is a very generous rating as the boat will out
sail that rating on average by a significant amount.   But it is a
rating and as I said before all ratings are imprecise and it is like
debating the number of angels on the head of a pin.

Better to race Albergs against each other, besides the only thing
prettier than an Alberg to look at is a bunch of them together out
racing.

Take care, I'll be coming down with the Great Lakes bunch to Annapolis
for the Chesapeake/Great Lakes Team Races in September, 'till then, see
y'all ;).

John Birch, Sunstone KC-65

FINNUS505 at aol.com wrote:
> 
> From: FINNUS505 at aol.com
> 
> Hi John,
> I read with interest your PHRF discussion, and maybe you can clear something
> up for me, which other people on the list may find of interest as well.
> the various %'s that describe the headsails; are these %'s of fortriangle
> area, or just the 'J' measurement?  The 160-170 figure you mention for a big
> #1, for instance.  Just for curiosity, what are the approximate foot, luff
> and leach lengths of that sail? (In feet, vs. metric, for us yanks :)  )
> Thx, John,
> Lee
> Stargazer #255
> 
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