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Frank's
suggestion for changing the crew weight rule
At the World Council meeting in Whitstable, the
Japan Tasar Association stated that they feel strongly that the crew weight
rule should be changed, and asked for comments and suggestions. Tasar
designer Frank Bethwaite has written suggesting that we should require only
three quarters of the difference between 130 kg and the crew weight to
be carried as ballast. With this change, rule C.6.2 would read:
In the event that the weight of the
crew, thus weighed, shall be less than 130 kg, such crew may race the
TASAR, provided that, throughout the event, ballast equal in weight to at
least the three quarters of the difference between the crew weight
and 130 kg is carried secured in the cockpit.
The ballast carried need not exceed 12 kg.
Frank's letter suggesting this, and a second
letter explaining his reasons, follow:
First letter:
July 1, 2002
Re: invitation to comment on Crew Weight
proposals.
In this case I regard myself as
sinner-in-chief. I wrote the original Tasar (then Nova) rule in 1972. By
about 1985 I regretted that I had not thought harder in 1972 about future
"legitimate" lighter crews such as the Japanese. In 1994/5
came the observations and experience which lead up to "The Third
Factor", and the much gentler and more accurate 49er Performance
Equalisation rule. From this I learned that the whole subject is much more
complex than it appears on the surface.
In 2001 I had a second opportunity, with the
59er, to do a better job than I did in 1972.
For the 59er I have written "Everybody
is welcome to race with us, but if you do not weigh 330lbs (150kg) you will
carry three quarters of the difference as ballast."
In my opinion the Tasar class would always
have been better served if I had written this in 1972. This (i.e. carrying
3/4 of the difference as ballast) is what I would
now recommend.
Sincerely,
Frank Bethwaite
Second letter:
July 14, 2002
Re: Logic for suggesting reduced crew
weight ballast
Over the years I have learned much, but it
has never occurred to me to write down the logic behind what I now
believe. My present theoretical starting points are: -
1. There is a design wind (DW) for every crew
for every point of sailing where the apparent wind is forward of the
beam.
2. Whatever the crew weight the DW close hauled will be less than the DW on
a reach.
3. On all points of sailing with a DW, heavier crews will sail faster than
lighter crews in all winds at and stronger than the DW.
The first part of the logic is that all
sailboats necessarily sail in one of seven modes.
There are three points of sailing:
4. Close hauled, - DW applies.
5. Crosswind -
between close hauled and apparent wind on beam, ie. DW applies.
6. Downwind - Apparent wind aft of beam so DW does not apply.
And there are three wind strengths:
7. Calm to breakout (minimum planing speed)
8. Breakout to DW
9. DW and stronger
So the seven modes are:
A. Close hauled in Light (Displacement)
B. Close hauled in Mod (Planing)
C. Close hauled in Strong (Planing, overpowered)
D. Reach in Light (Displacement)
E. Reach in Mod (Planing)
F. Reach in Strong (Planing, overpowered)
G. Run
10. Drag tests on hulls always show that
hulls develop less drag when lightly loaded than when more heavily loaded.
11. If other factors are equal (eg wind, sail area etc) this drag difference
suggests that more lightly loaded boats should beat more heavily loaded
boats.
Long observation confirms that in many
lightly built classes with modest sail area and no performance equalisation
rule, very light crews absolutely dominate the race results. In these
classes, heavier crews can never win.
The reason is that heavier crews must
necessarily sail slower in 5 of the 7 modes ie. A, B, D, E, and G. They will
sail faster in 2 of the 7 ie. C and F.
So the statistical bias against the heavier
crew is 3 of 7 (5 slower but 2 faster) and this statistical disadvantage of
3 in 7 is overwhelming.
Against this theory, what have we done?
In the case of the Nova, now Tasar “Full
compensation” rule, I now realise that I unwittingly loaded the dice even
more heavily the other way.
A lighter crew who carries full compensation
ballast:
- Has lost all advantage, so has no plusses at all.
- Is disadvantaged in modes C and F
- AND is also
disadvantaged in the upper parts of modes B and E, because with
the lesser righting moment he/she will reach the DW sooner and sail slower
thereafter in B and E as well.
So the statistical bias against the fully
compensated crew is 4 of 7 (4 slower
and none faster). This is worse than the bias the other way if no ballast is
carried.
No perfect solution exists. As between flat
water and waves, and boats with fixed beam and those with sliding wings, and
ocean races with no turns and gravel pit racing with myriad turns,
everything counts and everything changes as the race environment changes.
But the irreducible facts are those above.
I make no apology for writing the “Full
compensation” rule in 1972 now thirty years ago. At that time we were
faced with a crisis in that the philosophical raison d’etre of the NS14
class was being threatened by a new situation in which adult helms and
lighter, generally male adolescent forward hands were winning and displacing
adult helms and adult, always heavier and generally female forward hands. I
did what I could to stem the hemorrhage. I am proud that I did it. I am
proud that it worked and that as a result the Tasar class is a haven for
magnificent women. None of this changes the fact that in the light of what
we know now the rule is far too draconian, and is grossly unfair to lighter
crews such as the Japanese.
Back to the technicalities:
No system can hope to equalise performance over a wide range of crew weight.
The best that can be done is to select, or design for, a target mean weight,
and establish a system which will approximately equalise the finishing
scores, over a series of races to a particular specification, of crews
within a range of say plus or minus ten per cent of that target weight. If
we accept that that is the best we can do, it is now self-evident that a
system of no compensation is too heavily biased toward lighter crews, and
that a system of full compensation is too heavily biased toward heavier
crews. The ideal has to be some intermediate system which balances the
pluses and the minuses more equitably.
I have no crystal ball.
In 2002 I have written “150kg and three
quarter compensation” as my best estimate of what I think will best serve
the 59er class in the years ahead. I suggest to the Tasar class that they
will be better served world-wide if they opt for “130kg and three quarter
compensation”, than if they stay with the full compensation rule.
Sincerely,
Frank Bethwait
Posted
2002-07-14
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