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problems arise. For example, the MORC recently adjusted their old age
allowance to permit older boats to be competitive.


The International Measurement System (IMS) is a measurement system
intended for racer/cruisers. The IOR was not fair to racer/cruisers, so the
Measurement Handicap System (MHS) was invented, in 1981, and
accepted internationally, as the IMS in 1985.


With a diverse collection of boats, relative performance varies not just
with design, but also with race conditions. A 33 footer can beat a 40
footer upwind in moderate wind, but the 40 footer will probably come out
ahead in heavier winds, or on a reach.



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The IMS uses a Velocity Prediction Program (VPP) to predict speed on
different points of sail in different wind strengths. From the predictions,
and the distance, course type and wind strength of a race, a time
allowance is computed for each boat and subtracted from the boat's
elapsed time to give corrected time.


IMS rule designers believe the key to fairly handicapping diverse hull
shapes is measuring a large number of points all over the hull and
appendages, measuring sail area accurately, and using an inclination test
(which is the same as the IOR). The VPP uses these measurements to
account for heeling, crew on the rail, the immersed shape, and other
factors.


The IMS VPP doesn't yet account for dynamic drag of a boat pitching in
waves, nor for appendage shapes which result in reduced drag. Some
parameters are based upon incomplete experimental evidence. For
example, the VPP predicts a greater benefit from full battens than is
realized in practice.


IMS defines a "General Purpose Rating," which is a predicted time per
mile around a particular course, in 10 knots of wind. A typical IMS 40
footer has a GPR around 595 s/M.


The Performance Handicap Rating Factor (PHRF) is a subjective rating
rule. PHRF was developed to handicap monohulls that didn't fit under
the rubric of other handicap systems. It has since become the most
popular handicapping system in the US, being almost universally used in
club racing.


PHRF assigns a boat a rating, in s/M, which is multiplied by the length
of the course and subtracted from the boat's elapsed time to give
corrected time.


Ratings are assigned by a committee of the local racing authority, formed
from representatives of the member clubs. The initial rating for a boat is
based upon any information available, such as the boat's rating in another
area, ratings under other handicap systems, information from the
designer, ratings of similar boats, and a set of standard adjustments to
basic ratings (e.g. fixed prop, extra large sails, etc.) All ratings are
multiples of 3 s/M. For example, a J/24 rates around 171 s/M, and a J/35
around 69 s/M in many areas.


Since ratings are assigned and administrated locally, they may account for
local conditions. A good heavy air boat would rate faster in San Francisco
Bay, than in Long Island Sound.



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A member may appeal a rating, presenting evidence, such as race results,
which supports the appeal. The local committee's decision may be
appealed to a committee of PHRF handicappers from all over the country.


Although PHRF is subjective, it still attempts to rate the boat, in racing
trim, with a perfect crew. Just because a boat never wins, or always wins
doesn't mean its rating should or shouldn't be adjusted.


Using this system, the slower the race, the smaller the percentage by
which a faster boat must beat a slower boat. To correct this, some PHRF
races are handicapped by multiplying a boat with rating R's elapsed time
by (C / ((C - Rav) + R)), where Rav is the fleet's average rating, and C
is a constant around 600-700, to compute corrected time. This system is
called "time on time", the previous, more common, system is "time on
distance."


The two systems only differ substantially when ratings span a large range
(> 30 s/M), or races are long (in time). It is not clear which system is
ultimately fairer.


The Portsmouth Yardstick (PY) is a statistically based rating rule. The
PY was developed by the Dixie Inland Yacht Racing Association to
handicap any boat, including multihulls, which are excluded from all the
previously described handicap systems, based on performance in races.


The PY begins with a boat which is well sailed, and ubiquitous, called the
"Primary Yardstick." This boat is assigned a Portsmouth Number (PN),
which is the time the boat takes to travel a fixed, but unspecified
distance. In the US, the Thistle the primary yardstick, and its PN is 83.


Elapsed times are collected for races. The fastest boat of each type in a
race is assumed to have sailed a perfect race. The ratios of the fastest
boat's time to the fastest yardstick boat's time, normalized by the
yardstick boat's PN are averaged over all races to compute that boat's
PN. Statistical techniques are used to discard outlying data points. A
class with a large quantity of data, and no recent change in PN may
become a "Secondary Yardstick," used in the same fashion as the Primary
Yardstick. The Laser and J/24 are examples of Secondary Yardsticks.


The usual way to handicap with Portsmouth numbers is to multiply
elapsed time by 100/(PN) to compute corrected time. This is a "time on
time" system (see PHRF).


In addition, PY has begun to compute numbers for different wind
strengths. The Primary Yardstick is defined to have the same number for
all wind strengths. Using these numbers, clubs can more fairly handicap



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races in various wind strengths.


Since the PY data are not broken down by course type, it assumed that
boats racing under the PY are racing courses similar to an Olympic,
triangle or Gold Cup course.


Below are formulas for converting among different system's ratings.
Accuracy of these conversions may vary. (And indeed, the last one has
been called into question by one reader, so you should probably treat it as
suspect).


PN = PHRF/6 + 55 PHRF = GPR - 550 PHRF = 2160/sqrt(IOR) - 198


Since we know that the IMS GPR is the time taken to cover a mile (of a
particular course), in 10 knots of wind, we can estimate a boat's speed
over this course given its PHRF rating:


v = 3600 / (PHRF + 550)


So, a J/24's (171 s/M) speed is 4.99 knots, a J/35's (69 s/m) is 5.81
knots. The J/35 is 16% faster. Note that the standard PHRF increment
of 3 s/m represents around a 0.4% change in boat speed.


Using the IOR conversion, a one tonner might rate 72 s/M, whereas they
are actually much faster than that, rating around 54 s/M PHRF. This
illustrates the "advantage" designers can take of the IOR.



3.6   Who/What is US Sailing, how do I join, should I

      join?



United States Sailing Association (US Sailing), formerly USYRU, is the
governing body for sailboat racing in the US. Its goals are to govern,
promote, and represent sailboat racing and to promote the sport of sailing.
Activities include sailing courses; certification of instructors, race officers,
judges, etc; holding of various national championships; management of the
olympic sailing team; and updating and publication of the International
Yacht Racing Rules every four years. Basic membership is $35/year, but
various discount programs are available through many yacht clubs. All
active racing sailors should be members of US Sailing. (sc) The directory
they provide has the addresses of every racing class known to man. (wh)


Address: US Sailing Box 209, Goat Island Marina Newport, RI 02840
(401) 849-5200 Fax: (401) 849-5208


telex: 704592 USYRU NORT UD



                                 20




compuserve #:75530,502 email or "Go SAILING FORUM" for the "US
SAILING connection." Executive Director monitors 75410,2126 three
times daily for members' or organizations' queries. (tl)



3.7   Where can I find out about collegiate sailing?



US Sailing publishes a college sailing directory, available for $7 from the
address above. (sc)


Jay Allen also says: [There is a college sailing mailing list. The address to
subscribe is:


majordomo@westweb.com


and one should write in the message:


subscribe icyra



3.8   What about keels?



Courtesy of Matt Pedersen:


(Definitions used in this discussion: length refers to the fore and aft
length of the keel, depth refers to how far the keel sticks into the water,
width is side/side width)


General discussion of Keels:


Keels help you sail in a straight line. They are also a great place to put a
bilge, bilge pump, and tankage. What you want is a keel that is very
narrow in width when going to weather, and a little fatter going
downwind. I don't know how to make my keel do this, but when I do
figure it out you'll be the first to know. Narrow width keels also stall out
(lose their lifting ability) at lower speeds when compared to a fatter keel.
This is a negative.


Longer keels are harder to knock off course than shorter keels. Longer
keels are harder to put back on course than shorter keels. Longer keels
have more wetted surface than shorter keels, which hurts light air
performance.


Deeper keels go to windward better than shallow keels. Deeper keels get
the ballast lower in the boat, which helps sail carrying ability. Deeper



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keels find the bottom sooner than shallow keels.


About wing keels:


Winged keels have a lot more weight down low which dramatically
increases the stability they provide. The wings supposedly help
hydrodynamics. I don't think it's all that great. They do increase draft a
little going to weather (the wing hangs down lower as you heel). I'm not
real convinced that a wing keel when heeled and slightly deeper, but with
a right angle in it is more efficient at getting lift than a standard fin.
Wing keels are good at catching kelp, or anything else floating in the
water. They also stick in the mud better, if that's what you want. To be
fair they are a way to get shoal draft and a little stiffness too.


Bulb Keels:


These are basically a keel with a big torpedo shaped blob of lead at the
bottom. They are not more efficient than a straight fin. They do get more
weight down low, which helps in sail carrying ability.


Scheel keels:


Scheel keels are kind of like bulbs at the bottom of the keel, but they look
cooler. They may have some hydrodynamic improvement over a straight
fin, I don't know. They get ballast way down low. It's interesting that
many designers use a Scheel keel instead of a wing keel, even though they
have to pay a royalty on it. That says something about how difficult it is
to design a truly good wing keel. By the way Henry Scheel designs great
looking boats.


Recent history of keel design:


Now if you look at the design of fin keels over the years, you will see a
great deal of theory being applied to get you the fastest shape possible.
Let's see, there was the swept back "Sharks fin" of the early seventies. It
looks fast, therefore it must be fast. They were "proven" to be slow, so
you don't see them much anymore. However, David Pedrick (who
designed Dennis Conner's Stars and Stripes) has resurrected them for the
latest Freedom boats. Gee, maybe they are fast after all.


Then there was the "Peterson" fin. Straight leading and trailing edges.
High aspect ratio. Still pretty fast, but it doesn't put most of its weight
down low, where it does the most good. But then the IOR rule really
didn't care about that.


Then there was the winged keel of the eighties. They are great on big



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tubby meter boats with draft limited by some rule, and you want a lot of

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