You vs. "Them"
Comparing boats on the fly
How well are you doing compared to your main competition?
PHRF handicaps are pretty straightforward in time-on-distance scoring – if
your boat has a rating 10 points lower than another boat, you give them 10
seconds per mile. Sailors usually think this is an easy number to deal
with, even though many haven't a clue how far they actually
sailed.
Time-on-time scoring is less intuitive than time-on-distance. A
boat's rating gets converted to a (non-linear) correction factor. Each boat's
actual finish time
is then
multiplied by its correction factor, and the corrected times are compared to
determine finish places. By this point, the relationship between handicap ratings and
finish places has become pretty convoluted. (See how
to score for an explanation of the formal scoring calculations.)
Seconds per hour
An easy way to handle time-on-time is to convert the handicap rating into a
seconds-per-hour difference between two boats. You can then estimate the
correction easily based on the time sailed. (That's assuming you acurately time
your race, as you should.)
The process is a little more complicated, because you have to calculate the
seconds-per-hour difference for each PHRF rating in the fleet, a laborious
process at best. But I've saved you that drudge work, and summed it up in a You vs.
"Them" table listing the boats currently racing in the two GMSC
keelboat fleets this season.
Using the table
How well must you do against "them"?
Look up the correction between your boat and their boat in the table.
- Find your boat under "Your Boat"
- Find their boat under "Their Boat"
(Should I run through that again?)
- The number in the intersection is the seconds-per-hour difference between the two
boats, for each hour your boat sails.
Example
You sail a J-27, your nearest competition sails an S2 7.9 (we'll leave out the
sail numbers to protect the not-quite innocent).
The intersection of the "Your Boat" J-27 and the "Their
Boat" S2 7.9 is 241. That means you give them 241 seconds (4:01) per hour.
Did you beat them?
Any time you sail exactly one hour, the calculation is simple:
- Add the seconds-per-hour difference to 1 hour.
- That determines the "break-even" time, the actual time the other boat must sail to tie you.
- If they sail longer, you beat them.
For any other elapsed time you sail, the calculation isn't much more
difficult:
- Determine the hours you sailed (e.g., 1:36:00 is 1.6 hours).
- Multiply that number time the seconds-per-hour difference.
- Add the result to your time.
- That determines the actual time the other boat must sail to tie you.
- If they sail longer, you beat them.
Example 1
You sail exactly 1 hour (3600 seconds) in your J-27. Adding the correction of
241 gives a "break-even" time of 3841 seconds (64:01). That 64:01 is the
actual time that the S2 has to sail in order to tie you. If they sail 64:00, they beat you (don't complain to
the scorekeeper). At 64:02, you beat them.
Example 2
You sailed 1:14:43 in your J-27. For estimating, that's close enough to 1 1/4
hours (1:15:00). Multiplying the correction of 241 times 1 1/4 gives 301 seconds,
essentially 5 minutes. Add that to your 1:14:43 to
find that their "break-even" time is about 1:19:44, which is the
approximate actual time that the S2 has to beat in order to beat you.
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