Maybe it's time for us to put all our ways, methods and formulae for
calculating PH on the table for Colin to see.
Personally PH is very high on my wish list and if at all feasible I
would like to adopt a common universal method if there is such a thing
(a way of ducking the firing line!). Perhaps this very lively discussion
can be carried forward in the interests of possibly developing a
'standard' universally acceptable PH system - or are the needs &
conditions unique to each club/regatta so far apart that we can't come
to agree on one accepted method, or even three or four along the lines
of IMS, PHRF etc? To me it seems as though each club has their own
backyard hashed system, some better than others; we do and it was
certainly not developed by a mathematician or statistician so I doubt
it's robustness.
This is what I do: PH is calculated using the formula c=e*r where c is
corrected time, r is the rating and e the elapsed time. The PH value (r)
is determined anew for each race and weighted 3/4ths of the previous
races' rating plus 1/4 of the current races' rating to dampen chance
wild oscillations. [Each new entry to the series is allocated the same
rating as the current lowest rated skipper]. I go to a spreadsheet to
calculate (competitors elapsed time/winners elapsed time) which gives a
new r value (range 0<r<1), the winners' new r value will be 1. Note I
use the winners time, not an nth competitors time and there are no
clamps or exclusions of the top or bottom percent. This new r value is
weighted 1/4 to 3/4 with the old r value and is used for the next race
(input into Sailwave edit+competitor default rating; I use custom rating
system in scoring properties and input the equation e*r in the c= box;
e=c/r & r=c/e) .
Perhaps the formula in a Sailwave custom PH facility might look
something like this
I have graphed the changes of r over two seasons and note all the common
failings of a PH system (1) it discriminates against very consistent
sailors who never seem to win a handicap series; (2) the value of r only
changes by ~3% (max 5%) and (3) the problems with establishing an
initial PH value. My observations and conclusions are well described and
are more eloquently put in an article titled "Handicapping algorithms
for measured performance HCing of keel boats" by Rod McCubbin passed
onto to me by Huw Pearce.
Nice one, Rob! Encapsulates a lot of the difficulties with PH, especially
how to encourage the very consistent sailors (up to the handicapper to get
the initial PH 'correct'?). I'd be happy to use (and more importantly, sell
to the sailors) a formula along the lines that Rob suggests (even better if
the 2 weighting factors could be series variables, rather than built in).
Mike
Maybe it's time for us to put all our ways, methods and formulae for
calculating PH on the table for Colin to see.
Personally PH is very high on my wish list and if at all feasible I
would like to adopt a common universal method if there is such a thing
(a way of ducking the firing line!). Perhaps this very lively discussion
can be carried forward in the interests of possibly developing a
'standard' universally acceptable PH system - or are the needs &
conditions unique to each club/regatta so far apart that we can't come
to agree on one accepted method, or even three or four along the lines
of IMS, PHRF etc? To me it seems as though each club has their own
backyard hashed system, some better than others; we do and it was
certainly not developed by a mathematician or statistician so I doubt
it's robustness.
This is what I do: PH is calculated using the formula c=e*r where c is
corrected time, r is the rating and e the elapsed time. The PH value (r)
is determined anew for each race and weighted 3/4ths of the previous
races' rating plus 1/4 of the current races' rating to dampen chance
wild oscillations. [Each new entry to the series is allocated the same
rating as the current lowest rated skipper]. I go to a spreadsheet to
calculate (competitors elapsed time/winners elapsed time) which gives a
new r value (range 0<r<1), the winners' new r value will be 1. Note I
use the winners time, not an nth competitors time and there are no
clamps or exclusions of the top or bottom percent. This new r value is
weighted 1/4 to 3/4 with the old r value and is used for the next race
(input into Sailwave edit+competitor default rating; I use custom rating
system in scoring properties and input the equation e*r in the c= box;
e=c/r & r=c/e) .
Perhaps the formula in a Sailwave custom PH facility might look
something like this
I have graphed the changes of r over two seasons and note all the common
failings of a PH system (1) it discriminates against very consistent
sailors who never seem to win a handicap series; (2) the value of r only
changes by ~3% (max 5%) and (3) the problems with establishing an
initial PH value. My observations and conclusions are well described and
are more eloquently put in an article titled "Handicapping algorithms
for measured performance HCing of keel boats" by Rod McCubbin passed
onto to me by Huw Pearce.
Maybe it's time for us to put all our ways, methods and formulae for
calculating PH on the table for Colin to see.
Personally PH is very high on my wish list and if at all feasible I
would like to adopt a common universal method if there is such a thing
(a way of ducking the firing line!). Perhaps this very lively discussion
can be carried forward in the interests of possibly developing a
'standard' universally acceptable PH system - or are the needs &
conditions unique to each club/regatta so far apart that we can't come
to agree on one accepted method, or even three or four along the lines
of IMS, PHRF etc? To me it seems as though each club has their own
backyard hashed system, some better than others; we do and it was
certainly not developed by a mathematician or statistician so I doubt
it's robustness.
This is what I do: PH is calculated using the formula c=e*r where c is
corrected time, r is the rating and e the elapsed time. The PH value (r)
is determined anew for each race and weighted 3/4ths of the previous
races' rating plus 1/4 of the current races' rating to dampen chance
wild oscillations. [Each new entry to the series is allocated the same
rating as the current lowest rated skipper]. I go to a spreadsheet to
calculate (competitors elapsed time/winners elapsed time) which gives a
new r value (range 0<r<1), the winners' new r value will be 1. Note I
use the winners time, not an nth competitors time and there are no
clamps or exclusions of the top or bottom percent. This new r value is
weighted 1/4 to 3/4 with the old r value and is used for the next race
(input into Sailwave edit+competitor default rating; I use custom rating
system in scoring properties and input the equation e*r in the c= box;
e=c/r & r=c/e) .
Perhaps the formula in a Sailwave custom PH facility might look
something like this
I have graphed the changes of r over two seasons and note all the common
failings of a PH system (1) it discriminates against very consistent
sailors who never seem to win a handicap series; (2) the value of r only
changes by ~3% (max 5%) and (3) the problems with establishing an
initial PH value. My observations and conclusions are well described and
are more eloquently put in an article titled "Handicapping algorithms
for measured performance HCing of keel boats" by Rod McCubbin passed
onto to me by Huw Pearce.
Our club uses an Excel spreadsheet devised by the handicapping group for the Forth area. In it's simplest form it calculates the Standard Corrected Time for each race or fleet within the race and then calculates out each boats achieved performance.
Their is a bit of statistics to go along with how it does this and a better explanation can be found at
You can also download a copy of the spreadsheet and have a look at it for yourselves.
From this we take the achieved performance subtract the original handicap and get a performance factor. We then divide this by four and carry these numbers forward for four races. After 4 races these numbers are averaged and the handicap is adjusted by this average either up or down to take out the swings that some races create.
The spreadsheet will throw out any realy fast or slow race results and we will not use these for our calculations.
As with all the systems it seems to work for us.
Trevor Mackay
Sailing Secretary
Cramond Boat Club
Rob Walker wrote:
Dear all Sailwave PH users,
Maybe it's time for us to put all our ways, methods and formulae for
calculating PH on the table for Colin to see.