## PHRF Overview |

Rating Systems:

Two different concepts are presently being used:

- __Measurement Systems__ i.e **IOR ** and **IMS**. (mostly International
use i.e. 1Ton, ¾Ton etc..)

- __Performance Systems__ i.e. **PHRF, ASPN, Portsmouth Numbers.** (Regional
and Club oriented)

**NStYA **is presently committed to the **PHRF** performance system.

Performance handicapping systems are based on the speed potential of a yacht, and the ratings have been derived from observations of previous race data. Base ratings, have been determined from past performance of a class or similar type yachts, and some simple measurements are taken to make adjustments, i.e. larger sails, propulsion and others...

Sail and Rig Measurements may be done by the owner, but for consistency **NStYA** prefers that an
experienced local handicapper to be present both to measure and calculate the yacht rating.

Time Correction Method:

There are two methods which apply ratings to convert ** "elapsed time"** to obtain

**:**

*"corrected time"*
- **"Time on Distance"** usually **Time Allowances (TA)**in sec/mile.

- **"Time on Time"** using **Time Correction Factors (TCF)** in sec/hr.

**PHRF** is primarily a **"Time on Distance"** (TA) method, **NStYA **uses the ** Time
Correction Factor** (TCF) conversion to convert to "Time on Time". To calculate TCF:

TCF = 695 / (525 + PHRF Rating).

Then multiply each "**elapsed time**" in minutes by the TCF. The results are the
"**corrected elapsed time**" in minutes.

Measurements and Adjustments:

**PHRF** requires 9 sail measurements and the** Spinnaker Pole Length (SPL).** Five on the mainsail,
which must be removed to be accurately measured, and there are 2 each on the jib and spinnaker. These
measurements are used to calculate the ** actual sail area** of the yacht.

Rig measurements required are: **I, H **, and** J.**** (H** is only required if significantly
different than** I.**).

These measurements are used to calculate the theoretical sail area of the yacht. In addition there are adjustments for propulsion types, rudder and other variables.

Calculations are then done to determine the ** sail area factor** or

**SAF**for each sail, this calculation is then applied to a

**SAF**

*adjustment table*to determine the amount of deviation from the standard index value of 1.0000.

**PHRF** uses adjustment increments of 3 sec/mile.

PHRF Base Ratings

Base ratings lists are available from various sources, most conform to the following *"Standard
Configuration"*

1. Spinnaker pole length is equal to **"J"**

2. Spinnaker maximum width is 180% of **"J"**

3. Spinnaker maximum length is 95% of jib stay length.

4. Perpendicular from Clew to Luff of largest headsail is between 150% and 155%
of** "J"**

5. Yacht is in racing condition.

6. Yacht has a folding or feathering propeller, a two blade fixed propeller in
aperture, or a retractable outboard motor.

7. Hull and appendages are unmodified.

8. **IOR** batten length restrictions are followed, except in cases where the
standard yacht has full length battens.

For further information contact your local club measurer or

Contact: NSYA