Screening Golf Balls for Overall Distance and Symmetry

Notice to Manufacturers - Clarification of Testing Method

Title: Screening Golf Balls for Overall Distance and Symmetry

Notice #: B2013-001

Supersedes Notice #: N/A

Effective Date: 1 January 2014

Relevant Protocol: Actual Launch Conditions Overall Distance and Symmetry Test Procedure (Phase II) (Revision 2.0.0, February 28, 2011)

Relevant Section within Protocol

Section 4.5 states that “Intermediate screening procedures may be used to determine ball conformance and increase testing efficiency. However, no ball will be ruled non-conforming unless it has been tested according to this protocol.”

Background / Reason for Clarification

Since the adoption of Phase II of the updated Overall Distance Standard, the USGA and The R&A have used fifteen test conditions (combinations of speed and spin) to evaluate the aerodynamics of a golf ball within the Indoor Test Range (“ITR”). The screening procedure used relies on a subset of nine conditions selected from the larger set.

On the whole, this screening has produced good agreement with the full test for most golf balls. However, a recent study has identified an alternative subset that produces better agreement for more golf balls. In an effort to provide manufacturers with the best estimate of Overall Distance for screened golf balls, the USGA and The R&A will adopt the revised screening conditions effective January 1, 2014.

Revised ITR Screening Procedure

Method of Determination

Between 2009 and May 2013, 622 different ball types received full tests using the ITR and the distance resulting from each test was recorded. Distance was then recalculated using every possible subset of nine of the collected fifteen test conditions (1,716 in total), while ensuring that the two settings at 278 ft/s were included in each subset (Conditions 1 and 2).

For each possible subset, the average, standard deviation, maximum and minimum errors among the 622 ball types were recorded and compared to the results of the full test. Particular attention was paid to the range: the maximum error (positive value) minus the minimum error (negative value). Finally, the combinations were ranked according to error range in order to identify the best candidates for improved screening.

Revised ITR Screening for Conformance Testing

A complete list of the ITR test conditions and indications of the previously used and improved screening subset are given in the table below:

Condition

Nominal  Speed

(ft/s)

Nominal Spin

(rev/s)

Previous Screening

Revised Screening

1

278

35

2

278

52

3

220

30

4

220

38

 

 

5

220

49

 

6

161

29

7

161

47

 

8

130

30

 

 

9

130

39

10

130

48

 

11

108

29

 

12

108

44

13

96

30

 

 

14

95

36

15

93

42

 

 

Using the new subset of conditions reduces the total range of screening-associated error from ±6 yards to ±2.

Use

Golf balls will be subject to the full set of ITR conditions in all cases where the estimated distance using screening methods exceeds 315.5 yards, where there is a likelihood of asymmetric behavior, or in any other situation which suggests unique or unusual performance or behaviour.

Going forward, this screening procedure will continue to be reviewed and monitored to ensure efficacy. Any future changes will be communicated promptly.