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Racing adjustments and comparison rules, and Nack57

Posted By: Nack Ballard
Date: Friday, 10 November 2017, at 1:42 a.m.

In Response To: Racing adjustments and comparison rules (Stick)

I believe Jeremy is saying that you can get your Keith adjustments FIRST (if or as necessary), then apply whatever smooth-position race formula you normally use.

For anyone not familiar with Nack57:

.....Subtract 33, double, and use the nearest (integer) square root.

Example: Leader's pipcount is 73.
.................Subtract 33 = 40, double = 80.
.................Nearest square root is 9, that's your take point.

This formula exactly duplicates the take points in the GST (Gold Standard Table), with the single exception that it rounds a pip low at 111.
By comparison, the widely used Trice's 10%+2 formula is a pip high at 61, 79, 80, 89, 90, 100, 110, 120, 121, 122...)

The "57" (or "5, 7") offers some reminders:

..........(1) Below 57, it is better to use a short-race formula.
..........(2) One good short-race formula is from Trice: "Subtract 5, divide by 7, round down."
..........(3) If you count with Naccel, add 57 instead of subtracting 33.
..........(4) Nack was born in 1957.

The GST (Gold Standard Table) was derived from a "one-checker model," which is not the same as testing low/minimal wastage for 15 checkers. After reviewing my initial Nack57 post, Neil Kazaross did a huge number of 15-vs-15-checker minimal-wastage rollouts to compare with GST, and discovered that subtracting 32 is slightly more accurate than subtracting 33.

The difference between subtracting 32 (instead of 33) in the first step of the Nack57 formula does NOT yield answers a pip apart up and down the line, as one might think. They only do so at certain changeover counts; e.g., at 78 and 88, for which the once-assumed-perfect GST actually has the take differential a pip low.

[The parallel adjustment for Naccel users is to add 58 instead of 57 for the same step (slightly altering step (3) above). For that reason, Naccel-ers might prefer to call this adjusted formula "Nack58." For (1) above, you can leave it at 57 or change to 58 (or even as low as 55), does not matter. For (2), be sure to use subt5 div7 (not subt5 div8!). Finally, ignore (4) or kindly knock a year off my age.]

Nack

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