What is the IMCS (INDEXED MAST CHECK SYSTEM) measurement for masts?

The IMCS measurement system is the industry standard established by Fiberspar in 1994 to measure the stiffness of a mast. This has replaced the old MCS system which was ineffective when comparing masts of different lengths. With a little more arithmetic, every mast stiffness can be normalized to 465cm length (which Surf Magazine has set as the industry standard), and the stiffnesses of different length masts can be compared. Of course the average sailor on the street doesn't have to know the arithmetic. He just has to know what IMCS stiffness is recommended for his sails.

To figure out the IMCS for any given mast, you follow the following formula:

(Overall Length)3
IMCS =
(Mid-Point Deflection) X (465)2

 

For example, compare a 430cm mast with mid point deflection 159mm and a 460cm mast with mid point deflection of 184mm. Under the old MCS system the 430cm would have a 27 MCS rating and the 460cm would have a 25 MCS rating. But whoa!, the 430cm mast is actually softer mast than the 460cm if it were extended 30cm, and to compare the MCS numbers of these two masts wouldnÕt make sense. Under the IMCS system the 430cm is 23 IMCS and the 460cm is 25 IMCS which is a true reflection of their relative stiffnesses.

Converting "MCS" into "IMCS" numbers

To convert the MCS number for a given length mast into IMCS, multiply by the factor below.
Mast Length
(cm)		 Multiply MCS
by this factor:
540 1.35
530 1.30
520 1.25
510 1.20
500 1.16
490 1.11
480 1.07
470 1.02
460 0.98
450 0.94
440 0.90
430 0.86
420 0.82
410 0.78
400 0.74
390 0.70

For Example: A Reflex 5000 430 with an MCS of 25 multiplied by 0.86 equals an IMCS number of 21.