What's IMCS ?

dariusz333 · Joined: 05 May 2001 Posts: 3

Im trying to get a
sail for my mast, and
specs on my mast are
4.65m lenght and 48mm dia. How to find out
IMCS, whatever that is?

Derek

spyder · Joined: 24 Sep 1996 Posts: 2790 Location: oahu

Normally the sail has a spec for the IMCS (or stiffness rating) of the mast. It should say :
recommended mast 460/25

which means a 460 cm length with a stiffness rating of 25.

As for the full meaning of IMCS here is an explaination:

Indexed MCS Measurement For Masts

The INDEXED MCS measurement system was developed to compare stiffnesses between masts of different lengths.

MCS numbers only mean a stiffer or softer mast when comparing masts of the same length. For example: compare the 430/25 and 460/25. Even though the 430 has the same MCS stiffness number (25), when a 30cm carbon base extension is added to reach the 460 length, the stiffness is actually softer than the 460/25. By indexing all masts to one length (465cm), it is possible to use the MCS concept and compare masts of different lengths.

Indexed MCS uses some arithmetic to relate every mast stiffness to 465cm length for more precise relative stiffness numbers.

INDEXED MCS = OVERALL LENGTH CUBED DIVIDED BY MID POINT DEFLECTION X 465 SQUARED

Example: Compare a 430cm with a mid-point deflection of 172 and a 460cm with a mid-point deflection of 184.

dariusz333 · Joined: 05 May 2001 Posts: 3

Thank you very much for
the explanation.
Since I have only length,
bottom diameter and BIC catalogue number, how should I search for a new sail? How important is IMCS at this point?
Sorry for so naive questions, but Im just
getting in to this sport
Derek

spyder · Joined: 24 Sep 1996 Posts: 2790 Location: oahu

sounds like an older mast. Probably is pretty stiff. Most modern sails wont work very well on that mast unfortunately.

However, if you get an older sail, it might work ok for now.

the 465 length will fit larger sails such as a 6.5. You need to check the LUFF length printed on the sail bag/sail. It should be greater than this mast length, OR have an adjustable head cap, which the mast can protrude out (but not too much 10cm is reasonable).

dariusz333 · Joined: 05 May 2001 Posts: 3

It is an older model (1990), and it is pretty stiff. I guess, the only way for me to buy another sail, would be to actually try it before buying it.
Thanks for all your help.
Greatly appreciated.

Regards,
Derek T.

DoranWelch · Joined: 15 Aug 2000 Posts: 10

Unless you really cant afford it, I would buy a a modern rig. The differences are so great that it will allow you to improve much more quickly. Anything in the last few years is fine.