From: shweeja02@cc.curtin.edu.au (James Hwee)
Subject: Re: Mast stiffness measurement
Organization: Curtin University of Technology
Date: Thu, 17 Dec 1992 21:56:59 GMT

In article <line4fINNcts@exodus.Eng.Sun.COM>, srnelson@speedsail.Eng.Sun.COM (Scott R. Nelson) writes:

> Some of the advertised masts have an MCS number like 25 or 30 and
> some don't.  What does the MCS measurement mean?
> 
> How is the MCS number related to the DIN number?

The MCS form of measurement is now becoming a standard replacing the DIN
measurements that have been used for quite some time now. The MCS
measurement comes in the form of something like 25/5 which means that
25cm of mast will flex 5cm with a given load (X kgs).  Most manufacturers
and retailers have dropped the 5cm bit from the jargon and have made that
a constant.  So now they speak about masts with a rating of MCS 25 and
MCS 30, for example (note the "/5" bit is left out).  So you can now see
that a MCS 25 mast is softer than a MCS 30.

> How can I figure out what the stiffness is of my current fiberglass
> masts that came with my O'Brien and F2 boards?

That's getting pretty technical and if it's not written on your mast the
only other place that I can think of that could help is your retailer
who should have product info. guides with all the specs of masts, new and
old.

> What is the difference in behavior between fiberglass, epoxy,
> aluminum and carbon fiber masts?  Obviously fiberglass is likely
> to be the heaviest and carbon fiber the lightest, but what other
> differences should I expect?

Some other differences that come to mind are strength and flex response.
Because carbon fibre is stronger than glass fibre you need less carbon fibre
material to make an equally strong mast.  It is for this reason that carbon
fibre masts weigh in at about 1.5 - 2kgs.  But Carbon fibre is not *THE*
material for every function.  It is more fragile and hence isn't the best
choice for high impact disciplines such as wave-sailing.

The flex response refers to amount of time that the mast takes to return
to its "original" position after flexing under a load such as a gust of
wind.  Carbon fibre masts are said to be 4 times faster than glass and 
twice as fast as aluminium masts.  This makes for a far more comfortable 
sail with the sail retaining its designed shape longer with each gust.

> Are there any other advantages of a 2-piece mast over a 1-piece mast
> besides being able to put it inside my car instead of on top?

2-piece masts are excellent for travelling and convenience, but that is, 
I'm afraid, where my praise stops.  The have of weak spot, and that is
the ferrule where the two masts pieces meet.  This point is notorious
for breakage especially amongst the modern racing sails that require huge
amounts of downhaul.  How do I know, I've broken two (2) 2-piece masts
before!

Another less important point is that they don't have *exactly* the same
flex curve as their 1-piece equivelant, but then again who can tell the
diff.

> Once I understand the answers to all of these questions, is there
> anything else that is important for me to understand about masts?

Nowadays, sail makers design their sails around a particular mast.
If they know how the mast that their sail is going to be rigged on behaves
then they can design that sail with much greater ease.  So to cut a long
story short, if you want to get the most out of your sail, rig it on
the right mast.  (Haven't I heard someone say that before?)

> Thanks for any and all responses.

No probs.

> Scott R. Nelson

If anyone has any additions or corrections that they'd like to add,
go right ahead.

Later,
James
-- 
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   James Hwee   WA42               Internet : SHWEEJA02@cc.curtin.edu.au
   Curtin University
   Perth, West Oz.
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