From: grant@genova.oas.olivetti.com (Grant Grundler)
Newsgroups: rec.windsurfing
Subject: Re: Mast stiffness measurement
Keywords: MCS, DIN, mast stiffness
Date: 15 Dec 92 00:00:17 GMT
Reply-To: grant@genova.oas.olivetti.com (Grant Grundler)
Organization: Olivetti Research California

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

> I've seen masts advertised as 6.6 or 7.5 DIN, but I don't have a
> clue what that translates to.  What does the DIN measurement mean?

DIN == Deutsche Industrie Norm (German Industrial Standard for english
speakers)

From a previous posting by brunnerj@bechtel.Colorado.EDU (John Brunner):
| In the summer 1991 edition of "Performance Windsurf Report" (a free
magazine I p
| icked up at a local shop) there was an article on how MCS stiffness
measurements
| are made.

| The article also says that the DIN test involved hanging a weight 420cm
| from the mast base and measuring tip deflection.

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

| 1.  Support the mast horizontally, with the supports 5cm from the base
|       and tip.  Measure the distance between supports.
| 2.  Measure the vertical deflection of the mast at the quarter points,
|       due to the mast weight only.
| 3.  Hang a 30kg mass from the mast halfway between supports, and measure
|       deflections at the quarter points again.
| 4.  Subtract deflection w/out weight from deflection with weight to give
|       net deflection.
| 5.  The overall MCS stiffness is given by dividing the distance between
|       supports by the midpoint deflection.
| 6.  The stiffness percentages are given by dividing the deflections at the
|        1/4 and 3/4 points by the midpoint deflection.  The shape of the
|        mast curve determines these numbers (i.e. whether a mast is
|        constant curve or flex top).
|
| Example:
|
| Total mast length = 460cm
| Deflection length = 460 - 2(5) = 450cm
| Point spacing = 450 / 4 = 112.5cm
|
|                              1/4     1/2     3/4 point
|                             ----    ----    ----
| Deflection w/out weight      0.6     1.1     0.9
| Deflection w/ weight        12.2    19.1    14.7
|                             ----    ----    ----
| Net deflection              11.6    18.0    13.8
|
| Overall stiffness = 450 / 18.0 = 25
| Stiffness percentages:  11.6 / 18.0 = .64 x 100 = 64% @ 1/4 point
|                         13.8 / 18.0 = .76 x 100 = 76% @ 3/4 point
 
> How is the MCS number related to the DIN number?

Only somewhat - go to a shop and you will see several masts with the same
MCS but slightly different DINS.

> 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?

Behaviour I don't know. But fiberglass doesn't like being in the sun and after
two or three years of usage it starts to show.  Aluminum two peice tend
to corrode
at the joint. Carbon masts tend to be more sensitive to abuse.  I have
owned fiberglass
aluminum, expoxy, and carbon masts. I have been careful with the carbon
mast and no
problems yet.  I broke an aluminum mast becuase it had corroded away. My epoxy
masts have held up really well over the past two years (I sail in the S.F. bay)
and my only comlaint is they are heavy (wave masts, sigh...).

> How can I tell if a mast is constant curve or flex top?

from a post by toma@hpfcso.FC.HP.COM (Tom Albertz):
|    Grant emailed me and asked me to post the percentages that fall
| into the different categories.  I can use my Fiberspar chart to approx.
|
| In all cases, the lower quarter defl. was from 62% to 64% of the midpoint
| defl., so very close.  All the flex top masts were 62 and 63%.  The combis
| were 63%; and the constant curves were 63 and 64%.
|
| The high quarterpoint defl. differences were a little more drastic.
| The flextops were 80+. the combis were 79%, and the constants were 76, 77%.

> 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?

What other advantages do you want?!
IMHO, The joint just makes the mast heavier, weaker, and more expensive.
(I could be wrong about more expensive...)
One piece carbon masts go down to about 1.7 or 1.8 Kg. for a 460 cm mast.
The same 2-piece mast weighs at least 0.2 Kg more (and I think it was
even 0.3 Kg).

grant
grant@oas.olivetti.com
From: kirk@hpcc01.corp.hp.com (Kirk Lindstrom)
Date: Wed, 16 Dec 1992 16:55:42 GMT
Subject: Re: How does one become a famous writer?
Organization: Shredding the water of SF Bay, HP-OCD