Sport Today

    L8r...

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|Raytheon,_Marlborough,_Mass_|__________(US-775)____________|_________________|
|                    "Windsurfing is life, the rest is just details."         |
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|  BIG Certified Instructor  | My homepage: http://www.ultranet.com/~lefebvre |
+---Seatrend----Neil-Pryde---+----Fiberspar----Finworks-----Bare----Zeiner----+

2. If you use an MCS 25 mast in a sail designed for MCS 28 you will get nearly the same results as above
except that the luff midsection will flatten out long before the head and foot are properly loaded hence the
design "twist" in the head won't work as the designer intended. You can still sail it but once again the
performance will be diminished and the sail will be harder to handle.

3. Rig stability, top-end speed, and low end power will be diminished overall if the proper mast  stiffness is
not used. Some mast incompatability can be trimmed out using different downhaul, outhaul and batten tension
tweaks but in order to get stability, either the top end or low end will be compromised. If you rig for top end,
the low end will suck and vice versa. You can't get both, even with the correct mast it will always be a compromise
to make the lift/drag ratio in the sail fit the conditions. You can flatten for top end or you can fatten for low end
but either way the extremes are somewhat mutually exclusive.  Rigging the sail on the correct stiffness mast to
the designers measurements works really well on North sails and gives you the best blend of stability, top end
and power. But you will still need to tweak or change sails as the conditions change. This is why the highest
level course racers have trimmer lines so they can tweak the downhaul and outhaul on the fly during a race to
optimize it for changes in wind speed and for different points of sail.

4. A stiff mast is better for pumping as it rebounds more quickly and  doesn't flex as much during the "pump". Stiff masts
also seem to work better for heavy weights during pumping  onto a plane as they have the body strength and weight
to get the most out of the mast.
A softer mast is bettter for top end  in gusty conditions; for lighter less powerful sailors;  and for high wind survival
as they bend sooner and will let the top of the sail twist off  earlier.
Another thing to consider is the bend ratio (flex top vs constant curve). This can have a big effect on your ability to
rig the sail and also to get the most out of it.
I'm a light weight (150#)  so I have found that the 94 North Xcellerators' which have a little more flex in the top
( Larry Herbig says about 5% more top flex) than the 95 Xcellerators. The flex top 94's work a little better for me as
I will never be able to generate the  the power of the big tall guys and on the top end having a little more twist a little earlier
enables me to stay sheeted in a little longer and use the twist to generate additional speed.  I find the 95 constant curves
are a bit more stable, but I get launched more often.

sailquik US 3704
F2/CFX/North Sails/North Masts/True Ames/Rainbow Duffy Series/
Chinook/Wavelength/Body Glove/SSA/ Free Advice on all of above.

Phone= (301) 872-9459

 Pete

 http://www.w3w.com/3w/3wcc01.html

Top-end speed is increased with a softer mast.  This is quite
significant.  In my experience, I used a shorter mast as well
which "softened" it even further.  (Nominal was 460/28, used
430/25).

Upwindability was better.  Again, a flatter sail has lower
drag.  This assumes you have sufficient windspeed.  

Power is reduced for low wind and getting on a plane.  You will
fall off plane quicker in the holes.  A direct result is that
pumping effectiveness is less.  Head twist plays a detrimental
role as well.  (See next point.)

Stability I think is increased to a point, but I'm not sure.  
On one hand the flex will allow the sail to flatten more in
gusts and twist the head.  The flip side is that your sail is
changing shape, and you have to adjust.  I think the former
plays a bigger role.

Acceleration is less.  Again, the top twists off more easily.  
If it held its shape, you would accelerate more.  (Related to
power.)

Survival mode: Softer is flatter, more stable.  The rig is not
as "tightly strung." and may take more abuse before something
breaks.  This part is pure speculation.

Heavy/Light weights: Lighter folks should use a softer mast.  
Fat boys need lots of power to get going, lightweights don't.

You can probably go down in stiffness further than you can go
up.  That is, if the nominal mast is 28, you can get to 25 or
24 (difference of 3-4), but I wouldn't go much past 30
(diff of 2-3).

Paul -- US366 (Maui)

I would beg to differ with this one, as a general statement, which seems to
contradict the rest of your message. A softer mast would generally provide
less power because of the tendency to twist off more often. You may be
faster with a softer mast on a particular sail in overpowered conditions
because it's forgiving qualities. I think you'd be faster on a slightly
smaller sail with the right mast. I.e. it's more important to have the right
mast for your sail, size, and ability.

As a lightweight, I sail better on masts that are at the low end or 1 or 2
mcs point below the recommended for the sail. However, if you're heavier,
you generate greater bending forces on the mast so you need the mast to be
stiffer - at the upper end of the mcs range for the sail - to go fast
otherwise it spends to much time in twist off mode - not the best shape for
a sail.  

Good sailing,

Tae

|> Many manufacturers have masts with the same stiffness, but different
|> percentages of carbon.  Has anyone noticed a difference based on
|> carbon content, besides price?
|>
|> Rob
|>

Yes, weight is reduced. I'm eagerly looking forward to trying
out the '96 90% carbon Pryde masts.
--
Paul Scrutton - My views may not agree with those
                of employer.

Rob

                      Monty Spindler rules !

                                (Even if his masts break so easily)

mmm... the problem here is "slalom", not "carbon".
carbon wave masts are very sturdy, I have yet to break my north space tech
(30% carbon) in european waves.

--
Colas Nahaboo, Koala, Dyade (Bull) INRIA Sophia,
http://www.inria.fr/koala/colas