> I was wondering what the consensus is on how Mast Stiffness affects the
>performance for a given sail. For example, if a particular sail requires a
>IMCS of 28, what would the affect be if a IMCS of 30 is used or an IMCS of 25?
>How is this in regards to stability, top-end speed, low-end power? Which is
>better for low wind pumping to a plane? Which is better for hi wind survival?
>Which is better for heavy weights? Which is better for light weights?
Lots of questions! My general thoughts (opionions!):
A softer mast will make the sail flatter than normal, and
change in behavior is due mostly to this fact. I will cast
things in terms of using a softer mast.
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
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
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)