It may depend on the mast brand and sail brand as to how much effect
"too much (more than about 15 cm) extension up the base of the mast.
That's why the "high end" mast extensions Mfg.'s. all make 0; 15 cm;
30 cm; and 45-48 cm bases.
This all comes back to the "setup" (mast, mast extension, and sail
design) that the designer had in mind when designing the luff curve and
panel loading layout for the sail.
If you have a low foot batten, and the designer intended for the mast
extension to end below the footbatten you may find that the footbatten
does not rotate correctly.
Because the design of the sail intended for the mast to bend (very
slightly perhaps) down where the footbatten rotates around the mast.
Certainly this is about the stiffest part of the mast, but it can bend
Put a long "un bendable" extension up inside that area of the mast and
there's no way the mast can bend correctly nor will the footbatten
really work as it was designed.
Yes, you can back off the footbatten tension (taking some draft out of
the lower panels in your sail) and get the footbatten to rotate
correctly, but there will be some small vertical wrinkles along the
improperly tensioned foot batten and the sail will be flatter and softer
down near the tack.
Can you get away with the stiffer lower section in your sails.
Again, it depends on the design, and if you wish to get the full
performance that the design offers, you need the right length extension
just as you need the right specification mast.
Also (not so much with modern masts that have the full bottom section
reinforced for hoop strength) on some masts or with some extensions I've
seen the mast break at the top of the extension due to "point loading"
at an area of the mast never intended to get that sort of loads.
It's like you are expecting a mast made to bend to a certain curve to
bend differently because you've "stiffened" the very bottom section with
the long extension. The mast still bends, but only above the extension.
So, not a very good idea, and normally used by those not looking for the
full performance from their mast and sail combo.
Hope this helps,
> I will ask a stupid question out of boredom,
> Anybody think a tall mast extension 48cm set on a low setting (10cm or
> less) would change the mast bend in the lower section any (as opposed
> to a stubby)?
> I doubt it but I thought I would ask.