Sport Today

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.

Most I have heard say yes it does affect it, But I use mine like this
on occasion.  Form the looks of things, I can't tell if the mast bends
much or at all down there.  I have used my 45cm extension at the last
notch(45cm) and didn't like the looseness compared to how it feels when
25 cm is inside the mast.  But haven't had a bad experience with either
config.

J

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.
Why?
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
slightly.
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 agree with JRobb, I've seen a lot of posts that say it matters. All
I have is 2 tall extensions and stubby, but if I had a medium, I would
do a check on my 7.5, which is not looking just right.

It does change mast bend by stiffening the lower section and creating a
more full entry below the boom than the same mast with less base
extending upwards inside the mast.  Whether you can actually see this
is another matter, as is whether the change can be described as
unhelpful.  All depends on the particular combination of mast and sail.
 Like Roger says, a batten that begins very low on the sail
-particularly one that has a cam- will tend to "push" forward
(actually, the mast doesn't move as far away).  For a no-cam batten you
might find the batten to be a bit sticky when it rotates.  For some cam
sails you might find that the batten will not rotate at all -or only
with a swift kick.  Cam design and mast diameter play additional roles
here.

What I would be more concerned about is breaking your mast if the mast
is on the softer side of the IMCS.  Though many mast manufacturers have
increased the reinforcing areas below the boom, I certainly would not
want 40cm of extra extension inside my 430 wave mast when going through
the rinse cycle.  

-Dan