OzOne wrote:


Our backstays have a huge range, downwind the chocks come out at the
front of the mast and it's allowed to crank waaaay forward. Some go
into reverse bend but IMHO that's slower.


I'd say mast inveresion is not a good idea. Do people ever break masts?
I'd think that moving the mast past vertical forward would reduce sail
efficiency downwind by promoting upward flow...?

Cheers

... I'm guessing Donal's boat is heavier (but
possibly not that much so) and will want the top leach telltale stalling
a little more of the time.

OzOne wrote:
Works pretty much the same for any easily driven boat.
Donals benny fit in here as do most fin keelers.

The percent time spent with the leach telltales backwinding? IMHO the
ideal varies with type/category of boat, but I'm not really sure what
the determining factors are. Some boats I've sailed that were
magnificent at pinching, got best VMG (in relatively smooth water) with
the leach telltale backed about 75% of the time. OTOH lightweight boats
with high aspect ratio do better with the leach telltale backwinding 10%
of the time.

The leach telltale backwinding shows that the differential pressure
across the sail has increased to the point where flow off the leach is
yanked backwards. DP is what drives the boat, ideally you'd want the
leach telltale *just about* to backwind but not actually doing it. Maybe
we need some kind of aero smoke trail prodcut derived from resublimated
thiotimoline.



BTW this is a North guide, my setup is a little different.
Note just how finicky the Etchells is to setup and YES, we do change
the entire rig setup every race.

What kind of sails do you use? Most of the one designers here use North
but the smaller shops do have inroads in some of the classes




Our backstays have a huge range, downwind the chocks come out at the
front of the mast and it's allowed to crank waaaay forward. Some go
into reverse bend but IMHO that's slower.

Kinda risky too, I'd think. Is the forward end of the mast partners flat
or contoured to match the mast?


We have a puller to pull the mast forwar and the same system can work
in reverse to pull it back. You cannot have cleats on the lines,
they're used only to alter the chocking at the partners.

Interesting way of regulating the tuning.

... We use multi
stepped nylon block here controlled by yet another string.

Same here, although I molded a set of epoxy blocks with a graphite
finish. The steps are 10, 5, and 2 mm... they're light & slick...
everybody wanted me to make them a set too, great for psyching peole out
in the parking lot!



Backstay does come on pretty early, it's essential to control forestay
sag in such a high pointing boat. Mainsails are cut pretty tight
leeched up high and respond t the backstay by opening up.
Ya gotta be real careful here because again, we need he leech pressure
to drive us high.

What do you mean by 'leach pressure'?


I learned more in my first 3 months in a Etchells about tune and rig
setup than I've ever learned in a season in anything else.

After reading the class tuning guide they sound very very sensitive.

Fresh Breezes- Doug King

DSK wrote:



The leach telltale backwinding shows that the differential pressure
across the sail has increased to the point where flow off the leach is
yanked backwards.

That'll be 'yankee' for leeward flow separation.

Cheers