Capt. JG wrote:

From the Harken website... http://www.harken.com/blocks/bksty.php

On masthead rigs it is the primary control for headstay tension, which
affects genoa shape. Ease the backstay to add draft to the genoa for more
power in light-to-medium conditions; tension the backstay to remove draft
for better pointing in heavy air.

You got it all wrong. Adjustable back stay is a fancy turnbuckle on
my boat, with flip up adjuster handles, tension in the headstay can
be increased or decreased, though not enough to actually move the
masthead enough to grossly influence weather helm.

Genoa shape is governed by luff tension independant of headstay sag.
A stretchy genoa luff cannot accomplish as much improvement in
windward performance as a sail change, except in marginally
increased wind conditions, which exceeded, demand a smaller sail,
sheeted inboard of the usual genoa track and very flat.

It is so funny to watch genoa drivers struggle with heel and helm,
when a smaller properly set sail can so easily outperform them to
windward, especially since the right sail will last for years while
a baggy genoa may not have survived it's first race, shapewise.

One should not expect to actually stretch a forestay and the luff
hanging from it to any good effect.

While I must admit the adjustable backstay has some utility,
presetting the shrouds tighter aft and allowing the wind to do it's
work is a far superior sail shaping solution, cruisingwise, if you
want to automatically flatten the middle of the main in rising
winds, not a bad idea in the right circumstances. Overall main shape
is governed by it's luff tension, cunningham or gooseneck downhaul,
along with, of course, it's clew outhaul.

The backstay is not a sail control, but with enough adjustment,
matched in antiphase with the headstay adjustment, can give a
modicum of weather helm adjustment, though it would only suit a
small adjustment for a given sail combination in a small range of
wind conditions.

Better a strong jib halyard hoist and a stretchy luff rope, not
wire, though a wire to rope splice in the halyard is nice to
minimise warp under wind.



Backstay tension also affects mast bend,

depending on lower shrouds, automatically

flattening the main and extending its range before a reef is required. It
also changes mast rake, especially off the wind where dumping the rig
forward reduces weather helm for reaching and running.

Can yours move the masthead even 3 inches? Better to reduce sail
according to weather helm dictats. A jib downhaul can allow a man to
safely change a jib in seconds, only hanking it on at the foredeck,
possibly changing the sheets, and halyard shackle, and leaving the
doused genny siezed on deck, hanked on below the pennant for the 75%
working jib, depending on winds, and it's self tending club boom,
ready to instantly rise again in easing winds. That is why hanks
should be few and for taming the jib on deck only. It's halyard
should control it's shape by stretching the luff and taking away
some of the forestay load. Maximum stretch in a genny luff should be
at about half of the headstay tension. A wire luff genny is not
really adjustable, sail cloth can stretch a lot, and can be used and
abused.

Light air sails are fragile.

On fractional rigs, the primary affect of the backstay is to shape the main
through mast bend. Since the main is so important on a fractionally rigged
boat (comprising the majority of sail area)

Not in a lot of furler genny only boats I see go by

, the system has to be designed
for convenient adjustment. It should be adjusted frequently, so if you can't
tolerate having crew moving off the rail to tweak the backstay every time,
place it where the main trimmer is invited to make fine adjustments to
backstay tension. It should be as natural as dropping the traveler or
trimming the fine-tune.

The fine-tune what?

The traveller is the original hi-tech toy nobody really needs or
uses properly. A good boom vang can do what a traveller does and
more, and it doesn't get in the way.

Terry K