Lets make sure we're talking about the same thing: Line goes from becket on
boom, to a block on transom, back to block on boom, to block on other side
of transom, and over the cleat.
> It seems to me that there is only one movable "pulley" on
> either tack. Consequently, this system produces a 2/1 advantage.
Actually its closer to a 3:1 - since there are 3 lines coming from the
moveable pulley side.
What makes this unbalanced is the fact that the transom blocks are spread
apart, and so its not really quite a 3:1 because of the angle of the leads.
One one tack you get a better advantage because you have 2 lines pulling in
the direction of the load, but on the other tack, only 1 and the other two
are not at a good angle (i.e. it takes more than x pounds of force on the
block to put x pounds of force in the direction you want it to go). Also,
with this 3:1 setup, for the same relative wind angle, you have to have
different amounts of sheeting on each tack for the same angle of attack of
the sails. With a 4:1 rig, theres two lines from the boom to each side of
the transom, so its more balanced.
With all that said, my opinion is that it isn't all that big of a deal, or
it really depends where/how you sail. There are certainly downsides to the
arrangement:
* With a 4:1 arrangement, it takes an obscene length of line to ease up the
main good for a run. This line is all over the cockpit when beating.
* There's another block and its associated friction
* The differing amounts of sheeting for each tack is no big deal, because
you should kick the powerplant into low gear by easing sheets after a tack
anyways, then sheet in as you build speed.
* Tacking can be slower because you have to pull a lot more sheet in when
adjusting.
* 4:1 isn't needed by many sailors (SF bay excepted!).
With all THAT said, I'll probably experiment with both setups this season.
A balanced 3:1 would be possible with one more turning block near the cleat
in the center of the transom. Start the line at a padeye on the boom, down
to center of the transom, turn it to one of the sides, up to the boom, down
to the other side, back to the cleat.
-Eric Johnson 1988 P19 #461 "Victoria", Bothell, WA