Subject: keen Croatian
W raises
centre mainsheet issue > Uncle Al talks main leech tension
On 12/6/07, Al Schonborn < uncle-al3854@cogeco.ca>
wrote:
Hi,
Mato:
Small
world! I feel like I already know you, having just this morning read
the log of the cruise you did with Ralph this summer. And there, the
subject of a centre mainsheet came up. I will give you my short answer
first and then add a bit of detail below - in green, which is I why I
have switched to Rich Text Format for this reply.
I am
very much in favour of the centre-only mainsheet system, which is safer
for the very reason that you mention: less risk to the gybes. The
reason that almost no W's use this system is that it was made illegal
in the Class Rules in the mid-1970's - politics, I believe, when the
WIC was formed, and the Brits wanted us North Americans to give up one
of the rules changes that we had approved but that UKWA had not.
Regardless, unless you plan to do serious racing, no one will care if
you have a centre mainsheet system.
More
in green below.
Best
regards,
Uncle
Al (W3854)
----- Original
Message -----
From:
"Mato Ilijic" <mail.mato@gmail.com>
To: <uncle-al3854@cogeco.ca>
Cc: "Ralph
Roberts"
Sent:
Wednesday, December 05, 2007 7:23 PM
Hi Al!
My name is Mato, and I began Wayfarering last year. My main interest is
day sailing and cruising. Keeping a close eye on your web site, I came
across a photo that picked my interest. It's a photo of you in a
Wayfarer with centre only mainsheet system (mainsheet not going to the
transom at all).
I'm interested in this solution because I hate it when the mainsheet
gets caught under the rear corner of the boat in a gybe.
That
is definitely a problem, especially with glass W's. Over here in
Canada, some guys cut out bottom corners of a large square plastic jug
and fit one over each corner of the transom. I am told that this
prevents the sheet from catching.
But, from documents on your web sites, I also understood
the advantages of a transom bridle, and the benefit of not exerting
excessive downward pull on the sail.
These
are very small advantages. The thing I actually like best about the
bridle is that I can easily see how close to "block to block" I am
sheeting, i.e. I can easily see whether I am 2 or 4 cm. from being
"block to block" (i.e. the distance between boom and bridle block >
block to block = zero cm. between these). In other words I can remember
and duplicate settings more easily. But this is for serious racing
only!!
Since you obviously have experience with both systems, I
would be grateful if you could share with me your opinion on the
matter. I suppose that the biggest difference in performance between
the two systems, is on a close hauled course.
Yes.
How would you compare the centre-only boat's performance
to the bridle boat's in such a situation - in terms of angle towards
the wind and speed? If it's only a minor difference, then I would
really prefer the centre-only system for cruising.
The
difference in upwind potential is less than minor. The boat should be
able to point just as well with a centre mainsheet system as with any
other system.
The
real difference is made by mainsail leech tension. Mike McNamara once
told me, "You point off your mainsail leech." After nearly 40 years of
racing, I was surprised by this, since one instinctively thinks of the
jib as creating the pointing. I still am not quite sure why it works,
but I do know that it does! In this year's Chesapeake Bay
Cruise,
I saw an extreme example of this: see our pictures from the day we had
a four-hour beat to Tangier Island. About halfway down that page, you can see
that some of our guys sailed with the top of the mainsail twisted off
to leeward while closehauled. This looks pretty but is slow!! On our
boat, we put on lots of boom vang (North American for "kicker") to keep
the mainsail leech tight even when we eased the main out to keep the
boat from heeling too much. The rule of thumb is that your top batten
should be parallel to the boom. So, you sheet in - regardless of the
system you use, until the top batten is properly aligned with the boom.
And if there's more wind than you can hike down, you tension the vang,
such that when you ease the mainsheet to spill wind, the upper batten
still remains parallel to the boom. The other guys on our cruise were
letting their mains twist off too much and we outpointed them to the
extent that, three or four times, we ended up so far ahead, that we
hove to and had a beer while we waited for them to catch up. All this
without our working hard or hiking: the whole difference was mainsail
leech tension!!
There
are other small subtleties but they would take too long to discuss and
only confuse the issue. One item is worth mentioning however: in very
light winds, the weight of the boom will make the mainsail leech hook
to windward, in which case I modify my batten rule to read: top batten
parallel to the centre line of the boat, i.e. in drifters, I sail with
the boom end out more or less over the corner of the transom, which
gets my top batten about parallel to the centre line of the boat.
To
illustrate the point about avoiding too much mainsail twist, I can give
you two pictures from the regatta for which I am just doing the photos
text. These pics were taken from the committee boat a few moments after
the start:
Above:
Notice how my crew (who
was sailing my boat that day, 3rd from right) and I (2nd
from right, sailing a friend's boat) have very little
twist in our mainsail leeches, while Colin (right) is sailing with
too little leech tension - either too little mainsheet tension or too
little vang tension. And notice how his top batten is nowhere near
parallel to his boom.
Moments
later: Colin (right) has fallen right
down into Tom and me (600). Again, notice how our main (600) has a nice
even angle to the wind all the way up, and a nice, tight leech (aft
edge of the sail). With the vang on good and tight, we can ease for a
puff and keep this shape and keep pointing, but look at what happens to
the sail (929) that has too little leech tension!!
A compromise would be a centre bridle similar to what some 470 (above) and 505 sailors use. But,
again this has a disadvantage of making it more difficult for the
sailors to move between rear and front part of the boat, which we
sometimes need to do on a cruise.
Not
necessary, I think!!
Best regards,
Mato Ilijic
W10435 - Pinčika
Croatia
P.S. While sailing with the centre-only system, did you ever feel that
the increase of force exerted on the swivelling block was beyond or
close to the limit of its designed tolerances?
No.
But make sure you have the swivel block attached to something good and
solid, since as you say, it will be taking more load! (Al's
note: here I suggested separate blocks on the boom but Mato pointed out
why this would not work, and suggested that to spread the load on the
boom, a T-bar might be advisable - see Mato's reply below)
We
cleat our mainsheet all the time, even though books tell you not to.
It's too much work to hold the sheet all the time and the argument can
be made that a tired sailor will make (more) mistakes. In tricky
conditions, I do however, always have the sheet in my hand. If a gust
hits, I can have the main uncleated faster than the wind can make the
boat heel, no problem!
Hope
this has helped, Mato. Do feel free to stay in touch, and let me know
if I can help in any other way.
-----
Original Message -----
From:
"Mato Ilijic" <mail.mato@gmail.com>
To: "Al
Schonborn" <uncle-al3854@cogeco.ca>
Cc: "Ralph
Roberts"
Sent:
Thursday, December 06, 2007 8:47 AM
Hi Al!
Thank you very much for your reply! It makes things much more clear to
me, and also makes me more confident in switching to centre-only
system. I've already done a decent amount of mathematics to analyze the
relationship between downward and sideways component of sheet tension
in various systems. But, sailing with Ralph I learned that usually with
boats, practice proves much more valuable than theory. I'm happy I can
forget all those formulas, geometry and ratios now, and just go ahead
with the change with piece of mind.
Best regards,
Mato
P.S. I'm curious about the whole politics/negotiations which led to the
forbidding of this system in the rules. Perhaps enough time has passed
since than, so if you remember the story, maybe you could share it...
Just one more thing on the centre-system in case you intend to put the
story on web site:
I'm afraid it wouldn't work to install a fiddle block on a cleat base,
and have two blocks on the boom apart. If we imagine the boat on a
broad reach, or sailing downwind, then the plane in which the sheet
travels from the becket on the fiddle block up to the boom to the first
block, then down to the fiddle and up again to the second block on the
boom - this plane would not be the same as the plane in which the sheet
travels from helm's hand to the fiddle and up to the boom. I think
there would be some friction because the sheet would try to twist the
fiddle block. If we feel that the transfer of the force into a single
point on the boom is risky, than one could make a metal T-shaped slide
(about 20 or 30 cm long) which would be inserted into the boom track.
This metal slide could then hold the boom-side blocks and distribute
the pressure along wider strip of the boom.
Am I wrong perhaps with this? I won't be able to sail before
spring/summer so my first opportunity to test it will not be very soon
unfortunately.
Best regards,
Mato
-----
Original Message -----
To:
Mato Ilijic (W10435)
Cc:
Ralph Roberts
Sent:
Thursday, December 06, 2007 1:15 PM
Hi,
Mato:
Just a
quick note since I'm getting ready for a new computer tonight and so
will be off duty for the next day or so, trying to get it all set up.
Glad
the answer was what you wanted to hear. Nothing prevents us from
raising the centre mainsheet idea these days, but for me, it's a low
priority item. I like my present system and would say that the cruising
sailors would be the most interested - and they are not really subject
to our Class Rules in any case.
Read
your second email, too, and agree that you'd need to go with the t-bar
ideas if boom strain is a concern - and I'm not an expert in that field
(to put it mildly!!)
Talk
to you soon,
Uncle
Al (W3854)
... and
a heart-warming comment on all this from Mato's cruise partner, Ralph
Roberts (W9885):
-----
Original Message -----
From:
Ralph Roberts (W9885)
Sent:
Thursday, December 06, 2007 5:10 AM
Hi Al,
So glad you copied me your
explanation of leech tension, although I was well aware of the
instruction that the top batten should be parallel (have no problem
spelling that word now, after having to write it out a hundred times
for spelling it wrong at school 50+ years ago!) to the boom, I never
really quite understood the mechanics of how to do this and why it
mattered. The photos you included couldn't have shown and explained
more clearly exactly what was needed to be achieved with
regard to leech tension and sail shape. One thing's for sure - you just
never stop learning when you start sailing! Now looking forward to
putting this into practice next year.
Thanks for reply to earlier
e-mail re Croatian log - will reply in a minute as I work my way up
today's e-mails! Mato would certainly make an excellent ambassador for
Wayfarer sailing in the Adriatic - could be a younger version of Ken
Jensen and possibly even repeat what Ken achieved in Scandinavia. I am
sure he will be delighted with your comprehensive reply to him.
Best wishes, Ralph
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