twisted mainsheet lines

Archives
1

Posted by kcogden2001 (kcogden@…>)

I keep having difficulty with the mainsheet twisting where it runs
between the three blocks on the boom and the two blocks on the
coachroof. I once saw something on the internet which specifically
addressed this problem and had a diagram of how the main sheet had
to be reeved through these blocks to avoid this twisting problem,
but I can’t relocate the web page. Anyone out there have any ideas
on this?

2

Posted by macks011 (macks04@…>)

Braided line developes a twist as it runs repeatedly through the
sheeves. Unavoidable. Depending on who’s blocks you have, you either
use fixed shackle blocks or you use universal swivel blocks with a
set screw at the shackle which locks them in one orientation or
another.







— In freedomyachts2003@yahoogroups.com, “kcogden2001”
<kcogden@e…> wrote:

I keep having difficulty with the mainsheet twisting where it runs
between the three blocks on the boom and the two blocks on the
coachroof. I once saw something on the internet which specifically
addressed this problem and had a diagram of how the main sheet had
to be reeved through these blocks to avoid this twisting problem,
but I can’t relocate the web page. Anyone out there have any ideas
on this?

3

Posted by David G. Evans (dgevans@…>)

The best thing I’ve done is to lock the aftmost block so that it can’t rotate. The forward blocks have to rotate as they fair the line back from wherever the boom is. The aft block (as I reeve the sheet) only feeds the line in parallel paths to the traveler.

----- Original Message -----
From: kcogden2001
To: freedomyachts2003@yahoogroups.com
Sent: Sunday, April 25, 2004 8:07 AM
Subject: [freedomyachts2003] twisted mainsheet lines
I keep having difficulty with the mainsheet twisting where it runs between the three blocks on the boom and the two blocks on the coachroof. I once saw something on the internet which specifically addressed this problem and had a diagram of how the main sheet had to be reeved through these blocks to avoid this twisting problem, but I can’t relocate the web page. Anyone out there have any ideas on this?

4

Posted by Kevin Ogden (kcogden@…>)

Thanks, will have to try the fixed blocks idea. Best regards.

----- Original Message -----
From: macks011
To: freedomyachts2003@yahoogroups.com
Sent: Sunday, April 25, 2004 10:59 PM
Subject: [freedomyachts2003] Re: twisted mainsheet lines
Braided line developes a twist as it runs repeatedly through the sheeves. Unavoidable. Depending on who’s blocks you have, you either use fixed shackle blocks or you use universal swivel blocks with a set screw at the shackle which locks them in one orientation or another.— In freedomyachts2003@yahoogroups.com, “kcogden2001” <kcogden@e…> wrote:> I keep having difficulty with the mainsheet twisting where it runs > between the three blocks on the boom and the two blocks on the > coachroof. I once saw something on the internet which specifically > addressed this problem and had a diagram of how the main sheet had > to be reeved through these blocks to avoid this twisting problem, > but I can’t relocate the web page. Anyone out there have any ideas > on this?

5

Posted by ajlorman (ajlorman@…>)

My mainsheet is so twisted that I can barely separate the blocks. In
doing some research, I note that the F-30 owner’s manual says to use
1/2" line, which my boat has, but they run through original Harken
blocks which have a maximum line diameter of 7/16". Beyond replacing
the blocks with new Garhauers and putting in a 7/16" line, I’m
wondering whether there is simply a different way to rig the
mainsheet without endangering the boom. Has anyone done this?
Harken’s web page, for example, shows a big boat setup that is
basically a triple block on the boom feeing to a triple block on the
traveler. I don’t know how to calculate mechanical advantage of
blocks. Does anyone know the mechanical advantage of the original
set-up? That would help in picking a replacement.

Al Lorman
F-30 Ab Initio

– In freedomyachts2003@yahoogroups.com, “David G. Evans”
<dgevans@e…> wrote:

The best thing I’ve done is to lock the aftmost block so that it
can’t rotate. The forward blocks have to rotate as they fair the line
back from wherever the boom is. The aft block (as I reeve the sheet)
only feeds the line in parallel paths to the traveler.
----- Original Message -----
From: kcogden2001
To: freedomyachts2003@yahoogroups.com
Sent: Sunday, April 25, 2004 8:07 AM
Subject: [freedomyachts2003] twisted mainsheet lines

I keep having difficulty with the mainsheet twisting where it
runs
between the three blocks on the boom and the two blocks on the
coachroof. I once saw something on the internet which
specifically
addressed this problem and had a diagram of how the main sheet
had
to be reeved through these blocks to avoid this twisting problem,
but I can’t relocate the web page. Anyone out there have any
ideas
on this?

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6

Posted by JoanJohn@… (JoanJohn@…)

The more the sheeves, the more the twisting. You’ve got to get larger sheeves or smaller line, and lock the block on the traaveler so it won’t rotate. (There is usually a small square insert on the shaft where it swivels that can be reversed to acheive this). Then again, if your line has been stressed for too long, it will loose its memory and never want to come out a twist.

As for mechanical advantage, just count the number of pulleys, subract one (the last one just turns the line at the traveler) and that is the number of working pulleys and hence your advantage.

Don’t go crazy with establishing too much advantage: the more sheeves/blocks you run the line through, the more length it takes. Consider that when the boom is full out and you have a three-to-one advantage (three working pulleys, with the line starting from a becket block on the traveler) you will need four times that distance in rope length to have something left over to handle in the cockpit, and so on up the scale. It makes things pretty messy in the cockpit when you are close hauled!

Good luck.

John Ernst

7

Posted by ajlorman (ajlorman@…>)

Sounds like good advice to me. I’ll start with a new mainsheet (7/16)
and new blocks and see if that solves the problem.

Many thanks.

Al Lorman

Freedomyachts2003@yahoogroups.com, JoanJohn@a… wrote:

The more the sheeves, the more the twisting. You’ve got to get
larger
sheeves or smaller line, and lock the block on the traaveler so it
won’t rotate.
(There is usually a small square insert on the shaft where it
swivels that can
be reversed to acheive this). Then again, if your line has been
stressed for
too long, it will loose its memory and never want to come out a
twist.

As for mechanical advantage, just count the number of pulleys,
subract one
(the last one just turns the line at the traveler) and that is the
number of
working pulleys and hence your advantage.

Don’t go crazy with establishing too much advantage: the more
sheeves/blocks
you run the line through, the more length it takes. Consider that
when the
boom is full out and you have a three-to-one advantage (three
working pulleys,
with the line starting from a becket block on the traveler) you
will need four
times that distance in rope length to have something left over to
handle in
the cockpit, and so on up the scale. It makes things pretty messy
in the
cockpit when you are close hauled!

Good luck.

John Ernst