I have several similarly rigged blocks for lifting my dinghy and its motor.
Top and bottom blocks have two sheaves. The top block has a place to
dead-end the beginning of the line (I forget what that's called!). Anyway
the line goes down, around the first sheave, up to the same side sheave,
then down and outboard to the next sheave, up to the final sheave and then
to my hand for pulling.

I use good quality woven line and the line develops twist whenever there is
a load being lifted. Not much twist develops without a load. I can remove
the line and clear out all the twist. When I re-rig and then load, the
twists start coming back.

I believe something about this setup forces a twist in the line WHEN LOADED.
I am thinking that the line that crosses over from one vertical plane of
sheaves to the other must ride on the edge of the sheave as it enters and
then gradually gets "rolled" as it finally meets the groove in the sheave.

Anyone know what is happening?
Is there a way to rig this kind of purchase without getting a twist?
-- - - - - - - - - - - - - - - - -
Bill Graves RKBA!

On Mon, 09 Aug 2004 05:50:52 GMT, "William Graves"
wrote:

I have several similarly rigged blocks for lifting my dinghy and its motor.
Top and bottom blocks have two sheaves. The top block has a place to
dead-end the beginning of the line (I forget what that's called!). Anyway
the line goes down, around the first sheave, up to the same side sheave,
then down and outboard to the next sheave, up to the final sheave and then
to my hand for pulling.

I use good quality woven line and the line develops twist whenever there is
a load being lifted. Not much twist develops without a load. I can remove
the line and clear out all the twist. When I re-rig and then load, the
twists start coming back.

I believe something about this setup forces a twist in the line WHEN LOADED.
I am thinking that the line that crosses over from one vertical plane of
sheaves to the other must ride on the edge of the sheave as it enters and
then gradually gets "rolled" as it finally meets the groove in the sheave.

Anyone know what is happening?
Is there a way to rig this kind of purchase without getting a twist?
-- - - - - - - - - - - - - - - - -
Bill Graves RKBA!



You can get blocks that won't swivel. I had that problem in my
mainsheet and a new block fixed it.

Dick Locke wrote:
On Mon, 09 Aug 2004 05:50:52 GMT, "William Graves"
wrote:


I have several similarly rigged blocks for lifting my dinghy and its motor.
Top and bottom blocks have two sheaves. The top block has a place to
dead-end the beginning of the line (I forgetwhatthat'scalled!.Anyway
the line goes down, around the first sheave, up to the same side sheave,
then down and outboard to the next sheave, up to the final sheave and then
to my hand for pulling.

I use good quality woven line and the line develops twist whenever there is
a load being lifted. Not much twist develops without a load. I can remove
the line and clear out all the twist. When I re-rig and then load, the
twists start coming back.

I believe something about this setup forces a twist in the line WHEN LOADED.
I am thinking that the line that crosses over from one vertical plane of
sheaves to the other must ride on the edge of the sheave as it enters and
then gradually gets "rolled" as it finally meets the groove in the sheave.

Anyone know what is happening?
Is there a way to rig this kind of purchase without getting a twist?
-- - - - - - - - - - - - - - - - -
Bill Graves RKBA!




You can get blocks that won't swivel. I had that problem in my
mainsheet and a new block fixed it.

I lashed one built in swivel on a block using string to prevent it
from turning more than about 1/2 turn. In another case with multi
blocks, re reeving the lines, essentially reversing the direction
the line went through one of the blocks seemed to stop it, but the
lines tended to rub against each other which while stopping the
twisting, made the tackle a little slow to run out unless under a
reasonable strain.

Some lines seem more likely to twist up under load. Perhaps a badly
balanced lay up by the mfgr?

Terry K

Terry Spragg wrote:
Dick Locke wrote:

On Mon, 09 Aug 2004 05:50:52 GMT, "William Graves"
wrote:


I have several similarly rigged blocks for lifting my dinghy and its
motor.
Top and bottom blocks have two sheaves. The top block has a place to
dead-end the beginning of the line (I
forgetwhatthat'scalled!.Anyway
the line goes down, around the first sheave, up to the same side sheave,
then down and outboard to the next sheave, up to the final sheave and
then
to my hand for pulling.

I use good quality woven line and the line develops twist whenever
there is
a load being lifted. Not much twist develops without a load. I can
remove
the line and clear out all the twist. When I re-rig and then load, the
twists start coming back.

I believe something about this setup forces a twist in the line WHEN
LOADED.
I am thinking that the line that crosses over from one vertical plane of
sheaves to the other must ride on the edge of the sheave as it enters
and
then gradually gets "rolled" as it finally meets the groove in the
sheave.

Anyone know what is happening?
Is there a way to rig this kind of purchase without getting a twist?
-- - - - - - - - - - - - - - - - -
Bill Graves RKBA!




You can get blocks that won't swivel. I had that problem in my
mainsheet and a new block fixed it.


I lashed one built in swivel on a block using string to prevent it from
turning more than about 1/2 turn. In another case with multi blocks, re
reeving the lines, essentially reversing the direction the line went
through one of the blocks seemed to stop it, but the lines tended to rub
against each other which while stopping the twisting, made the tackle a
little slow to run out unless under a reasonable strain.

Some lines seem more likely to twist up under load. Perhaps a badly
balanced lay up by the mfgr?

Terry K

What Terry said. Plus many braided ropes have cores with
*some* twist. The only exceptions are solid braid, braid on braid and
parallel filament cores.

On reeving a 4:1 tackle using side by side double blocks: I presume
that one of the blocks is a plain double block and the other has a strop
in line with one sheave and possibly a V jammer for that sheave.
(basically the setup for my kicking strap). First lay out the blocks
on the bench with the pin on one horizontal and for the other vertical.
Start from the strop, reeve the line through one sheave of the other
block, back to the sheeve on the first block NOT under the strop, back
to the other block and through its other sheave in the opposite
direction and to the first block round the sheave under the strop in the
opposite direction to the other sheave on that block and finally to your
hand. Given reasonably smooth line thats the correct size for the
blocks, there is very little extra friction. It should never twist more
than about 1/8 turn when loaded.

Also I think you could do with LESS effective swivels, They are only
there to give you flexibilty in hooking on and to let you streighten the
tackle before you hoist the tender so if they stopped swiveling under
load it would actually help.

On Mon, 09 Aug 2004 05:50:52 GMT, "William Graves"
wrote:

The top block has a place to
dead-end the beginning of the line (I forget what that's called!).

===========================

It's called a becket. (spelling is correct)

Take the rope and tie it between a tree and a car bumper, etc.
Stretch the rope until it has more load than what would be expected in
service. Do this several times - no matter if three strand or double
braid. This will 'set' the rope and will 'proof' it for the load
applied. This will prevent (but not totally eliminate) any tendancy to
twist under load.
Do not add twist to the rope by coiling it without reversing every
other turn when storing, etc.

This should keep the twists and potential 'hockles' from you rope.

;-)



In article , I.M.
wrote:

Terry Spragg wrote:
Dick Locke wrote:

On Mon, 09 Aug 2004 05:50:52 GMT, "William Graves"
wrote:


I have several similarly rigged blocks for lifting my dinghy and its
motor.
Top and bottom blocks have two sheaves. The top block has a place to
dead-end the beginning of the line (I
forgetwhatthat'scalled!.Anyway
the line goes down, around the first sheave, up to the same side sheave,
then down and outboard to the next sheave, up to the final sheave and
then
to my hand for pulling.

I use good quality woven line and the line develops twist whenever
there is
a load being lifted. Not much twist develops without a load. I can
remove
the line and clear out all the twist. When I re-rig and then load, the
twists start coming back.

I believe something about this setup forces a twist in the line WHEN
LOADED.
I am thinking that the line that crosses over from one vertical plane of
sheaves to the other must ride on the edge of the sheave as it enters
and
then gradually gets "rolled" as it finally meets the groove in the
sheave.

Anyone know what is happening?
Is there a way to rig this kind of purchase without getting a twist?
-- - - - - - - - - - - - - - - - -
Bill Graves RKBA!




You can get blocks that won't swivel. I had that problem in my
mainsheet and a new block fixed it.


I lashed one built in swivel on a block using string to prevent it from
turning more than about 1/2 turn. In another case with multi blocks, re
reeving the lines, essentially reversing the direction the line went
through one of the blocks seemed to stop it, but the lines tended to rub
against each other which while stopping the twisting, made the tackle a
little slow to run out unless under a reasonable strain.

Some lines seem more likely to twist up under load. Perhaps a badly
balanced lay up by the mfgr?

Terry K

What Terry said. Plus many braided ropes have cores with
*some* twist. The only exceptions are solid braid, braid on braid and
parallel filament cores.

On reeving a 4:1 tackle using side by side double blocks: I presume
that one of the blocks is a plain double block and the other has a strop
in line with one sheave and possibly a V jammer for that sheave.
(basically the setup for my kicking strap). First lay out the blocks
on the bench with the pin on one horizontal and for the other vertical.
Start from the strop, reeve the line through one sheave of the other
block, back to the sheeve on the first block NOT under the strop, back
to the other block and through its other sheave in the opposite
direction and to the first block round the sheave under the strop in the
opposite direction to the other sheave on that block and finally to your
hand. Given reasonably smooth line thats the correct size for the
blocks, there is very little extra friction. It should never twist more
than about 1/8 turn when loaded.

Also I think you could do with LESS effective swivels, They are only
there to give you flexibilty in hooking on and to let you streighten the
tackle before you hoist the tender so if they stopped swiveling under
load it would actually help.