Stus-List Gybe preventer

Josh Muckley muckleyj at
Sat Mar 16 12:49:38 EDT 2019

My rigger advised that a mid boom preventer can break the boom in a bad
enough situation.

My setup is difficult to explain but bear with me. To start, I have a metal
eye projecting out of the boom where the main sheet attaches to the boom.
To this eye I have cow hitched a small continuous loop of amsteel.  The
loop lives there 24/7 and is the boom side attachment point for the port or
stbd gybe preventer.  It is about 1/4 distance from the end of the boom.  I
also have adjustable fiddle blocks with snap shackles that hold my check
stays.  When preparing to go down wind, I detach the check stay and lash it
to the cabin top hand rail.  This leaves one end of the fiddle block
attached to the toe rail and one end free.  I attach the free end to the
amsteel loop at the boom and  detach the toe rail side.  I lead the toe
rail side forward, outside the side stays and outside the life lines, and
attach it to the toe rail.  I find that it doesn't need to be too far
forward - halfway between the bow and mast is fine.  Once the gybe is
performed the adjustable block can be tightened and then the main sheet and
traveler snugged.  To perform another gybe the fiddle blocks are eased and
the main sheet brought in to allow reaching the boom attachment.  Release
the block and attach to the lifeline for stowage.  Perform the gybe and
attach the opposite side's fiddle block which was pre-arranged.  As you
describe this setup does have the disadvantage of being "unreachable" when
the boom is all the way out.  Additionally, despite being adjustable, the
adjustments require leaving the cockpit.  It was really just a matter of
convenience and using much of what I already had without further cluttering
the deck.

Your idea of using a line prerigged from the boom end seems good however,
the way my reefing lines are setup they would not lead smoothly out of the
boom end. Consider chafe and adjustability.

As an alternative to your idea of using the old reef line, consider
attaching a fixed length of line that leads from the boom end and is lashed
to the middle (reachable part) of the boom for normal stowage.  During down
wind runs you could then reach the line and unlash it.  Make it to your
preventer which is pre-rigged a fixture such as the bow cleat or tow rail.
The preventer attachment point would best be stowed near the midship so
that quick attachment could be achieved.  A simple and effective forward
fixture is the bow cleat.  You can even turn the preventer line around the
bow cleat and lead it back to the stern cleat allowing for easy cockpit
adjustments.  Turks head knots and/or soft shackles make connecting and
disconnecting quick and easy while also preventing damage to your metal

Josh Muckley
S/V Sea Hawk
1989 C&C 37+
Solomons, MD

On Sat, Mar 16, 2019, 11:44 AM David Knecht via CnC-List <
cnc-list at> wrote:

> I have been thinking aobut rigging a preventer on my boat so re-read this
> old discussion of how people rig them. End boom attachment sounds
> preferable, but does that have to run outside the shrouds?  If so, then you
> would have to rig it before letting the main out while you can stlill get
> to the end of the boom.  Then, how do you gybe when you want to?
>   I have a single reef point on my new main, so I have an extra internal
> boom line and sheave  from the second reef setup that exits at the rear of
> the boom.  I am thinking that if i put a long enough line with a snap
> shackle at the end where it exits the boom, I could use that as a
> preventer.  Before letting the main out downwind, you would grab the
> shackle and run it forward to the toe rail near the bow and clip it in and
> then have control from the stopper on the cabin top.   Thoughts?  Dave
> PS- No expectation of offshore/big waves racing in my future so this is a
> cruising/club racing solution
> S/V Aries
> 1990 C&C 34+
> New London, CT
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