If you where to undo the Vang from the mast and attach it to the toe rail , to use it as a preventer , are you putting more force on the boom than the standard vang ? I am worried that I may be putting more force to a weak part of the boom because of the angle.

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MAGNESIUM said..
If you where to undo the Vang from the mast and attach it to the toe rail , to use it as a preventer , are you putting more force on the boom than the standard vang ? I am worried that I may be putting more force to a weak part of the boom because of the angle.

A vang probably wouldn't ever suffer the shock loading that a preventer experiences in an unintentional jibe so I highly doubt that the boom would be up to it let alone the anchor point. As the vang normally has a lot of purchase I doubt that many systems would have enough line to facilitate anchoring the vang much forward of the mast and in any event to do so would probably interfere with the shrouds.

Apparently mid mounted boom brakes have a nasty reputation for snapping booms. Don't think there is a good substitute for end of boom to a point fairly far forward to improve the angle and lessen the forces.

Personally with a 7/8 rig and swept back spreaders in a reasonably fast boat I prefer to tack down wind if the sea or swell is causing rolling which pretty much obviates the need for a preventer in most situations.

I don't run big mast head kites dead square with a pinched in IOR style stern.

The bottom line is that using an "amidships" preventer-the failure of which can (and has) killed-that has a force multiplier factor of something over twelve , when rigging a bow preventer would reduce the factor to a little over two, is just poor seamanship.
... John Harries


The Maritime NZ report into the accident of the Yacht Platino showed that the closer the preventer is to perpendicular from the boom the smaller the multiplier effect is on the loads.

Therefore rig a preventer as close to the bow as possible

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julesmoto said..

MAGNESIUM said..
If you where to undo the Vang from the mast and attach it to the toe rail , to use it as a preventer , are you putting more force on the boom than the standard vang ? I am worried that I may be putting more force to a weak part of the boom because of the angle.

A vang probably wouldn't ever suffer the shock loading that a preventer experiences in an unintentional jibe so I highly doubt that the boom would be up to it let alone the anchor point. As the vang normally has a lot of purchase I doubt that many systems would have enough line to facilitate anchoring the vang much forward of the mast and in any event to do so would probably interfere with the shrouds.

Apparently mid mounted boom brakes have a nasty reputation for snapping booms. Don't think there is a good substitute for end of boom to a point fairly far forward to improve the angle and lessen the forces.

Personally with a 7/8 rig and swept back spreaders in a reasonably fast boat I prefer to tack down wind if the sea or swell is causing rolling which pretty much obviates the need for a preventer in most situations.

I don't run big mast head kites dead square with a pinched in IOR style stern.

Select to expand quote

cammd said..
The bottom line is that using an "amidships" preventer-the failure of which can (and has) killed-that has a force multiplier factor of something over twelve , when rigging a bow preventer would reduce the factor to a little over two, is just poor seamanship.
... John Harries


The Maritime NZ report into the accident of the Yacht Platino showed that the closer the preventer is to perpendicular from the boom the smaller the multiplier effect is on the loads.

Therefore rig a preventer as close to the bow as possible

Great answers guys thanks , it confirmed my fears

And if you rig your preventer with a long enough line it can be used to good effect during a planned gybe