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S/V Wyndwitch - Morgan 24
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Discussion Starter · #1 ·
Hi listers. Anyone have experience with a boat once equipt with a mainsail with shelf and zipper?

Have you then gone on to use a loose footed main ?
Was the loose footed main better?
Or did the change improve performance in windier conditions while having loss of performance in light wind?

TIA

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We went to a loose footed main and have enjoyed improved performance ever since, regardless of wind strength. The sail has a better shape when it isn't restricted by being attached to the boom along its foot. Unless you have a Park Avenue boom specifically designed for it (and probably located within 3" of a flush deck) any "end plate" effect involving the boom, "shelf" or zipper may simply create more turbulence rather than improving performance.
 

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Shelf foot mains have basically been replaced by loose foot mains. I've had both and the advantage of the loose footed is its easier to adjust sail shape with the outhaul due to the reduced friction.
 

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There really isnt much (aerodynamic) difference between a shelf foot (w or w/o zipper) and a loose foot config.; although, the loose foot is much much easier to adjust.

To make the shelf foot 'work', be sure that the slugs, etc. and the 'groove' on the boom are WELL lubricated (McLube, etc.); and if possible, increase the mechanical advantage of the block system used to adjust 'the outhaul' - a minimum of 4:1 or better should be standard and really should be arranged so that you can adjust the outhaul from near the base of the mast (or from the cockpit !!!!).
The outhaul, although used by most sailors for 'flattening and/or depowering', is really your adjustment between 'power' and 'speed' output of the sail - low gear / high gear.

The zipper will help 'flatten' the bottom sections of the sail - good for 'depowering' above moderate wind conditions and especially good for flattening for 'very light' winds where invisible 'separation stalls' are common. Use the zipper in combo with the multi-part outhaul tackle.

If youre considering a new main; then, do consider a loose foot for easier 'adjustability'.

;-)
 

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S/V Wyndwitch - Morgan 24
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473 Posts
Discussion Starter · #5 ·
There really isnt much (aerodynamic) difference between a shelf foot (w or w/o zipper) and a loose foot config.; although, the loose foot is much much easier to adjust.

To make the shelf foot 'work', be sure that the slugs, etc. and the 'groove' on the boom are WELL lubricated (McLube, etc.); and if possible, increase the mechanical advantage of the block system used to adjust 'the outhaul' - a minimum of 4:1 or better should be standard and really should be arranged so that you can adjust the outhaul from near the base of the mast (or from the cockpit !!!!).
The outhaul, although used by most sailors for 'flattening and/or depowering', is really your adjustment between 'power' and 'speed' output of the sail - low gear / high gear.

The zipper will help 'flatten' the bottom sections of the sail - good for 'depowering' above moderate wind conditions and especially good for flattening for 'very light' winds where invisible 'separation stalls' are common. Use the zipper in combo with the multi-part outhaul tackle.

If youre considering a new main; then, do consider a loose foot for easier 'adjustability'.

;-)
Thanks for everyone's input it was as i suspected but did not have any comparative experience.

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