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howieP 20th November 2008 10:29 AM

Open Top Sails
Hi All,

A question on flex top sails.

Do you guys used to offset your extension by an increment to compensate the overshoot of the mast over the head strap of small sails in order to attain a better sail twist?

I found that no matter how I tighten the head strap of my open top sail, still I can't prevent the mast from shooting out for an inch or so on the top after downhauling.

The open top design is to broden mast compatibility of the sail. Can I ask if the designer would have a practice to take into account the undesired shortening of luff when they're marking the recommended luff. As a end-user, do I have to manually lengthen my extension by an extra step to combat effect of the overshoot?


Roger 21st November 2008 12:37 AM

It's good to keep the head cap strap as short as possible, but having it stick out an inch or so is certainly OK.
Actually, I use Sailworks sails, and for all of them that have an adjustable head cap (on a strap with buckles) I like to leave about 1/2-1.0" of mast showing at the top so I can be sure that the plastic headcap and strap is seated over the end of the mast correctly.
Where you might get into trouble is with a very small sail on a mast that's far too long, and also too stiff. You can easily rig the sail way down at the bottom of the mast so the sail and the mast are not as compatible.
It's best to keep the extension of the headcap to a minimum so the sail is on the softer and more responsive area of the mast.
Yes, you can add whatever you have extending out the top of the sail to the extension on the bottom if you are trying to rig "by the numbere" (I.E. North sails in particular).
This will keep your downhaul as close to what the designer had in mind as possilbe.
But remember, downhaul is perhaps the "most important" tuning parameter, so just because the sail/sail bag suggest a particular # of cm's does not mean you cannot put a little less downhaul on the rig for improved low end, or conversely, you can downhaul beyond the recommendations to loosen the top of your rig and flatten the lower panels to give you better overpowered stability and range.
It's all about tuning your rig for the conditions, and changing the "tune" as conditions change (within the sails range) or rigging a larger or smaller sail if conditions change beyond the tuning range of the sail you have rigged.
Hope this helps,

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