Appropriate amount of headstay sag?

May 17, 2004
5,025
Beneteau Oceanis 37 Havre de Grace
Your mention of the sail's age/use and three pictures showing the luff pretty eased brings to mind the possibility that 'easing the luff bolt rope' will result in better shape and control. 'Easing the luff bolt rope' is not the same as easing luff tension. In the last several months I've eased the luff bolt rope on 4 older mains and a jib, and the effect was substantial each time. Turns out bolt ropes shrink rapidly up to a point with age/use, such that (a) the rope tensions before full hoist, (b) tension on the halyard and/or Cunningham has less (possibly negligible) effect on draft position, and (c) the luff deveops myriad small wrinkles. Easing the luff bolt rope involves removing a little stitching at the tack and any reef points. It's a DIY thing but it seems most ask a sailmaker to do it.
Thanks. Interesting point that I might need to check out this winter.


It looks like you could move the jib cars forward to me. Too much draft at the head compared to the foot for my boat for sure.
I agree there’s lots of draft up there and the top always breaks first when I luff. But the cars are already pretty forward; definitely pulling more down than back.
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In the past when I tried pushing them even further forward it was hard to get any pull on the lower part of the sail at all.
 
May 17, 2004
2,099
Other Catalina 30 Tucson, AZ
Thanks. Interesting point that I might need to check out this winter.



I agree there’s lots of draft up there and the top always breaks first when I luff. But the cars are already pretty forward; definitely pulling more down than back.
View attachment 217466

In the past when I tried pushing them even further forward it was hard to get any pull on the lower part of the sail at all.
The ideal is to have the sail break evenly from top to bottom. If the foot flutters, bottom luffs or bottom telltails break first - move the lead aft. If the leech flutters, top luffs or top telltails break first - move the lead forward. Do you have telltails?
 
May 17, 2004
5,025
Beneteau Oceanis 37 Havre de Grace
The ideal is to have the sail break evenly from top to bottom. If the foot flutters, bottom luffs or bottom telltails break first - move the lead aft. If the leech flutters, top luffs or top telltails break first - move the lead forward. Do you have telltails?
Yes, we have three sets of telltales, so we can easily see the difference at different heights from twist. It seems like even with the car very far forward, with the sheet pointed very high, much higher than bisecting the leech/foot angle, the top windward telltale breaks way before the bottom. This is true even when the sheet is putting so much tension on the leech that it’s closing in. Not sure if it’s the cut of the sail or the way it’s stretched over time.
 
May 17, 2004
2,099
Other Catalina 30 Tucson, AZ
David: OK, I didn't see them in the picture. With all the sail trim controls for the main and jib together with the various settings for each point of sail and wind conditions the 2 items I never messed with was headstay sag and mastbend. I had a nice backstay adjuster Garhauer gave me but I treated it like fancy hub caps on a car - they looked nice but didn't do anything. I couldn't bend the Catalina 30 mast if I wanted to - all I could do was rack it and that created more problems. I'd concentrate on getting 100% efficiency out of all my controls before messing with head stay sag.