Old sails performance

[Kelly Purinton]

Last week I read a posting that mentioned the difference between the performance of a new main sail versus an old one. The new sail performed much better than the old. (Obviously). As I remember it - the old sail provided for a lot of heel and not much drive. Can anyone educate me about this phenomenon? Thanks - Kelly"Daisy Sail"Daysailor

 

[Don Evans]

Heres the skinny...

There are entire books written on this subject, but here is my "filtered" version. A sail is like an airplane wing, or lifting body. When the wind passes by a sail,the air flow is divided between going by the front side (which is concave), and the backside (which is convex). Since the air takes slightly longer to complete the passage on the backside (more distance to travel) than the frontside, a partial vacuum (negative or lesser pressure), or lift is produced. This lift raises airplanes, and moves sailboats forward.Now if the sail (wing) was blown out, had a belly in the sail, or a bulge in the wing, the wind surrounding this would not be laminar (smooth). So instead of moving the sail forward it would stall and be inefficient. This causes more heel (sideways force), and not propulsion or forward drive. There are also effects produced between the flatter upper sail and the blown out lower belly of the sail. But it all comes down to poor laminar flow around the sail.I replaced my mainsail 2 years ago, and the effect was dramatic. I gained about 1-2 knots of speed and my boats heeling was reduced.Hope this has helped Kelly.Don

 

[Kelly Purinton]

So you're saying...

So you're saying that if my sails date from the Jurassic period (which I believe they do), I should think about changing them. I took them to a well respected sail loft for cleaning and an inspection, and I thought I heard laughter all the way back to the car. So that's why...Thanks - Kelly

 

[Don Evans]

Sounds Like

You suspect the answer already. If the sails were not used much over their life, and they were stored properly they may be OK. But if their original, I'd say replace them. Ultra violet light attacks the stitching and the dacron cloth. The wind stretches cloth and stitching, eventually breaking down the fibers. Besides the profiled "belly", look very carefully at the stitching. It will show breaks, fuzziness and general deterioration.You may be able to find good used sails for your daysailor. Do some internet searches. If you can only afford to replace one this year, I'd say to the headsail first. Mainsail next year.You mentioned in another post the inability to sail well to weather. Do you have a centreboard problem (board stuck-up)? A lot of the daysailors have this problem. This will also affect your forward progress.Don

 

[Kelly Purinton]

reply to sailing to windward

No Don, the centerboard works fine. I can get about 45 degrees off the wind and no closer. But I'm still learning and perhaps new sails will help me cover more distance. (i.e. get to where I;m going!) In the meantime - there's nothing like a reliable outboard. Thanks.