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Lift from Asymmetrical?

Aug 2, 2010
350
J-Boat J/88 Cobourg
Not having used an assym before, and hopefully moving into one this spring, I have been watching trim videos and reading articles. One thing I have seen a couple of times is the use of luff telltales which surprised me as this will be a running sail for me. The A2 lists wind angles from 135 down to about 155 which for me is going to be most of the time I use it in W-L racing.
Will luff telltales really fly at these angles showing lift?

Dan
 
May 17, 2004
2,099
Beneteau Oceanis 37 LE Havre de Grace
Yes, they should. Remember that although the true wind angle might be pretty far back the apparent wind angle is further forward. You should be able to trim the spinnaker out far enough that it’s an airfoil, not just a parachute. Often you’ll want to trim out so that the first few inches of luff are curling around - that’s a good indication that the apparent wind is entering the sail from the luff and following it to create lift.
 
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Likes: shemandr
Jan 1, 2006
4,361
Slickcraft 26 Greenport, NY
Even a symmetrical spinnaker properly trimmed will have a foot or so of attached airflow on the luff. If going DDW there may be flow over the leach too. I think it was North U many years ago held that there is even some attached flow over the shoulders. Why not on an asymmetical?
 
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Likes: danstanford
Jan 13, 2009
270
J Boat 92 78 Sandusky
Lots of experience with A sails on my sprit boat. A2 can sail those angles but true wind better be 12 or above. Less than that it drags in the water or is slow. I have an A1.5 that can sail at 150 in 8 true. Newer A sail designs have a lot of windward projection for deeper sailing angles.
 
Aug 2, 2010
350
J-Boat J/88 Cobourg
Lots of experience with A sails on my sprit boat. A2 can sail those angles but true wind better be 12 or above. Less than that it drags in the water or is slow. I have an A1.5 that can sail at 150 in 8 true. Newer A sail designs have a lot of windward projection for deeper sailing angles.
Jump, The polars for my boat show 6 knots best VMG is just over 140 degrees and 8 knots it is just over 150 degrees so I will be watching the performance against the polar objectives. We will predominately be racing against symmetrical spinnaker boats so I will have to be diligent about not soaking and I think steering to telltales has really helped me to keep from pinching upwind.

Thanks for the feedback,
Dan
 
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Likes: Apex
Aug 2, 2010
350
J-Boat J/88 Cobourg
Yes, they should. Remember that although the true wind angle might be pretty far back the apparent wind angle is further forward. You should be able to trim the spinnaker out far enough that it’s an airfoil, not just a parachute. Often you’ll want to trim out so that the first few inches of luff are curling around - that’s a good indication that the apparent wind is entering the sail from the luff and following it to create lift.
David, you are absolutely right on the apparent. The polar shows 6 knots true at 140 true and 90 apparent!
It is all about speed at that point I guess, I keep thinking back to the AC Cats with sails acting as if they were going upwind while they were clearly going downwind!
 
Nov 26, 2012
1,129
Hunter 34 Berkeley
Yes. You can get lift on a spinnaker. Even a symmetrical spinnaker will develop lift if flown right. That is when we do that thing where we ease it out until it curls a little.
 
Jan 13, 2009
270
J Boat 92 78 Sandusky
1570541814909.png

My boat in 8 knots with A1.5. 8knots true is where we are competitive on w/ls. At 10 knots the symmetrical boats are 10-20 degrees lower and we have troubles. A 323 doing 6 knots VMG downwind in 8 knots?? Does it foil? Check the target speeds on the attached sheet for a J/92. Very close to real world speeds except at 18 knots and above where boats speeds are in the teens.
 

Attachments

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Likes: Handidude
Aug 2, 2010
350
J-Boat J/88 Cobourg
View attachment 170611
My boat in 8 knots with A1.5. 8knots true is where we are competitive on w/ls. At 10 knots the symmetrical boats are 10-20 degrees lower and we have troubles. A 323 doing 6 knots VMG downwind in 8 knots?? Does it foil? Check the target speeds on the attached sheet for a J/92. Very close to real world speeds except at 18 knots and above where boats speeds are in the teens.
Laughing here, I am in the throes of closing on a J/88 and the questions are related to that boat. Until the paperwork is complete I planned on not changing my profile.
Kind of excited at the thought of planning, I have to say!!!!
I am not sure if I will have better luck than you against the symmetric boats but we sure do have a few nights with less than 8 knots true so I hope she is able to match the polars though they don't go below 6. She comes with a really big A2 and she only displaces about 5,000 lbs so I am hoping for the best. From what I can read, she is fast upwind in the light and heavy airs but mid-range I might suffer against some of the longer boats.
Most likely she is faster than I am for a while....
 
Aug 2, 2010
350
J-Boat J/88 Cobourg
96 Metres is the listed size for the A2. We also have an A1.3 that despite it's numbering is for winds over 17. The boat is a 2016 and the sails are of that vintage so I do not know if they are the latest models.
 
Jan 13, 2009
270
J Boat 92 78 Sandusky
J/88 - ok! I mistakenly posted targets for class 105% job and 80 sq mtr spinn. I race with a 155% jib in 6knots and have 5.7-6kts boat speed at 25-29 degrees apparent. Downwind the spinn trimmer drives the boat. It is all about maintaining pressure so apparent wind angle fluctuates a lot.
 
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Likes: danstanford
Jul 15, 2014
7
S2 9.2A Ford Yacht Club
I frequently use mine on upwind legs. Works great in lighter air. Trim it like a chute and keep the edge talking to you. Then adjust the main so it doesn't backwind and doesn't add to much heel. You'll figure it out. It's fun.