| Aspect ratio questions #186754 08/02/09 09:00 AM 08/02/09 09:00 AM |
Joined: Feb 2009 Posts: 171 Cary, NC Storz OP
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Posts: 171 Cary, NC | Just curious what aspect ratio means in reference to a mainsail, and how(given two sails with the same area) it effects performance.
Thanks!
Ryan 1983 Isotope
| | | Re: Aspect ratio questions
[Re: Ventucky Red]
#186762 08/02/09 10:25 AM 08/02/09 10:25 AM |
Joined: Sep 2007 Posts: 531 Lake Murray SC FasterDamnit
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Posts: 531 Lake Murray SC | High aspect ratio = Long and skinny
Low aspect ratio = short and fat
High aspect has lower drag and vs lift generated, ie: higher potential speed in our application. The lift created by sails is generated in the first 30% (from the luff). In a lightweight platform like a cat, that does not need a lot of force to overcome it's inertia and drag thru the water, high aspect allows for higher speeds for a given wind.
Last edited by FasterDamnit; 08/02/09 10:26 AM.
Race cheap, race faster, Damnit!
E-Scow 24' ULDB
18HT hulls plus Gcat 5.7 rig = 18GT!
| | | Re: Aspect ratio questions
[Re: Storz]
#186768 08/02/09 11:30 AM 08/02/09 11:30 AM |
Joined: Feb 2004 Posts: 3,528 Looking for a Job, I got credi... scooby_simon Hull Flying, Snow Sliding.... |
Hull Flying, Snow Sliding....
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Posts: 3,528 Looking for a Job, I got credi... | Just curious what aspect ratio means in reference to a mainsail, and how(given two sails with the same area) it effects performance.
Thanks! The true definition of aspect ratio is simply luff length / foot length.
F16 - GBR 553 - SOLD I also talk sport here | | | Re: Aspect ratio questions
[Re: scooby_simon]
#186773 08/02/09 03:26 PM 08/02/09 03:26 PM |
Joined: Jan 2005 Posts: 6,049 Sebring, Florida. Timbo
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Posts: 6,049 Sebring, Florida. | OK, to answer your question relative to two sails with the same total sail area, the one with the longer luff (and thereby a shorter foot) will be the one with a higher aspect ratio.
The new (to some) Square Top type mainsails you see on most newer designs (F-16, F18, A cats, etc.) were developed because with a fixed rule to total sail area, the sail makers figured out that they can generate the most lift by having a shorter foot and longer luff. In effect they were moving the sail area from the foot up to the top, in the square head, vs. the older triangle sail designs like you would see on most boats prior to the advent of the Square Tops.
So, if you have a choice but are limited to a rule for "Total Sail Area" you would be wise to have a "high aspect ratio" type sail made. It will have a square top and look much more like a rectangle than the older triangle type sails. It will also generate more lift and less drag.
You can also keep the same luff length, same mast, and just add the square top, shorten the foot to keep the same sail area.
Blade F16 #777
| | | Re: Aspect ratio questions
[Re: Timbo]
#186777 08/02/09 05:07 PM 08/02/09 05:07 PM |
Joined: Feb 2009 Posts: 171 Cary, NC Storz OP
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Posts: 171 Cary, NC | Thanks for the info. The Isotope rules say it must have 185sq ft of total sail area so next year when I get new sails I'll def go for something with a high aspect ratio
Ryan 1983 Isotope
| | | Re: Aspect ratio questions
[Re: Timbo]
#186778 08/02/09 05:10 PM 08/02/09 05:10 PM |
Joined: Jul 2001 Posts: 851 US Western Continental Shelf hobiegary
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Posts: 851 US Western Continental Shelf | You can also keep the same luff length, same mast, and just add the square top, shorten the foot to keep the same sail area. Then rake the mast back a little to compensate for having moved the Center of Effort (CE) forward (by reducing the sail area in the aft part of the sail, increasing the sail area in the forward part of the sail). Gary
Santa Monica Bay Mystere 6.0 "Whisk" <--- R.I.P. | | | Re: Aspect ratio questions
[Re: ThunderMuffin]
#186784 08/02/09 06:26 PM 08/02/09 06:26 PM |
Joined: Feb 2009 Posts: 171 Cary, NC Storz OP
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Posts: 171 Cary, NC | Does the class have a specified sailmaker? You might have to put class sails on it. I'll make sure to find out
Last edited by Storz; 08/02/09 06:26 PM.
Ryan 1983 Isotope
| | | Re: Aspect ratio questions
[Re: Storz]
#186785 08/02/09 06:32 PM 08/02/09 06:32 PM |
Joined: Dec 2005 Posts: 1,121 Eastern NC, USA tshan
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Posts: 1,121 Eastern NC, USA | It seems to be open as the pics I've seen have all shapes of sails.
BTW, there was a sail number 1100 on the banner at Carolina Sailing club - is that your boat?
Tom | | | Re: Aspect ratio questions
[Re: tshan]
#186786 08/02/09 06:53 PM 08/02/09 06:53 PM |
Joined: Feb 2009 Posts: 171 Cary, NC Storz OP
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Posts: 171 Cary, NC | ^^ Not mine, the owner of that boat (Howard Alexander I believe) must have sold his old sails at some point to the guy that I got my boat from, or one of the previous owners
Last edited by Storz; 08/02/09 06:56 PM.
Ryan 1983 Isotope
| | | Re: Aspect ratio questions
[Re: tshan]
#186789 08/02/09 07:33 PM 08/02/09 07:33 PM |
Joined: Nov 2005 Posts: 807 Hillsborough, NC USA Isotope235
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Posts: 807 Hillsborough, NC USA | It seems to be open as the pics I've seen have all shapes of sails.
BTW, there was a sail number 1100 on the banner at Carolina Sailing club - is that your boat? There is no restriction on sailmaker or shape - just total area. If you take a look at http://www.carolinasailingclub.org/xoops/modules/news/article.php?storyid=154, you'll see a few different shapes. I believe the dacron pin-top sails were all made by North (although one could be Kelly or Schurr). All the smoke-color pentex sails were made from SailRite kits. Most were sewn by the skippers themselves. | | | Re: Aspect ratio questions
[Re: Isotope235]
#186792 08/02/09 09:06 PM 08/02/09 09:06 PM | Scarecrow
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Unregistered | Are you required to have a jib? Is there a limit to mast height? | | |
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