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Forums > Land Yacht Sailing > Sail making > Stall Pack
Author Stall Pack
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TAS
1964 Posts
Posted 10/4/2011, 10:42 pm        Report
Now here is a thought. A Wing will Stall at low speeds so to a Sail. With both there is a tendency to loose Pressure from the lower/Upwind Surface to the Upper/Down Wind Surface in Flight. This lose will also increase with increased speed and generated Lift, this can be observed on large inter continental jets as a Large Wing Tip Vortex. Thus the Stall Pack or Truncation was developed to reduce this inefficiency.. So I am at this time beginning an experiment with a Stall Pack for Land Yacht Sails.. "Nutter" mumble Rhubarb rhubarb did I hear?? Any body care to comment on this thought?? Perhaps it has been tried before an I am simply reinventing the wheel?? Ron
WA
1102 Posts
Posted 10/4/2011, 11:55 pm        Report
If your sail top was wide as on a wing it would possibly have some merit but as most sails have an angle substantialy less than 180 degrees your stallpacck would have to be as wide as the tip of the sail = 0.0mm/0.0" .Never the less I would like to see one of that width constructed and full colour photos of its construction process posted here
WA
1102 Posts
Posted 10/4/2011, 11:57 pm        Report
Nikrum said...
Perhaps it has been tried before an I am simply reinventing the wheel?? Ron
Would that wheel include the tyre?
TAS
1964 Posts
Posted 11/4/2011, 8:10 am        Report
Jeeeeeesuuuuus! TP1 I's gonna come over there and Shove your head fair where the son don't shine. Those wheels are starting to get to me. I am beginning to think some are Deaf in the Eyes and Mind as well. They aren't Hearing what is being said or like yourself just Stirring the Pot. Bleedin' Sod. What are you saying about the Stall Pack/Truncation thought??? Given that the Sail top/Tip will be 350mm and is capable of Flight all-be-it perpendicular the theory remains true, however the gained eficiency is what comes into questin as the speeds are not as high as those gained by powered Aircraft but are Greater than those of a Soft Fixed Wing/Hang Glider and both craft have or still use the same technology. If there is a flying surface then the Angle of attack will determine whether of no there is a pressure gradient therefore the Higher pressure will try to escape to the lower pressure area thus attempting to negate any lift gain = inefficiency. If this pressure lose can be negated then the Flying Surface should become more efficient?? Look carefully about you the next time you go out Land Sailing and you will note that there are many different sail formats about you some with the Leech Edge passing up around a batten before dropping back to the Luff Pocket to others who's leach rises and changes direction around each Sail Batten until reach in their Luff Pocket. So in some cases, were a Stall Pack/Truncation would be of little use where as others the reverse could well be true. I am no expert on Aerodynamics but I do have some knowledge, of which I would like to increase as our chosen Sport relies on it. Proper use , as with Greenbird, will increase speed capability, lower drag amongst the benefits. Least ways those are my thoughts. Ron
Posted 11/4/2011, 9:03 am        Report
Nikrum, The fat head on your sails does the efficiency gain for you, because the leech end is unsupported. So you can't get one side having a high pressure and one side having a low pressure, thereby creating a vortex, because then the fat head just weathervanes around and suddenly there's no pressure inequality any more. A winglet may be useful for something like a landyacht with a solid wing instead of a sail, but for sails it would be trying to solve a problem that doesn't exist.
TAS
1964 Posts
Posted 11/4/2011, 12:44 pm        Report
Who're you call in Fat Head Boy????? Well now I wasn't to know that. However it is only a little fat head 350mm or less but there is some Luff pocket design change as we are hauling more tension on the top 700mm. Anyway that is an easy prove. I will have to make some sort of Smoke generator and attach it to the Mast Top and observe the effects in wind. What is more I like to experiment.. Ron
WA
1102 Posts
Posted 11/4/2011, 2:53 pm        Report
Sounds loik youf'e been experimentin wiff drugs
TAS
1964 Posts
Posted 11/4/2011, 5:49 pm        Report
Don't gotta experiment with them. Doctors are doing enough of that with me as it is. Ron
WA
5189 Posts
Posted 11/4/2011, 9:31 pm        Report
nebbian said...
Nikrum, The fat head on your sails does the efficiency gain for you, because the leech end is unsupported. So you can't get one side having a high pressure and one side having a low pressure, thereby creating a vortex, because then the fat head just weathervanes around and suddenly there's no pressure inequality any more. A winglet may be useful for something like a landyacht with a solid wing instead of a sail, but for sails it would be trying to solve a problem that doesn't exist.
we were tempted to try one on VINDICATOR's 4m wing , but I placed some telltales up there to see what was going on. they just stream straight at all times. it would probably be more effective to fit fairings over you wheels, or your body.
TAS
1964 Posts
Posted 11/4/2011, 10:00 pm        Report
Thanks, It is all food for thought. Before I fit anything I will run some tests first, Heavy Angle of Attack first. Ron
 
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