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Old Oct 09, 2014, 07:31 AM
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Discussion
wind speed and wing loading

is there any possible way to determine,
if it is possible to fly certain slope RC with known wing loading and wind speed?
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Old Oct 09, 2014, 09:00 AM
Just Toss It !!!
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Yes.....It is called "Experience".
A scientific way?.....Not likely.
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Old Oct 09, 2014, 09:38 AM
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You'd also need to know,......

....your lift coefficient or in lieu of that wind direction to your slope and angle of slope
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Old Oct 09, 2014, 11:22 AM
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Yes, Empirically.
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Old Oct 09, 2014, 11:59 AM
That Freeking Laird Guy
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Matin hit the nail on the head. Too many variables to use a "scientific" method, Wind speed tells you nothing about the amount of lift available, not to mention the dozen other factors that affect the lift. Then you have about 50 variable on the plane side. Wing loading alone tells you very little. A big plane for instance will handle a high loading much better than a smaller version of the same plane. Then you have airfoil, aspect ratio, CG, sweep, drag coeficients, etc etc etc........
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Old Oct 09, 2014, 12:18 PM
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i wasn't looking for scientific way, only your experience on the subject
so i may estimate if it is possible or not
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Old Oct 09, 2014, 12:25 PM
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goly:

Simply put, a highly wing loaded glider needs a tall steep hill and a strong wind to fly. Whether your glider will fly a specific hill and condition is dependent on many things. For most of us we look/feel; evaluate; toss; and hope for the best.

In general, the higher the wing loading your glider has, the faster that glider needs to fly (to generate the increased lift needed to support the increased weight). To fly faster you will have to fly at a steeper descent (all gliders need to fly in a slight dive to generate speed). Therefore you need a slope that generates enough vertical lift (to match that descent) so the glider can maintain an above ground altitude. The "walk of shame" to the bottom of the hill is the unhappy result of too little slope lift.

Wind speed is important to generating slope lift (more is better than less); but so is wind direction (straight in is best), slope angle (steeper generates more lift than flatter), slope shape (concave (i.e. bowls) are better than convex (i.e. small hillock ).

Also important is the "shape" of the aircraft. Gliders that are well built, tuned correctly (i.e. proper CG) and are clean and efficient will fly in less (and more) lift than those that are poorly constructed/maintained, out of tune, warped wings etc.

And last but not least is the pilot. A pilot that can fly accurately and smoothly with the minimum of inputs will usually fly faster and in less lift than one that is constantly making corrections and is "all over the place." Good pilots have a natural/learned ability to "pump" their glider up to amazing speeds.

If you have an aircraft and slope in mind, post a pic and I am sure we can help you figure whether it will fly or not.

Dawson
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Old Oct 09, 2014, 12:35 PM
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You can develop you own " wing loading to wind speed" rules for a specific hill for your airplanes. At Peterson Butte in the Willamette Valley, I found that most of my planes needed the wind speed to match my wing loading. My F-20 at 30 oz / square foot needs a 30 mph on that slope to fly well. My bigger TD planes at 10 oz / square foot only needed a steady 10 mph wind at the lip of the hill. Most of my slope planes are closer to 20 oz / square foot and fly well in 20 mph wind. I can add ballast to go faster and land harder.

It would be interesting to hear from others on what wing loading and wind speeds work for a specific slope and specific model.

For instance, more experienced pilots can fly heaver planes at Point Fermin because they can get it flying on step.
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Old Oct 09, 2014, 01:06 PM
That Freeking Laird Guy
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Quote:
Originally Posted by dawsonh View Post
goly:

Simply put, a highly wing loaded glider needs a tall steep hill and a strong wind to fly.

Dawson
Not necessarily, I have a glider with a 35oz wing loading that I aerotow and it thermals quite well. It will fly on the slope in very light wind. that's why I said wing loading alone tells you nothing. BTW, The glider is my 1/3rd scale L-213 which weights in at about 30lbs, and has about 1900 sq.in. of wing giving it a wing loading around 35oz/sqft.
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Old Oct 09, 2014, 01:15 PM
Phil.T-tailer
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Quote:
Originally Posted by goly View Post
i wasn't looking for scientific way, only your experience on the subject
so i may estimate if it is possible or not
Is it possible? - one sure-fire way - do birds(*) slope soar there without flapping their wings?
if they can - you can too !

(* and if its crows slope soaring, then theres definitely good lift !)

Phil.
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Old Oct 09, 2014, 01:30 PM
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At Point Fermin, when the Pelican's are slope soaring, guys are flying PSS.
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Old Oct 10, 2014, 11:34 AM
S.L.O.P.E.
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find someone else to be the first "penguin off the iceberg".... personally I prefer Matin or DC812 to be my penquins...
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Old Oct 10, 2014, 02:10 PM
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Quote:
Originally Posted by goly View Post
i wasn't looking for scientific way, only your experience on the subject
so i may estimate if it is possible or not
Goly

If you are new to sloping best thing to do is go to a slope and introduce your self to who ever is flying and ask questions.

Post up where you are located and there might be someone around on RCG to show you.

Come to CR Fest Oct 18th.

Ray
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Old Oct 10, 2014, 05:04 PM
characters welcome!
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United States, CA, Bear Valley Springs
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First throw something that you KNOW is going to fly and go from there.
About as scientific as it gets.

mw
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Old Oct 10, 2014, 09:53 PM
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Another thing I do is check the wind speed in the weather report and then measure the wind speed on the hill to get a correlation between the two. After a few different weather reports and hill speeds, you can predict what you will have on the hill when the weather report says 10 mph South. For Peterson Butte in the Willamette Valley, the difference seems to be a consistent 10 MPH more at the hill for reports at the Corvallis Airport of steady south wind above 10 mph. Corvallis 10, Hill 20,: Corvallis 15, hill 25 etc.
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Last edited by TomFlyer; Oct 10, 2014 at 09:54 PM. Reason: More information
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