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Weight or wing loading?



 
 
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  #1  
Old February 17th 15, 05:53 PM posted to rec.aviation.soaring
Jim Lewis[_2_]
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Default Weight or wing loading?

Does wing loading have any affect on thermalling ability of a glider (pilot's ability is another topic)?

I am ignoring here the smaller turn radius, and so greater ability of a lighter wing-loaded glider to work narrow-diameter thermals. In a given thermal with a diameter that can be worked with identical airspeed and bank angle by two gliders, one with lower wing loading, does smaller wing loading have any affect on the rate at which the gliders climb in the thermal?

Given gliders each weighing 800 lbs., but one has a wing loading just 75% of the other, wouldn't they both still require a minimum of 800 lbs of thermal force to hold altitude and wouldn't they both climb at the same rate in stronger but identical (whatever that means) thermal force? I'm remembering F=ma (more usefully, a = F/m) from physics classes MANY years ago. "Wing loading", or whatever its equivalent would be, does not appear in the force formula.

Whatever the answer may be it certainly will not improve my poor thermalling. Just curious.


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  #2  
Old February 17th 15, 06:17 PM posted to rec.aviation.soaring
kirk.stant
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Default Weight or wing loading?

On Tuesday, February 17, 2015 at 11:53:58 AM UTC-6, Jim Lewis wrote:
Does wing loading have any affect on thermalling ability of a glider (pilot's ability is another topic)?


Indirectly, yes. It's sink rate at thermalling speed that has a direct effect on a glider's climb rate, if you assume a huge homogeneous thermal (or wave, for a more realistic example).

Remember the escalator analogy: Thermalling is like walking down an up escalator; higher wingloading means greater sink rate which equals walking faster down the up escalator - so you go up slower than the guy walking slower (lower wingloading = lower sink rate) down the up escalator.

That being said, unless the wing loading differences are huge, a skilled pilot in a heavier glider can often outclimb a less skilled pilot in a floater. It has a lot to do with thermalling technique and instrumentation.

So, if Joe Waterwings joins your thermal and starts to outclimb you (in your low wingloading segelfloater), follow him!

Oh, and ALWAYS start thermalling at 40 - 45 degrees of bank - then adjust as required.

And also, lower wingloading doesn't always equal lower sink rate, which depends on other factors such as drag, aspect ratio, etc, so wingloading comparisons have to be kept between similar gliders to be meaningful.

Kirk
66
min 8psf in my LS6

  #3  
Old February 17th 15, 06:34 PM posted to rec.aviation.soaring
[email protected]
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Default Weight or wing loading?

On Tuesday, February 17, 2015 at 12:53:58 PM UTC-5, Jim Lewis wrote:
Does wing loading have any affect on thermalling ability of a glider (pilot's ability is another topic)?

I am ignoring here the smaller turn radius, and so greater ability of a lighter wing-loaded glider to work narrow-diameter thermals. In a given thermal with a diameter that can be worked with identical airspeed and bank angle by two gliders, one with lower wing loading, does smaller wing loading have any affect on the rate at which the gliders climb in the thermal?

Given gliders each weighing 800 lbs., but one has a wing loading just 75% of the other, wouldn't they both still require a minimum of 800 lbs of thermal force to hold altitude and wouldn't they both climb at the same rate in stronger but identical (whatever that means) thermal force? I'm remembering F=ma (more usefully, a = F/m) from physics classes MANY years ago. "Wing loading", or whatever its equivalent would be, does not appear in the force formula.

Whatever the answer may be it certainly will not improve my poor thermalling. Just curious.


All other variables being equal- not likely, the glider with the lowest span loading will climb the best.
UH
  #4  
Old February 18th 15, 10:11 AM posted to rec.aviation.soaring
Per Carlin
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Default Weight or wing loading?

If we remove all the teoretical aspects. In can when flyging an unloaded Ls1-f (35kg/m^2) bank inside a Std class gaggle (Discus2 @ 50km/m^2). Which do you think is closer to the core of the thermal and climbing better?
 




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