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#31
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Wing Loading / climb rate
On Mon, 13 Feb 2017 10:50:31 -0700, Dan Marotta wrote:
If the lifting force exactly matched the weight of the glider then, in still air, wouldn't the glider not lose altitude? Or are you saying that the sink rate of the glider is cause by drag? On 2/13/2017 6:46 AM, Tango Whisky wrote: Le lundi 13 février 2017 04:52:04 UTC+1, Jim a écrit : Yes, I have enjoyed slower-flying thermal-working too. It's lots of fun. My curiosity about wing loading and climb rate really is limited to non-thermalling, non-turning flight. I was wondering about the possible relationship of wing loading to lifting force. Likely an unrealistic circumstance in actual flying though. Just a curiosity. Well, on a good soaring day, about 70-80% of the flight is non-thermalling, non-turning flight. And the lifting force always matches the weight of the glider, regardless of wing loading. Lift generated must equal the glider's weight. If it didn't, the rate of sink would not be a constant relative to the air mass for a given trim setting and airspeed. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#32
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Wing Loading / climb rate
On Monday, February 13, 2017 at 8:50:39 PM UTC+3, Dan Marotta wrote:
If the lifting force exactly matched the weight of the glider then, in still air, wouldn't the glider not lose altitude? Or are you saying that the sink rate of the glider is cause by drag? On 2/13/2017 6:46 AM, Tango Whisky wrote: Le lundi 13 février 2017 04:52:04 UTC+1, Jim a écrit : Yes, I have enjoyed slower-flying thermal-working too. It's lots of fun. My curiosity about wing loading and climb rate really is limited to non-thermalling, non-turning flight. I was wondering about the possible relationship of wing loading to lifting force. Likely an unrealistic circumstance in actual flying though. Just a curiosity. Well, on a good soaring day, about 70-80% of the flight is non-thermalling, non-turning flight. And the lifting force always matches the weight of the glider, regardless of wing loading. As I'm sure you know, lift = weight is exactly true for a powered aircraft in straight and level flight. It's only an approximation for a glider, where in fact lift plus drag together exactly equal weight. But as the lift is typically 40 - 60 times the drag we usually take a shortcut and ignore that. In a glider with airbrakes deployed and in a steady speed 45 degree dive lift and drag are equal and both 70.71% of the weight. But that's not how we fly when trying to maximize performance. |
#33
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Wing Loading / climb rate
I think this is exactly what originally asked. Thus, equal weight gliders, the one with bigger wing area (reduced wing loading) can fly slower and gain altitude better in weaker thermals compared to the glider with a heavier wing loading.
Then again, you WANT wing loading in the case of a ridge where a heavier wing loading glider helps. This from a guy that has time on the PA ridges at max @9lbs in a ASW-20 A and C, vs. heavier 20 B's. Bigger wing area also adds to surface drag which hurts performance. There is a reason the term "light wing floater" was coined. |
#34
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Wing Loading / climb rate
That's what I was thinking. Ignore the small part of the sum. Thanks,
nice refresher! On 2/13/2017 12:01 PM, Bruce Hoult wrote: On Monday, February 13, 2017 at 8:50:39 PM UTC+3, Dan Marotta wrote: If the lifting force exactly matched the weight of the glider then, in still air, wouldn't the glider not lose altitude? Or are you saying that the sink rate of the glider is cause by drag? On 2/13/2017 6:46 AM, Tango Whisky wrote: Le lundi 13 février 2017 04:52:04 UTC+1, Jim a écrit : Yes, I have enjoyed slower-flying thermal-working too. It's lots of fun. My curiosity about wing loading and climb rate really is limited to non-thermalling, non-turning flight. I was wondering about the possible relationship of wing loading to lifting force. Likely an unrealistic circumstance in actual flying though. Just a curiosity. Well, on a good soaring day, about 70-80% of the flight is non-thermalling, non-turning flight. And the lifting force always matches the weight of the glider, regardless of wing loading. As I'm sure you know, lift = weight is exactly true for a powered aircraft in straight and level flight. It's only an approximation for a glider, where in fact lift plus drag together exactly equal weight. But as the lift is typically 40 - 60 times the drag we usually take a shortcut and ignore that. In a glider with airbrakes deployed and in a steady speed 45 degree dive lift and drag are equal and both 70.71% of the weight. But that's not how we fly when trying to maximize performance. -- Dan, 5J |
#35
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Wing Loading / climb rate
On Monday, February 13, 2017 at 10:16:11 PM UTC+3, Charlie M. (UH & 002 owner/pilot) wrote:
I think this is exactly what originally asked. Thus, equal weight gliders, the one with bigger wing area (reduced wing loading) can fly slower and gain altitude better in weaker thermals compared to the glider with a heavier wing loading. *Only* because at the slower speed it can turn tighter and the thermal might be stronger in the middle. Note that low wing loading doesn't equate to low sink. Sink comes from the drag and modern construction gives low drag despite high wing loadings. That classic floater the K8 has a min sink of 132 fpm at 32.4 knots with 4.48 lb/sq ft. The 1-26 has min sink of 174 fpm (at a speed I couldn't find) with 4.38 lb/sq ft. An LS8 has min sink of 116 fpm with 6.56 lb/sq ft (dry, 190lb pilot). ASW28 110 fpm. Diana claims 88.6 fpm despite a high wing loading. |
#36
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Wing Loading / climb rate
Oh, I agree. I also noted that the increased wing area adds to drag. We stated the same thing in different ways.
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