Wing Loading / climb rate

Thank you Tim. I am beginning to understand it all.

JIm

On Friday, February 3, 2017 at 7:40:25 AM UTC-7, Tim Taylor wrote:
You need to factor in the increased thermal speed and larger diameter circles. Unless the core of the thermal is large the climb rate is reduced significantly more than just the glide calculations predict. In the "real world" higher wing loading gives an advantage, but not as much as many think unless you are flying mostly on streets. In the mountains I often do better with a 9.5 to 10 pound wing loading because I can maneuver better and work small diameter thermals.

Exactly what we have found in Arizona - much depends on the thermal profile and especially the ability to stay in a strong, narrow thermal core.

Mike

On Sunday, February 5, 2017 at 3:24:58 AM UTC+11, Mike the Strike wrote:
On Friday, February 3, 2017 at 7:40:25 AM UTC-7, Tim Taylor wrote:
You need to factor in the increased thermal speed and larger diameter circles. Unless the core of the thermal is large the climb rate is reduced significantly more than just the glide calculations predict. In the "real world" higher wing loading gives an advantage, but not as much as many think unless you are flying mostly on streets. In the mountains I often do better with a 9.5 to 10 pound wing loading because I can maneuver better and work small diameter thermals.

Exactly what we have found in Arizona - much depends on the thermal profile and especially the ability to stay in a strong, narrow thermal core.

Mike

I often feel like on the exceptionally hot and high Australian days, that it feels like I just can't fit in the thermals at high altitudes. Lighter aircraft don't seem to have the same trouble. My theory is that a thermals diameter doesn't vary substantially with height, however due to density altitude/TAS, my thermalling radius does vary substantially. Or at least that's my excuse.

Any thoughts on whether this is true, that the diameter of thermals remains constant at altitude, or widens slower than the circling radius considering TAS?

On Friday, February 3, 2017 at 1:26:02 PM UTC-5, Jim wrote:
Thank you Tim. I am beginning to understand it all.

JIm

Those of us who flew hang gliders/paragliders already understand this relation between weight, area and efficency. Hang gliders have a lower sink rate and better glide than paragliders but the much larger area of PG allows them to slow down and turn very tight circles in lift so they can outclimb HG much of the time.

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.

Le lundi 13 février 2017 04:52:04 UTC+1, Jim a écritÂ*:
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.

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.

Yes. I understand that. If the glider is not to accelerate downward the total "lifting force" equals the current gross weight (and drag vector too I guess) of the glider. My silly curiosity has been about exactly the point you make. Everything else being equal ( I know, never happens), does a wing that supports 10 lbs per square foot of wing area require the same TOTAL"lifting force" as a wing that supports 5 lbs per square foot of wing area - but has twice the wing area? IF this is the case it would suggest that the glider with half the wing loading but twice the wing area could be sustained by a smaller "lifting force".

This is just a curiosity. I don't think this has ever entered into my decision making during flight. Not that I understand that either.

On Monday, February 13, 2017 at 8:36:35 PM UTC+3, Jim wrote:

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.

Yes. I understand that. If the glider is not to accelerate downward the total "lifting force" equals the current gross weight (and drag vector too I guess) of the glider. My silly curiosity has been about exactly the point you make. Everything else being equal ( I know, never happens), does a wing that supports 10 lbs per square foot of wing area require the same TOTAL"lifting force" as a wing that supports 5 lbs per square foot of wing area - but has twice the wing area? IF this is the case it would suggest that the glider with half the wing loading but twice the wing area could be sustained by a smaller "lifting force".

They both need exactly the same total lifting force. The one with twice the wing area needs half the lifting force per square foot.

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.

--
Dan, 5J

On Mon, 13 Feb 2017 09:36:34 -0800, Jim wrote:

Yes. I understand that. If the glider is not to accelerate downward
the total "lifting force" equals the current gross weight (and drag
vector too I guess) of the glider. My silly curiosity has been about
exactly the point you make. Everything else being equal ( I know, never
happens), does a wing that supports 10 lbs per square foot of wing area
require the same TOTAL"lifting force" as a wing that supports 5 lbs per
square foot of wing area - but has twice the wing area? IF this is the
case it would suggest that the glider with half the wing loading but
twice the wing area could be sustained by a smaller "lifting force".

Depends how you define 'lifting force'.

If you define it as the total lift generated by the wing, then it will
not vary with the wing area because it will always match the weight of
the glider.

If, OTOH , you define it as the lift generated by a square foot or square
meter of wing, then doubling the wing area will halve the 'lifting forge'
per unit of wing area because, again because the total lift generated by
the wing will match the glider's weight.

What does change as the wing area is varies are a number of factors that
contribute to the wing's total lift and drag, such as skin friction
(varies with wing area) and tip vortex drag (varies inversely with wing
span for a fixed wing area).

For a descriptive treatment, i.e. minimal numbers or equations, of this
and other topics I suggest you read:

Stick and Rudder - Wolfgang Langwiesche

or visit the av8n website, http://www.av8n.com/

Both are written to give a private pilot a better understanding of how
and aircraft flies and both are equally applicable to gliding.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |