Speed of a vario

On Tuesday, August 11, 2020 at 6:45:05 AM UTC-7, wrote:
At 11:23 11 August 2020, s6 wrote:
If I remember ok it is the time it takes to reach 80% of the
thermal strength.

Actually (1− 1/e) (approximately 63 percent)
J.
Also, the time constant of the electronics is after mechanical lags, so the delay may be somewhat longer.

jfitch wrote on 8/11/2020 8:22 AM:
On Tuesday, August 11, 2020 at 6:45:05 AM UTC-7, wrote:
At 11:23 11 August 2020, s6 wrote:
If I remember ok it is the time it takes to reach 80% of the
thermal strength.

Actually (1− 1/e) (approximately 63 percent)
J.
Also, the time constant of the electronics is after mechanical lags, so the delay may be somewhat longer.

And then there is the time constant of the glider, which does not reach a steady
upward speed immediately; ie, the glider is a mechanical filter for lift with, I'm
guessing, a time constant between 1 second (low wing loading with stiff wings) and
3 seconds (high wing loading with bendy wings). Jon may have included the glider
lag in his "mechanical lags".
.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Tuesday, August 11, 2020 at 8:54:37 PM UTC-7, Eric Greenwell wrote:
jfitch wrote on 8/11/2020 8:22 AM:
On Tuesday, August 11, 2020 at 6:45:05 AM UTC-7, wrote:
At 11:23 11 August 2020, s6 wrote:
If I remember ok it is the time it takes to reach 80% of the
thermal strength.

Actually (1− 1/e) (approximately 63 percent)
J.
Also, the time constant of the electronics is after mechanical lags, so the delay may be somewhat longer.

And then there is the time constant of the glider, which does not reach a steady
upward speed immediately; ie, the glider is a mechanical filter for lift with, I'm
guessing, a time constant between 1 second (low wing loading with stiff wings) and
3 seconds (high wing loading with bendy wings). Jon may have included the glider
lag in his "mechanical lags".
.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
Yes, the glider is part of the mechanical lags. First a new angle of attack and/or airspeed has to establish over the wing. This itself has a time constant, as velocity gradients are always gradual. Then the wings bend. Then the fuselage begins to move - at that moment an inertial sensor can see it. After some movement the air in the tube from the triple probe begins to move. After some more time the hysteresis in the pressure sensor is overcome and it sends a signal to the electronics. From there the lags are electrical or software.

I'm not convinced that your butt can tell the difference between a horizontal and vertical gust. Take as an example a gust from ahead. This will increase both lift and drag. A sharp edged 10 knot gust will give you approximately 1.36G kick. That is about the same as a 4 knot vertical gust. You may sort out which was which by differentiating airspeed, and I think that is what the Butterfly attempts to do in its inertial system. Your butt has no airspeed sensor.

On Wednesday, August 12, 2020 at 12:35:39 PM UTC-4, jfitch wrote:

I'm not convinced that your butt can tell the difference between a horizontal and vertical gust. Take as an example a gust from ahead. This will increase both lift and drag. A sharp edged 10 knot gust will give you approximately 1.36G kick. That is about the same as a 4 knot vertical gust. You may sort out which was which by differentiating airspeed, and I think that is what the Butterfly attempts to do in its inertial system. Your butt has no airspeed sensor.

Gusts, like the wind in general, are 3D. The "useless gusts" we've all encountered might well be horizontal plus vertical downwards.

T8