Search found 40 matches

by kcaldwel
Sat Oct 22, 2016 12:19 am
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Well, I would debate that John's data is better. He used a GPS for speed information, which gives ground speed, not airspeed, and has a very slow update speed. The wind speed variation with height would not be taken into account at all. I doubt he would even see the pitch phugoid from the GPS speed ...
by kcaldwel
Fri Oct 21, 2016 4:58 am
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I'm honoured to be in a poetry album! I pulled some points out of the file in areas where the airspeed was the most stable. Now I'm trying to decide which is the most realistic way to plot the data. If I use all the points I have, I have a weird bumpy polar (V1). I think this may actually be the fir...
by kcaldwel
Wed Oct 19, 2016 11:16 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I got a couple of flights with the Eagle Tree Guardian in my home-built e-Supra out over the sea yesterday. It was quite overcast, 11.5 degrees, very light wind, and some rain showers. I have only glanced at the file so far, but the speed stability looks pretty good. This is all in cruise camber. I ...
by kcaldwel
Thu Oct 06, 2016 5:38 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I never understand most of the posts by "old"! The phugoid on typical RC gliders doesn't seem to increase under normal conditions, so it is damped to some extent. The disturbances come from the pilot or the air often enough to re-excite the oscillation before it can decay. I suspect FF gli...
by kcaldwel
Thu Oct 06, 2016 4:43 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

It's a very long time since I studied aircraft dynamics, so I've been doing a bit of reading on pitch phugoids. The long period pitch phugoid on a full-scale sailplane is a bit longer, approximately 17 seconds. An RC sailplane appears to have a 10 or 11 second period typically. The pilot in a full-s...
by kcaldwel
Thu Oct 06, 2016 3:47 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

It is amazing how much the gliders are oscillating, because I cannot really see it from the ground. It looks like it is flying along in a well-trimmed glide, but the speed and sink rate are consistently oscillating. I am not very good at trying to damp it out by hand, even with the vario. Yes, the l...
by kcaldwel
Thu Oct 06, 2016 1:03 am
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Well, I tired my simple logic switch airspeed autopilot today. And the winner is - pitch oscillations! I tried a few different ramp speeds, and had it set-up so I could vary the amount of trim the logic switches added from the ground, but the results were always the same: rapidly increasing pitch os...
by kcaldwel
Mon Oct 03, 2016 8:11 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

It's only 3 points, and all at different camber settings which should all have their separate polar curves, but it is a start! It looks like best L/D and min sink speed may be quite close together, near 8.3m/sec? More data needed. If I could get the oscillations to stop, I might be able to get enoug...
by kcaldwel
Mon Oct 03, 2016 6:47 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I've got a few more points that look like they might be reasonably good. One is at high speed with camber in reflex, from 11:25:57.130 to 11:26:15.050: average speed = 33.16knots (17.06m/sec, 61.4kph) L/D = 9.22 Sink rate = 1.85m/sec (364 ft/min) One is at low speed with camber at my minimum thermal...
by kcaldwel
Mon Oct 03, 2016 5:10 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I have taken all the aileron differential out of my sailplanes, actually measuring the degrees of throw up and down on the ailerons and flaps so the angles are the same in all flight modes and flap settings. I find that makes the turns much more efficient and easier to fly. If you have any different...
by kcaldwel
Mon Oct 03, 2016 3:51 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Additionally a log with the performance of Kevins flight calculated the original way inside oXs: Red=Average sink m/s --> longtimecalulation over 140 sec. was -0.40 m/s Blue= glideratio (left scale x 10) --> longtimecalulation over 140 sec. was 24.3 Kevin4.png If we want to stay with this method, w...
by kcaldwel
Mon Oct 03, 2016 3:13 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Thanks again Bernd! I was trying different speeds and flap settings during those flights, so I'll have to see what configuration that was. Too ambitious for the first go! I really want to get enough points to make a polar curve. I would still like to get a polar plot of the glider performance withou...
by kcaldwel
Mon Oct 03, 2016 2:52 am
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Thanks for looking at the file Bernd, I'd almost given up on it after some more time on it today. I am very disappointed by the oscillations. It is impossible to see them from the ground, but the glider does it continuously. I ma very impressed you are able to damp them out listening to the vario. I...
by kcaldwel
Sat Oct 01, 2016 12:47 am
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I finally got some data out over the sea with my 3.8M X2 e-glider. It weighs about 1700g. The tide was out when I started, but my beach was shrinking by the time I finished. It was mid-day, with very light on-shore winds, 13C, pressure 101.6kPa, water surface temperature about 14C. The air was very ...
by kcaldwel
Thu Aug 04, 2016 3:44 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Your speed control on that data is very good! I think taking the average over some long periods of that data should give a pretty representative number for L/D and sink rate in your different flight modes. Yes, I think "as it really flies" numbers including the phugoids may be of more use....
by kcaldwel
Wed Aug 03, 2016 8:41 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Bernd,

Is that flight data using manual speed control, or do you have the feedback loop of speed to elevator working? That is pretty smooth flying either way!

I've got to get out with my Xplorer and get some data. I was off to a competition for the first time in 44 years, now I'm tired!

Kevin
by kcaldwel
Mon Jul 18, 2016 8:48 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Looks nice! I've been flying rather than testing, so I don't have any new data. I did check the csv file I posted above, and it appears the L/D calculation is out by a factor of 10. When I calculate L/D using the instantaneous airspeed reported in knots converted to m/sec, and the average vertical s...
by kcaldwel
Thu Jun 23, 2016 6:24 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I managed to get a data file where everything worked, and no SD card error, with my old foam highly modified Calypso. It was a thermally day so the data is not of much use, but I did get some intervals that it calculated the glide ratio. I was using the Eagle Tree Guardian during the glides. The spe...
by kcaldwel
Fri Jun 03, 2016 9:57 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Section 9.1 in the files I downloaded yesterday also still lists the T1 and T2 telemetry fields, and seems to show that TEST_1, TEST_2 and TEST_3 are valid sources. I guess that no longer works though? "#define T1_SOURCE GLIDER_RATIO // select between TEST_1, TEST_2, TEST_3, GLIDER_RATIO , SECO...
by kcaldwel
Fri Jun 03, 2016 4:13 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Thanks! I couldn't see a definition of the SECONDS_SINCE_T0 and AVERAGE_VSPEED_SINCE_TO. I thought these were seconds since take-off and average vertical speed since take-off, which didn't sound that useful? From your description, I think these are the values I need to log. They seem to actually be ...
by kcaldwel
Thu Jun 02, 2016 10:55 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I'm having trouble getting the TEST_1, TEST_2, TEST_3 values to be sent as telemetry values. I have the #define T1_SOURCE TEST_1 and #define T2_SOURCE TEST_2 lines uncommented, and #define ACCX_SOURCE TEST_3 set, but those are not showing up on my Taranis telemetry. I set #define ACCY_SOURCE GLIDER_...
by kcaldwel
Fri May 06, 2016 9:29 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

Nice! All that space in the fuselage... It will be interesting to see how the Taranis works as a speed stabilizer. I can get my Eagle Tree Guardian stabilizer into my e-Supra I think, but it will be trickier on the e-Xplorer. There isn't much space, and the roll control is on SBus. I particularly li...
by kcaldwel
Thu May 05, 2016 10:27 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

I've got my swapable pod with an oXs ready to go. The oXs has airspeed (calibrated per above), vario, altimeter and 5Hz GPS. I laid up the saddle on my Xplorer 2 fuse, just in front of the wing. It is mainly Kevlar, and flexible enough to adapt to my e-Supra fuse as well. the connection will run und...
by kcaldwel
Wed Apr 20, 2016 11:45 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: oXs glider performance measurement
Replies: 58
Views: 37530

Re: oXs glider performance measurement

oXs Airspeed calibration Apr1_16 KC.jpg I have run some calibration tests on the oXs airspeed. I originally used a set-up with a water manometer on a 1:3 slope as Richard Johnson did when he calibrated full-scale airspeed instruments for his famous performance measurement tests. This applies a know...
by kcaldwel
Fri Feb 12, 2016 6:19 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: GPS sensor
Replies: 418
Views: 210714

Re: GPS sensor

I read shortly issues/3043. I think that FRSKY GPS is also expected in 1/10 of knot/h. OpenTx team as far I know has always expected that GPS speed would be in 1/10 of knot/h. If you are using oXS, please use in oXs the setup that ask for sending GPS speed in knot/h and not in km/h. The conversion ...
by kcaldwel
Fri Feb 12, 2016 2:50 am
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: GPS sensor
Replies: 418
Views: 210714

Re: GPS sensor

Just as a heads-up, I am getting an OXS GPS speed reading of about 2x the actual in a test against a calibrated car speedometer and another GPS. The N2 airspeed sensor is also reading the same, about 2x too high, using the 47.1 ratio in the Taranis telemetry. This is with a B model Taranis using Ope...
by kcaldwel
Thu Feb 11, 2016 9:01 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: openXsensor and the new telemetry in OpenTX 2.1
Replies: 31
Views: 17757

Re: openXsensor and the new telemetry in OpenTX 2.1

I just did some test runs with an OXS GPS, and a N2 Industries airspeed sensor on my car. It seems both are reporting near 2x the actual speeds in kph, as verified by the calibrated car speedometer and another GPS, using OpenTx 2.1.7. Both the Taranis telemetry display and the log file show the spee...
by kcaldwel
Thu Feb 04, 2016 4:17 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: GPS sensor
Replies: 418
Views: 210714

Re: GPS sensor

OXS GPS Connector.JPG I have now built three OXS vario/altimeter/GPS modules. They are all working great! Thanks to mstrens for all his work. I found some nice little connectors on eBay with wires on both sides that makes having a connector for the GPS fairly easy. It fits on the board nicely with ...
by kcaldwel
Sat Dec 05, 2015 5:05 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: GPS sensor
Replies: 418
Views: 210714

Re: GPS sensor

I agree with Carbo. We are almost always flying in a wind gradient with height with an RC glider. Even in straight flight descending downwind into the gradient should show increasing total energy with an airspeed probe compensated vario, and descending upwind into the gradient should should show an ...
by kcaldwel
Fri Dec 04, 2015 9:56 pm
Forum: OpenXVario - an open source vario supported by the open source firmwares!!
Topic: GPS sensor
Replies: 418
Views: 210714

Re: GPS sensor

I finally got it, on about the 14th attempt. Yep, shows 124 degrees 58W now, which is much closer to home! Perhaps this change needs to be fed back to the GPS stream, which has a few less things in it? I expect a few more people interested in triangle racing will be primarily interested in the highe...

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