[danstrider]

I'll build a prototype thermal sniffer using a thermistor and see how close I can get to the original design. Who knows, I may be able to improve it over time and this will teach me more about locating thermals.

Awesome! That's what research is all about

[Rick Masters]

Alan provided me with that information in hope of finding interest among pilots schooled in electronics. He was hoping to build a Snooper II and make some sensitivity changes. I disagreed with his approach, finding the original Thermal Snooper, which we had arrived at over a year or so of flight testing and prototyping in Owens Valley, to be ideal. But I contacted the world distance record holder for hang gliding at the time, a guy who runs his own forum, suggesting he work with Alan on the Snooper II. He refused.

I think Alan patented the Thermal Snooper in 1987, in which case it would be public domain now. I'm sure, looking down from that great thermal in the sky, Alan would love to see his work developed further.

Here's a list of over 6,500 modern thermistors (cheap*) to choose from. Good luck!


Thermistors-R-Us
http://www.digikey.com/product-search/en/sensors-transducers/thermistors-ntc/1966148
http://www.digikey.com/product-search/en/sensors-transducers/thermistors-ptc/1967095?k=thermistors

* This word is to hang glider pilots as the bell was to Pavlov's dogs, so I add it to provide encouragement.

[danstrider]

I cannot find a patent for the thermal snooper, but the name was trademarked in May of 1988 and expired in 1995:
https://trademarks.justia.com/737/27/th ... 27616.html

Found another interesting article on alternate updraft sensors to the traditional variometer:
http://www.foundcollection.com/25_0c6b6 ... 3504_1.htm

Please find attached two updated documents:
* The Thermal Snooper II article with circuit diagrams
* A formatted copy of Rick Masters' "Explorations with the Thermal Snooper" article

For anyone looking to reproduce Alan Fisher's Thermal Snooper from 1987, the necessary CMOS parts all appear to still be available from Digikey as of 2016 Jan 1st.

Dan

[Rick Masters]

Found another interesting article on alternate updraft sensors to the traditional variometer:
http://www.foundcollection.com/25_0c6b6 ... 3504_1.htm

A New Instrument for Locating Thermals
by Peter C. Masak, Neal F. Current and Gary Barnett
Soaring Pilot Magazine, Jan ~1994

The Thermal Snooper
    The Thermal Snooper was a device originally intended for hang glider pilots. It used a glass bead thermistor to measure the rate of change of temperature over time. If the temperature was increasing with time, the instrument would sound an audible beep, whereas when the temperature decreased, the tone would change to a distinctly different and lower pitched sound.
    By mounting the device on the crossbars of a hang glider, pilots claimed to be able to locate thermals better. In an interesting account written by hang glider pilot/author Rick Masters, Rick described how he was able to use the device in conjunction with a variometer for homing in on thermals. Mr. Masters felt that the device identified the presence of a nearby thermal more remotely than the standard variometer. This effect he attributed to the shedding of turbulent but warmer eddies (as in figure 2) at the boundaries of thermals, which the temperature based thermal snooper identified.
    To evaluate the potential use of this device on modern sailplanes, Peter Masak mounted the same device on an ASW-20. Although there was no question that the device measured something, it was also clear that frequently the indications on the unit did not correspond at all with recognizable atmospheric events. This was determined by flying side by side with another pilot in a Ventus. On numerous occasions we would pull up into a strong thermal and frequently there was no indication at all. It appeared that the device, like a normal variometer, required total energy compensation. The temperature changes involved in dolphining up and down by several hundred feet appeared to be at least an order of magnitude higher than the temperature changes due to transitioning in or out of a thermal at one altitude. Thus, control motions of the sort normally used to fly a sailplane would result in effects which masked the desired signal.
    Secondly, the device appeared to work better at low altitude than near cloudbase. This observation appeared to be consistent with another author who concluded that temperature based devices were not likely to work since the temperature difference between the thermal and the surrounding air, although large at the surface, was often zero or negative at higher altitudes near cloudbase. This may explain why hang glider pilots seem to have accepted the idea of a temperature based variometer, whereas sailplane pilots (who generally fly higher) have not.

    I met with national sailplane champion Peter Massak at the Pines Cafe in Independence a few months after "Explorations with the Thermal Snooper" was published in Soaring Magazine in August 1987. He borrowed one of my Snoopers for testing on sailplanes. He was disappointed in the results but I was certain the lack of correlation was due to the sailplane's higher speed and its inability to core thermals as efficiently as a hang glider. What I mean by this is that I've out-climbed gaggles of sailplanes in the same thermal in a hang glider in the White Mountains of California - and not just by a little bit! - by circling tightly in the core while the sailplanes were working the periphery, where the lift wasn't as good and, particularly in this case, where all the junk was sloughing off the thermal, leading to confusing boops and beeps for the sailplane pilot while my own Thermal Snooper was silent as my vario screamed.
    Massak also points out that as temperatures equalize at high altitudes, the Thermal Snooper doesn't seem to do anything. Duh! I never used my Snooper at those altitudes. I used the vario up there. I used the Snooper for finding and coring thermals in the areas where they were the strongest. That's what it's for.
    Sailplanes are no fun to fly with, by the way. Just when they start to get small below you, after you've elevatored up past them in the core and you feel like bragging, they leave like snotty kids picking up their marbles and going home, never to be seen again.

[Bill Cummings]

Dan,
I talked with my friend that has the snooper.
I forwarded your contact information to him with an email.
(A copy/paste of your PM to me.)
He tells me that the beeper thing is broke off but that it could be fixed.
So keep me posted if I can be of more help facilitating this transaction.
Bill C.

[cascpa]

I got my thermal snooper in the late eighties from one of my mentors, Paul Basil, God rest his soul. One of the best uses i found for it was at launch at Dry Canyon during one of the early fly-ins there. We used it to establish timing on thermals for launch cycles. It was a classic Memorial Day at Alamo. i launched around 3pm, topped out at 16,500, soared Sierra Blanca and boated around over town waiting for the sun to set and the wonders to subside. We had just left the snooper sitting next to launch. Given the strength of the day, I believe it gave enough information to significantly improve launch safety that day.

Charlie S.

[Harry]

Given the strength of the day, I believe it gave enough information to significantly improve launch safety that day.

Another good reason to build one.

I'm currently looking over dozens of spec sheets for parts. The open source suggestions by kiamartin make perfect sense and are crystal clear to me.
I really like the idea of using 2 thermistors in a calibrated bridge circuit.

[Rick Masters]

Mazourka Peak , where I did most of the testing of the Thermal Snooper in 1986. (Giant panorama photo http://images.summitpost.org/original/448920.jpg

Yes, I would use the TS to great effect in judging the quality of thermals rolling into launch. I would wait for it to BEEP (temperature rising) excitedly, count to ten, watch the streamers to verify the wind was straight into takeoff. If the Snooper went quiet, I would run. If it started BOOPING (temperature falling), I would wait for a longer cycle. This worked every time - until I got to the point in my thinking that pilots who flew without Snoopers were endangering themselves. (Much of my Owens Valley flying was solo, without a driver or bystanders. I would leave a motorcycle at the base of the mountain and drive my 4WD up to the top. I was usually alone on the mountain. I had to eliminate as much risk as possible. The Snooper was a godsend. Yes, this was very hardcore and not recommended. )

From a PM:

...did you experience the "BOOPS" while descending between thermals?

Absolutely.

Leaving the thermal as it climbs, deliberately or otherwise , one immediately enters cooler air, triggering BOOPS. Usually, I would ride a thermal to its limit and leave when lift approached minimum sink. At this point in a thermal's life, it is dispersing into the surrounding cooler air but has cooled significantly itself - so leaving a thermal at high altitude will not excite the Snooper as much as getting "dumped" or using racing strategy (leaving the thermal early) along a thermal corridor.

For the Snooper II, Alan Fisher was trying to modify the sensitivity of the Thermal Snooper to achieve a simpler response rather than receiving a "confusing" series of BOOPS and BEEPS. I tried to explain that the series of BOOPS and BEEPS was the correct response in mixing air where parcels shed from a thermal are drifting along the flight path. The Snooper is correctly describing the swirling air.

I'll be very interested in learning what you all find but keep in mind that dampening the response of the instrument degrades its utility. Remember the old adage, "If it ain't broke, don't fix it." I'm cynical enough now to think people who try to "improve" the TS without first mastering the original are wasting their time.

[Rick Masters]

On the question of audio filters:

    BOOPS and BEEPS occur in the vicinity of the thermal.
    Descending from the upper reaches of a thermal will result in what sounds like random BEEPS with occasional BOOPS. This is neither noise nor raw data, but INFORMATION. However, since this information is of no immediate use to the XC hang glider pilot, who is simply descending from cooler to warmer layers toward an area where he plans to again search for thermals, I frequently wished I could quiet down the Snooper and wait for a stronger series of BEEPS or BOOPS. The ideal way to do this is may be with always-on shaded green and red LEDs, with audio enabled when the Snooper gets excited. The range of audio-triggering should be controlled by the pilot through a sensitivity adjustment and must contain a bypass where filtering is disabled.

    Remember, the BOOPS, indicating cooler air but not necessarily sink, are just as valuable as BEEPS, indicating warmer air but not necessarily lift, when you are passing through tumbling air in the vicinity of a thermal. The primary purpose of the SNOOPER is to indicate the presence of a thermal in the vicinity by getting excited. Nothing more. Its purpose is not to indicate the presence of lift or warm air or sink or cool air. Most pilots receiving a Snooper for the first time are concentrating on looking for the warmer air "because that's where the lift is." This preconception limits the effective use of the Snooper because a thermal variometer best detects tumbling parcels of air shed from a thermal. These parcels are both warm and cool, and segments of the tumbling air are both rising and falling. The entire parcel, containing tumbling elements, can itself be rising or falling and be rotating along any point of a horizontal or vertical axis. Many "small thermals" we think we were in during our soaring careers were probably these parcels, and as we skillfully worked lift through half a turn and sink through the other, the main thermal, nearby, escaped us.

1) The primary purpose of the Snooper is to get excited, signaling to the pilot that he should initiate a search pattern. If the thermal is of adequate size, he will encounter it.

2) The secondary purpose of the Snooper is to verify the core of the thermal. When the hang glider centers the core, the Snooper will quiet down in the warm central rising air.

3) The third purpose of the Snooper is to tell the pilot when the thermal is topping out. The thermal will begin to slowly BOOP as the variometer indicates decreasing lift. Eventually the Snooper will fall silent as cooler upper air dominates. On racing or XC flights, the decreasing rising speed of the thermal can indicate it is time to go rather than wasting time thinking you have drifted outside the core and searching for it.

4) The fourth purpose of the Snooper is to indicate the presence of eddies. These atmospheric ripples do not have a changing temperature component so the Snooper will remain silent. Shears and the path of shears can also be recognized by the astute pilot.

-- Note to soaring parachutists --
    I am discussing the Thermal Snooper for use by hang glider and sailplane pilots.
    It would seem to me the height of stupidity and hubris to go searching for large, powerful, tumbling masses of swirling air on something so ridiculously inadequate as a parachute.
-- Don't bring a knife to a gunfight. Get an airframe. --

[Harry]

I replied to Rick in a PM, but I'll post it public as well. I was able to get my own design working today. The above description makes sense to me after studying the original design. On mine, I replaced the beeper circuit with LEDs to indicate warming or cooling air mass.

My design uses two diode sensors and one IC and seems to be rather sensitive, which is a good thing. Now all I have to do is fine tune it, box it up, and take it for a test flight.