Slopetrashuk Posted December 23, 2015 Share Posted December 23, 2015 Spencer Lisenby established a New Dynamic Soaring world record 513 mph flying his Kinetic 130 at Weldon, with a wind up to 60 mph. 513 mph is 825,6 km/h, an impressive 229 m/s. Andy Ellison Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 23, 2015 Share Posted December 23, 2015 I started thinking about the energy contained in a model travelling at 500+ mph and stopped - it was getting scary! A fantastic achievement all the same. How on earth do they visually track a model travelling at that speed at low altitude? Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted December 23, 2015 Share Posted December 23, 2015 Well done that man! Quote Link to comment Share on other sites More sharing options...
Cuban8 Posted December 23, 2015 Share Posted December 23, 2015 Are we pretty much at the limit of performance now - is any limitation that might exist either in the equipment or the human controlling the model? Perhaps both? Quote Link to comment Share on other sites More sharing options...
Dickw Posted December 23, 2015 Share Posted December 23, 2015 Fantastic achievement. Would loved to have seen (and heard!) it. Dick Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 23, 2015 Share Posted December 23, 2015 I'd have thought compressibility factors will kick in above 600mph or so depending on wing sections, weather conditions etc., then you are facing the same sub- and transonic issues as full size designers. I am amazed anyone can track and control a model at 500, but what would be possible with some fancy electronics aiding the pilot? Quote Link to comment Share on other sites More sharing options...
Geoff S Posted December 23, 2015 Share Posted December 23, 2015 Posted by Ian Jones on 23/12/2015 09:59:31: oops twitchy finger, double posted. Edited By Ian Jones on 23/12/2015 10:00:10 Better not try dynamic soaring at 500 mph then Unbelievable achievement and all without an engine. Not really my thing at all but I'm still full of admiration. Geoff Quote Link to comment Share on other sites More sharing options...
FilmBuff Posted December 23, 2015 Share Posted December 23, 2015 Posted by Bob Cotsford on 23/12/2015 09:56:34: I started thinking about the energy contained in a model travelling at 500+ mph and stopped - it was getting scary! A fantastic achievement all the same. How on earth do they visually track a model travelling at that speed at low altitude? The old Kinetic Energy equation of "Half Mass x Velocity Squared" give around 262K Joules, assuming V=229m/s and M=10Kg Not sure how to calibrate that... My BMW Mini travelling at 30mph packs around 98K Joules Edited By FilmBuff on 23/12/2015 12:57:51 Quote Link to comment Share on other sites More sharing options...
AVC Posted December 23, 2015 Share Posted December 23, 2015 I'm always impressed with these records. More than 800 km/h just using the wind and aerodynamics, it's simply amazing! Quote Link to comment Share on other sites More sharing options...
FilmBuff Posted December 23, 2015 Share Posted December 23, 2015 Mind you, if we think of the wind energy on his flight path, assuming a 100m x 100m box (conservative) and the 60mph (27m/s) wind and an air density of 1.125 kg/cubic metre then around 110 Mega Joules of wind energy is hitting the slope. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted December 23, 2015 Share Posted December 23, 2015 Posted by FilmBuff on 23/12/2015 13:07:49: Mind you, if we think of the wind energy on his flight path, assuming a 100m x 100m box (conservative) and the 60mph (27m/s) wind and an air density of 1.125 kg/cubic metre then around 110 Mega Joules of wind energy is hitting the slope. People are often surprised that ice yachts (with very low 'rolling' resistance) can sail at speeds up to 90mph in a 20mph wind. They think wind velocity rather its energy is the limiting factor. One thing you learn in sailing is that the apparent wind moves forward the faster you go (obvious if you think about it). I just wonder how that works with dynamic soaring when a glider has a 500 mph headwind. Geoff Quote Link to comment Share on other sites More sharing options...
Peter Garsden Posted December 26, 2015 Share Posted December 26, 2015 I have just posted a story on the LMMGA website, but I could only find a You Tube Video of an earlier record of 505mph? Is it posted anywhere? If so I will edit the story which you can read here **LINK** Quote Link to comment Share on other sites More sharing options...
Slopetrashuk Posted December 26, 2015 Author Share Posted December 26, 2015 No, no new video available yet. Will update when I find it. Andy Quote Link to comment Share on other sites More sharing options...
cymaz Posted December 26, 2015 Share Posted December 26, 2015 Bravo, what AA achievement. I saw some video of a 400+ mph DSS . Apparently the plane was on the video but I couldn't keep up with it! Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 26, 2015 Share Posted December 26, 2015 Posted by Bob Cotsford on 23/12/2015 10:19:46: I'd have thought compressibility factors will kick in above 600mph or so Actually Bob compressibility factors come in even earlier than that. At 500mph+ he's already in the compressable flow regime. DS is tricky to understand from a conventional aerodynamics point if view - add in compressibility and the mind boggles! I'm really not sure that he can continue to extract energy from the wind any more once the flow becomes highly compressable - but I'd be very happy to see him prove me wrong! As folks have said a tremendous achivement. There has to be a great TV documentary in that. When I tell people that the fastest R/C aircraft are actually gliders and then tell them the speeds these guys can reach they are amazed. BEB Quote Link to comment Share on other sites More sharing options...
cymaz Posted December 26, 2015 Share Posted December 26, 2015 Posted by cymaz on 26/12/2015 10:07:35: Bravo, what AA achievement. I saw some video of a 400+ mph DSS . Apparently the plane was on the video but I couldn't keep up with it! Here is 505mph ! Quote Link to comment Share on other sites More sharing options...
Daithi O Buitigh Posted December 28, 2015 Share Posted December 28, 2015 Impressive - but regarding 'transonic', remember that there was a 60 mph wind there and, while his ground speed was 500 mph plus, his airspeed was just over 450 mph (still flamin' fast though). Quote Link to comment Share on other sites More sharing options...
Slopetrashuk Posted December 28, 2015 Author Share Posted December 28, 2015 I beg to differ. With a 60mph wind his airspeed when crossing the shear with a groundspeed of 513 behind the ridge would be 573mph. Assuming no losses. Thats how DS works. Andy. Quote Link to comment Share on other sites More sharing options...
Daithi O Buitigh Posted December 28, 2015 Share Posted December 28, 2015 Back to front there - the speed recorded is the ground speed (as in full size records). The airspeed is the sped which is registered on a pitot tube and, if the tailwind is 'x' mph, the airspeed is groundspeed minus tailwind velocity with the opposite happening in the event of a headwind. That's how a Fieseler Storch was recorded at taking off at zero groundspeed (the wind velocity was enough to give sufficient airspeed for that to happen). Airspeed is the difference between groundspeed and the wind speed. Airspeed is constant in a flight (all factors being equal) which is why it takes longer for a flight against a headwind to travel from point A to point B (and faster if it's a tailwind) Quote Link to comment Share on other sites More sharing options...
Slopetrashuk Posted December 28, 2015 Author Share Posted December 28, 2015 Daithi, i dont mean to be rude but you clearly dont understand rc glider dynamic soaring. There are no pitots in use here and the recorded groundspeed is taken on the leeward side of the ridge with the model heading back upwards towards the radar. As the model passes back through the shear (from zero wind to 60mph wind) at a groundspeed of 513mph its airspeed (speed of airflow over wing) will instantaneously increase by the airspeed (if we assume no losses). 513+60=573. As the model turns back downwind on the windward side its airspeed will alter but this is not where the speed measurement is taken. The prime reason that DS works is because when the leeward side turn is made, there is no tailwind and no headwind. Therefore no slowing of the model and no change in airspeed. The transitions through the shear boundary layer between leeward and windward always increase airspeed. That is how you can get a rc glider to 513mph! Andy EllisonSlope Soaring ColumnistRCM&E Magazine. Quote Link to comment Share on other sites More sharing options...
Slopetrashuk Posted December 28, 2015 Author Share Posted December 28, 2015 An abridged version of my origibal articles here: http://www.speedfreeks.com/about.phpAndy. Quote Link to comment Share on other sites More sharing options...
Daithi O Buitigh Posted December 28, 2015 Share Posted December 28, 2015 While I will freely admit I don't know anything about DSS, I do know a fair bit about radar, having worked on maintenance of the Early Warning radar back when we actually had a reasonable sized air force. Radar will show the speed relative to it's fixed location (the ground speed). Now if an aircraft is showing as travelling at 513 mph on radar and if it's heading into a 60 mph headwind, then it's IAS will be 513 - 60 = 453 mph. If it has a 60 mph tail wind, then it's IAS will be 513 +60 = 573 mph/. Radar doesn't take into account the speed or vector of the wind - it simply measures what it sees. That's why they Mach numbers will vary according to conditions. Mach 1 is 761.2 at zero feet, 15C and is the IAS and not the ground speed. The Mach number will change plus or minus depending on wind vector. 513 ground speed is a fantastic figure (I'm not disputing that) - all I'm saying is that is the ground speed and NOT the air speed Quote Link to comment Share on other sites More sharing options...
Slopetrashuk Posted December 28, 2015 Author Share Posted December 28, 2015 Well actually what you said was that the airspeed was actually 60mph lower than the groundspeed. At the point the radar reading is taken on the leeward side of the ridge, groundspeed = airspeed as there is zero headwind or tailwind. Andy Quote Link to comment Share on other sites More sharing options...
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