THE Research Development Com mittee San Fernando Valley Silent Flyers has making glide angle meas urements RC saliplanes since December 1977 testing provides fundamental information about aerodynamics models Because sailplane club test sailplanes Although RC sailplanes probably easiest type model measure other RC airplanes large free-flight models mini RC gear installed could also tested glide polar graph relates airplanes airspeed its sink rate graph does two things defines straight line performance airplane tells pilot optimum speed fly function air conditions polar can used calculate lift-to-drag ratios profile drag coefficient induced drag coeffi cients spanwise efficiency factor maximum coefficient lift coefficient lift minimum sink coefficient lift maximum LID etc polars same plane different weights Reynolds Number effects can deduced quanti fied information about airspeed alone useful other analyses pilot can adjust planes speed achieve maximum actual glide angle 0 T Ye L Pett R Har L Blew B Rav WWats ALL Di 153 1 demoliansa Deffyplm 2 0 13530 IU 12213404 Haty 124H sjuO65 14s1tz 21331041 196 Mirage 17981 2792 16844juu [ 331193916811 2619 18513252 157 31 @0e 337 146W 439 1 7628b esp Dick Harty sights through inclinc simple home-made device up Knowing comas possible calculate drag coefficient spanwise maximum cofficient lift imum sink maximum 18 Model Aviation Laying out tne course 100-it tape Also ShOwn tfle two Inclinometers mounted photo light stands different air conditions knows planes polar method measure ment provides complete ac curate glide polar relatively short time devised Bill Watson author during very short brainstonning session method would useless continuing interest participation members R&D committee Measurement Procedure polar idealized graph formed data points relating sink rate airspeed data point result flight constant speed through measured course time course altitude lost course measured altitude measured glider passes through imaginary vertical plane Two inclinometers measured distance apart record angles glider forms horizon latitude calculated means ofatrigonometric formula end course altitude measured again difference between two altitudes course altitude lost Airspeed length course divided time course Sinkrate altitude lost divided time between altitude measurements fly straight line rather U-shaped course glider first passes through vertical measurement plane ume urine iiau group Fernando Valley Flyers four tested sailplanes L R Bob Sutton Bill Watson Goose Ted Yee close facsimile Eagle 128 Rich Harty Dick Harty Paragon Michael Bame Chris Adams authors Mirage Lorin Blewett bob-tail Sailaire picture August 1979 19 05101520 25 30 35 40 4Sftmc051015 20 25 3o 40 ASftlsec measured distance glider passes through second vertical plane parallel first point U-turn started usually takes 10 20 seconds complete glider passes back through second plane through first its altitude again measured Both time between altitude measurements time beyond second plane measured Flying U-shaped course reduces errors example light winds distance lost leg due headwinds almost regained other due tailwinds Also errors might result using two sets inclinometers avoided assumed plane flies same speed U-turn since turns very broad flat its performance seriously degraded important experiment run very calm air end start runs dawn stop data scatter indicates air beginning move air calm data scatter amazingly small air moving data useless Using course length 800 ft total flight 1600 fL usually able fly course twice launch seems about 20 runs sufficient form respectable polar everyone organized air still can expect get two complete polars two-hour session Equipment essential measuring equip ment simple easy construct consists two inclinometers two plumb lines holders form second vertical plane two stop watches Second ary equipment includes long tape measure lay out course base scale weigh planes compass align verti cal planes programable calculator computer process data calcula tions can done regular calculator rather tedious Inclinometers can home-made illustration board wood mounted photographic light stands read angles nearest half degree very easy Light stands also used support plumb bobs Six people required successfully make measurements pilot two inclinometers timer two watches signaller second plane data recorder two people retrieve launch mechanism can greatly increase efficiency Interpretation Data Almost flying mistakes adverse conditions will cause increase apparent sink rate gliders Only lift excess sink measurement errors will show decrease gliders sink rate difficult fly airplane such way sink rate artificially low wind increases actual distance flown resulting increased sink rate except region slower minimum sink speed appears measurement errors small compared errors caused flying mistakes Small flying errors observed course showed clearly data flying high quality data scatter large can assumed air still Since errors cause in20 Model Aviation 1 __________________ minimum sink 2 3 24 ftiec sink 1-- - - 2 aEAGLE128 4MIRAGE SAILAIRE _4G0E 6i--- - * jFIg2v-i ------- 1~ usc 700 ALTITUDE MEASUREMENT h n0sin9/sin(74 hi K time h2 -h2 turn L use 800 speed otal time-time turn SPEED AND SINKRATE slnkrate h-h2/total time L/D speed/sinkrate "N crease sink rate tendency data points fill envelope below true polar few points poking out because slight measurement errors lift course polar line generally drawn through some areas above uppermost points data shows significant scatter drawing polar line through points requires subjective judgment have doubts about polars drawn plot points given draw own difference might exceed 10% would expect closer 5% case Eagle 128 polar formed just five points variation will much larger case dont expect pin point accuracy polar dont make judgments based small differences SaiIpIane gliders rudder elevator polyhedral variety wing sections used very simple 30% high points no inflection points surfaces exception Goose has very slight reflex upper surface trailing edge Sailaire Paragon have flat-bottom sections no Phillips entry Eagle Paragon Mirage have forward 30% wing formed stringers turbu lators rather smooth sheeting Goose Sailaire sheeted high point except Sailaires tip panels about one-half wing use stringers like others Future Direction R&D Committee SFVSF continuing test gliders effects Reynolds Number variations wing thickness flaps seem to big questions answered method allows straightforward testing issues method might also used quantify performance existing designs soaring community may make informed selections relationship between glide polars actual airplanes may better understood Accurate polar data glider allows pilot fly precisely can judge air conditions flying speed leads greater instrumentation such variom eters airspeed indicators total energy systems glide polar measurement system can used calibrate such instruments hope article will stimulate other groups make measurements No parti cular expertise requiredafter few sessions will experts Bill Watson 16-ft version Goose constructed especially L/D trials Wing foam covered cardstock using Douglas fir box beam elliptical dihedral Unfortunately combination strong enough extended testingdata insufficient draw conclusion
Edition: Model Aviation - 1979/08
Page Numbers: 18, 19, 20, 21
THE Research Development Com mittee San Fernando Valley Silent Flyers has making glide angle meas urements RC saliplanes since December 1977 testing provides fundamental information about aerodynamics models Because sailplane club test sailplanes Although RC sailplanes probably easiest type model measure other RC airplanes large free-flight models mini RC gear installed could also tested glide polar graph relates airplanes airspeed its sink rate graph does two things defines straight line performance airplane tells pilot optimum speed fly function air conditions polar can used calculate lift-to-drag ratios profile drag coefficient induced drag coeffi cients spanwise efficiency factor maximum coefficient lift coefficient lift minimum sink coefficient lift maximum LID etc polars same plane different weights Reynolds Number effects can deduced quanti fied information about airspeed alone useful other analyses pilot can adjust planes speed achieve maximum actual glide angle 0 T Ye L Pett R Har L Blew B Rav WWats ALL Di 153 1 demoliansa Deffyplm 2 0 13530 IU 12213404 Haty 124H sjuO65 14s1tz 21331041 196 Mirage 17981 2792 16844juu [ 331193916811 2619 18513252 157 31 @0e 337 146W 439 1 7628b esp Dick Harty sights through inclinc simple home-made device up Knowing comas possible calculate drag coefficient spanwise maximum cofficient lift imum sink maximum 18 Model Aviation Laying out tne course 100-it tape Also ShOwn tfle two Inclinometers mounted photo light stands different air conditions knows planes polar method measure ment provides complete ac curate glide polar relatively short time devised Bill Watson author during very short brainstonning session method would useless continuing interest participation members R&D committee Measurement Procedure polar idealized graph formed data points relating sink rate airspeed data point result flight constant speed through measured course time course altitude lost course measured altitude measured glider passes through imaginary vertical plane Two inclinometers measured distance apart record angles glider forms horizon latitude calculated means ofatrigonometric formula end course altitude measured again difference between two altitudes course altitude lost Airspeed length course divided time course Sinkrate altitude lost divided time between altitude measurements fly straight line rather U-shaped course glider first passes through vertical measurement plane ume urine iiau group Fernando Valley Flyers four tested sailplanes L R Bob Sutton Bill Watson Goose Ted Yee close facsimile Eagle 128 Rich Harty Dick Harty Paragon Michael Bame Chris Adams authors Mirage Lorin Blewett bob-tail Sailaire picture August 1979 19 05101520 25 30 35 40 4Sftmc051015 20 25 3o 40 ASftlsec measured distance glider passes through second vertical plane parallel first point U-turn started usually takes 10 20 seconds complete glider passes back through second plane through first its altitude again measured Both time between altitude measurements time beyond second plane measured Flying U-shaped course reduces errors example light winds distance lost leg due headwinds almost regained other due tailwinds Also errors might result using two sets inclinometers avoided assumed plane flies same speed U-turn since turns very broad flat its performance seriously degraded important experiment run very calm air end start runs dawn stop data scatter indicates air beginning move air calm data scatter amazingly small air moving data useless Using course length 800 ft total flight 1600 fL usually able fly course twice launch seems about 20 runs sufficient form respectable polar everyone organized air still can expect get two complete polars two-hour session Equipment essential measuring equip ment simple easy construct consists two inclinometers two plumb lines holders form second vertical plane two stop watches Second ary equipment includes long tape measure lay out course base scale weigh planes compass align verti cal planes programable calculator computer process data calcula tions can done regular calculator rather tedious Inclinometers can home-made illustration board wood mounted photographic light stands read angles nearest half degree very easy Light stands also used support plumb bobs Six people required successfully make measurements pilot two inclinometers timer two watches signaller second plane data recorder two people retrieve launch mechanism can greatly increase efficiency Interpretation Data Almost flying mistakes adverse conditions will cause increase apparent sink rate gliders Only lift excess sink measurement errors will show decrease gliders sink rate difficult fly airplane such way sink rate artificially low wind increases actual distance flown resulting increased sink rate except region slower minimum sink speed appears measurement errors small compared errors caused flying mistakes Small flying errors observed course showed clearly data flying high quality data scatter large can assumed air still Since errors cause in20 Model Aviation 1 __________________ minimum sink 2 3 24 ftiec sink 1-- - - 2 aEAGLE128 4MIRAGE SAILAIRE _4G0E 6i--- - * jFIg2v-i ------- 1~ usc 700 ALTITUDE MEASUREMENT h n0sin9/sin(74 hi K time h2 -h2 turn L use 800 speed otal time-time turn SPEED AND SINKRATE slnkrate h-h2/total time L/D speed/sinkrate "N crease sink rate tendency data points fill envelope below true polar few points poking out because slight measurement errors lift course polar line generally drawn through some areas above uppermost points data shows significant scatter drawing polar line through points requires subjective judgment have doubts about polars drawn plot points given draw own difference might exceed 10% would expect closer 5% case Eagle 128 polar formed just five points variation will much larger case dont expect pin point accuracy polar dont make judgments based small differences SaiIpIane gliders rudder elevator polyhedral variety wing sections used very simple 30% high points no inflection points surfaces exception Goose has very slight reflex upper surface trailing edge Sailaire Paragon have flat-bottom sections no Phillips entry Eagle Paragon Mirage have forward 30% wing formed stringers turbu lators rather smooth sheeting Goose Sailaire sheeted high point except Sailaires tip panels about one-half wing use stringers like others Future Direction R&D Committee SFVSF continuing test gliders effects Reynolds Number variations wing thickness flaps seem to big questions answered method allows straightforward testing issues method might also used quantify performance existing designs soaring community may make informed selections relationship between glide polars actual airplanes may better understood Accurate polar data glider allows pilot fly precisely can judge air conditions flying speed leads greater instrumentation such variom eters airspeed indicators total energy systems glide polar measurement system can used calibrate such instruments hope article will stimulate other groups make measurements No parti cular expertise requiredafter few sessions will experts Bill Watson 16-ft version Goose constructed especially L/D trials Wing foam covered cardstock using Douglas fir box beam elliptical dihedral Unfortunately combination strong enough extended testingdata insufficient draw conclusion
Edition: Model Aviation - 1979/08
Page Numbers: 18, 19, 20, 21
THE Research Development Com mittee San Fernando Valley Silent Flyers has making glide angle meas urements RC saliplanes since December 1977 testing provides fundamental information about aerodynamics models Because sailplane club test sailplanes Although RC sailplanes probably easiest type model measure other RC airplanes large free-flight models mini RC gear installed could also tested glide polar graph relates airplanes airspeed its sink rate graph does two things defines straight line performance airplane tells pilot optimum speed fly function air conditions polar can used calculate lift-to-drag ratios profile drag coefficient induced drag coeffi cients spanwise efficiency factor maximum coefficient lift coefficient lift minimum sink coefficient lift maximum LID etc polars same plane different weights Reynolds Number effects can deduced quanti fied information about airspeed alone useful other analyses pilot can adjust planes speed achieve maximum actual glide angle 0 T Ye L Pett R Har L Blew B Rav WWats ALL Di 153 1 demoliansa Deffyplm 2 0 13530 IU 12213404 Haty 124H sjuO65 14s1tz 21331041 196 Mirage 17981 2792 16844juu [ 331193916811 2619 18513252 157 31 @0e 337 146W 439 1 7628b esp Dick Harty sights through inclinc simple home-made device up Knowing comas possible calculate drag coefficient spanwise maximum cofficient lift imum sink maximum 18 Model Aviation Laying out tne course 100-it tape Also ShOwn tfle two Inclinometers mounted photo light stands different air conditions knows planes polar method measure ment provides complete ac curate glide polar relatively short time devised Bill Watson author during very short brainstonning session method would useless continuing interest participation members R&D committee Measurement Procedure polar idealized graph formed data points relating sink rate airspeed data point result flight constant speed through measured course time course altitude lost course measured altitude measured glider passes through imaginary vertical plane Two inclinometers measured distance apart record angles glider forms horizon latitude calculated means ofatrigonometric formula end course altitude measured again difference between two altitudes course altitude lost Airspeed length course divided time course Sinkrate altitude lost divided time between altitude measurements fly straight line rather U-shaped course glider first passes through vertical measurement plane ume urine iiau group Fernando Valley Flyers four tested sailplanes L R Bob Sutton Bill Watson Goose Ted Yee close facsimile Eagle 128 Rich Harty Dick Harty Paragon Michael Bame Chris Adams authors Mirage Lorin Blewett bob-tail Sailaire picture August 1979 19 05101520 25 30 35 40 4Sftmc051015 20 25 3o 40 ASftlsec measured distance glider passes through second vertical plane parallel first point U-turn started usually takes 10 20 seconds complete glider passes back through second plane through first its altitude again measured Both time between altitude measurements time beyond second plane measured Flying U-shaped course reduces errors example light winds distance lost leg due headwinds almost regained other due tailwinds Also errors might result using two sets inclinometers avoided assumed plane flies same speed U-turn since turns very broad flat its performance seriously degraded important experiment run very calm air end start runs dawn stop data scatter indicates air beginning move air calm data scatter amazingly small air moving data useless Using course length 800 ft total flight 1600 fL usually able fly course twice launch seems about 20 runs sufficient form respectable polar everyone organized air still can expect get two complete polars two-hour session Equipment essential measuring equip ment simple easy construct consists two inclinometers two plumb lines holders form second vertical plane two stop watches Second ary equipment includes long tape measure lay out course base scale weigh planes compass align verti cal planes programable calculator computer process data calcula tions can done regular calculator rather tedious Inclinometers can home-made illustration board wood mounted photographic light stands read angles nearest half degree very easy Light stands also used support plumb bobs Six people required successfully make measurements pilot two inclinometers timer two watches signaller second plane data recorder two people retrieve launch mechanism can greatly increase efficiency Interpretation Data Almost flying mistakes adverse conditions will cause increase apparent sink rate gliders Only lift excess sink measurement errors will show decrease gliders sink rate difficult fly airplane such way sink rate artificially low wind increases actual distance flown resulting increased sink rate except region slower minimum sink speed appears measurement errors small compared errors caused flying mistakes Small flying errors observed course showed clearly data flying high quality data scatter large can assumed air still Since errors cause in20 Model Aviation 1 __________________ minimum sink 2 3 24 ftiec sink 1-- - - 2 aEAGLE128 4MIRAGE SAILAIRE _4G0E 6i--- - * jFIg2v-i ------- 1~ usc 700 ALTITUDE MEASUREMENT h n0sin9/sin(74 hi K time h2 -h2 turn L use 800 speed otal time-time turn SPEED AND SINKRATE slnkrate h-h2/total time L/D speed/sinkrate "N crease sink rate tendency data points fill envelope below true polar few points poking out because slight measurement errors lift course polar line generally drawn through some areas above uppermost points data shows significant scatter drawing polar line through points requires subjective judgment have doubts about polars drawn plot points given draw own difference might exceed 10% would expect closer 5% case Eagle 128 polar formed just five points variation will much larger case dont expect pin point accuracy polar dont make judgments based small differences SaiIpIane gliders rudder elevator polyhedral variety wing sections used very simple 30% high points no inflection points surfaces exception Goose has very slight reflex upper surface trailing edge Sailaire Paragon have flat-bottom sections no Phillips entry Eagle Paragon Mirage have forward 30% wing formed stringers turbu lators rather smooth sheeting Goose Sailaire sheeted high point except Sailaires tip panels about one-half wing use stringers like others Future Direction R&D Committee SFVSF continuing test gliders effects Reynolds Number variations wing thickness flaps seem to big questions answered method allows straightforward testing issues method might also used quantify performance existing designs soaring community may make informed selections relationship between glide polars actual airplanes may better understood Accurate polar data glider allows pilot fly precisely can judge air conditions flying speed leads greater instrumentation such variom eters airspeed indicators total energy systems glide polar measurement system can used calibrate such instruments hope article will stimulate other groups make measurements No parti cular expertise requiredafter few sessions will experts Bill Watson 16-ft version Goose constructed especially L/D trials Wing foam covered cardstock using Douglas fir box beam elliptical dihedral Unfortunately combination strong enough extended testingdata insufficient draw conclusion
Edition: Model Aviation - 1979/08
Page Numbers: 18, 19, 20, 21
THE Research Development Com mittee San Fernando Valley Silent Flyers has making glide angle meas urements RC saliplanes since December 1977 testing provides fundamental information about aerodynamics models Because sailplane club test sailplanes Although RC sailplanes probably easiest type model measure other RC airplanes large free-flight models mini RC gear installed could also tested glide polar graph relates airplanes airspeed its sink rate graph does two things defines straight line performance airplane tells pilot optimum speed fly function air conditions polar can used calculate lift-to-drag ratios profile drag coefficient induced drag coeffi cients spanwise efficiency factor maximum coefficient lift coefficient lift minimum sink coefficient lift maximum LID etc polars same plane different weights Reynolds Number effects can deduced quanti fied information about airspeed alone useful other analyses pilot can adjust planes speed achieve maximum actual glide angle 0 T Ye L Pett R Har L Blew B Rav WWats ALL Di 153 1 demoliansa Deffyplm 2 0 13530 IU 12213404 Haty 124H sjuO65 14s1tz 21331041 196 Mirage 17981 2792 16844juu [ 331193916811 2619 18513252 157 31 @0e 337 146W 439 1 7628b esp Dick Harty sights through inclinc simple home-made device up Knowing comas possible calculate drag coefficient spanwise maximum cofficient lift imum sink maximum 18 Model Aviation Laying out tne course 100-it tape Also ShOwn tfle two Inclinometers mounted photo light stands different air conditions knows planes polar method measure ment provides complete ac curate glide polar relatively short time devised Bill Watson author during very short brainstonning session method would useless continuing interest participation members R&D committee Measurement Procedure polar idealized graph formed data points relating sink rate airspeed data point result flight constant speed through measured course time course altitude lost course measured altitude measured glider passes through imaginary vertical plane Two inclinometers measured distance apart record angles glider forms horizon latitude calculated means ofatrigonometric formula end course altitude measured again difference between two altitudes course altitude lost Airspeed length course divided time course Sinkrate altitude lost divided time between altitude measurements fly straight line rather U-shaped course glider first passes through vertical measurement plane ume urine iiau group Fernando Valley Flyers four tested sailplanes L R Bob Sutton Bill Watson Goose Ted Yee close facsimile Eagle 128 Rich Harty Dick Harty Paragon Michael Bame Chris Adams authors Mirage Lorin Blewett bob-tail Sailaire picture August 1979 19 05101520 25 30 35 40 4Sftmc051015 20 25 3o 40 ASftlsec measured distance glider passes through second vertical plane parallel first point U-turn started usually takes 10 20 seconds complete glider passes back through second plane through first its altitude again measured Both time between altitude measurements time beyond second plane measured Flying U-shaped course reduces errors example light winds distance lost leg due headwinds almost regained other due tailwinds Also errors might result using two sets inclinometers avoided assumed plane flies same speed U-turn since turns very broad flat its performance seriously degraded important experiment run very calm air end start runs dawn stop data scatter indicates air beginning move air calm data scatter amazingly small air moving data useless Using course length 800 ft total flight 1600 fL usually able fly course twice launch seems about 20 runs sufficient form respectable polar everyone organized air still can expect get two complete polars two-hour session Equipment essential measuring equip ment simple easy construct consists two inclinometers two plumb lines holders form second vertical plane two stop watches Second ary equipment includes long tape measure lay out course base scale weigh planes compass align verti cal planes programable calculator computer process data calcula tions can done regular calculator rather tedious Inclinometers can home-made illustration board wood mounted photographic light stands read angles nearest half degree very easy Light stands also used support plumb bobs Six people required successfully make measurements pilot two inclinometers timer two watches signaller second plane data recorder two people retrieve launch mechanism can greatly increase efficiency Interpretation Data Almost flying mistakes adverse conditions will cause increase apparent sink rate gliders Only lift excess sink measurement errors will show decrease gliders sink rate difficult fly airplane such way sink rate artificially low wind increases actual distance flown resulting increased sink rate except region slower minimum sink speed appears measurement errors small compared errors caused flying mistakes Small flying errors observed course showed clearly data flying high quality data scatter large can assumed air still Since errors cause in20 Model Aviation 1 __________________ minimum sink 2 3 24 ftiec sink 1-- - - 2 aEAGLE128 4MIRAGE SAILAIRE _4G0E 6i--- - * jFIg2v-i ------- 1~ usc 700 ALTITUDE MEASUREMENT h n0sin9/sin(74 hi K time h2 -h2 turn L use 800 speed otal time-time turn SPEED AND SINKRATE slnkrate h-h2/total time L/D speed/sinkrate "N crease sink rate tendency data points fill envelope below true polar few points poking out because slight measurement errors lift course polar line generally drawn through some areas above uppermost points data shows significant scatter drawing polar line through points requires subjective judgment have doubts about polars drawn plot points given draw own difference might exceed 10% would expect closer 5% case Eagle 128 polar formed just five points variation will much larger case dont expect pin point accuracy polar dont make judgments based small differences SaiIpIane gliders rudder elevator polyhedral variety wing sections used very simple 30% high points no inflection points surfaces exception Goose has very slight reflex upper surface trailing edge Sailaire Paragon have flat-bottom sections no Phillips entry Eagle Paragon Mirage have forward 30% wing formed stringers turbu lators rather smooth sheeting Goose Sailaire sheeted high point except Sailaires tip panels about one-half wing use stringers like others Future Direction R&D Committee SFVSF continuing test gliders effects Reynolds Number variations wing thickness flaps seem to big questions answered method allows straightforward testing issues method might also used quantify performance existing designs soaring community may make informed selections relationship between glide polars actual airplanes may better understood Accurate polar data glider allows pilot fly precisely can judge air conditions flying speed leads greater instrumentation such variom eters airspeed indicators total energy systems glide polar measurement system can used calibrate such instruments hope article will stimulate other groups make measurements No parti cular expertise requiredafter few sessions will experts Bill Watson 16-ft version Goose constructed especially L/D trials Wing foam covered cardstock using Douglas fir box beam elliptical dihedral Unfortunately combination strong enough extended testingdata insufficient draw conclusion