Mv ARTICLE Primer Aerodynamics September 1992 issue led us basic aero dynamic principles object new article simple Once understand functions aerodynamics next step learning apply produce type flight desire could free flight control line radio controleach its facets Applying basic aero dynamic laws can compared building house first lay down foundation can build variety configurations However solid foundation whatever erected thereon will ultimately fail objective explain balance performance factors need provide solid jumping-off point obtaining ultimate flight performance want will assume studied Primer Aerodynamics now understand air reacts various aircraft shapes pass through producing work process described basic force arrangements FAs fact establish flight envelope design Obviously science involved producing FA mysteries science will explained two-part article first step project determine type flight desired else will relate objective becomes para mount approach design duration model would far different speed model example Designing aircraft probably worlds greatest act compromise practically aspect design intertwined some other aspect Thus have continually making decisions important decision made favors overall objective have established No matter desired type flight youre aiming first step set wing its efficient angle attack angle incidence known always measured relative line offlight will rest settings Once angle established becomes sacred design other adjustments done keep wing flying predetermined angle question determining wings efficient angle good modelers since us have access engineering data needed accurately determine setting S flight surfaces generally referred airfoils respect models usually apply term shape revealed take cross section particular flight surface great airfoil cross sections vary greatly contours thus efficient angle attack produce liftand process drag Lift positive force interested drag negative undesirable Besides necessity over coming gravity greatest detriment aircraft efficiency drag Reducing drag productive simplest cheapest path improved performance Generally speaking aircrafts airfoils produce major portion total drag Thus becomes important choose correct airfoil shape desired flight objective example airfoil best suited duration model would have far different contour designed maximum speed amount drag produced two airfoils would also considerably different Airfoil contour shapes have under continual development since Wright brothers put first flat plate wind tunnel soon found curved surface vastly superior flat plate respects Airfoil science has become very sophisticated today have curvatures specially suited almost design objective gains study factor modelers point view have too very complex flight objectives needs can filled relatively few different types classes airfoil contours Basically call types undercambered flat-bottom semisymmetrical symmetrical all-important lifting ability well drag production various airfoil sections pretty well conforms sequence listing undercambered sections produce liftand greatest drag airfoils have point will operate maximum efficiency point occurs somewhere usable angle attack range extends zero lift stall angle varies speed flying respect angle attack point maximum efficiency occurs ratio lift drag greatest As airfoils flown increasing speeds amounts lift drag increase square increase speed 28 Model Aviation author designed simple electric-powered duration model uses complex force arrangement control power provide minimum sink rate glide Applying elementary aerodynamic concepts will help design improve model airplane U Hal deBolt aircraft level flight some point speed reached drag will increase faster lift So airfoils efficiency determined angle flown speed involved can summarized saying airfoil should flown its best angle attack within its speed range Violating either two factors will reduce aerodynamic efficiency various airfoil contours have greatly different reactions factor speed example symmetrical section will continue have excellent lift-to-drag LiD ratio far higher speeds will some other styles So expected flying speed model design important consideration other choosing airfoil undercambered airfoils produce greatest lift process also produce greatest drag efficient speed range also very shallow com parison high weight-to-power ratios early aircraft relegated slow speeds undercambered foils suited well Continuing development has created some relatively efficient undercambered foils suit speed range duration-style models quite well also useful anticipated weight model will high Another factor consider airfoils stable other styles consideration choosing airfoil style note its entry portion portion airfoil just aft leading edge relates line flight foil its optimum angle attack Some offer much cleaner entry others thus producing less drag equal lift flat-bottom styles developed aircraft got beyond crawling stage actually walking sudden designers recognized importance drag Generally speaking foils retain highlift characteristics obtained upper curvature undercambered foils get nice drag reduction replacing undercamber flat bottom Popularized famous Clark Y flatbottom foils have seen continuous wide spread usage stable undercambered fathers suit average model very well lower drag higher speed all-important Semisymmetrical shapes development flat-bottom style NACA Editors note NACA old National Advisory Council Aeronautics predecessor todays National Aeronautics Space Administration [NASA] scientists created nice drag reduction changing flat bottom convex curve upper curve class airfoil similar flat-bottom airfoil section similar amount lift can expected However factor profile drag considered [LWRI 07 ooI 015 IozI 076 iizl 185 Izs 292 5231 351 3651 35 30 zzl iisl RI 0 I47I08I0I09I0SI 101 I08114118120I19115I091 Ic CLARK Y Muse RadIus 15 0 125125151 75110152025304015016070809095 100 UPR 345 65 79 I96114 117 114 lios927452280 LWR345165090400300000000 LWR 0 120612861-3841447 l 42 1566 f-s 7 [562 [525 [461 jss I3osIz1sI1l7Io68 j0 16 STA0 125 25 575 1015202530 4050 6070809095 100 UPR0237327445255856687177431572566257458328181101016 LWR023732744525585668.7177437572566251458328181101016 February 1993 29 No RaUua 07 STAM 0 11251251 5 175 110 115120125130140150160170 801901 95 100 UPR 07 218 316 655 565 653 178 853 90 915 896 823 71 575 408 223 0I251251517511011520125301401501601701001901951100 UPR j 0 LII 30 45 55 1631 8700 110399 88 74 55 290 hose Radios 248 0 1251 251 575 101520253040506070809095 100 0 211 37115011 606 683 791 87 917 938 925 857 75 61 441 245 134 016 foils upper curvature remains same flat-bottom airfoil added convex curve bottom increases overall profile area section will result increase drag Usually compromise struck design airfoils upper curve reduced lowered compensate addition bottom given speed lift would less such airfoil flat bottom however reduced drag convex-bottom section would enable increase flying speed turn would result easy restoration lost lift So using convex-bottom airfoil can produce much lift flat-bottom section along increase flying speed modeling especially control line radio control semisymmetrical airfoil sections have proven very useful widely employed except specialized purposes angle attack net lift course zero Add positive angle line flight lift produced could change 125 ounces positive direction decrease 75 ounces other direction thereby providing net 50 ounces useful lift An amazing aspect using symmetrical foils small amount angle attack necessary produce enough lift model maintain level flight Incidence angles two degrees prove ample Obviously angle attack increased lift produced increases dramatically gradually tilt symmetrical section higher higher angles attack will reach angle rear lower curvature becomes parallel line flight As angle approached net aerodynamic force produced will direction angle attack bottom curvature will producing downward aerodynamic force reason important especially tapered wing sure airfoil section progressively changed towards wing tip tip-sections airfoil does have greater amount C/P travel assure wing designers often use tip airfoils have inherently less C/P travel does center foil maximum stability use symmetrical section tip ideal solution symmetrical wing airfoils used wing tip wing tip some stall less abruptly others situation calling use progressively different airfoils advance center wing tip bottom line symmetrical airfoils can produce excellent lift minimum drag having no C/P travel very stable What also good about latest Symmetrical airfoils should considered ultimate least theory maximum performance consid eration shape name implies such airfoil sections upper lower curves identical class airfoil provides greatest stability least drag can produce useful lift Symmetrical sections widely used aircraft applications other lifting surfaces minimum drag desired Examples usage can anything door handles struts ____ landing gear such stream lining purposes low speeds thickness ratio 31 length three times thickness produces least drag symmetrical section has characteristics different other styles Remember said Primer Aerodynamics forward curvature foil pushes air molecules closer together aft airfoils high point low-pressure area exists because molecules have time return original spacing curvature symmetrical section identical both top bottom Therefore zero angle attack foil producing aerodynamic forces equally both up down directions being true might ask can does symmetrical section produce useful lift What happens sections angle attack changed zero differential lift between top bottom created favoring direction angle increased An example could section developing 100 ounces aero dynamic force both directions zero 0 iupper surface -- -- 22 /ower surface e NACA 65-O/5 4 C NACA 652-015 example highly developed modern symmetrical airfoil sections has proven have good lift minimum drag great stability Lets consider another factor Airfoil shapes other symmetrical ones display what called center pressure lift movement angle attack incidence changes As angle attack increases center pressure C/P moves forward away its original position does occur symmetrical sections Since models center-of-gravity fixed obvious wings C/P moves forward its original position will create unstable less stable condition respect models pitch attitude hear wild tales about certain designs having tip stall problems Quite often problem can traced using airfoil outer part wingspan has center pressure moves forward soon er C/P center-section airfoil NACA/NASA research has conducted general category airfoils making highly developed performance objectives craft established should have decided upon style airfoil will use next step decide upon amount incidence will use particular airfoil would like quote ironclad law unfortunately fact best L/D angle style airfoil varieseven airfoils similar style aerodynamicist studying airfoil data would reveal desired point such data available modelers However have extensive experience draw upon simple solution average modeler research what has used designs similar designing thinking about decision need realize airfoils other symmetrical ones com mence lifting some angle incidence less zero Generally speaking can say high-lift sections commence lifting angle incidence low .40 others between value 00 Thus set high-lift section 30 angle attack common setting foil would actually flying angle 7 relative its angle zero lift So style airfoil definite consideration youre selecting angle incidence Continued page 127 30 Model Aviation Charles St info & directions call Dr Sandy Frank 817-599-7131 Sponsor WEATHERFORD AERO MODELING SOCIETY FL APR 3Fort Myers FL El 2nd Annual Swap Shop & Auction 900 am -400 pm 800 am Sellers Corkscrew Woodlands Esif 19 W off 75 Corkscrew Rd 1/4 M 75 Larger Hall Tables $10 Advance Reservations Definitely Recommended Admission $2 Paul Barfos 1002 Washington Ave Lehigh FL 33936 PH 813-368-0214 Sponsor SW FLORIDA AERO CLUB LISTING AD INFORMATION NORMAL LISTING AMA sanction issued event event will listed automatically Contest Calendar section listing will give date place name eventplus competition events flying site Contest Director name address Use Supplementary paid Ad space suggested description unusual special events deviations AMA rules significant aspects meet Paid ads may helpful promoting funfly-type meets give directions flying site SUPPLEMENTARY ADS Larger ads can inserted Contest Calendar section paying fee ads accepted AMA-sanctioned events FEE Fees based ad size whether sponsor AMAchartered club AD POLICY SIZE 1/s-in wide either /4 1/2 2/4-in high full size ad appears Contest Calendar section PRICING 3/4$8 1/2$16 2/4$24 time ad run payable advance AMA-chartered clubs pay half rate AD PREPARATION advertiser must prepare Supplementary Ad Ads must full size see above Ads made up dark black white background will reproduce well recommended ad made heavy paper lightweight cardboard PLEASE DO NOT USE PHOTOGRAPHS ON ADS SUBMITTAL DEADLINE effort will made include Supplementary Ads received 14th month issue reaching readers approximately fourth week following month However cannot guaranteed ads published space-available basis normally two-month lead time required inserting Supplementary Ad same deadline will apply sanctioned events listings Questions about either Supplementary Ads regular Sanctioned Events listings should directed Debbie Brown AMAs Competition Department Send ads AMA HO Attention Competition Dept Renew 93 Built FlewlLehman Continued page 20 tempera paints later covered engine area clear dope should also mention tops bottoms fuselages midwing sheeted areas covered classroom tablet backings As project neared completion put several hours covering wings installing hardware radio engine maiden flight Pan Am took place evening April 16 Uncertain outcome made arrangements student present Joshua Smucker young man likely become pilot accompanied full throttle airliner sluggish fresh spring grass did take off fly nicely Unfortunately covering wing began loosen after two laps bring down remarked handy have throttle control cases like too dark repairs second flight Joshua went out again three evenings later time went extremely well Joshua outside circle throttle did takeoffs touch-and-goes slow approaches Communication hand signal week later April 23 students built Pan Am took turns being copilot enjoyed immensely After safety lesson person took turn throttle control about five laps before handing transmitter next pilot Later transferred engine radio Swissair second class its session Both classes preferred high-speed flight after deliberating beauty slow planned approaches gentle flybys persisted flying full tilt Throughout sessions however no matter what kids did throttle planes handled well enriching enjoy able venture kids made sure knew highlight school year Its too bad well probably never know what effect experience futures youngsters Wouldnt neat least came across article 20 30 years now wrote letter editor her/Lehmberg Continued page 27 same altitudethough lot closer little up stick will drop tail increase sink releasing stick will give nice touchdown Like Feather Merchants 72-inch version has wide stall tolerance stalled still mushes along instead pitching down can exploit tight turns glide using some up elevator strong rudder Oh yesI almost forgot Dont think ailerons Feather Merchant want everyone builds Feather Merchant have ball would like picturemaybe have questions problems like drop line 21337 Oak Park Lane Anderson CA 96007 An SASE would appreciated remember reading somewhere closing seems appropriate See ya Chicken House yhear /doBolt Continued page 30 Im going break off discussion point remainder fairly lengthy Save portion continuity reference study concluding part Part Two will cover process developing force arrangements model get ultimate flight performance Ill also talk about trimming methods continued lectricslKopski Continued page 76 fancy wiring harness incorporating double-pole double-throw center-off DPDTCO DP on-off-on switch associated wiring also requires battery made up two half-packs having same cell count cell type idea behind scheme use two packs connected series high power same two packs connected parallel cruise power connection accomplished servo-driven switch described above Thus in-flight switching between two available voltage levelsand off wellis readily accomplished Andjust theres no misunderstanding cells arrangement charged senes Ni-Cds never charged parallel wiring diagram gives details actual use plane motor prop configured cruise climb slightly voltage available paralleled half-packs half voltage higher voltage associated cells series results relatively aggressive climb capability needed center-off switch option allows charge conservation during thermaling Since much total flight time likely occur cruise power levels battery efficiency during periods considerable interest argued parallel-connected half-packs afford increased efficiency since half nominally operating half total motor current Cells tend display somewhat higher capacity lower drain rates conversely somewhat lower capacity higher currents February 1993 127 II
Edition: Model Aviation - 1993/02
Page Numbers: 28, 29, 30, 127
Mv ARTICLE Primer Aerodynamics September 1992 issue led us basic aero dynamic principles object new article simple Once understand functions aerodynamics next step learning apply produce type flight desire could free flight control line radio controleach its facets Applying basic aero dynamic laws can compared building house first lay down foundation can build variety configurations However solid foundation whatever erected thereon will ultimately fail objective explain balance performance factors need provide solid jumping-off point obtaining ultimate flight performance want will assume studied Primer Aerodynamics now understand air reacts various aircraft shapes pass through producing work process described basic force arrangements FAs fact establish flight envelope design Obviously science involved producing FA mysteries science will explained two-part article first step project determine type flight desired else will relate objective becomes para mount approach design duration model would far different speed model example Designing aircraft probably worlds greatest act compromise practically aspect design intertwined some other aspect Thus have continually making decisions important decision made favors overall objective have established No matter desired type flight youre aiming first step set wing its efficient angle attack angle incidence known always measured relative line offlight will rest settings Once angle established becomes sacred design other adjustments done keep wing flying predetermined angle question determining wings efficient angle good modelers since us have access engineering data needed accurately determine setting S flight surfaces generally referred airfoils respect models usually apply term shape revealed take cross section particular flight surface great airfoil cross sections vary greatly contours thus efficient angle attack produce liftand process drag Lift positive force interested drag negative undesirable Besides necessity over coming gravity greatest detriment aircraft efficiency drag Reducing drag productive simplest cheapest path improved performance Generally speaking aircrafts airfoils produce major portion total drag Thus becomes important choose correct airfoil shape desired flight objective example airfoil best suited duration model would have far different contour designed maximum speed amount drag produced two airfoils would also considerably different Airfoil contour shapes have under continual development since Wright brothers put first flat plate wind tunnel soon found curved surface vastly superior flat plate respects Airfoil science has become very sophisticated today have curvatures specially suited almost design objective gains study factor modelers point view have too very complex flight objectives needs can filled relatively few different types classes airfoil contours Basically call types undercambered flat-bottom semisymmetrical symmetrical all-important lifting ability well drag production various airfoil sections pretty well conforms sequence listing undercambered sections produce liftand greatest drag airfoils have point will operate maximum efficiency point occurs somewhere usable angle attack range extends zero lift stall angle varies speed flying respect angle attack point maximum efficiency occurs ratio lift drag greatest As airfoils flown increasing speeds amounts lift drag increase square increase speed 28 Model Aviation author designed simple electric-powered duration model uses complex force arrangement control power provide minimum sink rate glide Applying elementary aerodynamic concepts will help design improve model airplane U Hal deBolt aircraft level flight some point speed reached drag will increase faster lift So airfoils efficiency determined angle flown speed involved can summarized saying airfoil should flown its best angle attack within its speed range Violating either two factors will reduce aerodynamic efficiency various airfoil contours have greatly different reactions factor speed example symmetrical section will continue have excellent lift-to-drag LiD ratio far higher speeds will some other styles So expected flying speed model design important consideration other choosing airfoil undercambered airfoils produce greatest lift process also produce greatest drag efficient speed range also very shallow com parison high weight-to-power ratios early aircraft relegated slow speeds undercambered foils suited well Continuing development has created some relatively efficient undercambered foils suit speed range duration-style models quite well also useful anticipated weight model will high Another factor consider airfoils stable other styles consideration choosing airfoil style note its entry portion portion airfoil just aft leading edge relates line flight foil its optimum angle attack Some offer much cleaner entry others thus producing less drag equal lift flat-bottom styles developed aircraft got beyond crawling stage actually walking sudden designers recognized importance drag Generally speaking foils retain highlift characteristics obtained upper curvature undercambered foils get nice drag reduction replacing undercamber flat bottom Popularized famous Clark Y flatbottom foils have seen continuous wide spread usage stable undercambered fathers suit average model very well lower drag higher speed all-important Semisymmetrical shapes development flat-bottom style NACA Editors note NACA old National Advisory Council Aeronautics predecessor todays National Aeronautics Space Administration [NASA] scientists created nice drag reduction changing flat bottom convex curve upper curve class airfoil similar flat-bottom airfoil section similar amount lift can expected However factor profile drag considered [LWRI 07 ooI 015 IozI 076 iizl 185 Izs 292 5231 351 3651 35 30 zzl iisl RI 0 I47I08I0I09I0SI 101 I08114118120I19115I091 Ic CLARK Y Muse RadIus 15 0 125125151 75110152025304015016070809095 100 UPR 345 65 79 I96114 117 114 lios927452280 LWR345165090400300000000 LWR 0 120612861-3841447 l 42 1566 f-s 7 [562 [525 [461 jss I3osIz1sI1l7Io68 j0 16 STA0 125 25 575 1015202530 4050 6070809095 100 UPR0237327445255856687177431572566257458328181101016 LWR023732744525585668.7177437572566251458328181101016 February 1993 29 No RaUua 07 STAM 0 11251251 5 175 110 115120125130140150160170 801901 95 100 UPR 07 218 316 655 565 653 178 853 90 915 896 823 71 575 408 223 0I251251517511011520125301401501601701001901951100 UPR j 0 LII 30 45 55 1631 8700 110399 88 74 55 290 hose Radios 248 0 1251 251 575 101520253040506070809095 100 0 211 37115011 606 683 791 87 917 938 925 857 75 61 441 245 134 016 foils upper curvature remains same flat-bottom airfoil added convex curve bottom increases overall profile area section will result increase drag Usually compromise struck design airfoils upper curve reduced lowered compensate addition bottom given speed lift would less such airfoil flat bottom however reduced drag convex-bottom section would enable increase flying speed turn would result easy restoration lost lift So using convex-bottom airfoil can produce much lift flat-bottom section along increase flying speed modeling especially control line radio control semisymmetrical airfoil sections have proven very useful widely employed except specialized purposes angle attack net lift course zero Add positive angle line flight lift produced could change 125 ounces positive direction decrease 75 ounces other direction thereby providing net 50 ounces useful lift An amazing aspect using symmetrical foils small amount angle attack necessary produce enough lift model maintain level flight Incidence angles two degrees prove ample Obviously angle attack increased lift produced increases dramatically gradually tilt symmetrical section higher higher angles attack will reach angle rear lower curvature becomes parallel line flight As angle approached net aerodynamic force produced will direction angle attack bottom curvature will producing downward aerodynamic force reason important especially tapered wing sure airfoil section progressively changed towards wing tip tip-sections airfoil does have greater amount C/P travel assure wing designers often use tip airfoils have inherently less C/P travel does center foil maximum stability use symmetrical section tip ideal solution symmetrical wing airfoils used wing tip wing tip some stall less abruptly others situation calling use progressively different airfoils advance center wing tip bottom line symmetrical airfoils can produce excellent lift minimum drag having no C/P travel very stable What also good about latest Symmetrical airfoils should considered ultimate least theory maximum performance consid eration shape name implies such airfoil sections upper lower curves identical class airfoil provides greatest stability least drag can produce useful lift Symmetrical sections widely used aircraft applications other lifting surfaces minimum drag desired Examples usage can anything door handles struts ____ landing gear such stream lining purposes low speeds thickness ratio 31 length three times thickness produces least drag symmetrical section has characteristics different other styles Remember said Primer Aerodynamics forward curvature foil pushes air molecules closer together aft airfoils high point low-pressure area exists because molecules have time return original spacing curvature symmetrical section identical both top bottom Therefore zero angle attack foil producing aerodynamic forces equally both up down directions being true might ask can does symmetrical section produce useful lift What happens sections angle attack changed zero differential lift between top bottom created favoring direction angle increased An example could section developing 100 ounces aero dynamic force both directions zero 0 iupper surface -- -- 22 /ower surface e NACA 65-O/5 4 C NACA 652-015 example highly developed modern symmetrical airfoil sections has proven have good lift minimum drag great stability Lets consider another factor Airfoil shapes other symmetrical ones display what called center pressure lift movement angle attack incidence changes As angle attack increases center pressure C/P moves forward away its original position does occur symmetrical sections Since models center-of-gravity fixed obvious wings C/P moves forward its original position will create unstable less stable condition respect models pitch attitude hear wild tales about certain designs having tip stall problems Quite often problem can traced using airfoil outer part wingspan has center pressure moves forward soon er C/P center-section airfoil NACA/NASA research has conducted general category airfoils making highly developed performance objectives craft established should have decided upon style airfoil will use next step decide upon amount incidence will use particular airfoil would like quote ironclad law unfortunately fact best L/D angle style airfoil varieseven airfoils similar style aerodynamicist studying airfoil data would reveal desired point such data available modelers However have extensive experience draw upon simple solution average modeler research what has used designs similar designing thinking about decision need realize airfoils other symmetrical ones com mence lifting some angle incidence less zero Generally speaking can say high-lift sections commence lifting angle incidence low .40 others between value 00 Thus set high-lift section 30 angle attack common setting foil would actually flying angle 7 relative its angle zero lift So style airfoil definite consideration youre selecting angle incidence Continued page 127 30 Model Aviation Charles St info & directions call Dr Sandy Frank 817-599-7131 Sponsor WEATHERFORD AERO MODELING SOCIETY FL APR 3Fort Myers FL El 2nd Annual Swap Shop & Auction 900 am -400 pm 800 am Sellers Corkscrew Woodlands Esif 19 W off 75 Corkscrew Rd 1/4 M 75 Larger Hall Tables $10 Advance Reservations Definitely Recommended Admission $2 Paul Barfos 1002 Washington Ave Lehigh FL 33936 PH 813-368-0214 Sponsor SW FLORIDA AERO CLUB LISTING AD INFORMATION NORMAL LISTING AMA sanction issued event event will listed automatically Contest Calendar section listing will give date place name eventplus competition events flying site Contest Director name address Use Supplementary paid Ad space suggested description unusual special events deviations AMA rules significant aspects meet Paid ads may helpful promoting funfly-type meets give directions flying site SUPPLEMENTARY ADS Larger ads can inserted Contest Calendar section paying fee ads accepted AMA-sanctioned events FEE Fees based ad size whether sponsor AMAchartered club AD POLICY SIZE 1/s-in wide either /4 1/2 2/4-in high full size ad appears Contest Calendar section PRICING 3/4$8 1/2$16 2/4$24 time ad run payable advance AMA-chartered clubs pay half rate AD PREPARATION advertiser must prepare Supplementary Ad Ads must full size see above Ads made up dark black white background will reproduce well recommended ad made heavy paper lightweight cardboard PLEASE DO NOT USE PHOTOGRAPHS ON ADS SUBMITTAL DEADLINE effort will made include Supplementary Ads received 14th month issue reaching readers approximately fourth week following month However cannot guaranteed ads published space-available basis normally two-month lead time required inserting Supplementary Ad same deadline will apply sanctioned events listings Questions about either Supplementary Ads regular Sanctioned Events listings should directed Debbie Brown AMAs Competition Department Send ads AMA HO Attention Competition Dept Renew 93 Built FlewlLehman Continued page 20 tempera paints later covered engine area clear dope should also mention tops bottoms fuselages midwing sheeted areas covered classroom tablet backings As project neared completion put several hours covering wings installing hardware radio engine maiden flight Pan Am took place evening April 16 Uncertain outcome made arrangements student present Joshua Smucker young man likely become pilot accompanied full throttle airliner sluggish fresh spring grass did take off fly nicely Unfortunately covering wing began loosen after two laps bring down remarked handy have throttle control cases like too dark repairs second flight Joshua went out again three evenings later time went extremely well Joshua outside circle throttle did takeoffs touch-and-goes slow approaches Communication hand signal week later April 23 students built Pan Am took turns being copilot enjoyed immensely After safety lesson person took turn throttle control about five laps before handing transmitter next pilot Later transferred engine radio Swissair second class its session Both classes preferred high-speed flight after deliberating beauty slow planned approaches gentle flybys persisted flying full tilt Throughout sessions however no matter what kids did throttle planes handled well enriching enjoy able venture kids made sure knew highlight school year Its too bad well probably never know what effect experience futures youngsters Wouldnt neat least came across article 20 30 years now wrote letter editor her/Lehmberg Continued page 27 same altitudethough lot closer little up stick will drop tail increase sink releasing stick will give nice touchdown Like Feather Merchants 72-inch version has wide stall tolerance stalled still mushes along instead pitching down can exploit tight turns glide using some up elevator strong rudder Oh yesI almost forgot Dont think ailerons Feather Merchant want everyone builds Feather Merchant have ball would like picturemaybe have questions problems like drop line 21337 Oak Park Lane Anderson CA 96007 An SASE would appreciated remember reading somewhere closing seems appropriate See ya Chicken House yhear /doBolt Continued page 30 Im going break off discussion point remainder fairly lengthy Save portion continuity reference study concluding part Part Two will cover process developing force arrangements model get ultimate flight performance Ill also talk about trimming methods continued lectricslKopski Continued page 76 fancy wiring harness incorporating double-pole double-throw center-off DPDTCO DP on-off-on switch associated wiring also requires battery made up two half-packs having same cell count cell type idea behind scheme use two packs connected series high power same two packs connected parallel cruise power connection accomplished servo-driven switch described above Thus in-flight switching between two available voltage levelsand off wellis readily accomplished Andjust theres no misunderstanding cells arrangement charged senes Ni-Cds never charged parallel wiring diagram gives details actual use plane motor prop configured cruise climb slightly voltage available paralleled half-packs half voltage higher voltage associated cells series results relatively aggressive climb capability needed center-off switch option allows charge conservation during thermaling Since much total flight time likely occur cruise power levels battery efficiency during periods considerable interest argued parallel-connected half-packs afford increased efficiency since half nominally operating half total motor current Cells tend display somewhat higher capacity lower drain rates conversely somewhat lower capacity higher currents February 1993 127 II
Edition: Model Aviation - 1993/02
Page Numbers: 28, 29, 30, 127
Mv ARTICLE Primer Aerodynamics September 1992 issue led us basic aero dynamic principles object new article simple Once understand functions aerodynamics next step learning apply produce type flight desire could free flight control line radio controleach its facets Applying basic aero dynamic laws can compared building house first lay down foundation can build variety configurations However solid foundation whatever erected thereon will ultimately fail objective explain balance performance factors need provide solid jumping-off point obtaining ultimate flight performance want will assume studied Primer Aerodynamics now understand air reacts various aircraft shapes pass through producing work process described basic force arrangements FAs fact establish flight envelope design Obviously science involved producing FA mysteries science will explained two-part article first step project determine type flight desired else will relate objective becomes para mount approach design duration model would far different speed model example Designing aircraft probably worlds greatest act compromise practically aspect design intertwined some other aspect Thus have continually making decisions important decision made favors overall objective have established No matter desired type flight youre aiming first step set wing its efficient angle attack angle incidence known always measured relative line offlight will rest settings Once angle established becomes sacred design other adjustments done keep wing flying predetermined angle question determining wings efficient angle good modelers since us have access engineering data needed accurately determine setting S flight surfaces generally referred airfoils respect models usually apply term shape revealed take cross section particular flight surface great airfoil cross sections vary greatly contours thus efficient angle attack produce liftand process drag Lift positive force interested drag negative undesirable Besides necessity over coming gravity greatest detriment aircraft efficiency drag Reducing drag productive simplest cheapest path improved performance Generally speaking aircrafts airfoils produce major portion total drag Thus becomes important choose correct airfoil shape desired flight objective example airfoil best suited duration model would have far different contour designed maximum speed amount drag produced two airfoils would also considerably different Airfoil contour shapes have under continual development since Wright brothers put first flat plate wind tunnel soon found curved surface vastly superior flat plate respects Airfoil science has become very sophisticated today have curvatures specially suited almost design objective gains study factor modelers point view have too very complex flight objectives needs can filled relatively few different types classes airfoil contours Basically call types undercambered flat-bottom semisymmetrical symmetrical all-important lifting ability well drag production various airfoil sections pretty well conforms sequence listing undercambered sections produce liftand greatest drag airfoils have point will operate maximum efficiency point occurs somewhere usable angle attack range extends zero lift stall angle varies speed flying respect angle attack point maximum efficiency occurs ratio lift drag greatest As airfoils flown increasing speeds amounts lift drag increase square increase speed 28 Model Aviation author designed simple electric-powered duration model uses complex force arrangement control power provide minimum sink rate glide Applying elementary aerodynamic concepts will help design improve model airplane U Hal deBolt aircraft level flight some point speed reached drag will increase faster lift So airfoils efficiency determined angle flown speed involved can summarized saying airfoil should flown its best angle attack within its speed range Violating either two factors will reduce aerodynamic efficiency various airfoil contours have greatly different reactions factor speed example symmetrical section will continue have excellent lift-to-drag LiD ratio far higher speeds will some other styles So expected flying speed model design important consideration other choosing airfoil undercambered airfoils produce greatest lift process also produce greatest drag efficient speed range also very shallow com parison high weight-to-power ratios early aircraft relegated slow speeds undercambered foils suited well Continuing development has created some relatively efficient undercambered foils suit speed range duration-style models quite well also useful anticipated weight model will high Another factor consider airfoils stable other styles consideration choosing airfoil style note its entry portion portion airfoil just aft leading edge relates line flight foil its optimum angle attack Some offer much cleaner entry others thus producing less drag equal lift flat-bottom styles developed aircraft got beyond crawling stage actually walking sudden designers recognized importance drag Generally speaking foils retain highlift characteristics obtained upper curvature undercambered foils get nice drag reduction replacing undercamber flat bottom Popularized famous Clark Y flatbottom foils have seen continuous wide spread usage stable undercambered fathers suit average model very well lower drag higher speed all-important Semisymmetrical shapes development flat-bottom style NACA Editors note NACA old National Advisory Council Aeronautics predecessor todays National Aeronautics Space Administration [NASA] scientists created nice drag reduction changing flat bottom convex curve upper curve class airfoil similar flat-bottom airfoil section similar amount lift can expected However factor profile drag considered [LWRI 07 ooI 015 IozI 076 iizl 185 Izs 292 5231 351 3651 35 30 zzl iisl RI 0 I47I08I0I09I0SI 101 I08114118120I19115I091 Ic CLARK Y Muse RadIus 15 0 125125151 75110152025304015016070809095 100 UPR 345 65 79 I96114 117 114 lios927452280 LWR345165090400300000000 LWR 0 120612861-3841447 l 42 1566 f-s 7 [562 [525 [461 jss I3osIz1sI1l7Io68 j0 16 STA0 125 25 575 1015202530 4050 6070809095 100 UPR0237327445255856687177431572566257458328181101016 LWR023732744525585668.7177437572566251458328181101016 February 1993 29 No RaUua 07 STAM 0 11251251 5 175 110 115120125130140150160170 801901 95 100 UPR 07 218 316 655 565 653 178 853 90 915 896 823 71 575 408 223 0I251251517511011520125301401501601701001901951100 UPR j 0 LII 30 45 55 1631 8700 110399 88 74 55 290 hose Radios 248 0 1251 251 575 101520253040506070809095 100 0 211 37115011 606 683 791 87 917 938 925 857 75 61 441 245 134 016 foils upper curvature remains same flat-bottom airfoil added convex curve bottom increases overall profile area section will result increase drag Usually compromise struck design airfoils upper curve reduced lowered compensate addition bottom given speed lift would less such airfoil flat bottom however reduced drag convex-bottom section would enable increase flying speed turn would result easy restoration lost lift So using convex-bottom airfoil can produce much lift flat-bottom section along increase flying speed modeling especially control line radio control semisymmetrical airfoil sections have proven very useful widely employed except specialized purposes angle attack net lift course zero Add positive angle line flight lift produced could change 125 ounces positive direction decrease 75 ounces other direction thereby providing net 50 ounces useful lift An amazing aspect using symmetrical foils small amount angle attack necessary produce enough lift model maintain level flight Incidence angles two degrees prove ample Obviously angle attack increased lift produced increases dramatically gradually tilt symmetrical section higher higher angles attack will reach angle rear lower curvature becomes parallel line flight As angle approached net aerodynamic force produced will direction angle attack bottom curvature will producing downward aerodynamic force reason important especially tapered wing sure airfoil section progressively changed towards wing tip tip-sections airfoil does have greater amount C/P travel assure wing designers often use tip airfoils have inherently less C/P travel does center foil maximum stability use symmetrical section tip ideal solution symmetrical wing airfoils used wing tip wing tip some stall less abruptly others situation calling use progressively different airfoils advance center wing tip bottom line symmetrical airfoils can produce excellent lift minimum drag having no C/P travel very stable What also good about latest Symmetrical airfoils should considered ultimate least theory maximum performance consid eration shape name implies such airfoil sections upper lower curves identical class airfoil provides greatest stability least drag can produce useful lift Symmetrical sections widely used aircraft applications other lifting surfaces minimum drag desired Examples usage can anything door handles struts ____ landing gear such stream lining purposes low speeds thickness ratio 31 length three times thickness produces least drag symmetrical section has characteristics different other styles Remember said Primer Aerodynamics forward curvature foil pushes air molecules closer together aft airfoils high point low-pressure area exists because molecules have time return original spacing curvature symmetrical section identical both top bottom Therefore zero angle attack foil producing aerodynamic forces equally both up down directions being true might ask can does symmetrical section produce useful lift What happens sections angle attack changed zero differential lift between top bottom created favoring direction angle increased An example could section developing 100 ounces aero dynamic force both directions zero 0 iupper surface -- -- 22 /ower surface e NACA 65-O/5 4 C NACA 652-015 example highly developed modern symmetrical airfoil sections has proven have good lift minimum drag great stability Lets consider another factor Airfoil shapes other symmetrical ones display what called center pressure lift movement angle attack incidence changes As angle attack increases center pressure C/P moves forward away its original position does occur symmetrical sections Since models center-of-gravity fixed obvious wings C/P moves forward its original position will create unstable less stable condition respect models pitch attitude hear wild tales about certain designs having tip stall problems Quite often problem can traced using airfoil outer part wingspan has center pressure moves forward soon er C/P center-section airfoil NACA/NASA research has conducted general category airfoils making highly developed performance objectives craft established should have decided upon style airfoil will use next step decide upon amount incidence will use particular airfoil would like quote ironclad law unfortunately fact best L/D angle style airfoil varieseven airfoils similar style aerodynamicist studying airfoil data would reveal desired point such data available modelers However have extensive experience draw upon simple solution average modeler research what has used designs similar designing thinking about decision need realize airfoils other symmetrical ones com mence lifting some angle incidence less zero Generally speaking can say high-lift sections commence lifting angle incidence low .40 others between value 00 Thus set high-lift section 30 angle attack common setting foil would actually flying angle 7 relative its angle zero lift So style airfoil definite consideration youre selecting angle incidence Continued page 127 30 Model Aviation Charles St info & directions call Dr Sandy Frank 817-599-7131 Sponsor WEATHERFORD AERO MODELING SOCIETY FL APR 3Fort Myers FL El 2nd Annual Swap Shop & Auction 900 am -400 pm 800 am Sellers Corkscrew Woodlands Esif 19 W off 75 Corkscrew Rd 1/4 M 75 Larger Hall Tables $10 Advance Reservations Definitely Recommended Admission $2 Paul Barfos 1002 Washington Ave Lehigh FL 33936 PH 813-368-0214 Sponsor SW FLORIDA AERO CLUB LISTING AD INFORMATION NORMAL LISTING AMA sanction issued event event will listed automatically Contest Calendar section listing will give date place name eventplus competition events flying site Contest Director name address Use Supplementary paid Ad space suggested description unusual special events deviations AMA rules significant aspects meet Paid ads may helpful promoting funfly-type meets give directions flying site SUPPLEMENTARY ADS Larger ads can inserted Contest Calendar section paying fee ads accepted AMA-sanctioned events FEE Fees based ad size whether sponsor AMAchartered club AD POLICY SIZE 1/s-in wide either /4 1/2 2/4-in high full size ad appears Contest Calendar section PRICING 3/4$8 1/2$16 2/4$24 time ad run payable advance AMA-chartered clubs pay half rate AD PREPARATION advertiser must prepare Supplementary Ad Ads must full size see above Ads made up dark black white background will reproduce well recommended ad made heavy paper lightweight cardboard PLEASE DO NOT USE PHOTOGRAPHS ON ADS SUBMITTAL DEADLINE effort will made include Supplementary Ads received 14th month issue reaching readers approximately fourth week following month However cannot guaranteed ads published space-available basis normally two-month lead time required inserting Supplementary Ad same deadline will apply sanctioned events listings Questions about either Supplementary Ads regular Sanctioned Events listings should directed Debbie Brown AMAs Competition Department Send ads AMA HO Attention Competition Dept Renew 93 Built FlewlLehman Continued page 20 tempera paints later covered engine area clear dope should also mention tops bottoms fuselages midwing sheeted areas covered classroom tablet backings As project neared completion put several hours covering wings installing hardware radio engine maiden flight Pan Am took place evening April 16 Uncertain outcome made arrangements student present Joshua Smucker young man likely become pilot accompanied full throttle airliner sluggish fresh spring grass did take off fly nicely Unfortunately covering wing began loosen after two laps bring down remarked handy have throttle control cases like too dark repairs second flight Joshua went out again three evenings later time went extremely well Joshua outside circle throttle did takeoffs touch-and-goes slow approaches Communication hand signal week later April 23 students built Pan Am took turns being copilot enjoyed immensely After safety lesson person took turn throttle control about five laps before handing transmitter next pilot Later transferred engine radio Swissair second class its session Both classes preferred high-speed flight after deliberating beauty slow planned approaches gentle flybys persisted flying full tilt Throughout sessions however no matter what kids did throttle planes handled well enriching enjoy able venture kids made sure knew highlight school year Its too bad well probably never know what effect experience futures youngsters Wouldnt neat least came across article 20 30 years now wrote letter editor her/Lehmberg Continued page 27 same altitudethough lot closer little up stick will drop tail increase sink releasing stick will give nice touchdown Like Feather Merchants 72-inch version has wide stall tolerance stalled still mushes along instead pitching down can exploit tight turns glide using some up elevator strong rudder Oh yesI almost forgot Dont think ailerons Feather Merchant want everyone builds Feather Merchant have ball would like picturemaybe have questions problems like drop line 21337 Oak Park Lane Anderson CA 96007 An SASE would appreciated remember reading somewhere closing seems appropriate See ya Chicken House yhear /doBolt Continued page 30 Im going break off discussion point remainder fairly lengthy Save portion continuity reference study concluding part Part Two will cover process developing force arrangements model get ultimate flight performance Ill also talk about trimming methods continued lectricslKopski Continued page 76 fancy wiring harness incorporating double-pole double-throw center-off DPDTCO DP on-off-on switch associated wiring also requires battery made up two half-packs having same cell count cell type idea behind scheme use two packs connected series high power same two packs connected parallel cruise power connection accomplished servo-driven switch described above Thus in-flight switching between two available voltage levelsand off wellis readily accomplished Andjust theres no misunderstanding cells arrangement charged senes Ni-Cds never charged parallel wiring diagram gives details actual use plane motor prop configured cruise climb slightly voltage available paralleled half-packs half voltage higher voltage associated cells series results relatively aggressive climb capability needed center-off switch option allows charge conservation during thermaling Since much total flight time likely occur cruise power levels battery efficiency during periods considerable interest argued parallel-connected half-packs afford increased efficiency since half nominally operating half total motor current Cells tend display somewhat higher capacity lower drain rates conversely somewhat lower capacity higher currents February 1993 127 II
Edition: Model Aviation - 1993/02
Page Numbers: 28, 29, 30, 127
Mv ARTICLE Primer Aerodynamics September 1992 issue led us basic aero dynamic principles object new article simple Once understand functions aerodynamics next step learning apply produce type flight desire could free flight control line radio controleach its facets Applying basic aero dynamic laws can compared building house first lay down foundation can build variety configurations However solid foundation whatever erected thereon will ultimately fail objective explain balance performance factors need provide solid jumping-off point obtaining ultimate flight performance want will assume studied Primer Aerodynamics now understand air reacts various aircraft shapes pass through producing work process described basic force arrangements FAs fact establish flight envelope design Obviously science involved producing FA mysteries science will explained two-part article first step project determine type flight desired else will relate objective becomes para mount approach design duration model would far different speed model example Designing aircraft probably worlds greatest act compromise practically aspect design intertwined some other aspect Thus have continually making decisions important decision made favors overall objective have established No matter desired type flight youre aiming first step set wing its efficient angle attack angle incidence known always measured relative line offlight will rest settings Once angle established becomes sacred design other adjustments done keep wing flying predetermined angle question determining wings efficient angle good modelers since us have access engineering data needed accurately determine setting S flight surfaces generally referred airfoils respect models usually apply term shape revealed take cross section particular flight surface great airfoil cross sections vary greatly contours thus efficient angle attack produce liftand process drag Lift positive force interested drag negative undesirable Besides necessity over coming gravity greatest detriment aircraft efficiency drag Reducing drag productive simplest cheapest path improved performance Generally speaking aircrafts airfoils produce major portion total drag Thus becomes important choose correct airfoil shape desired flight objective example airfoil best suited duration model would have far different contour designed maximum speed amount drag produced two airfoils would also considerably different Airfoil contour shapes have under continual development since Wright brothers put first flat plate wind tunnel soon found curved surface vastly superior flat plate respects Airfoil science has become very sophisticated today have curvatures specially suited almost design objective gains study factor modelers point view have too very complex flight objectives needs can filled relatively few different types classes airfoil contours Basically call types undercambered flat-bottom semisymmetrical symmetrical all-important lifting ability well drag production various airfoil sections pretty well conforms sequence listing undercambered sections produce liftand greatest drag airfoils have point will operate maximum efficiency point occurs somewhere usable angle attack range extends zero lift stall angle varies speed flying respect angle attack point maximum efficiency occurs ratio lift drag greatest As airfoils flown increasing speeds amounts lift drag increase square increase speed 28 Model Aviation author designed simple electric-powered duration model uses complex force arrangement control power provide minimum sink rate glide Applying elementary aerodynamic concepts will help design improve model airplane U Hal deBolt aircraft level flight some point speed reached drag will increase faster lift So airfoils efficiency determined angle flown speed involved can summarized saying airfoil should flown its best angle attack within its speed range Violating either two factors will reduce aerodynamic efficiency various airfoil contours have greatly different reactions factor speed example symmetrical section will continue have excellent lift-to-drag LiD ratio far higher speeds will some other styles So expected flying speed model design important consideration other choosing airfoil undercambered airfoils produce greatest lift process also produce greatest drag efficient speed range also very shallow com parison high weight-to-power ratios early aircraft relegated slow speeds undercambered foils suited well Continuing development has created some relatively efficient undercambered foils suit speed range duration-style models quite well also useful anticipated weight model will high Another factor consider airfoils stable other styles consideration choosing airfoil style note its entry portion portion airfoil just aft leading edge relates line flight foil its optimum angle attack Some offer much cleaner entry others thus producing less drag equal lift flat-bottom styles developed aircraft got beyond crawling stage actually walking sudden designers recognized importance drag Generally speaking foils retain highlift characteristics obtained upper curvature undercambered foils get nice drag reduction replacing undercamber flat bottom Popularized famous Clark Y flatbottom foils have seen continuous wide spread usage stable undercambered fathers suit average model very well lower drag higher speed all-important Semisymmetrical shapes development flat-bottom style NACA Editors note NACA old National Advisory Council Aeronautics predecessor todays National Aeronautics Space Administration [NASA] scientists created nice drag reduction changing flat bottom convex curve upper curve class airfoil similar flat-bottom airfoil section similar amount lift can expected However factor profile drag considered [LWRI 07 ooI 015 IozI 076 iizl 185 Izs 292 5231 351 3651 35 30 zzl iisl RI 0 I47I08I0I09I0SI 101 I08114118120I19115I091 Ic CLARK Y Muse RadIus 15 0 125125151 75110152025304015016070809095 100 UPR 345 65 79 I96114 117 114 lios927452280 LWR345165090400300000000 LWR 0 120612861-3841447 l 42 1566 f-s 7 [562 [525 [461 jss I3osIz1sI1l7Io68 j0 16 STA0 125 25 575 1015202530 4050 6070809095 100 UPR0237327445255856687177431572566257458328181101016 LWR023732744525585668.7177437572566251458328181101016 February 1993 29 No RaUua 07 STAM 0 11251251 5 175 110 115120125130140150160170 801901 95 100 UPR 07 218 316 655 565 653 178 853 90 915 896 823 71 575 408 223 0I251251517511011520125301401501601701001901951100 UPR j 0 LII 30 45 55 1631 8700 110399 88 74 55 290 hose Radios 248 0 1251 251 575 101520253040506070809095 100 0 211 37115011 606 683 791 87 917 938 925 857 75 61 441 245 134 016 foils upper curvature remains same flat-bottom airfoil added convex curve bottom increases overall profile area section will result increase drag Usually compromise struck design airfoils upper curve reduced lowered compensate addition bottom given speed lift would less such airfoil flat bottom however reduced drag convex-bottom section would enable increase flying speed turn would result easy restoration lost lift So using convex-bottom airfoil can produce much lift flat-bottom section along increase flying speed modeling especially control line radio control semisymmetrical airfoil sections have proven very useful widely employed except specialized purposes angle attack net lift course zero Add positive angle line flight lift produced could change 125 ounces positive direction decrease 75 ounces other direction thereby providing net 50 ounces useful lift An amazing aspect using symmetrical foils small amount angle attack necessary produce enough lift model maintain level flight Incidence angles two degrees prove ample Obviously angle attack increased lift produced increases dramatically gradually tilt symmetrical section higher higher angles attack will reach angle rear lower curvature becomes parallel line flight As angle approached net aerodynamic force produced will direction angle attack bottom curvature will producing downward aerodynamic force reason important especially tapered wing sure airfoil section progressively changed towards wing tip tip-sections airfoil does have greater amount C/P travel assure wing designers often use tip airfoils have inherently less C/P travel does center foil maximum stability use symmetrical section tip ideal solution symmetrical wing airfoils used wing tip wing tip some stall less abruptly others situation calling use progressively different airfoils advance center wing tip bottom line symmetrical airfoils can produce excellent lift minimum drag having no C/P travel very stable What also good about latest Symmetrical airfoils should considered ultimate least theory maximum performance consid eration shape name implies such airfoil sections upper lower curves identical class airfoil provides greatest stability least drag can produce useful lift Symmetrical sections widely used aircraft applications other lifting surfaces minimum drag desired Examples usage can anything door handles struts ____ landing gear such stream lining purposes low speeds thickness ratio 31 length three times thickness produces least drag symmetrical section has characteristics different other styles Remember said Primer Aerodynamics forward curvature foil pushes air molecules closer together aft airfoils high point low-pressure area exists because molecules have time return original spacing curvature symmetrical section identical both top bottom Therefore zero angle attack foil producing aerodynamic forces equally both up down directions being true might ask can does symmetrical section produce useful lift What happens sections angle attack changed zero differential lift between top bottom created favoring direction angle increased An example could section developing 100 ounces aero dynamic force both directions zero 0 iupper surface -- -- 22 /ower surface e NACA 65-O/5 4 C NACA 652-015 example highly developed modern symmetrical airfoil sections has proven have good lift minimum drag great stability Lets consider another factor Airfoil shapes other symmetrical ones display what called center pressure lift movement angle attack incidence changes As angle attack increases center pressure C/P moves forward away its original position does occur symmetrical sections Since models center-of-gravity fixed obvious wings C/P moves forward its original position will create unstable less stable condition respect models pitch attitude hear wild tales about certain designs having tip stall problems Quite often problem can traced using airfoil outer part wingspan has center pressure moves forward soon er C/P center-section airfoil NACA/NASA research has conducted general category airfoils making highly developed performance objectives craft established should have decided upon style airfoil will use next step decide upon amount incidence will use particular airfoil would like quote ironclad law unfortunately fact best L/D angle style airfoil varieseven airfoils similar style aerodynamicist studying airfoil data would reveal desired point such data available modelers However have extensive experience draw upon simple solution average modeler research what has used designs similar designing thinking about decision need realize airfoils other symmetrical ones com mence lifting some angle incidence less zero Generally speaking can say high-lift sections commence lifting angle incidence low .40 others between value 00 Thus set high-lift section 30 angle attack common setting foil would actually flying angle 7 relative its angle zero lift So style airfoil definite consideration youre selecting angle incidence Continued page 127 30 Model Aviation Charles St info & directions call Dr Sandy Frank 817-599-7131 Sponsor WEATHERFORD AERO MODELING SOCIETY FL APR 3Fort Myers FL El 2nd Annual Swap Shop & Auction 900 am -400 pm 800 am Sellers Corkscrew Woodlands Esif 19 W off 75 Corkscrew Rd 1/4 M 75 Larger Hall Tables $10 Advance Reservations Definitely Recommended Admission $2 Paul Barfos 1002 Washington Ave Lehigh FL 33936 PH 813-368-0214 Sponsor SW FLORIDA AERO CLUB LISTING AD INFORMATION NORMAL LISTING AMA sanction issued event event will listed automatically Contest Calendar section listing will give date place name eventplus competition events flying site Contest Director name address Use Supplementary paid Ad space suggested description unusual special events deviations AMA rules significant aspects meet Paid ads may helpful promoting funfly-type meets give directions flying site SUPPLEMENTARY ADS Larger ads can inserted Contest Calendar section paying fee ads accepted AMA-sanctioned events FEE Fees based ad size whether sponsor AMAchartered club AD POLICY SIZE 1/s-in wide either /4 1/2 2/4-in high full size ad appears Contest Calendar section PRICING 3/4$8 1/2$16 2/4$24 time ad run payable advance AMA-chartered clubs pay half rate AD PREPARATION advertiser must prepare Supplementary Ad Ads must full size see above Ads made up dark black white background will reproduce well recommended ad made heavy paper lightweight cardboard PLEASE DO NOT USE PHOTOGRAPHS ON ADS SUBMITTAL DEADLINE effort will made include Supplementary Ads received 14th month issue reaching readers approximately fourth week following month However cannot guaranteed ads published space-available basis normally two-month lead time required inserting Supplementary Ad same deadline will apply sanctioned events listings Questions about either Supplementary Ads regular Sanctioned Events listings should directed Debbie Brown AMAs Competition Department Send ads AMA HO Attention Competition Dept Renew 93 Built FlewlLehman Continued page 20 tempera paints later covered engine area clear dope should also mention tops bottoms fuselages midwing sheeted areas covered classroom tablet backings As project neared completion put several hours covering wings installing hardware radio engine maiden flight Pan Am took place evening April 16 Uncertain outcome made arrangements student present Joshua Smucker young man likely become pilot accompanied full throttle airliner sluggish fresh spring grass did take off fly nicely Unfortunately covering wing began loosen after two laps bring down remarked handy have throttle control cases like too dark repairs second flight Joshua went out again three evenings later time went extremely well Joshua outside circle throttle did takeoffs touch-and-goes slow approaches Communication hand signal week later April 23 students built Pan Am took turns being copilot enjoyed immensely After safety lesson person took turn throttle control about five laps before handing transmitter next pilot Later transferred engine radio Swissair second class its session Both classes preferred high-speed flight after deliberating beauty slow planned approaches gentle flybys persisted flying full tilt Throughout sessions however no matter what kids did throttle planes handled well enriching enjoy able venture kids made sure knew highlight school year Its too bad well probably never know what effect experience futures youngsters Wouldnt neat least came across article 20 30 years now wrote letter editor her/Lehmberg Continued page 27 same altitudethough lot closer little up stick will drop tail increase sink releasing stick will give nice touchdown Like Feather Merchants 72-inch version has wide stall tolerance stalled still mushes along instead pitching down can exploit tight turns glide using some up elevator strong rudder Oh yesI almost forgot Dont think ailerons Feather Merchant want everyone builds Feather Merchant have ball would like picturemaybe have questions problems like drop line 21337 Oak Park Lane Anderson CA 96007 An SASE would appreciated remember reading somewhere closing seems appropriate See ya Chicken House yhear /doBolt Continued page 30 Im going break off discussion point remainder fairly lengthy Save portion continuity reference study concluding part Part Two will cover process developing force arrangements model get ultimate flight performance Ill also talk about trimming methods continued lectricslKopski Continued page 76 fancy wiring harness incorporating double-pole double-throw center-off DPDTCO DP on-off-on switch associated wiring also requires battery made up two half-packs having same cell count cell type idea behind scheme use two packs connected series high power same two packs connected parallel cruise power connection accomplished servo-driven switch described above Thus in-flight switching between two available voltage levelsand off wellis readily accomplished Andjust theres no misunderstanding cells arrangement charged senes Ni-Cds never charged parallel wiring diagram gives details actual use plane motor prop configured cruise climb slightly voltage available paralleled half-packs half voltage higher voltage associated cells series results relatively aggressive climb capability needed center-off switch option allows charge conservation during thermaling Since much total flight time likely occur cruise power levels battery efficiency during periods considerable interest argued parallel-connected half-packs afford increased efficiency since half nominally operating half total motor current Cells tend display somewhat higher capacity lower drain rates conversely somewhat lower capacity higher currents February 1993 127 II