High-Lift Devices: For Models

HA G Lennor HIGH-LIF, EVICES FORELS next time build sport model boost its realism incorporating highlift devices design Conclusion two-part article ONE OFTEN overlooked solution quest realistic sport flying incorporate flaps other high-lift devices model Part two-part article discussed theory application HLDs model airplanes concluding installment explains design construction actuation underappreciated devices high-lift devices have successfully used fall two broad categories 1 Trailing edge slotted flaps either internally externally hinged 2 Leading edge fixed slots NASA-developed leading edge droop As can see group comprises two subcategories What follows discussion four types high-lift devices Slotted flaps must designed slot narrows steadily lower upper surface flap deployed Also airflow slot should merge smoothly airflow around wing flap An appreciable length lipthe upper surface slotis advantage Ideally upper contours wing flap should form smooth curve Deployment limited 40 degrees greater extension results high added drag little increase lift Internally hinged slotted flap flap design pivoted internally eliminating underwing protections pivot supports recessed ends flap clean installation nose flap airfoil has rather blunt upper curvature leading edge Although reduces its efficiency flap easily actuated using linkage 80 Model Aviation Small RC models such Sparrowhawk benefit internally hinged slotted flaps 36-oz plane has awing area 174 sq ft wing loading 218 oz per sq ft Power load ing 2533 oz per cu engine displacement An OS Max 15 engine turns 7 x 6 pro peller Internally hinged flaps actuated Inboard end 7 7 Crane shown flaps deployed right-hand spoiler raised STOL model wing combines full-span internally hinged slotted flaps full-span leading edge fixed slots extremely high lifting capability 101 5-oz plane has wing area 446 sq ft wing loading 2275 oz per sq ft Power loading 2255 oz per cu engine displacement An OS Max 45 FSR provides motivation Crane its final landing approach moving about 20 mph flaps fully ex tended Note extreme nose-up angle produced leading edge fixed slots Figure 1 Internally hinged slotted flaps pivot supports recessed ends flap clean Installation As shown smaller models require 132-thlck skins 1116thlck ribs larger ones need l/1•4hick skins /32-thick ribs shown diagram Internally hinged slotted flaps excellent small RC models diagram shows construction small stress-skinned almost sparless wing Since type flap actuated its inboard end tends become twisted forces acting during deployment diagram upper lower skins ribs can withstand high degree torsion Smaller models such Sparrowhawk use A2-thick skins 1A6-thick ribs larger models such Harrier need A6-thick skins %2-thick ribs Externally hinged slotted flap Its essential hinge type flap minimum two points fully C 078 CSLOT LIP L8SPAR1/16-TRI002 C SM MODELS/32 BALSA ASHROUDR 16 BALSA RIBSPIVOT / \40 3/32 PLY CONSTRUCTION 1/16 BALSA SHEETI/B BALSA _-BALSA40 END RIB BALL-JOINT-WING8013/52 I/BxI/4/ /PLY A/ 15/16'PLAIN DRSlOTTEDPIVOT RIB I/B ODSPLIT MASSBALL-JOINT TUBEFLAP SERVOIS/ISIS/IS 1/322-56 BOLT DIHEDRALro VIEWSIDE 3/32 MW3/32 COLLARS END VIEW BUSH ALL PIVOT POINTS WITH I/B BRASS TUBE FUSELAGE NOTE FOR HIGH WING INVERT SERVO B LINKAGE ACTUATION __________________ SUPPORTS FLAP LEADING EDGE XIII I/B BALSA END RIB /jIiiJ1IIII/32 PLY RIB 51%IIII/2 BALSA RIB L II INTERNALLY HINGED SLOTTED FLAP- DESIGN-CONSTRUCTION S ACTUATION WING LEADING EDGE 1/16 BALSA3/B 3/IS BALSA ________ CSPARS1/4 a/S 0015I SLOTBALSA STROKE-I/B DIA BRASS 1/4 SOf I-I1S/1S 1/16TUBE BUSHING SHROUD00175CB A-- SA3/32 PlY PIVOT-40- PER FLAP SLOT--3/3/BALSAVS WEBA RIB BWEB''40 DESIGNaI/23/22MW/ PIVOT SHEATH ANCI-OR-OOSCCABLSHEATH/ 0265 CANCHORI/IS PLY W/h~ PLT CONSTRUCTION3/32 BALSA1/16 FAIRINGFLAP PIVOT RIB CORE SECTION A 2-56 COUPLERSHEATH SULLIVAN SOBANCHOR I/IS PLY FLES CABLE FLAP 4 PKR FLAP SERVO BALSA RIB'CYB CABLE-3/32 BALSA CLEVISRIB FLAP SUPPORT RIB LAP LEADING EDGEI_____________________________________________________ PIVOT DIA IMUSIC WIRE FLAP PIVOT RIB FUSE LADE SIDE .HDRN RIB PIVOT 3/32 1 DIA M WUUI 51 ~FLAP PIVOT RIB I/IS FLAP FLAP HORN RIB EXTENDED ACTUATION EXTERNALLY HINGED SLOTTED FLAP- DESIGN-CONSTRUCTION & ACThATION Figure 2 Externally hinged slotted flaps recommended larger models end used authors Harrier actuated flexible cable cable sheath well supported its ends securely anchored prevent buckling under load extended flaps increase wing chordand consequently wing area small amount better flap airfoil section attainable externally hinged slotted flaps results higher value CL max plywood flap supports pivot ribs permit secure attachment wing structure flaps can lowered speed drag produced external hinges minimized the____________________________________________ streamlined cross section type flap recommended larger models Continued page 195_____________________ Figure 3 Two types high-lift devices can ____________________ Incorporated wing leading edge LE NASA-designed droop top leading edge slot bottom leading edge droop decreases likelihood lowaltitude stall Fixed LE slots promote effec ______________________________ tive aileron response high angles attack August 1991 81 DESIGN OF LEADING EDGE SLOT WING 6 /STROKE / WING TRAILING DROOPED LEADING EDGE DESIGN OF DROOPED LEADING EDGE D24COO2CCONSTRUCTiON High-Lift/Lennon Continued page 81 used Harrier wing Probably simplest way actuate flaps flexible cable Nyrod shown diagram sort belicrank-and-rod arrangement frequently used operate ailerons would also job using cables sure anchor sheath ends securely support sheath its passage through rib keeps sheath buckling under load Recommended dimensions deflection maximum lift coefficient values both types flaps tabulated below FigPercent ofAngle ofCL NoTypeWing Chord DeflectionValues 17 SlottedInternal25%400220 Hinge 18 SlottedExternal25%400240 Hinge Leading edge fixed slots fixed leading edge slot provides additional incremental C[ max 04 stall angle eight degrees higher Thus wing both full-span leading edge fixed slots full-span internally hinged slotted flaps would generate CL total 220 plus 040 260 Leading edge slots promote effective aileron response high angles attack because acceleration air passing location forward ailerons Figure 3 shows design suggested construction leading edge fixed slots using balsa strips sanded shape Note conical shape slot Used full span Crane slots benefited model greatly see photo hand-tested before leaving factoiy best-in-the e J Pm Dax THE wdDx CO#4NECflON oryso doftynir local hobby shop cat FREE GloBee FlyOr St IndIanapolIs IN 48231 Phoee3174394579 FAX 317439-8928 increase wing area produced flaps already has doneThe unflapped areas will generate CL max basic wing airfoil leading edge slots add lift increment 04 basic section values Add 02 drooped leading edge flapped areas will develop CL max given table above flaps fully lowered Dont adjust figures increase wing area produced flaps already has doneThe unflapped areas will C generate L ma basic wing airfoil leading edge slots add lift increment 04 basic section values Add 02 drooped leading edge Using Harrier wing example Flapped wing area 356 sq x CLmax 2 40 Unflapped area drooped leading edge 220 sq inxCLmax 1202308 Total area 576 sq Total CL max 4 CL 1162 202 Because increased lift drag induce increase nose-down negative pitching moment types flaps cause marked change trim deployed recommended elevators comprising least 40% horizontal tail plane area installed counter pitching action permit flaring model touches down ground effect Try slotted flaps next model Theyll add realism performance appearance Youll have better-looking craft gives fun variety airEl Pushy Cat/Towers Continued page 95 unusually good view racecourse Although Texas Gem standard 100-hp 135 hp racing rpm Continued page 196 Leading edge droop NASA development recently introduced fullscale lightplanes help prevent often fatal low-altitude stalls As Figure 3 shows droop occupies outboard 38% wing leading edge sharp corners between drooped undrooped portions produce chordwise vortex effectively separates inner outer panels higher angles attack drooped portion behaves like very low aspect ratio wing substantially increasing both stall angle effectiveness ailerons results additional increase CL 02 10-degree-higher angle attack flying three models incorporating drooped leading edge found craft sometimes forced spin after two turns spin changed fast spiral dive ended instantly neutralized controls maximwn coefficient lift combination high-lift devices can determined few easy calculations flapped areas will develop CL max given table above flaps fully lowered Dont adjust figures Add realism ScaleWeightPrice A1/84oz$20 B1/66oz$25 C1/57112oz$25 01/5l2oz$25 E1/423oz$30 Scale precision-molded resin radial engines Front half intended cowled applications Easily detailed about 90 mm see photos C&D aluminum tubing scrap wire spray paint Looks great adds nose weight too fitting purposes up 20% diameter may trimmed affecting overall look Check Money Order Visa Master Card Frank Tiane Enierprises S&H included15300 ESTANCIA LANE WEST PALM BEACH FL 33414 TEL 407-795-6600 FAX 407-795-6677 August 1991 195 Diameter Cylinders 53/49 71/49 83/45 83/49 111/49 WHY SHOULD BUY GLOBEE GLOW