S fine Nordic A/2 its best light conditions thermal activity weak non-existent Jim Walters Photos Jim Land Mark Vercam men EVERY SERIOUS A/2 flier knows needs glider box can counted early morning later afternoon rounds thermal activity light non-existent Sno Bird may magic 3-mm model will deliver extra performance under light conditions need Still-air glide tests Sno-Bird clearly demonstrated model significantly better previous A/2 gliders Built winter 1974-75 up coming World Championships Plovdiv model tested under clear winter skies snow ground air temperature around 400F still death Sno-Bird would consistently average 70 sec floated off line 64 ft altitude line length plus arm reach same time next best model original sheeted version averaged respectable 65 sec new design proven itself better good margin model represents latest still-air version current Bird series features rather high aspect ratio 1731 simplified sheeted wing body construc tion circle tow/catapult tow hook wing section slightly modified Benedek D7457-d/2 section gained popularity early 1960s namely Norm Ingersolls Harbinger still quite competitive contemporary sections Certainly advantage section its depth permits maxi mum separation main spar chords resulting wing high strength-toweight ratio stab section close copy stab sections Ectenkovs EGl 172 Elton Drews Lively Lady earlier version built 1969 suc cessfully used qualify 70 72 74 team-selection finals 74 Taft used first two rounds its still-air performance paid off team position Construction Before beginning actual construction necessary make couple building aids cambered wing board rib templates Building conventional undercambered wing cambered board possible building sheeted wing especially heavy trailing edge would next impossible Also cambered board along proper planform shape LE somewhat straight TE swept forward give desired amount tip wash-out about 3/16 boards clear vertical grain cedar redwood 1 X 6 1 X 8 stock about 48 long board should flat pos sible measurable twist Trace 36 Model Aviation Top Widely respected Nordic A/2 circles Jim Walters displays Sno-Bird has 173-to-i aspect ratio features circle-tow catapult tow hook Above An accurate wing construction board imperativemade using table saw cut grooves matching lower surface remaining material right removed using block plane light sanding lower camber main rib onto end board using table saw cut grooves blade width full length approximately 3/16 intervals just match camber line see photo remaining material removed using block plane finally sanding block see photo board will take 2 4 hours build easily makes up ease building wooden strip approxi mately crewed forward edge board used indexing rib locations ensures straight lead ing edge other templates wing stab rib patterns made Y6 plywood per mit fast accurate slicing ribs par ticularly wing ribs feathered trailing edge see photo use wing rib pattern cut lower camber first piece balsa see photo push other end template against balsa piece cut upper camber see photo tapered tip ribs after cut ting lower camber rotate tem plate about leading edge obtain proper rib length shown sketch plan As can see airfoil section near tip deviates true section still retains adequate shape Wing Cut out wing rib index strips top border plan attach wooden strip trailing edge board using paper cement sparingly must remove reverse later build other wing Add wax paper prevent parts sticking board Trim lower inboard sheet exactly 5 X 26 long trim upper sheet yet After adding top sheet slight excess width allows neatly trim away area glue oozes out leaving neat trailing edge exactly right chord Pin lower sheet board aligning rib index strips glue 3/16 sq spruce leading edge may pre-shaped lower spar spar doubler using couple pre-cut wing ribs locating guide Use slightly thinned aliphatic glue joints except area around wing root tubing moderate curing epoxy used Next using paper rib index strips guide glue ribs position widening spar slots necessary plywood root rib edral rib must slanted match dihedral angles shown plan Add aluminum tubes top spars 1/32 verti cal grain balsa web between spars After completely dry lightly sand wing remove rough spots around spars shape leading edge sand lower sheet trailing edge lightly top sheet will fit smoothly Now comes easy part installation top sheet pins Cut top sheets slightly oversize sure check sheet width upper curvature Prepare tools ahead time Youll need approximately 150 size #16 #18 #32 rubberbands few pins thinned aliphatic glue Position lower wing half board using couple pins stuck through end ribs keep shifting Lightly apply glue mating surfaces gently position top sheet using couple pins end Now begin wrap bands clear around wing board see photo begin ning center working towards ends first fairly wide spacing 1- 1 adding bands between until en tire wing covered bands spaced approximately t bands apply light pressure ensures smooth accurate wing shape million pin holes top surface Re peat tip section allow dry overnight before removing board possible allow wing sections several days curing harden glue makes sanding leading edge lot easier trim trailing edge until wing near completion allows adjust chord slightly approach maximum permissible wing area easily trimmed using table saw Sanding October1976 37 Top Template insures accurate duplication ot ribs feathered edgesalso used tapered ribs Above Cut lower camber first up per camber key accurate ribs Right Template being used cut upper rib camber Below Closely spaced rubberbands apply pressure gluing upper sheet un sightly pinholes Right Table saw utilized heat-sink molding lead nose weight Sno-Bird leading-edge radius before joining panels permits easy inspection proper shape Attaching tip section cen ter section similar building handlaunch glider wing Just sand proper dihedral angles section double glue using moderate cure epoxy ali phatic Ambroid type glue Note bothersome ply wood dihedral bracesthis type wing construction just doesnt need Sand upper lower surfaces lightly 400-600 grit paper using care oversand Add root plywood rib trim excess aluminum tubing Add soft balsa tips trailing edge stiffeners Give three coats 50-50 dope plasticizer added use 3-4 drops di-butlyl-phthlate per ounce Tissue used adds un necessary weight tends produce warps Sanding sealer may applied lower surface believe natural roughness balsa grain upper surface aids turbulating wing Add trim numbers thread turbulator What appears aerodynamic fences external extensions wing ribs used strengthen trailing edge thread turbulator just aft IE does show photo TRIM EXCESSTOP AFTER INSTAuINO BUTT RIB 332DATUBlNG 1/810 AL TUaNG ii ii ii ii II m 1ThLTWTWGC __0 _____1 EDGEL WTF/G LOTHB 1/16 PLY-23/32 BALSATTRAILNO EDGE STIF RiDDER LSVER 032MW lAD NOSE WEIGHT 4 2 ____ 3/B PLY CORE 3/32 PLYFILL HOLE 1/16 PLj 3 REOD / D SEN 0 D2DW N DO SN OW NE~MER CU OU 3/32DAI-IOE RJWER EVER ON RT SOF1/B DIA HOLE 3/32 PLY 2 REOD 3/B LEAD NOSE1/4 DIA CLEAR WEIGHT 3/B PLY CORE 1/4 x 3/B MAPLE OR OAK HOOK SUPPORTS FOR COMPETE DETAILS OF TOWHOOK SEE ARTICLE IN JAN 1974 FLYING MODELS BY BOB HATSCHEK TOWHOOBCASTING KIT MAY BEOBTANED FROM JIM CROCKET F 1442 N FRUIT ST FRESMO CA 93726 Above Rudder stop stab stroker pulled Below rudder stop stroker shown forward allowing rudder stab deflect released picture thus pushing rudder a circletow position tight turn glide turn position wing leading edge Total weight wing should 160-180 grams depend ing density balsa sheeting Stabilizer Using same procedure cutting out wing tip ribs cut stab ribs false ribs fairly hard 8-l0# 1/32 medium 6-8 1/16 1/20 balsa Make series shims 1/32 sheet pack up lower spar forward edge trailing edge main tain proper airfoil shape Use fairly hard balsa trailing edge leading edge spars upper spar tapered 1/16 X 1/s Y6 sq Lay down notched trailing edge bottom spar add ribs add leading edge false ribs gussets thick tip rib Use ali phatic glue sparingly assembly Shape leading edge sand structure us ing 400 grit paper Give structure coat clear dope cover using superfine lightweight Japanese tissue Apply 3 coats 50-50 dope plasticizer Stab weight should 7-9 grams Fuselage Begin fuselage cutting core / 3-ply commercial lum beryard plywood fir okay sides 3/32 aircraft plywood Size cut outs core D/T timer type towhook types circle towhook ideas available present possess some advantages can readily adapted Sno-Bird Hatschek towhook used origi nal model permits low body pro file Using plywood wing root rib template match drill plywood side wing wires Now mark hole loca tions core drill two 14 diameter clearance holes through core eter epoxy access holes through edge core drill other 3/32 side yet make nose weight cut shape scrap i/i plywood melt scraps lead sinkers etc tomato can heated over Coleman stove Place plywood form over flat metal surface such table saw top pour lead exactly ply thickness see photo metal top serves heat-sink cool lead quickly weight should come out tween 90-100 grams Notch groove WINGRIBINDEXSTRIPS CUTFROM PLAN & ATTACH TOWING BOARD TURBULATOR CARPET THD SRRIJCE 3/32 SO SPRUCEluBE 3/323/16 SO SPRUCE1/Bx1/4 HARD BALSA TAPER TO 1/B SPRUCE & ROT SOFT BALSA -N ~ ~BLCEK BY LIlL3/3250BATAPE TOll 171 ILuVV3/16 WASHOUT BOTH TIPS l/32S1- BALSA TOP& ROT IFFENERS END HERE 1/B RIB TILT APPROX W FOR DIHED 1/32 ID BRASS TUBE STAB TILT FOR RT GLIDE 3/32 PLYZO32 MW XY1 TAB STROKER RUD R MWIRETOP VIEW HI D25 MW 02D BRASS lPLLlETE 3/32x1/2 TAPERTOl/iB, 3/B 1/B DIA1/iBDIA 1/B DIAHOLE020 BRASS 060 NUT 3/32 DIA II RUDDER TOBSION1/32 GA0-JBEND FROM A5 DT ANGLE SPRING U1MWHOLESOLDER3/32 GA CCWIPRD2D WIREPPRDRILL 1/32 HOLE P015 WIRES ~IjRTS1/16 ID RBASSSPRING FIBERGLASS TAILBOOM 35LGTUBINGRUDDER STOP-HD BALSAl/32IDAL TUNING 50 DI HIDAPPROX 20RU FW TUBE-DRILL FOR LT NE WT 3 RUDDER STOP EPOXY GROMMET LATE WITH 6-32 SCREWS & NUTSTO INSIDE FiR 060 SOREWOT LINE OBONUTSOLUER1/32 WIRE1/16,1/B K ONLY TO WIRE1/16 PLYSPRLCE1JFT 1/B SH --30-DDLB DACRON LINE STR TOW .TOWHOOKSH WING RIB PATTERN 1/16 PLYGLIDE RUR STOP STAB STROKERCTSEE SE AlL ABDEE OBOSCREW FORLAMINATE 2501/320/B & RUDDERSTFFENERTIP RIBSTAB ADJUSTHL BALSA ES RECOFALSEPOXY NUT TO15 LB MOHOFIL NYLON TO INSIDE OP BOOM TOWLINE PULL PIN 1/iBMED BALSA 3BREODSTAB RIB-CTR-3/32OBOSCREW& WASHER TO 1/B MED BALSA OTHERS 1/320R1/20l/Lj~ADJUST RUDDER STOP EPOXY TO FIN ADJUSTMENTS ESTAB RIB-TIPWING- 9l/~ STAB 4/2 RH SIDE025 MWRTGLIDETU 020ALSTAB STOPHINGE 1/16 PLY 2 REOD REOD STAB PLATFORM 1/16 PLY SNO-BIRD FlA NOR DIG GLIDER SPAN 89 WINGAREA 456sq 0 1 2 3 4 56LENGTH 43 STAB AREA 6Bsq ALL GMENSIONS IN INCHESDes9nad Drn JIM WALTERS October1976 39 Sno- Bird ply sides match fiberglass rod Using moderate cure epoxy assemble sides core hook supports tail boom using care align tailboom dry round edges except wing mates fuselage Now drill wire holes through other plywood side using holes first side guide Bend two wing wires install holes checking see wires come out parallel slight wash-in LE up right wing wash-in necessary keep right wing dipping during cata pult launches also tends keep model spinning turbulent air wires centered fuselage glued install wings rotate wires required slightly aft match high angle wing neglect wing will fit flush against fuselage sides youre satisfied fit-up carefully remove wings out disturbing wires apply epoxy through two access holes core Build fin soft sheet rudder i/s sheet Groove base fin match fiberglass rod add short piece aluminum tubing 1/32 ID after shaping fin proper airfoil shape epoxy tailboom has preroughened sand paper improve adhesion ad hesive Epoxy 3/32 plywood stab platform short piece fiberglass tube Com plete rudder circle-tow hardware shown plans differ slightly original Hatschek hardware pro duce same action Consult Bob Hats cheks article Flying Models January 1974 operation towhook Remember moderate pull should move rudder neutral relaxed torsion spring should just strong enough drive rudder against ex treme rudder stop Too stiff torsion spring will result too high towline pull straight tow model will straighten out circle proper time will go next unwanted cir cle hopefully accomplished trial error hopefully too much error stab stroker idea Paul Crow ley added original model tends prevent spin-in during circle-tow mode See photos raises trailing continued page 93 40 Model Aviation Left Normal towline pressure pulls rudder neutral position straight tow Below position two-way rudder stop allows rudder deflect circle turn launch spring pushes rudder glide-turn posi tion Development goes back 69 S no-Bird/Walters continued page 40 edge about 1/16 compensate tighter turn during circle-tow mode rudder offset actu ated same line pulls rudder stop forward consequently released moment launch simple de vice add however original model did possess spin-in tendencies towline use 50-lb-test lowstretch nylon monofilament line dia has about 3 ft stretch 2 kilogram load tow use reel using small plastic ring better yet just loop end loop around small finger left hand store line FAI Supply reel works nicely opening up coils line guide filing small notch 1/32 wide deep edge spool hook loop over prior winding Testing youre satisfied operation hook spring re lease set 5-6 lbs ready first test flight Fly test flights rela tively calm air preferably over 7-8 mph Hand glide adjust rudder stop stab adjustment screw slight right turn no apparent stall Fly first flight full towline length D/T set 20-30 sec jatch set will permit float model off line check glide its quite right will D/T come safely down After several flights floating model off line having made necessary stab rudder adjustments produce straight tow flat glide circling ap proximately once 30-50 sec ready big moment first circle tow Just set latch tow model before except instead floating off let circle line attached Once just begins come around wind begin tow straight bring model overhead let circle again prepared run downwind fast keep line slightly slack during downwind circle line tightens up model may pulled ground Most fliers find out hard way model will come out turn want too much spring force rudder torsion spring towhook may too far ward Learning circle tow real ex perience fliers first try find requires lot fancy footwork Most us have towed model ground time another try testing over grass possible youre ready launch pull down sharply release latch keep pressure deflect rudder zoom position release model should bank slightly right released gain altitude model turns too steep begins spiral decrease zoom rudder offset stalls severely increase rudder offset As previously mentioned tow reel hold several feet slack line releasing let slack go two-ring slips off easily youre fly ing strong wind its necessary keep 8-10 ft slack line available let out quickly keep load exceeding un latch force launch some slack necessary let tow-ring slide free conclusion remember win re quires possessing good model important have winning attitude essentially means committing some error should have control over commonly known shooting oneself foot winner person generally flies model its full potential time testing complete youre satisfied models per formance begin practice Fly flight purpose checking likely conditions keeping records flights work towards eliminating bad flight flight should flown though victory depended end result does October1976 93
Edition: Model Aviation - 1976/10
Page Numbers: 36, 37, 38, 39, 40, 93
S fine Nordic A/2 its best light conditions thermal activity weak non-existent Jim Walters Photos Jim Land Mark Vercam men EVERY SERIOUS A/2 flier knows needs glider box can counted early morning later afternoon rounds thermal activity light non-existent Sno Bird may magic 3-mm model will deliver extra performance under light conditions need Still-air glide tests Sno-Bird clearly demonstrated model significantly better previous A/2 gliders Built winter 1974-75 up coming World Championships Plovdiv model tested under clear winter skies snow ground air temperature around 400F still death Sno-Bird would consistently average 70 sec floated off line 64 ft altitude line length plus arm reach same time next best model original sheeted version averaged respectable 65 sec new design proven itself better good margin model represents latest still-air version current Bird series features rather high aspect ratio 1731 simplified sheeted wing body construc tion circle tow/catapult tow hook wing section slightly modified Benedek D7457-d/2 section gained popularity early 1960s namely Norm Ingersolls Harbinger still quite competitive contemporary sections Certainly advantage section its depth permits maxi mum separation main spar chords resulting wing high strength-toweight ratio stab section close copy stab sections Ectenkovs EGl 172 Elton Drews Lively Lady earlier version built 1969 suc cessfully used qualify 70 72 74 team-selection finals 74 Taft used first two rounds its still-air performance paid off team position Construction Before beginning actual construction necessary make couple building aids cambered wing board rib templates Building conventional undercambered wing cambered board possible building sheeted wing especially heavy trailing edge would next impossible Also cambered board along proper planform shape LE somewhat straight TE swept forward give desired amount tip wash-out about 3/16 boards clear vertical grain cedar redwood 1 X 6 1 X 8 stock about 48 long board should flat pos sible measurable twist Trace 36 Model Aviation Top Widely respected Nordic A/2 circles Jim Walters displays Sno-Bird has 173-to-i aspect ratio features circle-tow catapult tow hook Above An accurate wing construction board imperativemade using table saw cut grooves matching lower surface remaining material right removed using block plane light sanding lower camber main rib onto end board using table saw cut grooves blade width full length approximately 3/16 intervals just match camber line see photo remaining material removed using block plane finally sanding block see photo board will take 2 4 hours build easily makes up ease building wooden strip approxi mately crewed forward edge board used indexing rib locations ensures straight lead ing edge other templates wing stab rib patterns made Y6 plywood per mit fast accurate slicing ribs par ticularly wing ribs feathered trailing edge see photo use wing rib pattern cut lower camber first piece balsa see photo push other end template against balsa piece cut upper camber see photo tapered tip ribs after cut ting lower camber rotate tem plate about leading edge obtain proper rib length shown sketch plan As can see airfoil section near tip deviates true section still retains adequate shape Wing Cut out wing rib index strips top border plan attach wooden strip trailing edge board using paper cement sparingly must remove reverse later build other wing Add wax paper prevent parts sticking board Trim lower inboard sheet exactly 5 X 26 long trim upper sheet yet After adding top sheet slight excess width allows neatly trim away area glue oozes out leaving neat trailing edge exactly right chord Pin lower sheet board aligning rib index strips glue 3/16 sq spruce leading edge may pre-shaped lower spar spar doubler using couple pre-cut wing ribs locating guide Use slightly thinned aliphatic glue joints except area around wing root tubing moderate curing epoxy used Next using paper rib index strips guide glue ribs position widening spar slots necessary plywood root rib edral rib must slanted match dihedral angles shown plan Add aluminum tubes top spars 1/32 verti cal grain balsa web between spars After completely dry lightly sand wing remove rough spots around spars shape leading edge sand lower sheet trailing edge lightly top sheet will fit smoothly Now comes easy part installation top sheet pins Cut top sheets slightly oversize sure check sheet width upper curvature Prepare tools ahead time Youll need approximately 150 size #16 #18 #32 rubberbands few pins thinned aliphatic glue Position lower wing half board using couple pins stuck through end ribs keep shifting Lightly apply glue mating surfaces gently position top sheet using couple pins end Now begin wrap bands clear around wing board see photo begin ning center working towards ends first fairly wide spacing 1- 1 adding bands between until en tire wing covered bands spaced approximately t bands apply light pressure ensures smooth accurate wing shape million pin holes top surface Re peat tip section allow dry overnight before removing board possible allow wing sections several days curing harden glue makes sanding leading edge lot easier trim trailing edge until wing near completion allows adjust chord slightly approach maximum permissible wing area easily trimmed using table saw Sanding October1976 37 Top Template insures accurate duplication ot ribs feathered edgesalso used tapered ribs Above Cut lower camber first up per camber key accurate ribs Right Template being used cut upper rib camber Below Closely spaced rubberbands apply pressure gluing upper sheet un sightly pinholes Right Table saw utilized heat-sink molding lead nose weight Sno-Bird leading-edge radius before joining panels permits easy inspection proper shape Attaching tip section cen ter section similar building handlaunch glider wing Just sand proper dihedral angles section double glue using moderate cure epoxy ali phatic Ambroid type glue Note bothersome ply wood dihedral bracesthis type wing construction just doesnt need Sand upper lower surfaces lightly 400-600 grit paper using care oversand Add root plywood rib trim excess aluminum tubing Add soft balsa tips trailing edge stiffeners Give three coats 50-50 dope plasticizer added use 3-4 drops di-butlyl-phthlate per ounce Tissue used adds un necessary weight tends produce warps Sanding sealer may applied lower surface believe natural roughness balsa grain upper surface aids turbulating wing Add trim numbers thread turbulator What appears aerodynamic fences external extensions wing ribs used strengthen trailing edge thread turbulator just aft IE does show photo TRIM EXCESSTOP AFTER INSTAuINO BUTT RIB 332DATUBlNG 1/810 AL TUaNG ii ii ii ii II m 1ThLTWTWGC __0 _____1 EDGEL WTF/G LOTHB 1/16 PLY-23/32 BALSATTRAILNO EDGE STIF RiDDER LSVER 032MW lAD NOSE WEIGHT 4 2 ____ 3/B PLY CORE 3/32 PLYFILL HOLE 1/16 PLj 3 REOD / D SEN 0 D2DW N DO SN OW NE~MER CU OU 3/32DAI-IOE RJWER EVER ON RT SOF1/B DIA HOLE 3/32 PLY 2 REOD 3/B LEAD NOSE1/4 DIA CLEAR WEIGHT 3/B PLY CORE 1/4 x 3/B MAPLE OR OAK HOOK SUPPORTS FOR COMPETE DETAILS OF TOWHOOK SEE ARTICLE IN JAN 1974 FLYING MODELS BY BOB HATSCHEK TOWHOOBCASTING KIT MAY BEOBTANED FROM JIM CROCKET F 1442 N FRUIT ST FRESMO CA 93726 Above Rudder stop stab stroker pulled Below rudder stop stroker shown forward allowing rudder stab deflect released picture thus pushing rudder a circletow position tight turn glide turn position wing leading edge Total weight wing should 160-180 grams depend ing density balsa sheeting Stabilizer Using same procedure cutting out wing tip ribs cut stab ribs false ribs fairly hard 8-l0# 1/32 medium 6-8 1/16 1/20 balsa Make series shims 1/32 sheet pack up lower spar forward edge trailing edge main tain proper airfoil shape Use fairly hard balsa trailing edge leading edge spars upper spar tapered 1/16 X 1/s Y6 sq Lay down notched trailing edge bottom spar add ribs add leading edge false ribs gussets thick tip rib Use ali phatic glue sparingly assembly Shape leading edge sand structure us ing 400 grit paper Give structure coat clear dope cover using superfine lightweight Japanese tissue Apply 3 coats 50-50 dope plasticizer Stab weight should 7-9 grams Fuselage Begin fuselage cutting core / 3-ply commercial lum beryard plywood fir okay sides 3/32 aircraft plywood Size cut outs core D/T timer type towhook types circle towhook ideas available present possess some advantages can readily adapted Sno-Bird Hatschek towhook used origi nal model permits low body pro file Using plywood wing root rib template match drill plywood side wing wires Now mark hole loca tions core drill two 14 diameter clearance holes through core eter epoxy access holes through edge core drill other 3/32 side yet make nose weight cut shape scrap i/i plywood melt scraps lead sinkers etc tomato can heated over Coleman stove Place plywood form over flat metal surface such table saw top pour lead exactly ply thickness see photo metal top serves heat-sink cool lead quickly weight should come out tween 90-100 grams Notch groove WINGRIBINDEXSTRIPS CUTFROM PLAN & ATTACH TOWING BOARD TURBULATOR CARPET THD SRRIJCE 3/32 SO SPRUCEluBE 3/323/16 SO SPRUCE1/Bx1/4 HARD BALSA TAPER TO 1/B SPRUCE & ROT SOFT BALSA -N ~ ~BLCEK BY LIlL3/3250BATAPE TOll 171 ILuVV3/16 WASHOUT BOTH TIPS l/32S1- BALSA TOP& ROT IFFENERS END HERE 1/B RIB TILT APPROX W FOR DIHED 1/32 ID BRASS TUBE STAB TILT FOR RT GLIDE 3/32 PLYZO32 MW XY1 TAB STROKER RUD R MWIRETOP VIEW HI D25 MW 02D BRASS lPLLlETE 3/32x1/2 TAPERTOl/iB, 3/B 1/B DIA1/iBDIA 1/B DIAHOLE020 BRASS 060 NUT 3/32 DIA II RUDDER TOBSION1/32 GA0-JBEND FROM A5 DT ANGLE SPRING U1MWHOLESOLDER3/32 GA CCWIPRD2D WIREPPRDRILL 1/32 HOLE P015 WIRES ~IjRTS1/16 ID RBASSSPRING FIBERGLASS TAILBOOM 35LGTUBINGRUDDER STOP-HD BALSAl/32IDAL TUNING 50 DI HIDAPPROX 20RU FW TUBE-DRILL FOR LT NE WT 3 RUDDER STOP EPOXY GROMMET LATE WITH 6-32 SCREWS & NUTSTO INSIDE FiR 060 SOREWOT LINE OBONUTSOLUER1/32 WIRE1/16,1/B K ONLY TO WIRE1/16 PLYSPRLCE1JFT 1/B SH --30-DDLB DACRON LINE STR TOW .TOWHOOKSH WING RIB PATTERN 1/16 PLYGLIDE RUR STOP STAB STROKERCTSEE SE AlL ABDEE OBOSCREW FORLAMINATE 2501/320/B & RUDDERSTFFENERTIP RIBSTAB ADJUSTHL BALSA ES RECOFALSEPOXY NUT TO15 LB MOHOFIL NYLON TO INSIDE OP BOOM TOWLINE PULL PIN 1/iBMED BALSA 3BREODSTAB RIB-CTR-3/32OBOSCREW& WASHER TO 1/B MED BALSA OTHERS 1/320R1/20l/Lj~ADJUST RUDDER STOP EPOXY TO FIN ADJUSTMENTS ESTAB RIB-TIPWING- 9l/~ STAB 4/2 RH SIDE025 MWRTGLIDETU 020ALSTAB STOPHINGE 1/16 PLY 2 REOD REOD STAB PLATFORM 1/16 PLY SNO-BIRD FlA NOR DIG GLIDER SPAN 89 WINGAREA 456sq 0 1 2 3 4 56LENGTH 43 STAB AREA 6Bsq ALL GMENSIONS IN INCHESDes9nad Drn JIM WALTERS October1976 39 Sno- Bird ply sides match fiberglass rod Using moderate cure epoxy assemble sides core hook supports tail boom using care align tailboom dry round edges except wing mates fuselage Now drill wire holes through other plywood side using holes first side guide Bend two wing wires install holes checking see wires come out parallel slight wash-in LE up right wing wash-in necessary keep right wing dipping during cata pult launches also tends keep model spinning turbulent air wires centered fuselage glued install wings rotate wires required slightly aft match high angle wing neglect wing will fit flush against fuselage sides youre satisfied fit-up carefully remove wings out disturbing wires apply epoxy through two access holes core Build fin soft sheet rudder i/s sheet Groove base fin match fiberglass rod add short piece aluminum tubing 1/32 ID after shaping fin proper airfoil shape epoxy tailboom has preroughened sand paper improve adhesion ad hesive Epoxy 3/32 plywood stab platform short piece fiberglass tube Com plete rudder circle-tow hardware shown plans differ slightly original Hatschek hardware pro duce same action Consult Bob Hats cheks article Flying Models January 1974 operation towhook Remember moderate pull should move rudder neutral relaxed torsion spring should just strong enough drive rudder against ex treme rudder stop Too stiff torsion spring will result too high towline pull straight tow model will straighten out circle proper time will go next unwanted cir cle hopefully accomplished trial error hopefully too much error stab stroker idea Paul Crow ley added original model tends prevent spin-in during circle-tow mode See photos raises trailing continued page 93 40 Model Aviation Left Normal towline pressure pulls rudder neutral position straight tow Below position two-way rudder stop allows rudder deflect circle turn launch spring pushes rudder glide-turn posi tion Development goes back 69 S no-Bird/Walters continued page 40 edge about 1/16 compensate tighter turn during circle-tow mode rudder offset actu ated same line pulls rudder stop forward consequently released moment launch simple de vice add however original model did possess spin-in tendencies towline use 50-lb-test lowstretch nylon monofilament line dia has about 3 ft stretch 2 kilogram load tow use reel using small plastic ring better yet just loop end loop around small finger left hand store line FAI Supply reel works nicely opening up coils line guide filing small notch 1/32 wide deep edge spool hook loop over prior winding Testing youre satisfied operation hook spring re lease set 5-6 lbs ready first test flight Fly test flights rela tively calm air preferably over 7-8 mph Hand glide adjust rudder stop stab adjustment screw slight right turn no apparent stall Fly first flight full towline length D/T set 20-30 sec jatch set will permit float model off line check glide its quite right will D/T come safely down After several flights floating model off line having made necessary stab rudder adjustments produce straight tow flat glide circling ap proximately once 30-50 sec ready big moment first circle tow Just set latch tow model before except instead floating off let circle line attached Once just begins come around wind begin tow straight bring model overhead let circle again prepared run downwind fast keep line slightly slack during downwind circle line tightens up model may pulled ground Most fliers find out hard way model will come out turn want too much spring force rudder torsion spring towhook may too far ward Learning circle tow real ex perience fliers first try find requires lot fancy footwork Most us have towed model ground time another try testing over grass possible youre ready launch pull down sharply release latch keep pressure deflect rudder zoom position release model should bank slightly right released gain altitude model turns too steep begins spiral decrease zoom rudder offset stalls severely increase rudder offset As previously mentioned tow reel hold several feet slack line releasing let slack go two-ring slips off easily youre fly ing strong wind its necessary keep 8-10 ft slack line available let out quickly keep load exceeding un latch force launch some slack necessary let tow-ring slide free conclusion remember win re quires possessing good model important have winning attitude essentially means committing some error should have control over commonly known shooting oneself foot winner person generally flies model its full potential time testing complete youre satisfied models per formance begin practice Fly flight purpose checking likely conditions keeping records flights work towards eliminating bad flight flight should flown though victory depended end result does October1976 93
Edition: Model Aviation - 1976/10
Page Numbers: 36, 37, 38, 39, 40, 93
S fine Nordic A/2 its best light conditions thermal activity weak non-existent Jim Walters Photos Jim Land Mark Vercam men EVERY SERIOUS A/2 flier knows needs glider box can counted early morning later afternoon rounds thermal activity light non-existent Sno Bird may magic 3-mm model will deliver extra performance under light conditions need Still-air glide tests Sno-Bird clearly demonstrated model significantly better previous A/2 gliders Built winter 1974-75 up coming World Championships Plovdiv model tested under clear winter skies snow ground air temperature around 400F still death Sno-Bird would consistently average 70 sec floated off line 64 ft altitude line length plus arm reach same time next best model original sheeted version averaged respectable 65 sec new design proven itself better good margin model represents latest still-air version current Bird series features rather high aspect ratio 1731 simplified sheeted wing body construc tion circle tow/catapult tow hook wing section slightly modified Benedek D7457-d/2 section gained popularity early 1960s namely Norm Ingersolls Harbinger still quite competitive contemporary sections Certainly advantage section its depth permits maxi mum separation main spar chords resulting wing high strength-toweight ratio stab section close copy stab sections Ectenkovs EGl 172 Elton Drews Lively Lady earlier version built 1969 suc cessfully used qualify 70 72 74 team-selection finals 74 Taft used first two rounds its still-air performance paid off team position Construction Before beginning actual construction necessary make couple building aids cambered wing board rib templates Building conventional undercambered wing cambered board possible building sheeted wing especially heavy trailing edge would next impossible Also cambered board along proper planform shape LE somewhat straight TE swept forward give desired amount tip wash-out about 3/16 boards clear vertical grain cedar redwood 1 X 6 1 X 8 stock about 48 long board should flat pos sible measurable twist Trace 36 Model Aviation Top Widely respected Nordic A/2 circles Jim Walters displays Sno-Bird has 173-to-i aspect ratio features circle-tow catapult tow hook Above An accurate wing construction board imperativemade using table saw cut grooves matching lower surface remaining material right removed using block plane light sanding lower camber main rib onto end board using table saw cut grooves blade width full length approximately 3/16 intervals just match camber line see photo remaining material removed using block plane finally sanding block see photo board will take 2 4 hours build easily makes up ease building wooden strip approxi mately crewed forward edge board used indexing rib locations ensures straight lead ing edge other templates wing stab rib patterns made Y6 plywood per mit fast accurate slicing ribs par ticularly wing ribs feathered trailing edge see photo use wing rib pattern cut lower camber first piece balsa see photo push other end template against balsa piece cut upper camber see photo tapered tip ribs after cut ting lower camber rotate tem plate about leading edge obtain proper rib length shown sketch plan As can see airfoil section near tip deviates true section still retains adequate shape Wing Cut out wing rib index strips top border plan attach wooden strip trailing edge board using paper cement sparingly must remove reverse later build other wing Add wax paper prevent parts sticking board Trim lower inboard sheet exactly 5 X 26 long trim upper sheet yet After adding top sheet slight excess width allows neatly trim away area glue oozes out leaving neat trailing edge exactly right chord Pin lower sheet board aligning rib index strips glue 3/16 sq spruce leading edge may pre-shaped lower spar spar doubler using couple pre-cut wing ribs locating guide Use slightly thinned aliphatic glue joints except area around wing root tubing moderate curing epoxy used Next using paper rib index strips guide glue ribs position widening spar slots necessary plywood root rib edral rib must slanted match dihedral angles shown plan Add aluminum tubes top spars 1/32 verti cal grain balsa web between spars After completely dry lightly sand wing remove rough spots around spars shape leading edge sand lower sheet trailing edge lightly top sheet will fit smoothly Now comes easy part installation top sheet pins Cut top sheets slightly oversize sure check sheet width upper curvature Prepare tools ahead time Youll need approximately 150 size #16 #18 #32 rubberbands few pins thinned aliphatic glue Position lower wing half board using couple pins stuck through end ribs keep shifting Lightly apply glue mating surfaces gently position top sheet using couple pins end Now begin wrap bands clear around wing board see photo begin ning center working towards ends first fairly wide spacing 1- 1 adding bands between until en tire wing covered bands spaced approximately t bands apply light pressure ensures smooth accurate wing shape million pin holes top surface Re peat tip section allow dry overnight before removing board possible allow wing sections several days curing harden glue makes sanding leading edge lot easier trim trailing edge until wing near completion allows adjust chord slightly approach maximum permissible wing area easily trimmed using table saw Sanding October1976 37 Top Template insures accurate duplication ot ribs feathered edgesalso used tapered ribs Above Cut lower camber first up per camber key accurate ribs Right Template being used cut upper rib camber Below Closely spaced rubberbands apply pressure gluing upper sheet un sightly pinholes Right Table saw utilized heat-sink molding lead nose weight Sno-Bird leading-edge radius before joining panels permits easy inspection proper shape Attaching tip section cen ter section similar building handlaunch glider wing Just sand proper dihedral angles section double glue using moderate cure epoxy ali phatic Ambroid type glue Note bothersome ply wood dihedral bracesthis type wing construction just doesnt need Sand upper lower surfaces lightly 400-600 grit paper using care oversand Add root plywood rib trim excess aluminum tubing Add soft balsa tips trailing edge stiffeners Give three coats 50-50 dope plasticizer added use 3-4 drops di-butlyl-phthlate per ounce Tissue used adds un necessary weight tends produce warps Sanding sealer may applied lower surface believe natural roughness balsa grain upper surface aids turbulating wing Add trim numbers thread turbulator What appears aerodynamic fences external extensions wing ribs used strengthen trailing edge thread turbulator just aft IE does show photo TRIM EXCESSTOP AFTER INSTAuINO BUTT RIB 332DATUBlNG 1/810 AL TUaNG ii ii ii ii II m 1ThLTWTWGC __0 _____1 EDGEL WTF/G LOTHB 1/16 PLY-23/32 BALSATTRAILNO EDGE STIF RiDDER LSVER 032MW lAD NOSE WEIGHT 4 2 ____ 3/B PLY CORE 3/32 PLYFILL HOLE 1/16 PLj 3 REOD / D SEN 0 D2DW N DO SN OW NE~MER CU OU 3/32DAI-IOE RJWER EVER ON RT SOF1/B DIA HOLE 3/32 PLY 2 REOD 3/B LEAD NOSE1/4 DIA CLEAR WEIGHT 3/B PLY CORE 1/4 x 3/B MAPLE OR OAK HOOK SUPPORTS FOR COMPETE DETAILS OF TOWHOOK SEE ARTICLE IN JAN 1974 FLYING MODELS BY BOB HATSCHEK TOWHOOBCASTING KIT MAY BEOBTANED FROM JIM CROCKET F 1442 N FRUIT ST FRESMO CA 93726 Above Rudder stop stab stroker pulled Below rudder stop stroker shown forward allowing rudder stab deflect released picture thus pushing rudder a circletow position tight turn glide turn position wing leading edge Total weight wing should 160-180 grams depend ing density balsa sheeting Stabilizer Using same procedure cutting out wing tip ribs cut stab ribs false ribs fairly hard 8-l0# 1/32 medium 6-8 1/16 1/20 balsa Make series shims 1/32 sheet pack up lower spar forward edge trailing edge main tain proper airfoil shape Use fairly hard balsa trailing edge leading edge spars upper spar tapered 1/16 X 1/s Y6 sq Lay down notched trailing edge bottom spar add ribs add leading edge false ribs gussets thick tip rib Use ali phatic glue sparingly assembly Shape leading edge sand structure us ing 400 grit paper Give structure coat clear dope cover using superfine lightweight Japanese tissue Apply 3 coats 50-50 dope plasticizer Stab weight should 7-9 grams Fuselage Begin fuselage cutting core / 3-ply commercial lum beryard plywood fir okay sides 3/32 aircraft plywood Size cut outs core D/T timer type towhook types circle towhook ideas available present possess some advantages can readily adapted Sno-Bird Hatschek towhook used origi nal model permits low body pro file Using plywood wing root rib template match drill plywood side wing wires Now mark hole loca tions core drill two 14 diameter clearance holes through core eter epoxy access holes through edge core drill other 3/32 side yet make nose weight cut shape scrap i/i plywood melt scraps lead sinkers etc tomato can heated over Coleman stove Place plywood form over flat metal surface such table saw top pour lead exactly ply thickness see photo metal top serves heat-sink cool lead quickly weight should come out tween 90-100 grams Notch groove WINGRIBINDEXSTRIPS CUTFROM PLAN & ATTACH TOWING BOARD TURBULATOR CARPET THD SRRIJCE 3/32 SO SPRUCEluBE 3/323/16 SO SPRUCE1/Bx1/4 HARD BALSA TAPER TO 1/B SPRUCE & ROT SOFT BALSA -N ~ ~BLCEK BY LIlL3/3250BATAPE TOll 171 ILuVV3/16 WASHOUT BOTH TIPS l/32S1- BALSA TOP& ROT IFFENERS END HERE 1/B RIB TILT APPROX W FOR DIHED 1/32 ID BRASS TUBE STAB TILT FOR RT GLIDE 3/32 PLYZO32 MW XY1 TAB STROKER RUD R MWIRETOP VIEW HI D25 MW 02D BRASS lPLLlETE 3/32x1/2 TAPERTOl/iB, 3/B 1/B DIA1/iBDIA 1/B DIAHOLE020 BRASS 060 NUT 3/32 DIA II RUDDER TOBSION1/32 GA0-JBEND FROM A5 DT ANGLE SPRING U1MWHOLESOLDER3/32 GA CCWIPRD2D WIREPPRDRILL 1/32 HOLE P015 WIRES ~IjRTS1/16 ID RBASSSPRING FIBERGLASS TAILBOOM 35LGTUBINGRUDDER STOP-HD BALSAl/32IDAL TUNING 50 DI HIDAPPROX 20RU FW TUBE-DRILL FOR LT NE WT 3 RUDDER STOP EPOXY GROMMET LATE WITH 6-32 SCREWS & NUTSTO INSIDE FiR 060 SOREWOT LINE OBONUTSOLUER1/32 WIRE1/16,1/B K ONLY TO WIRE1/16 PLYSPRLCE1JFT 1/B SH --30-DDLB DACRON LINE STR TOW .TOWHOOKSH WING RIB PATTERN 1/16 PLYGLIDE RUR STOP STAB STROKERCTSEE SE AlL ABDEE OBOSCREW FORLAMINATE 2501/320/B & RUDDERSTFFENERTIP RIBSTAB ADJUSTHL BALSA ES RECOFALSEPOXY NUT TO15 LB MOHOFIL NYLON TO INSIDE OP BOOM TOWLINE PULL PIN 1/iBMED BALSA 3BREODSTAB RIB-CTR-3/32OBOSCREW& WASHER TO 1/B MED BALSA OTHERS 1/320R1/20l/Lj~ADJUST RUDDER STOP EPOXY TO FIN ADJUSTMENTS ESTAB RIB-TIPWING- 9l/~ STAB 4/2 RH SIDE025 MWRTGLIDETU 020ALSTAB STOPHINGE 1/16 PLY 2 REOD REOD STAB PLATFORM 1/16 PLY SNO-BIRD FlA NOR DIG GLIDER SPAN 89 WINGAREA 456sq 0 1 2 3 4 56LENGTH 43 STAB AREA 6Bsq ALL GMENSIONS IN INCHESDes9nad Drn JIM WALTERS October1976 39 Sno- Bird ply sides match fiberglass rod Using moderate cure epoxy assemble sides core hook supports tail boom using care align tailboom dry round edges except wing mates fuselage Now drill wire holes through other plywood side using holes first side guide Bend two wing wires install holes checking see wires come out parallel slight wash-in LE up right wing wash-in necessary keep right wing dipping during cata pult launches also tends keep model spinning turbulent air wires centered fuselage glued install wings rotate wires required slightly aft match high angle wing neglect wing will fit flush against fuselage sides youre satisfied fit-up carefully remove wings out disturbing wires apply epoxy through two access holes core Build fin soft sheet rudder i/s sheet Groove base fin match fiberglass rod add short piece aluminum tubing 1/32 ID after shaping fin proper airfoil shape epoxy tailboom has preroughened sand paper improve adhesion ad hesive Epoxy 3/32 plywood stab platform short piece fiberglass tube Com plete rudder circle-tow hardware shown plans differ slightly original Hatschek hardware pro duce same action Consult Bob Hats cheks article Flying Models January 1974 operation towhook Remember moderate pull should move rudder neutral relaxed torsion spring should just strong enough drive rudder against ex treme rudder stop Too stiff torsion spring will result too high towline pull straight tow model will straighten out circle proper time will go next unwanted cir cle hopefully accomplished trial error hopefully too much error stab stroker idea Paul Crow ley added original model tends prevent spin-in during circle-tow mode See photos raises trailing continued page 93 40 Model Aviation Left Normal towline pressure pulls rudder neutral position straight tow Below position two-way rudder stop allows rudder deflect circle turn launch spring pushes rudder glide-turn posi tion Development goes back 69 S no-Bird/Walters continued page 40 edge about 1/16 compensate tighter turn during circle-tow mode rudder offset actu ated same line pulls rudder stop forward consequently released moment launch simple de vice add however original model did possess spin-in tendencies towline use 50-lb-test lowstretch nylon monofilament line dia has about 3 ft stretch 2 kilogram load tow use reel using small plastic ring better yet just loop end loop around small finger left hand store line FAI Supply reel works nicely opening up coils line guide filing small notch 1/32 wide deep edge spool hook loop over prior winding Testing youre satisfied operation hook spring re lease set 5-6 lbs ready first test flight Fly test flights rela tively calm air preferably over 7-8 mph Hand glide adjust rudder stop stab adjustment screw slight right turn no apparent stall Fly first flight full towline length D/T set 20-30 sec jatch set will permit float model off line check glide its quite right will D/T come safely down After several flights floating model off line having made necessary stab rudder adjustments produce straight tow flat glide circling ap proximately once 30-50 sec ready big moment first circle tow Just set latch tow model before except instead floating off let circle line attached Once just begins come around wind begin tow straight bring model overhead let circle again prepared run downwind fast keep line slightly slack during downwind circle line tightens up model may pulled ground Most fliers find out hard way model will come out turn want too much spring force rudder torsion spring towhook may too far ward Learning circle tow real ex perience fliers first try find requires lot fancy footwork Most us have towed model ground time another try testing over grass possible youre ready launch pull down sharply release latch keep pressure deflect rudder zoom position release model should bank slightly right released gain altitude model turns too steep begins spiral decrease zoom rudder offset stalls severely increase rudder offset As previously mentioned tow reel hold several feet slack line releasing let slack go two-ring slips off easily youre fly ing strong wind its necessary keep 8-10 ft slack line available let out quickly keep load exceeding un latch force launch some slack necessary let tow-ring slide free conclusion remember win re quires possessing good model important have winning attitude essentially means committing some error should have control over commonly known shooting oneself foot winner person generally flies model its full potential time testing complete youre satisfied models per formance begin practice Fly flight purpose checking likely conditions keeping records flights work towards eliminating bad flight flight should flown though victory depended end result does October1976 93
Edition: Model Aviation - 1976/10
Page Numbers: 36, 37, 38, 39, 40, 93
S fine Nordic A/2 its best light conditions thermal activity weak non-existent Jim Walters Photos Jim Land Mark Vercam men EVERY SERIOUS A/2 flier knows needs glider box can counted early morning later afternoon rounds thermal activity light non-existent Sno Bird may magic 3-mm model will deliver extra performance under light conditions need Still-air glide tests Sno-Bird clearly demonstrated model significantly better previous A/2 gliders Built winter 1974-75 up coming World Championships Plovdiv model tested under clear winter skies snow ground air temperature around 400F still death Sno-Bird would consistently average 70 sec floated off line 64 ft altitude line length plus arm reach same time next best model original sheeted version averaged respectable 65 sec new design proven itself better good margin model represents latest still-air version current Bird series features rather high aspect ratio 1731 simplified sheeted wing body construc tion circle tow/catapult tow hook wing section slightly modified Benedek D7457-d/2 section gained popularity early 1960s namely Norm Ingersolls Harbinger still quite competitive contemporary sections Certainly advantage section its depth permits maxi mum separation main spar chords resulting wing high strength-toweight ratio stab section close copy stab sections Ectenkovs EGl 172 Elton Drews Lively Lady earlier version built 1969 suc cessfully used qualify 70 72 74 team-selection finals 74 Taft used first two rounds its still-air performance paid off team position Construction Before beginning actual construction necessary make couple building aids cambered wing board rib templates Building conventional undercambered wing cambered board possible building sheeted wing especially heavy trailing edge would next impossible Also cambered board along proper planform shape LE somewhat straight TE swept forward give desired amount tip wash-out about 3/16 boards clear vertical grain cedar redwood 1 X 6 1 X 8 stock about 48 long board should flat pos sible measurable twist Trace 36 Model Aviation Top Widely respected Nordic A/2 circles Jim Walters displays Sno-Bird has 173-to-i aspect ratio features circle-tow catapult tow hook Above An accurate wing construction board imperativemade using table saw cut grooves matching lower surface remaining material right removed using block plane light sanding lower camber main rib onto end board using table saw cut grooves blade width full length approximately 3/16 intervals just match camber line see photo remaining material removed using block plane finally sanding block see photo board will take 2 4 hours build easily makes up ease building wooden strip approxi mately crewed forward edge board used indexing rib locations ensures straight lead ing edge other templates wing stab rib patterns made Y6 plywood per mit fast accurate slicing ribs par ticularly wing ribs feathered trailing edge see photo use wing rib pattern cut lower camber first piece balsa see photo push other end template against balsa piece cut upper camber see photo tapered tip ribs after cut ting lower camber rotate tem plate about leading edge obtain proper rib length shown sketch plan As can see airfoil section near tip deviates true section still retains adequate shape Wing Cut out wing rib index strips top border plan attach wooden strip trailing edge board using paper cement sparingly must remove reverse later build other wing Add wax paper prevent parts sticking board Trim lower inboard sheet exactly 5 X 26 long trim upper sheet yet After adding top sheet slight excess width allows neatly trim away area glue oozes out leaving neat trailing edge exactly right chord Pin lower sheet board aligning rib index strips glue 3/16 sq spruce leading edge may pre-shaped lower spar spar doubler using couple pre-cut wing ribs locating guide Use slightly thinned aliphatic glue joints except area around wing root tubing moderate curing epoxy used Next using paper rib index strips guide glue ribs position widening spar slots necessary plywood root rib edral rib must slanted match dihedral angles shown plan Add aluminum tubes top spars 1/32 verti cal grain balsa web between spars After completely dry lightly sand wing remove rough spots around spars shape leading edge sand lower sheet trailing edge lightly top sheet will fit smoothly Now comes easy part installation top sheet pins Cut top sheets slightly oversize sure check sheet width upper curvature Prepare tools ahead time Youll need approximately 150 size #16 #18 #32 rubberbands few pins thinned aliphatic glue Position lower wing half board using couple pins stuck through end ribs keep shifting Lightly apply glue mating surfaces gently position top sheet using couple pins end Now begin wrap bands clear around wing board see photo begin ning center working towards ends first fairly wide spacing 1- 1 adding bands between until en tire wing covered bands spaced approximately t bands apply light pressure ensures smooth accurate wing shape million pin holes top surface Re peat tip section allow dry overnight before removing board possible allow wing sections several days curing harden glue makes sanding leading edge lot easier trim trailing edge until wing near completion allows adjust chord slightly approach maximum permissible wing area easily trimmed using table saw Sanding October1976 37 Top Template insures accurate duplication ot ribs feathered edgesalso used tapered ribs Above Cut lower camber first up per camber key accurate ribs Right Template being used cut upper rib camber Below Closely spaced rubberbands apply pressure gluing upper sheet un sightly pinholes Right Table saw utilized heat-sink molding lead nose weight Sno-Bird leading-edge radius before joining panels permits easy inspection proper shape Attaching tip section cen ter section similar building handlaunch glider wing Just sand proper dihedral angles section double glue using moderate cure epoxy ali phatic Ambroid type glue Note bothersome ply wood dihedral bracesthis type wing construction just doesnt need Sand upper lower surfaces lightly 400-600 grit paper using care oversand Add root plywood rib trim excess aluminum tubing Add soft balsa tips trailing edge stiffeners Give three coats 50-50 dope plasticizer added use 3-4 drops di-butlyl-phthlate per ounce Tissue used adds un necessary weight tends produce warps Sanding sealer may applied lower surface believe natural roughness balsa grain upper surface aids turbulating wing Add trim numbers thread turbulator What appears aerodynamic fences external extensions wing ribs used strengthen trailing edge thread turbulator just aft IE does show photo TRIM EXCESSTOP AFTER INSTAuINO BUTT RIB 332DATUBlNG 1/810 AL TUaNG ii ii ii ii II m 1ThLTWTWGC __0 _____1 EDGEL WTF/G LOTHB 1/16 PLY-23/32 BALSATTRAILNO EDGE STIF RiDDER LSVER 032MW lAD NOSE WEIGHT 4 2 ____ 3/B PLY CORE 3/32 PLYFILL HOLE 1/16 PLj 3 REOD / D SEN 0 D2DW N DO SN OW NE~MER CU OU 3/32DAI-IOE RJWER EVER ON RT SOF1/B DIA HOLE 3/32 PLY 2 REOD 3/B LEAD NOSE1/4 DIA CLEAR WEIGHT 3/B PLY CORE 1/4 x 3/B MAPLE OR OAK HOOK SUPPORTS FOR COMPETE DETAILS OF TOWHOOK SEE ARTICLE IN JAN 1974 FLYING MODELS BY BOB HATSCHEK TOWHOOBCASTING KIT MAY BEOBTANED FROM JIM CROCKET F 1442 N FRUIT ST FRESMO CA 93726 Above Rudder stop stab stroker pulled Below rudder stop stroker shown forward allowing rudder stab deflect released picture thus pushing rudder a circletow position tight turn glide turn position wing leading edge Total weight wing should 160-180 grams depend ing density balsa sheeting Stabilizer Using same procedure cutting out wing tip ribs cut stab ribs false ribs fairly hard 8-l0# 1/32 medium 6-8 1/16 1/20 balsa Make series shims 1/32 sheet pack up lower spar forward edge trailing edge main tain proper airfoil shape Use fairly hard balsa trailing edge leading edge spars upper spar tapered 1/16 X 1/s Y6 sq Lay down notched trailing edge bottom spar add ribs add leading edge false ribs gussets thick tip rib Use ali phatic glue sparingly assembly Shape leading edge sand structure us ing 400 grit paper Give structure coat clear dope cover using superfine lightweight Japanese tissue Apply 3 coats 50-50 dope plasticizer Stab weight should 7-9 grams Fuselage Begin fuselage cutting core / 3-ply commercial lum beryard plywood fir okay sides 3/32 aircraft plywood Size cut outs core D/T timer type towhook types circle towhook ideas available present possess some advantages can readily adapted Sno-Bird Hatschek towhook used origi nal model permits low body pro file Using plywood wing root rib template match drill plywood side wing wires Now mark hole loca tions core drill two 14 diameter clearance holes through core eter epoxy access holes through edge core drill other 3/32 side yet make nose weight cut shape scrap i/i plywood melt scraps lead sinkers etc tomato can heated over Coleman stove Place plywood form over flat metal surface such table saw top pour lead exactly ply thickness see photo metal top serves heat-sink cool lead quickly weight should come out tween 90-100 grams Notch groove WINGRIBINDEXSTRIPS CUTFROM PLAN & ATTACH TOWING BOARD TURBULATOR CARPET THD SRRIJCE 3/32 SO SPRUCEluBE 3/323/16 SO SPRUCE1/Bx1/4 HARD BALSA TAPER TO 1/B SPRUCE & ROT SOFT BALSA -N ~ ~BLCEK BY LIlL3/3250BATAPE TOll 171 ILuVV3/16 WASHOUT BOTH TIPS l/32S1- BALSA TOP& ROT IFFENERS END HERE 1/B RIB TILT APPROX W FOR DIHED 1/32 ID BRASS TUBE STAB TILT FOR RT GLIDE 3/32 PLYZO32 MW XY1 TAB STROKER RUD R MWIRETOP VIEW HI D25 MW 02D BRASS lPLLlETE 3/32x1/2 TAPERTOl/iB, 3/B 1/B DIA1/iBDIA 1/B DIAHOLE020 BRASS 060 NUT 3/32 DIA II RUDDER TOBSION1/32 GA0-JBEND FROM A5 DT ANGLE SPRING U1MWHOLESOLDER3/32 GA CCWIPRD2D WIREPPRDRILL 1/32 HOLE P015 WIRES ~IjRTS1/16 ID RBASSSPRING FIBERGLASS TAILBOOM 35LGTUBINGRUDDER STOP-HD BALSAl/32IDAL TUNING 50 DI HIDAPPROX 20RU FW TUBE-DRILL FOR LT NE WT 3 RUDDER STOP EPOXY GROMMET LATE WITH 6-32 SCREWS & NUTSTO INSIDE FiR 060 SOREWOT LINE OBONUTSOLUER1/32 WIRE1/16,1/B K ONLY TO WIRE1/16 PLYSPRLCE1JFT 1/B SH --30-DDLB DACRON LINE STR TOW .TOWHOOKSH WING RIB PATTERN 1/16 PLYGLIDE RUR STOP STAB STROKERCTSEE SE AlL ABDEE OBOSCREW FORLAMINATE 2501/320/B & RUDDERSTFFENERTIP RIBSTAB ADJUSTHL BALSA ES RECOFALSEPOXY NUT TO15 LB MOHOFIL NYLON TO INSIDE OP BOOM TOWLINE PULL PIN 1/iBMED BALSA 3BREODSTAB RIB-CTR-3/32OBOSCREW& WASHER TO 1/B MED BALSA OTHERS 1/320R1/20l/Lj~ADJUST RUDDER STOP EPOXY TO FIN ADJUSTMENTS ESTAB RIB-TIPWING- 9l/~ STAB 4/2 RH SIDE025 MWRTGLIDETU 020ALSTAB STOPHINGE 1/16 PLY 2 REOD REOD STAB PLATFORM 1/16 PLY SNO-BIRD FlA NOR DIG GLIDER SPAN 89 WINGAREA 456sq 0 1 2 3 4 56LENGTH 43 STAB AREA 6Bsq ALL GMENSIONS IN INCHESDes9nad Drn JIM WALTERS October1976 39 Sno- Bird ply sides match fiberglass rod Using moderate cure epoxy assemble sides core hook supports tail boom using care align tailboom dry round edges except wing mates fuselage Now drill wire holes through other plywood side using holes first side guide Bend two wing wires install holes checking see wires come out parallel slight wash-in LE up right wing wash-in necessary keep right wing dipping during cata pult launches also tends keep model spinning turbulent air wires centered fuselage glued install wings rotate wires required slightly aft match high angle wing neglect wing will fit flush against fuselage sides youre satisfied fit-up carefully remove wings out disturbing wires apply epoxy through two access holes core Build fin soft sheet rudder i/s sheet Groove base fin match fiberglass rod add short piece aluminum tubing 1/32 ID after shaping fin proper airfoil shape epoxy tailboom has preroughened sand paper improve adhesion ad hesive Epoxy 3/32 plywood stab platform short piece fiberglass tube Com plete rudder circle-tow hardware shown plans differ slightly original Hatschek hardware pro duce same action Consult Bob Hats cheks article Flying Models January 1974 operation towhook Remember moderate pull should move rudder neutral relaxed torsion spring should just strong enough drive rudder against ex treme rudder stop Too stiff torsion spring will result too high towline pull straight tow model will straighten out circle proper time will go next unwanted cir cle hopefully accomplished trial error hopefully too much error stab stroker idea Paul Crow ley added original model tends prevent spin-in during circle-tow mode See photos raises trailing continued page 93 40 Model Aviation Left Normal towline pressure pulls rudder neutral position straight tow Below position two-way rudder stop allows rudder deflect circle turn launch spring pushes rudder glide-turn posi tion Development goes back 69 S no-Bird/Walters continued page 40 edge about 1/16 compensate tighter turn during circle-tow mode rudder offset actu ated same line pulls rudder stop forward consequently released moment launch simple de vice add however original model did possess spin-in tendencies towline use 50-lb-test lowstretch nylon monofilament line dia has about 3 ft stretch 2 kilogram load tow use reel using small plastic ring better yet just loop end loop around small finger left hand store line FAI Supply reel works nicely opening up coils line guide filing small notch 1/32 wide deep edge spool hook loop over prior winding Testing youre satisfied operation hook spring re lease set 5-6 lbs ready first test flight Fly test flights rela tively calm air preferably over 7-8 mph Hand glide adjust rudder stop stab adjustment screw slight right turn no apparent stall Fly first flight full towline length D/T set 20-30 sec jatch set will permit float model off line check glide its quite right will D/T come safely down After several flights floating model off line having made necessary stab rudder adjustments produce straight tow flat glide circling ap proximately once 30-50 sec ready big moment first circle tow Just set latch tow model before except instead floating off let circle line attached Once just begins come around wind begin tow straight bring model overhead let circle again prepared run downwind fast keep line slightly slack during downwind circle line tightens up model may pulled ground Most fliers find out hard way model will come out turn want too much spring force rudder torsion spring towhook may too far ward Learning circle tow real ex perience fliers first try find requires lot fancy footwork Most us have towed model ground time another try testing over grass possible youre ready launch pull down sharply release latch keep pressure deflect rudder zoom position release model should bank slightly right released gain altitude model turns too steep begins spiral decrease zoom rudder offset stalls severely increase rudder offset As previously mentioned tow reel hold several feet slack line releasing let slack go two-ring slips off easily youre fly ing strong wind its necessary keep 8-10 ft slack line available let out quickly keep load exceeding un latch force launch some slack necessary let tow-ring slide free conclusion remember win re quires possessing good model important have winning attitude essentially means committing some error should have control over commonly known shooting oneself foot winner person generally flies model its full potential time testing complete youre satisfied models per formance begin practice Fly flight purpose checking likely conditions keeping records flights work towards eliminating bad flight flight should flown though victory depended end result does October1976 93
Edition: Model Aviation - 1976/10
Page Numbers: 36, 37, 38, 39, 40, 93
S fine Nordic A/2 its best light conditions thermal activity weak non-existent Jim Walters Photos Jim Land Mark Vercam men EVERY SERIOUS A/2 flier knows needs glider box can counted early morning later afternoon rounds thermal activity light non-existent Sno Bird may magic 3-mm model will deliver extra performance under light conditions need Still-air glide tests Sno-Bird clearly demonstrated model significantly better previous A/2 gliders Built winter 1974-75 up coming World Championships Plovdiv model tested under clear winter skies snow ground air temperature around 400F still death Sno-Bird would consistently average 70 sec floated off line 64 ft altitude line length plus arm reach same time next best model original sheeted version averaged respectable 65 sec new design proven itself better good margin model represents latest still-air version current Bird series features rather high aspect ratio 1731 simplified sheeted wing body construc tion circle tow/catapult tow hook wing section slightly modified Benedek D7457-d/2 section gained popularity early 1960s namely Norm Ingersolls Harbinger still quite competitive contemporary sections Certainly advantage section its depth permits maxi mum separation main spar chords resulting wing high strength-toweight ratio stab section close copy stab sections Ectenkovs EGl 172 Elton Drews Lively Lady earlier version built 1969 suc cessfully used qualify 70 72 74 team-selection finals 74 Taft used first two rounds its still-air performance paid off team position Construction Before beginning actual construction necessary make couple building aids cambered wing board rib templates Building conventional undercambered wing cambered board possible building sheeted wing especially heavy trailing edge would next impossible Also cambered board along proper planform shape LE somewhat straight TE swept forward give desired amount tip wash-out about 3/16 boards clear vertical grain cedar redwood 1 X 6 1 X 8 stock about 48 long board should flat pos sible measurable twist Trace 36 Model Aviation Top Widely respected Nordic A/2 circles Jim Walters displays Sno-Bird has 173-to-i aspect ratio features circle-tow catapult tow hook Above An accurate wing construction board imperativemade using table saw cut grooves matching lower surface remaining material right removed using block plane light sanding lower camber main rib onto end board using table saw cut grooves blade width full length approximately 3/16 intervals just match camber line see photo remaining material removed using block plane finally sanding block see photo board will take 2 4 hours build easily makes up ease building wooden strip approxi mately crewed forward edge board used indexing rib locations ensures straight lead ing edge other templates wing stab rib patterns made Y6 plywood per mit fast accurate slicing ribs par ticularly wing ribs feathered trailing edge see photo use wing rib pattern cut lower camber first piece balsa see photo push other end template against balsa piece cut upper camber see photo tapered tip ribs after cut ting lower camber rotate tem plate about leading edge obtain proper rib length shown sketch plan As can see airfoil section near tip deviates true section still retains adequate shape Wing Cut out wing rib index strips top border plan attach wooden strip trailing edge board using paper cement sparingly must remove reverse later build other wing Add wax paper prevent parts sticking board Trim lower inboard sheet exactly 5 X 26 long trim upper sheet yet After adding top sheet slight excess width allows neatly trim away area glue oozes out leaving neat trailing edge exactly right chord Pin lower sheet board aligning rib index strips glue 3/16 sq spruce leading edge may pre-shaped lower spar spar doubler using couple pre-cut wing ribs locating guide Use slightly thinned aliphatic glue joints except area around wing root tubing moderate curing epoxy used Next using paper rib index strips guide glue ribs position widening spar slots necessary plywood root rib edral rib must slanted match dihedral angles shown plan Add aluminum tubes top spars 1/32 verti cal grain balsa web between spars After completely dry lightly sand wing remove rough spots around spars shape leading edge sand lower sheet trailing edge lightly top sheet will fit smoothly Now comes easy part installation top sheet pins Cut top sheets slightly oversize sure check sheet width upper curvature Prepare tools ahead time Youll need approximately 150 size #16 #18 #32 rubberbands few pins thinned aliphatic glue Position lower wing half board using couple pins stuck through end ribs keep shifting Lightly apply glue mating surfaces gently position top sheet using couple pins end Now begin wrap bands clear around wing board see photo begin ning center working towards ends first fairly wide spacing 1- 1 adding bands between until en tire wing covered bands spaced approximately t bands apply light pressure ensures smooth accurate wing shape million pin holes top surface Re peat tip section allow dry overnight before removing board possible allow wing sections several days curing harden glue makes sanding leading edge lot easier trim trailing edge until wing near completion allows adjust chord slightly approach maximum permissible wing area easily trimmed using table saw Sanding October1976 37 Top Template insures accurate duplication ot ribs feathered edgesalso used tapered ribs Above Cut lower camber first up per camber key accurate ribs Right Template being used cut upper rib camber Below Closely spaced rubberbands apply pressure gluing upper sheet un sightly pinholes Right Table saw utilized heat-sink molding lead nose weight Sno-Bird leading-edge radius before joining panels permits easy inspection proper shape Attaching tip section cen ter section similar building handlaunch glider wing Just sand proper dihedral angles section double glue using moderate cure epoxy ali phatic Ambroid type glue Note bothersome ply wood dihedral bracesthis type wing construction just doesnt need Sand upper lower surfaces lightly 400-600 grit paper using care oversand Add root plywood rib trim excess aluminum tubing Add soft balsa tips trailing edge stiffeners Give three coats 50-50 dope plasticizer added use 3-4 drops di-butlyl-phthlate per ounce Tissue used adds un necessary weight tends produce warps Sanding sealer may applied lower surface believe natural roughness balsa grain upper surface aids turbulating wing Add trim numbers thread turbulator What appears aerodynamic fences external extensions wing ribs used strengthen trailing edge thread turbulator just aft IE does show photo TRIM EXCESSTOP AFTER INSTAuINO BUTT RIB 332DATUBlNG 1/810 AL TUaNG ii ii ii ii II m 1ThLTWTWGC __0 _____1 EDGEL WTF/G LOTHB 1/16 PLY-23/32 BALSATTRAILNO EDGE STIF RiDDER LSVER 032MW lAD NOSE WEIGHT 4 2 ____ 3/B PLY CORE 3/32 PLYFILL HOLE 1/16 PLj 3 REOD / D SEN 0 D2DW N DO SN OW NE~MER CU OU 3/32DAI-IOE RJWER EVER ON RT SOF1/B DIA HOLE 3/32 PLY 2 REOD 3/B LEAD NOSE1/4 DIA CLEAR WEIGHT 3/B PLY CORE 1/4 x 3/B MAPLE OR OAK HOOK SUPPORTS FOR COMPETE DETAILS OF TOWHOOK SEE ARTICLE IN JAN 1974 FLYING MODELS BY BOB HATSCHEK TOWHOOBCASTING KIT MAY BEOBTANED FROM JIM CROCKET F 1442 N FRUIT ST FRESMO CA 93726 Above Rudder stop stab stroker pulled Below rudder stop stroker shown forward allowing rudder stab deflect released picture thus pushing rudder a circletow position tight turn glide turn position wing leading edge Total weight wing should 160-180 grams depend ing density balsa sheeting Stabilizer Using same procedure cutting out wing tip ribs cut stab ribs false ribs fairly hard 8-l0# 1/32 medium 6-8 1/16 1/20 balsa Make series shims 1/32 sheet pack up lower spar forward edge trailing edge main tain proper airfoil shape Use fairly hard balsa trailing edge leading edge spars upper spar tapered 1/16 X 1/s Y6 sq Lay down notched trailing edge bottom spar add ribs add leading edge false ribs gussets thick tip rib Use ali phatic glue sparingly assembly Shape leading edge sand structure us ing 400 grit paper Give structure coat clear dope cover using superfine lightweight Japanese tissue Apply 3 coats 50-50 dope plasticizer Stab weight should 7-9 grams Fuselage Begin fuselage cutting core / 3-ply commercial lum beryard plywood fir okay sides 3/32 aircraft plywood Size cut outs core D/T timer type towhook types circle towhook ideas available present possess some advantages can readily adapted Sno-Bird Hatschek towhook used origi nal model permits low body pro file Using plywood wing root rib template match drill plywood side wing wires Now mark hole loca tions core drill two 14 diameter clearance holes through core eter epoxy access holes through edge core drill other 3/32 side yet make nose weight cut shape scrap i/i plywood melt scraps lead sinkers etc tomato can heated over Coleman stove Place plywood form over flat metal surface such table saw top pour lead exactly ply thickness see photo metal top serves heat-sink cool lead quickly weight should come out tween 90-100 grams Notch groove WINGRIBINDEXSTRIPS CUTFROM PLAN & ATTACH TOWING BOARD TURBULATOR CARPET THD SRRIJCE 3/32 SO SPRUCEluBE 3/323/16 SO SPRUCE1/Bx1/4 HARD BALSA TAPER TO 1/B SPRUCE & ROT SOFT BALSA -N ~ ~BLCEK BY LIlL3/3250BATAPE TOll 171 ILuVV3/16 WASHOUT BOTH TIPS l/32S1- BALSA TOP& ROT IFFENERS END HERE 1/B RIB TILT APPROX W FOR DIHED 1/32 ID BRASS TUBE STAB TILT FOR RT GLIDE 3/32 PLYZO32 MW XY1 TAB STROKER RUD R MWIRETOP VIEW HI D25 MW 02D BRASS lPLLlETE 3/32x1/2 TAPERTOl/iB, 3/B 1/B DIA1/iBDIA 1/B DIAHOLE020 BRASS 060 NUT 3/32 DIA II RUDDER TOBSION1/32 GA0-JBEND FROM A5 DT ANGLE SPRING U1MWHOLESOLDER3/32 GA CCWIPRD2D WIREPPRDRILL 1/32 HOLE P015 WIRES ~IjRTS1/16 ID RBASSSPRING FIBERGLASS TAILBOOM 35LGTUBINGRUDDER STOP-HD BALSAl/32IDAL TUNING 50 DI HIDAPPROX 20RU FW TUBE-DRILL FOR LT NE WT 3 RUDDER STOP EPOXY GROMMET LATE WITH 6-32 SCREWS & NUTSTO INSIDE FiR 060 SOREWOT LINE OBONUTSOLUER1/32 WIRE1/16,1/B K ONLY TO WIRE1/16 PLYSPRLCE1JFT 1/B SH --30-DDLB DACRON LINE STR TOW .TOWHOOKSH WING RIB PATTERN 1/16 PLYGLIDE RUR STOP STAB STROKERCTSEE SE AlL ABDEE OBOSCREW FORLAMINATE 2501/320/B & RUDDERSTFFENERTIP RIBSTAB ADJUSTHL BALSA ES RECOFALSEPOXY NUT TO15 LB MOHOFIL NYLON TO INSIDE OP BOOM TOWLINE PULL PIN 1/iBMED BALSA 3BREODSTAB RIB-CTR-3/32OBOSCREW& WASHER TO 1/B MED BALSA OTHERS 1/320R1/20l/Lj~ADJUST RUDDER STOP EPOXY TO FIN ADJUSTMENTS ESTAB RIB-TIPWING- 9l/~ STAB 4/2 RH SIDE025 MWRTGLIDETU 020ALSTAB STOPHINGE 1/16 PLY 2 REOD REOD STAB PLATFORM 1/16 PLY SNO-BIRD FlA NOR DIG GLIDER SPAN 89 WINGAREA 456sq 0 1 2 3 4 56LENGTH 43 STAB AREA 6Bsq ALL GMENSIONS IN INCHESDes9nad Drn JIM WALTERS October1976 39 Sno- Bird ply sides match fiberglass rod Using moderate cure epoxy assemble sides core hook supports tail boom using care align tailboom dry round edges except wing mates fuselage Now drill wire holes through other plywood side using holes first side guide Bend two wing wires install holes checking see wires come out parallel slight wash-in LE up right wing wash-in necessary keep right wing dipping during cata pult launches also tends keep model spinning turbulent air wires centered fuselage glued install wings rotate wires required slightly aft match high angle wing neglect wing will fit flush against fuselage sides youre satisfied fit-up carefully remove wings out disturbing wires apply epoxy through two access holes core Build fin soft sheet rudder i/s sheet Groove base fin match fiberglass rod add short piece aluminum tubing 1/32 ID after shaping fin proper airfoil shape epoxy tailboom has preroughened sand paper improve adhesion ad hesive Epoxy 3/32 plywood stab platform short piece fiberglass tube Com plete rudder circle-tow hardware shown plans differ slightly original Hatschek hardware pro duce same action Consult Bob Hats cheks article Flying Models January 1974 operation towhook Remember moderate pull should move rudder neutral relaxed torsion spring should just strong enough drive rudder against ex treme rudder stop Too stiff torsion spring will result too high towline pull straight tow model will straighten out circle proper time will go next unwanted cir cle hopefully accomplished trial error hopefully too much error stab stroker idea Paul Crow ley added original model tends prevent spin-in during circle-tow mode See photos raises trailing continued page 93 40 Model Aviation Left Normal towline pressure pulls rudder neutral position straight tow Below position two-way rudder stop allows rudder deflect circle turn launch spring pushes rudder glide-turn posi tion Development goes back 69 S no-Bird/Walters continued page 40 edge about 1/16 compensate tighter turn during circle-tow mode rudder offset actu ated same line pulls rudder stop forward consequently released moment launch simple de vice add however original model did possess spin-in tendencies towline use 50-lb-test lowstretch nylon monofilament line dia has about 3 ft stretch 2 kilogram load tow use reel using small plastic ring better yet just loop end loop around small finger left hand store line FAI Supply reel works nicely opening up coils line guide filing small notch 1/32 wide deep edge spool hook loop over prior winding Testing youre satisfied operation hook spring re lease set 5-6 lbs ready first test flight Fly test flights rela tively calm air preferably over 7-8 mph Hand glide adjust rudder stop stab adjustment screw slight right turn no apparent stall Fly first flight full towline length D/T set 20-30 sec jatch set will permit float model off line check glide its quite right will D/T come safely down After several flights floating model off line having made necessary stab rudder adjustments produce straight tow flat glide circling ap proximately once 30-50 sec ready big moment first circle tow Just set latch tow model before except instead floating off let circle line attached Once just begins come around wind begin tow straight bring model overhead let circle again prepared run downwind fast keep line slightly slack during downwind circle line tightens up model may pulled ground Most fliers find out hard way model will come out turn want too much spring force rudder torsion spring towhook may too far ward Learning circle tow real ex perience fliers first try find requires lot fancy footwork Most us have towed model ground time another try testing over grass possible youre ready launch pull down sharply release latch keep pressure deflect rudder zoom position release model should bank slightly right released gain altitude model turns too steep begins spiral decrease zoom rudder offset stalls severely increase rudder offset As previously mentioned tow reel hold several feet slack line releasing let slack go two-ring slips off easily youre fly ing strong wind its necessary keep 8-10 ft slack line available let out quickly keep load exceeding un latch force launch some slack necessary let tow-ring slide free conclusion remember win re quires possessing good model important have winning attitude essentially means committing some error should have control over commonly known shooting oneself foot winner person generally flies model its full potential time testing complete youre satisfied models per formance begin practice Fly flight purpose checking likely conditions keeping records flights work towards eliminating bad flight flight should flown though victory depended end result does October1976 93
Edition: Model Aviation - 1976/10
Page Numbers: 36, 37, 38, 39, 40, 93
S fine Nordic A/2 its best light conditions thermal activity weak non-existent Jim Walters Photos Jim Land Mark Vercam men EVERY SERIOUS A/2 flier knows needs glider box can counted early morning later afternoon rounds thermal activity light non-existent Sno Bird may magic 3-mm model will deliver extra performance under light conditions need Still-air glide tests Sno-Bird clearly demonstrated model significantly better previous A/2 gliders Built winter 1974-75 up coming World Championships Plovdiv model tested under clear winter skies snow ground air temperature around 400F still death Sno-Bird would consistently average 70 sec floated off line 64 ft altitude line length plus arm reach same time next best model original sheeted version averaged respectable 65 sec new design proven itself better good margin model represents latest still-air version current Bird series features rather high aspect ratio 1731 simplified sheeted wing body construc tion circle tow/catapult tow hook wing section slightly modified Benedek D7457-d/2 section gained popularity early 1960s namely Norm Ingersolls Harbinger still quite competitive contemporary sections Certainly advantage section its depth permits maxi mum separation main spar chords resulting wing high strength-toweight ratio stab section close copy stab sections Ectenkovs EGl 172 Elton Drews Lively Lady earlier version built 1969 suc cessfully used qualify 70 72 74 team-selection finals 74 Taft used first two rounds its still-air performance paid off team position Construction Before beginning actual construction necessary make couple building aids cambered wing board rib templates Building conventional undercambered wing cambered board possible building sheeted wing especially heavy trailing edge would next impossible Also cambered board along proper planform shape LE somewhat straight TE swept forward give desired amount tip wash-out about 3/16 boards clear vertical grain cedar redwood 1 X 6 1 X 8 stock about 48 long board should flat pos sible measurable twist Trace 36 Model Aviation Top Widely respected Nordic A/2 circles Jim Walters displays Sno-Bird has 173-to-i aspect ratio features circle-tow catapult tow hook Above An accurate wing construction board imperativemade using table saw cut grooves matching lower surface remaining material right removed using block plane light sanding lower camber main rib onto end board using table saw cut grooves blade width full length approximately 3/16 intervals just match camber line see photo remaining material removed using block plane finally sanding block see photo board will take 2 4 hours build easily makes up ease building wooden strip approxi mately crewed forward edge board used indexing rib locations ensures straight lead ing edge other templates wing stab rib patterns made Y6 plywood per mit fast accurate slicing ribs par ticularly wing ribs feathered trailing edge see photo use wing rib pattern cut lower camber first piece balsa see photo push other end template against balsa piece cut upper camber see photo tapered tip ribs after cut ting lower camber rotate tem plate about leading edge obtain proper rib length shown sketch plan As can see airfoil section near tip deviates true section still retains adequate shape Wing Cut out wing rib index strips top border plan attach wooden strip trailing edge board using paper cement sparingly must remove reverse later build other wing Add wax paper prevent parts sticking board Trim lower inboard sheet exactly 5 X 26 long trim upper sheet yet After adding top sheet slight excess width allows neatly trim away area glue oozes out leaving neat trailing edge exactly right chord Pin lower sheet board aligning rib index strips glue 3/16 sq spruce leading edge may pre-shaped lower spar spar doubler using couple pre-cut wing ribs locating guide Use slightly thinned aliphatic glue joints except area around wing root tubing moderate curing epoxy used Next using paper rib index strips guide glue ribs position widening spar slots necessary plywood root rib edral rib must slanted match dihedral angles shown plan Add aluminum tubes top spars 1/32 verti cal grain balsa web between spars After completely dry lightly sand wing remove rough spots around spars shape leading edge sand lower sheet trailing edge lightly top sheet will fit smoothly Now comes easy part installation top sheet pins Cut top sheets slightly oversize sure check sheet width upper curvature Prepare tools ahead time Youll need approximately 150 size #16 #18 #32 rubberbands few pins thinned aliphatic glue Position lower wing half board using couple pins stuck through end ribs keep shifting Lightly apply glue mating surfaces gently position top sheet using couple pins end Now begin wrap bands clear around wing board see photo begin ning center working towards ends first fairly wide spacing 1- 1 adding bands between until en tire wing covered bands spaced approximately t bands apply light pressure ensures smooth accurate wing shape million pin holes top surface Re peat tip section allow dry overnight before removing board possible allow wing sections several days curing harden glue makes sanding leading edge lot easier trim trailing edge until wing near completion allows adjust chord slightly approach maximum permissible wing area easily trimmed using table saw Sanding October1976 37 Top Template insures accurate duplication ot ribs feathered edgesalso used tapered ribs Above Cut lower camber first up per camber key accurate ribs Right Template being used cut upper rib camber Below Closely spaced rubberbands apply pressure gluing upper sheet un sightly pinholes Right Table saw utilized heat-sink molding lead nose weight Sno-Bird leading-edge radius before joining panels permits easy inspection proper shape Attaching tip section cen ter section similar building handlaunch glider wing Just sand proper dihedral angles section double glue using moderate cure epoxy ali phatic Ambroid type glue Note bothersome ply wood dihedral bracesthis type wing construction just doesnt need Sand upper lower surfaces lightly 400-600 grit paper using care oversand Add root plywood rib trim excess aluminum tubing Add soft balsa tips trailing edge stiffeners Give three coats 50-50 dope plasticizer added use 3-4 drops di-butlyl-phthlate per ounce Tissue used adds un necessary weight tends produce warps Sanding sealer may applied lower surface believe natural roughness balsa grain upper surface aids turbulating wing Add trim numbers thread turbulator What appears aerodynamic fences external extensions wing ribs used strengthen trailing edge thread turbulator just aft IE does show photo TRIM EXCESSTOP AFTER INSTAuINO BUTT RIB 332DATUBlNG 1/810 AL TUaNG ii ii ii ii II m 1ThLTWTWGC __0 _____1 EDGEL WTF/G LOTHB 1/16 PLY-23/32 BALSATTRAILNO EDGE STIF RiDDER LSVER 032MW lAD NOSE WEIGHT 4 2 ____ 3/B PLY CORE 3/32 PLYFILL HOLE 1/16 PLj 3 REOD / D SEN 0 D2DW N DO SN OW NE~MER CU OU 3/32DAI-IOE RJWER EVER ON RT SOF1/B DIA HOLE 3/32 PLY 2 REOD 3/B LEAD NOSE1/4 DIA CLEAR WEIGHT 3/B PLY CORE 1/4 x 3/B MAPLE OR OAK HOOK SUPPORTS FOR COMPETE DETAILS OF TOWHOOK SEE ARTICLE IN JAN 1974 FLYING MODELS BY BOB HATSCHEK TOWHOOBCASTING KIT MAY BEOBTANED FROM JIM CROCKET F 1442 N FRUIT ST FRESMO CA 93726 Above Rudder stop stab stroker pulled Below rudder stop stroker shown forward allowing rudder stab deflect released picture thus pushing rudder a circletow position tight turn glide turn position wing leading edge Total weight wing should 160-180 grams depend ing density balsa sheeting Stabilizer Using same procedure cutting out wing tip ribs cut stab ribs false ribs fairly hard 8-l0# 1/32 medium 6-8 1/16 1/20 balsa Make series shims 1/32 sheet pack up lower spar forward edge trailing edge main tain proper airfoil shape Use fairly hard balsa trailing edge leading edge spars upper spar tapered 1/16 X 1/s Y6 sq Lay down notched trailing edge bottom spar add ribs add leading edge false ribs gussets thick tip rib Use ali phatic glue sparingly assembly Shape leading edge sand structure us ing 400 grit paper Give structure coat clear dope cover using superfine lightweight Japanese tissue Apply 3 coats 50-50 dope plasticizer Stab weight should 7-9 grams Fuselage Begin fuselage cutting core / 3-ply commercial lum beryard plywood fir okay sides 3/32 aircraft plywood Size cut outs core D/T timer type towhook types circle towhook ideas available present possess some advantages can readily adapted Sno-Bird Hatschek towhook used origi nal model permits low body pro file Using plywood wing root rib template match drill plywood side wing wires Now mark hole loca tions core drill two 14 diameter clearance holes through core eter epoxy access holes through edge core drill other 3/32 side yet make nose weight cut shape scrap i/i plywood melt scraps lead sinkers etc tomato can heated over Coleman stove Place plywood form over flat metal surface such table saw top pour lead exactly ply thickness see photo metal top serves heat-sink cool lead quickly weight should come out tween 90-100 grams Notch groove WINGRIBINDEXSTRIPS CUTFROM PLAN & ATTACH TOWING BOARD TURBULATOR CARPET THD SRRIJCE 3/32 SO SPRUCEluBE 3/323/16 SO SPRUCE1/Bx1/4 HARD BALSA TAPER TO 1/B SPRUCE & ROT SOFT BALSA -N ~ ~BLCEK BY LIlL3/3250BATAPE TOll 171 ILuVV3/16 WASHOUT BOTH TIPS l/32S1- BALSA TOP& ROT IFFENERS END HERE 1/B RIB TILT APPROX W FOR DIHED 1/32 ID BRASS TUBE STAB TILT FOR RT GLIDE 3/32 PLYZO32 MW XY1 TAB STROKER RUD R MWIRETOP VIEW HI D25 MW 02D BRASS lPLLlETE 3/32x1/2 TAPERTOl/iB, 3/B 1/B DIA1/iBDIA 1/B DIAHOLE020 BRASS 060 NUT 3/32 DIA II RUDDER TOBSION1/32 GA0-JBEND FROM A5 DT ANGLE SPRING U1MWHOLESOLDER3/32 GA CCWIPRD2D WIREPPRDRILL 1/32 HOLE P015 WIRES ~IjRTS1/16 ID RBASSSPRING FIBERGLASS TAILBOOM 35LGTUBINGRUDDER STOP-HD BALSAl/32IDAL TUNING 50 DI HIDAPPROX 20RU FW TUBE-DRILL FOR LT NE WT 3 RUDDER STOP EPOXY GROMMET LATE WITH 6-32 SCREWS & NUTSTO INSIDE FiR 060 SOREWOT LINE OBONUTSOLUER1/32 WIRE1/16,1/B K ONLY TO WIRE1/16 PLYSPRLCE1JFT 1/B SH --30-DDLB DACRON LINE STR TOW .TOWHOOKSH WING RIB PATTERN 1/16 PLYGLIDE RUR STOP STAB STROKERCTSEE SE AlL ABDEE OBOSCREW FORLAMINATE 2501/320/B & RUDDERSTFFENERTIP RIBSTAB ADJUSTHL BALSA ES RECOFALSEPOXY NUT TO15 LB MOHOFIL NYLON TO INSIDE OP BOOM TOWLINE PULL PIN 1/iBMED BALSA 3BREODSTAB RIB-CTR-3/32OBOSCREW& WASHER TO 1/B MED BALSA OTHERS 1/320R1/20l/Lj~ADJUST RUDDER STOP EPOXY TO FIN ADJUSTMENTS ESTAB RIB-TIPWING- 9l/~ STAB 4/2 RH SIDE025 MWRTGLIDETU 020ALSTAB STOPHINGE 1/16 PLY 2 REOD REOD STAB PLATFORM 1/16 PLY SNO-BIRD FlA NOR DIG GLIDER SPAN 89 WINGAREA 456sq 0 1 2 3 4 56LENGTH 43 STAB AREA 6Bsq ALL GMENSIONS IN INCHESDes9nad Drn JIM WALTERS October1976 39 Sno- Bird ply sides match fiberglass rod Using moderate cure epoxy assemble sides core hook supports tail boom using care align tailboom dry round edges except wing mates fuselage Now drill wire holes through other plywood side using holes first side guide Bend two wing wires install holes checking see wires come out parallel slight wash-in LE up right wing wash-in necessary keep right wing dipping during cata pult launches also tends keep model spinning turbulent air wires centered fuselage glued install wings rotate wires required slightly aft match high angle wing neglect wing will fit flush against fuselage sides youre satisfied fit-up carefully remove wings out disturbing wires apply epoxy through two access holes core Build fin soft sheet rudder i/s sheet Groove base fin match fiberglass rod add short piece aluminum tubing 1/32 ID after shaping fin proper airfoil shape epoxy tailboom has preroughened sand paper improve adhesion ad hesive Epoxy 3/32 plywood stab platform short piece fiberglass tube Com plete rudder circle-tow hardware shown plans differ slightly original Hatschek hardware pro duce same action Consult Bob Hats cheks article Flying Models January 1974 operation towhook Remember moderate pull should move rudder neutral relaxed torsion spring should just strong enough drive rudder against ex treme rudder stop Too stiff torsion spring will result too high towline pull straight tow model will straighten out circle proper time will go next unwanted cir cle hopefully accomplished trial error hopefully too much error stab stroker idea Paul Crow ley added original model tends prevent spin-in during circle-tow mode See photos raises trailing continued page 93 40 Model Aviation Left Normal towline pressure pulls rudder neutral position straight tow Below position two-way rudder stop allows rudder deflect circle turn launch spring pushes rudder glide-turn posi tion Development goes back 69 S no-Bird/Walters continued page 40 edge about 1/16 compensate tighter turn during circle-tow mode rudder offset actu ated same line pulls rudder stop forward consequently released moment launch simple de vice add however original model did possess spin-in tendencies towline use 50-lb-test lowstretch nylon monofilament line dia has about 3 ft stretch 2 kilogram load tow use reel using small plastic ring better yet just loop end loop around small finger left hand store line FAI Supply reel works nicely opening up coils line guide filing small notch 1/32 wide deep edge spool hook loop over prior winding Testing youre satisfied operation hook spring re lease set 5-6 lbs ready first test flight Fly test flights rela tively calm air preferably over 7-8 mph Hand glide adjust rudder stop stab adjustment screw slight right turn no apparent stall Fly first flight full towline length D/T set 20-30 sec jatch set will permit float model off line check glide its quite right will D/T come safely down After several flights floating model off line having made necessary stab rudder adjustments produce straight tow flat glide circling ap proximately once 30-50 sec ready big moment first circle tow Just set latch tow model before except instead floating off let circle line attached Once just begins come around wind begin tow straight bring model overhead let circle again prepared run downwind fast keep line slightly slack during downwind circle line tightens up model may pulled ground Most fliers find out hard way model will come out turn want too much spring force rudder torsion spring towhook may too far ward Learning circle tow real ex perience fliers first try find requires lot fancy footwork Most us have towed model ground time another try testing over grass possible youre ready launch pull down sharply release latch keep pressure deflect rudder zoom position release model should bank slightly right released gain altitude model turns too steep begins spiral decrease zoom rudder offset stalls severely increase rudder offset As previously mentioned tow reel hold several feet slack line releasing let slack go two-ring slips off easily youre fly ing strong wind its necessary keep 8-10 ft slack line available let out quickly keep load exceeding un latch force launch some slack necessary let tow-ring slide free conclusion remember win re quires possessing good model important have winning attitude essentially means committing some error should have control over commonly known shooting oneself foot winner person generally flies model its full potential time testing complete youre satisfied models per formance begin practice Fly flight purpose checking likely conditions keeping records flights work towards eliminating bad flight flight should flown though victory depended end result does October1976 93