GOTTHEBUILT-UP Harry Schoaf looks scarey sure beats making em time weight 25% solid ribs Bet wont want cover wing THE method developed make possible production identical built-up ribs using minimum amount time effort object produce rib unit Fig 1 complete truss sheets glued place finished ribs may cutoff Naturally some preliminary work necessary order produce rib unit However once accomplished making ribs particular airfoil rapid very gratifying author has used method several years mostly flying scales has found strength weight ratio unequaled Once ribs place spars appearance striking almost prevents covering wing airfoil used illustrations 10 12 6 2FIG2 5 26 34 FIG 3 81012- l3J 911 14 Fig 3 begin select airfoil draw size desired show spar locations truss workallow cap strips usedand sizes rib pieces Curtiss C-72 used Curtiss Fledgling N2C1 model built scale ' ves span about 59 inches chord rib shown 7 inches Whatever chord being made have found advisable exceed 2 inches rib unit width makes insertion gluing truss sheets Fig 2 2-A reasonably easy Besides 2-in sheets handier work begin project select airfoil draw size desired show spar locations truss work allow cap strips used size rib pieces Note Fig 3 truss members numbered strongly suggest corresponding numbers put truss sheets order prevent later possible con fusion Have couple copies rib drawing made come handy reference later Glue drawing piece plywood Plexi glas whatever prefer make rib template used authentic scale truss arrange ment Fledgling rib happened work Out nicely truss zigzag between spars forming nice series triangles help maintain curvature sheets next step making surface sheet form blocks blocks should 2 inches wide thickness about least twice height airfoil system length equal sections chord plus inch inch half added end example N2C-l section about 7/g inches thick chord 7 inches form blocks measured 2 inches wide about 2 inches thick 10 inches long Having some white pine hand ideal job however other woods can used See Fig 5 Using template lay Out shape block taking care leading trailing edges same distance ends block necessary because later inter changeability Remember use cap strips contemplated must account cap thickness laying Out block lines Cutting form blocks means band saw time havent perhaps neighbor buddy does insure good smooth cut slowly wearing obtivisor magnifies nicely Sand out irregularities blocks almost ready order help along dryout surface sheets clamped up blocks cut grooves across faces intemal blocks band saw cuts about 3/32- deep spaced -5/32 apart See Fig 4 Both upper lower surface blocks shown Fig 5 Fledgling rib unit used 1/16 medium sheet top bottom surfaces estimated need 6 rib units cut 12 surface pieces soaked some boiling water 15 minutes clamped up form blocks let dry 20-24 hours warm oven would have reduced time-to-dry one-half perhaps no hurry rest sheets 22 Model Aviation Top Fig 2Chord example 7/2 innot advisable exceed 2 rib unit width makes reasonably easy labove insert glue truss sheets *///5/9~ . 6 4 2 soaked concentrated ammonia solution clamped dried found result method have little difference According big boys ammonia sheets should have very little spring-back reality little better boiled ones explanation believe balsa due its capsule cellular structure resists being thoroughly soaked re member Kon Tiki hence ammonia very effective Incidentally times past have clamped up two sheets time allowed little time dry True wont give piece same curve small consequence because after approximate curve stage Fig 6 illustrates surface sheets clamped up Attention may now given cutting truss sheets Refer rib drawing select sheet thickness various truss pieces differ try cut truss sheet its proper length Getting angle edge about right advantageous really much work certain get grain vertical direction Fig 2 order determine rib units needed produce required number ribs Ill refer Fledgling again planned cut ribs 116-in thick using 7-in hollow ground multitooth Sears veneer blade blade obtain able Sears stores has kerf about 1/16 inch So figured rib would takes inch plus hair thus 2-in rib unit would yield 14 15 ribs Since required 71 ribs six units yielded total 86 gave some spares came handy because some handling damage Now rib unit glue-up need top part upper surface form block lower part lower surface form block Place together shown Fig 7 attach suitable stops top block ends prevent fore aft movement dowel system would also work well Make dummy spars long enough project out side blocks Locate spars fixed side stops guides loose pieces shown Fig 7-A will need loose piece spar location removed proper truss piece inserted gluing Begin assembly clamping form blocks together surface sheets place will helpful place temporary spacer about 30% chord position keep surfaces fully separated Use ps during glue-up operation first pieces glued adjacent spars Once set remove spars should noted glues like Hot Stuff etc used mindful can penetrate balsa rib sheets may become part form block happening could disturb whole day same applies dummy spar Use material like Saran Wrap guard against unwanted joints Insert remaining truss sheets proper places voila its finished looks something like Fig 8 dried remove rib unit inspect internal glue joints Make certain joints solid Continue next rib unit glue-up proceed cut-off operationthe fun part couple ways cut off ribs band saw fence clamped place works very well however band saw gives rougher cut table saw plus band saw narrower kerf means ribs per rib unit table saw probably effective larger ribs table saw presents minor roadblock needs elim inated before cut standard blade insert has slot about blade comes through moves fence 1/16 inch blade cut rib being cut will break swept down crack sort work made up several wood inserts various blades Soft aluminum may also used August 198023 Fig 1 r b unt complete wth truss sheets glued place sothatfinished ribs may cut off Airfoil used n Ilustrat ons s Curtiss C72 found Curtiss Fledgling Fig 4 next step make surface sheet form blocks about 2 wide thickness about twice height airfoil system minimum length equal sections chord plus 11/2 added end Youll need study text point Fig 5 White pine ideal forthe job other woods may used ung srlesempIase isee Text lay out shape block Leading trailing edges must same distance block ends Insert new insert blank place carefully crank up running submerged blade cuts up insert makes its own slot insert can cut strips against fence paper thin See Fig 9 Make couple test cuts waste stock establish thickness rib desired proceed slice em off Occasionally may knock out truss piece due poor glue area pushing unit through too fast Move slowly carefully best results significant attribute built-up rib low weight Fledgling ribs averaged 30 grams solid rib same dimensions weighed 120 grams ratio 4 Fig 10 shows Fledglings lower wing root Fig 11 shows Fledgling rib unit lower wing 5-in chordofa Hawker Fury MK forcomparison Built-up ribs have fore aft compressive load capacity solid rib because just isnt much wood built-up planning use highly loaded covering such silk wise use solid rib 6 8 ribs occasional compression member between spars Ia full-scale practice procedure making ribs described above great big wing chords 5 6 inches up whatever salary will permit Smaller chords can built simpler method dont have big power tools dispos al Its great flat-bot tom sections especially want light structure Its method favored Fulton Hungerford case think may exercise genius producing magnifi cent wheels also mas ter model building inno vator Assuming have airfoil section laid out truss work established cut flat-bottom surface sheet sheet glue truss sheets have cut length See 5 TOP 0 LWR D REAR SPAR FRONT SPAR LOOSE PIECELOOSE PIECE IN PLACE TO LOCATE REAR SPAR FIG 7-A Fig 7 TopFor final glue-up need top part upper surface block lower part lower surface form block Stops B C D stop fore aft movement form blocks Above Details Fig 7A show loose pieces locate front rear spars 24 Model Aviation Fig 6 Note block foreground clamped together lower rib sheet place IOCk background forms rib upper sheet Grooves cut across face internal blocks Fig 4 speed up dry-out surface sheets Cuts made band sawsee text dimensions Left Fig 8First pieces glued adjacent spars removed Instant glues can penetrate balsa may glue surface sheets form blocks Saran Wrap protects against unwanted joints Below Fig 9Slicing off ribs table saw Carefully read instructions about various types saws jigging etc Wood soft alum inum inserts under rib pile prevent sliced-off rib being swept down crack saw table surface Procedures clearly described JJOTTHE 93UILT-UP III KUefl Fig 12 again wise number edge razor blade rib unit isnt too thick avoid errors choice use X-Acto longer blade thin piece dry cut bend over top sheet having shim stock used metal straightedge very just amply covered truss edges glue useful slice-off operaton Just careful dont pre-bend top surface keep blade vertical _________________ sheet truss work will adequately hold So much couple ways built-up shape Undercamber can easily made ribs Fm certain interested modelers will take pinning down bottom surface sheet over method extend twist bend idea form series wood pieces suit own inventive urges Thats Cutting ribs off achieved single- achieve progress idea spawns another 1 4- Fig 12 smaller chord wings big power tools available method can useddeveloped Fulton Hungerford flat-bottom sheet glue truss sheets cut length dry bend over top sheet truss edges just amply covered glue undercambered sections pin down bottom surface sheet over form series wood pieces August 198025 Top Fig 10The completed lower rib root Fledglings ribs weighs 30 grams Fig 11 below Fledgling rib unit lower wing 5-in chord Hawker Fury MK 1 shown comparison seems work consider goal properly built airplane
Edition: Model Aviation - 1980/08
Page Numbers: 22, 23, 24, 25
GOTTHEBUILT-UP Harry Schoaf looks scarey sure beats making em time weight 25% solid ribs Bet wont want cover wing THE method developed make possible production identical built-up ribs using minimum amount time effort object produce rib unit Fig 1 complete truss sheets glued place finished ribs may cutoff Naturally some preliminary work necessary order produce rib unit However once accomplished making ribs particular airfoil rapid very gratifying author has used method several years mostly flying scales has found strength weight ratio unequaled Once ribs place spars appearance striking almost prevents covering wing airfoil used illustrations 10 12 6 2FIG2 5 26 34 FIG 3 81012- l3J 911 14 Fig 3 begin select airfoil draw size desired show spar locations truss workallow cap strips usedand sizes rib pieces Curtiss C-72 used Curtiss Fledgling N2C1 model built scale ' ves span about 59 inches chord rib shown 7 inches Whatever chord being made have found advisable exceed 2 inches rib unit width makes insertion gluing truss sheets Fig 2 2-A reasonably easy Besides 2-in sheets handier work begin project select airfoil draw size desired show spar locations truss work allow cap strips used size rib pieces Note Fig 3 truss members numbered strongly suggest corresponding numbers put truss sheets order prevent later possible con fusion Have couple copies rib drawing made come handy reference later Glue drawing piece plywood Plexi glas whatever prefer make rib template used authentic scale truss arrange ment Fledgling rib happened work Out nicely truss zigzag between spars forming nice series triangles help maintain curvature sheets next step making surface sheet form blocks blocks should 2 inches wide thickness about least twice height airfoil system length equal sections chord plus inch inch half added end example N2C-l section about 7/g inches thick chord 7 inches form blocks measured 2 inches wide about 2 inches thick 10 inches long Having some white pine hand ideal job however other woods can used See Fig 5 Using template lay Out shape block taking care leading trailing edges same distance ends block necessary because later inter changeability Remember use cap strips contemplated must account cap thickness laying Out block lines Cutting form blocks means band saw time havent perhaps neighbor buddy does insure good smooth cut slowly wearing obtivisor magnifies nicely Sand out irregularities blocks almost ready order help along dryout surface sheets clamped up blocks cut grooves across faces intemal blocks band saw cuts about 3/32- deep spaced -5/32 apart See Fig 4 Both upper lower surface blocks shown Fig 5 Fledgling rib unit used 1/16 medium sheet top bottom surfaces estimated need 6 rib units cut 12 surface pieces soaked some boiling water 15 minutes clamped up form blocks let dry 20-24 hours warm oven would have reduced time-to-dry one-half perhaps no hurry rest sheets 22 Model Aviation Top Fig 2Chord example 7/2 innot advisable exceed 2 rib unit width makes reasonably easy labove insert glue truss sheets *///5/9~ . 6 4 2 soaked concentrated ammonia solution clamped dried found result method have little difference According big boys ammonia sheets should have very little spring-back reality little better boiled ones explanation believe balsa due its capsule cellular structure resists being thoroughly soaked re member Kon Tiki hence ammonia very effective Incidentally times past have clamped up two sheets time allowed little time dry True wont give piece same curve small consequence because after approximate curve stage Fig 6 illustrates surface sheets clamped up Attention may now given cutting truss sheets Refer rib drawing select sheet thickness various truss pieces differ try cut truss sheet its proper length Getting angle edge about right advantageous really much work certain get grain vertical direction Fig 2 order determine rib units needed produce required number ribs Ill refer Fledgling again planned cut ribs 116-in thick using 7-in hollow ground multitooth Sears veneer blade blade obtain able Sears stores has kerf about 1/16 inch So figured rib would takes inch plus hair thus 2-in rib unit would yield 14 15 ribs Since required 71 ribs six units yielded total 86 gave some spares came handy because some handling damage Now rib unit glue-up need top part upper surface form block lower part lower surface form block Place together shown Fig 7 attach suitable stops top block ends prevent fore aft movement dowel system would also work well Make dummy spars long enough project out side blocks Locate spars fixed side stops guides loose pieces shown Fig 7-A will need loose piece spar location removed proper truss piece inserted gluing Begin assembly clamping form blocks together surface sheets place will helpful place temporary spacer about 30% chord position keep surfaces fully separated Use ps during glue-up operation first pieces glued adjacent spars Once set remove spars should noted glues like Hot Stuff etc used mindful can penetrate balsa rib sheets may become part form block happening could disturb whole day same applies dummy spar Use material like Saran Wrap guard against unwanted joints Insert remaining truss sheets proper places voila its finished looks something like Fig 8 dried remove rib unit inspect internal glue joints Make certain joints solid Continue next rib unit glue-up proceed cut-off operationthe fun part couple ways cut off ribs band saw fence clamped place works very well however band saw gives rougher cut table saw plus band saw narrower kerf means ribs per rib unit table saw probably effective larger ribs table saw presents minor roadblock needs elim inated before cut standard blade insert has slot about blade comes through moves fence 1/16 inch blade cut rib being cut will break swept down crack sort work made up several wood inserts various blades Soft aluminum may also used August 198023 Fig 1 r b unt complete wth truss sheets glued place sothatfinished ribs may cut off Airfoil used n Ilustrat ons s Curtiss C72 found Curtiss Fledgling Fig 4 next step make surface sheet form blocks about 2 wide thickness about twice height airfoil system minimum length equal sections chord plus 11/2 added end Youll need study text point Fig 5 White pine ideal forthe job other woods may used ung srlesempIase isee Text lay out shape block Leading trailing edges must same distance block ends Insert new insert blank place carefully crank up running submerged blade cuts up insert makes its own slot insert can cut strips against fence paper thin See Fig 9 Make couple test cuts waste stock establish thickness rib desired proceed slice em off Occasionally may knock out truss piece due poor glue area pushing unit through too fast Move slowly carefully best results significant attribute built-up rib low weight Fledgling ribs averaged 30 grams solid rib same dimensions weighed 120 grams ratio 4 Fig 10 shows Fledglings lower wing root Fig 11 shows Fledgling rib unit lower wing 5-in chordofa Hawker Fury MK forcomparison Built-up ribs have fore aft compressive load capacity solid rib because just isnt much wood built-up planning use highly loaded covering such silk wise use solid rib 6 8 ribs occasional compression member between spars Ia full-scale practice procedure making ribs described above great big wing chords 5 6 inches up whatever salary will permit Smaller chords can built simpler method dont have big power tools dispos al Its great flat-bot tom sections especially want light structure Its method favored Fulton Hungerford case think may exercise genius producing magnifi cent wheels also mas ter model building inno vator Assuming have airfoil section laid out truss work established cut flat-bottom surface sheet sheet glue truss sheets have cut length See 5 TOP 0 LWR D REAR SPAR FRONT SPAR LOOSE PIECELOOSE PIECE IN PLACE TO LOCATE REAR SPAR FIG 7-A Fig 7 TopFor final glue-up need top part upper surface block lower part lower surface form block Stops B C D stop fore aft movement form blocks Above Details Fig 7A show loose pieces locate front rear spars 24 Model Aviation Fig 6 Note block foreground clamped together lower rib sheet place IOCk background forms rib upper sheet Grooves cut across face internal blocks Fig 4 speed up dry-out surface sheets Cuts made band sawsee text dimensions Left Fig 8First pieces glued adjacent spars removed Instant glues can penetrate balsa may glue surface sheets form blocks Saran Wrap protects against unwanted joints Below Fig 9Slicing off ribs table saw Carefully read instructions about various types saws jigging etc Wood soft alum inum inserts under rib pile prevent sliced-off rib being swept down crack saw table surface Procedures clearly described JJOTTHE 93UILT-UP III KUefl Fig 12 again wise number edge razor blade rib unit isnt too thick avoid errors choice use X-Acto longer blade thin piece dry cut bend over top sheet having shim stock used metal straightedge very just amply covered truss edges glue useful slice-off operaton Just careful dont pre-bend top surface keep blade vertical _________________ sheet truss work will adequately hold So much couple ways built-up shape Undercamber can easily made ribs Fm certain interested modelers will take pinning down bottom surface sheet over method extend twist bend idea form series wood pieces suit own inventive urges Thats Cutting ribs off achieved single- achieve progress idea spawns another 1 4- Fig 12 smaller chord wings big power tools available method can useddeveloped Fulton Hungerford flat-bottom sheet glue truss sheets cut length dry bend over top sheet truss edges just amply covered glue undercambered sections pin down bottom surface sheet over form series wood pieces August 198025 Top Fig 10The completed lower rib root Fledglings ribs weighs 30 grams Fig 11 below Fledgling rib unit lower wing 5-in chord Hawker Fury MK 1 shown comparison seems work consider goal properly built airplane
Edition: Model Aviation - 1980/08
Page Numbers: 22, 23, 24, 25
GOTTHEBUILT-UP Harry Schoaf looks scarey sure beats making em time weight 25% solid ribs Bet wont want cover wing THE method developed make possible production identical built-up ribs using minimum amount time effort object produce rib unit Fig 1 complete truss sheets glued place finished ribs may cutoff Naturally some preliminary work necessary order produce rib unit However once accomplished making ribs particular airfoil rapid very gratifying author has used method several years mostly flying scales has found strength weight ratio unequaled Once ribs place spars appearance striking almost prevents covering wing airfoil used illustrations 10 12 6 2FIG2 5 26 34 FIG 3 81012- l3J 911 14 Fig 3 begin select airfoil draw size desired show spar locations truss workallow cap strips usedand sizes rib pieces Curtiss C-72 used Curtiss Fledgling N2C1 model built scale ' ves span about 59 inches chord rib shown 7 inches Whatever chord being made have found advisable exceed 2 inches rib unit width makes insertion gluing truss sheets Fig 2 2-A reasonably easy Besides 2-in sheets handier work begin project select airfoil draw size desired show spar locations truss work allow cap strips used size rib pieces Note Fig 3 truss members numbered strongly suggest corresponding numbers put truss sheets order prevent later possible con fusion Have couple copies rib drawing made come handy reference later Glue drawing piece plywood Plexi glas whatever prefer make rib template used authentic scale truss arrange ment Fledgling rib happened work Out nicely truss zigzag between spars forming nice series triangles help maintain curvature sheets next step making surface sheet form blocks blocks should 2 inches wide thickness about least twice height airfoil system length equal sections chord plus inch inch half added end example N2C-l section about 7/g inches thick chord 7 inches form blocks measured 2 inches wide about 2 inches thick 10 inches long Having some white pine hand ideal job however other woods can used See Fig 5 Using template lay Out shape block taking care leading trailing edges same distance ends block necessary because later inter changeability Remember use cap strips contemplated must account cap thickness laying Out block lines Cutting form blocks means band saw time havent perhaps neighbor buddy does insure good smooth cut slowly wearing obtivisor magnifies nicely Sand out irregularities blocks almost ready order help along dryout surface sheets clamped up blocks cut grooves across faces intemal blocks band saw cuts about 3/32- deep spaced -5/32 apart See Fig 4 Both upper lower surface blocks shown Fig 5 Fledgling rib unit used 1/16 medium sheet top bottom surfaces estimated need 6 rib units cut 12 surface pieces soaked some boiling water 15 minutes clamped up form blocks let dry 20-24 hours warm oven would have reduced time-to-dry one-half perhaps no hurry rest sheets 22 Model Aviation Top Fig 2Chord example 7/2 innot advisable exceed 2 rib unit width makes reasonably easy labove insert glue truss sheets *///5/9~ . 6 4 2 soaked concentrated ammonia solution clamped dried found result method have little difference According big boys ammonia sheets should have very little spring-back reality little better boiled ones explanation believe balsa due its capsule cellular structure resists being thoroughly soaked re member Kon Tiki hence ammonia very effective Incidentally times past have clamped up two sheets time allowed little time dry True wont give piece same curve small consequence because after approximate curve stage Fig 6 illustrates surface sheets clamped up Attention may now given cutting truss sheets Refer rib drawing select sheet thickness various truss pieces differ try cut truss sheet its proper length Getting angle edge about right advantageous really much work certain get grain vertical direction Fig 2 order determine rib units needed produce required number ribs Ill refer Fledgling again planned cut ribs 116-in thick using 7-in hollow ground multitooth Sears veneer blade blade obtain able Sears stores has kerf about 1/16 inch So figured rib would takes inch plus hair thus 2-in rib unit would yield 14 15 ribs Since required 71 ribs six units yielded total 86 gave some spares came handy because some handling damage Now rib unit glue-up need top part upper surface form block lower part lower surface form block Place together shown Fig 7 attach suitable stops top block ends prevent fore aft movement dowel system would also work well Make dummy spars long enough project out side blocks Locate spars fixed side stops guides loose pieces shown Fig 7-A will need loose piece spar location removed proper truss piece inserted gluing Begin assembly clamping form blocks together surface sheets place will helpful place temporary spacer about 30% chord position keep surfaces fully separated Use ps during glue-up operation first pieces glued adjacent spars Once set remove spars should noted glues like Hot Stuff etc used mindful can penetrate balsa rib sheets may become part form block happening could disturb whole day same applies dummy spar Use material like Saran Wrap guard against unwanted joints Insert remaining truss sheets proper places voila its finished looks something like Fig 8 dried remove rib unit inspect internal glue joints Make certain joints solid Continue next rib unit glue-up proceed cut-off operationthe fun part couple ways cut off ribs band saw fence clamped place works very well however band saw gives rougher cut table saw plus band saw narrower kerf means ribs per rib unit table saw probably effective larger ribs table saw presents minor roadblock needs elim inated before cut standard blade insert has slot about blade comes through moves fence 1/16 inch blade cut rib being cut will break swept down crack sort work made up several wood inserts various blades Soft aluminum may also used August 198023 Fig 1 r b unt complete wth truss sheets glued place sothatfinished ribs may cut off Airfoil used n Ilustrat ons s Curtiss C72 found Curtiss Fledgling Fig 4 next step make surface sheet form blocks about 2 wide thickness about twice height airfoil system minimum length equal sections chord plus 11/2 added end Youll need study text point Fig 5 White pine ideal forthe job other woods may used ung srlesempIase isee Text lay out shape block Leading trailing edges must same distance block ends Insert new insert blank place carefully crank up running submerged blade cuts up insert makes its own slot insert can cut strips against fence paper thin See Fig 9 Make couple test cuts waste stock establish thickness rib desired proceed slice em off Occasionally may knock out truss piece due poor glue area pushing unit through too fast Move slowly carefully best results significant attribute built-up rib low weight Fledgling ribs averaged 30 grams solid rib same dimensions weighed 120 grams ratio 4 Fig 10 shows Fledglings lower wing root Fig 11 shows Fledgling rib unit lower wing 5-in chordofa Hawker Fury MK forcomparison Built-up ribs have fore aft compressive load capacity solid rib because just isnt much wood built-up planning use highly loaded covering such silk wise use solid rib 6 8 ribs occasional compression member between spars Ia full-scale practice procedure making ribs described above great big wing chords 5 6 inches up whatever salary will permit Smaller chords can built simpler method dont have big power tools dispos al Its great flat-bot tom sections especially want light structure Its method favored Fulton Hungerford case think may exercise genius producing magnifi cent wheels also mas ter model building inno vator Assuming have airfoil section laid out truss work established cut flat-bottom surface sheet sheet glue truss sheets have cut length See 5 TOP 0 LWR D REAR SPAR FRONT SPAR LOOSE PIECELOOSE PIECE IN PLACE TO LOCATE REAR SPAR FIG 7-A Fig 7 TopFor final glue-up need top part upper surface block lower part lower surface form block Stops B C D stop fore aft movement form blocks Above Details Fig 7A show loose pieces locate front rear spars 24 Model Aviation Fig 6 Note block foreground clamped together lower rib sheet place IOCk background forms rib upper sheet Grooves cut across face internal blocks Fig 4 speed up dry-out surface sheets Cuts made band sawsee text dimensions Left Fig 8First pieces glued adjacent spars removed Instant glues can penetrate balsa may glue surface sheets form blocks Saran Wrap protects against unwanted joints Below Fig 9Slicing off ribs table saw Carefully read instructions about various types saws jigging etc Wood soft alum inum inserts under rib pile prevent sliced-off rib being swept down crack saw table surface Procedures clearly described JJOTTHE 93UILT-UP III KUefl Fig 12 again wise number edge razor blade rib unit isnt too thick avoid errors choice use X-Acto longer blade thin piece dry cut bend over top sheet having shim stock used metal straightedge very just amply covered truss edges glue useful slice-off operaton Just careful dont pre-bend top surface keep blade vertical _________________ sheet truss work will adequately hold So much couple ways built-up shape Undercamber can easily made ribs Fm certain interested modelers will take pinning down bottom surface sheet over method extend twist bend idea form series wood pieces suit own inventive urges Thats Cutting ribs off achieved single- achieve progress idea spawns another 1 4- Fig 12 smaller chord wings big power tools available method can useddeveloped Fulton Hungerford flat-bottom sheet glue truss sheets cut length dry bend over top sheet truss edges just amply covered glue undercambered sections pin down bottom surface sheet over form series wood pieces August 198025 Top Fig 10The completed lower rib root Fledglings ribs weighs 30 grams Fig 11 below Fledgling rib unit lower wing 5-in chord Hawker Fury MK 1 shown comparison seems work consider goal properly built airplane
Edition: Model Aviation - 1980/08
Page Numbers: 22, 23, 24, 25
GOTTHEBUILT-UP Harry Schoaf looks scarey sure beats making em time weight 25% solid ribs Bet wont want cover wing THE method developed make possible production identical built-up ribs using minimum amount time effort object produce rib unit Fig 1 complete truss sheets glued place finished ribs may cutoff Naturally some preliminary work necessary order produce rib unit However once accomplished making ribs particular airfoil rapid very gratifying author has used method several years mostly flying scales has found strength weight ratio unequaled Once ribs place spars appearance striking almost prevents covering wing airfoil used illustrations 10 12 6 2FIG2 5 26 34 FIG 3 81012- l3J 911 14 Fig 3 begin select airfoil draw size desired show spar locations truss workallow cap strips usedand sizes rib pieces Curtiss C-72 used Curtiss Fledgling N2C1 model built scale ' ves span about 59 inches chord rib shown 7 inches Whatever chord being made have found advisable exceed 2 inches rib unit width makes insertion gluing truss sheets Fig 2 2-A reasonably easy Besides 2-in sheets handier work begin project select airfoil draw size desired show spar locations truss work allow cap strips used size rib pieces Note Fig 3 truss members numbered strongly suggest corresponding numbers put truss sheets order prevent later possible con fusion Have couple copies rib drawing made come handy reference later Glue drawing piece plywood Plexi glas whatever prefer make rib template used authentic scale truss arrange ment Fledgling rib happened work Out nicely truss zigzag between spars forming nice series triangles help maintain curvature sheets next step making surface sheet form blocks blocks should 2 inches wide thickness about least twice height airfoil system length equal sections chord plus inch inch half added end example N2C-l section about 7/g inches thick chord 7 inches form blocks measured 2 inches wide about 2 inches thick 10 inches long Having some white pine hand ideal job however other woods can used See Fig 5 Using template lay Out shape block taking care leading trailing edges same distance ends block necessary because later inter changeability Remember use cap strips contemplated must account cap thickness laying Out block lines Cutting form blocks means band saw time havent perhaps neighbor buddy does insure good smooth cut slowly wearing obtivisor magnifies nicely Sand out irregularities blocks almost ready order help along dryout surface sheets clamped up blocks cut grooves across faces intemal blocks band saw cuts about 3/32- deep spaced -5/32 apart See Fig 4 Both upper lower surface blocks shown Fig 5 Fledgling rib unit used 1/16 medium sheet top bottom surfaces estimated need 6 rib units cut 12 surface pieces soaked some boiling water 15 minutes clamped up form blocks let dry 20-24 hours warm oven would have reduced time-to-dry one-half perhaps no hurry rest sheets 22 Model Aviation Top Fig 2Chord example 7/2 innot advisable exceed 2 rib unit width makes reasonably easy labove insert glue truss sheets *///5/9~ . 6 4 2 soaked concentrated ammonia solution clamped dried found result method have little difference According big boys ammonia sheets should have very little spring-back reality little better boiled ones explanation believe balsa due its capsule cellular structure resists being thoroughly soaked re member Kon Tiki hence ammonia very effective Incidentally times past have clamped up two sheets time allowed little time dry True wont give piece same curve small consequence because after approximate curve stage Fig 6 illustrates surface sheets clamped up Attention may now given cutting truss sheets Refer rib drawing select sheet thickness various truss pieces differ try cut truss sheet its proper length Getting angle edge about right advantageous really much work certain get grain vertical direction Fig 2 order determine rib units needed produce required number ribs Ill refer Fledgling again planned cut ribs 116-in thick using 7-in hollow ground multitooth Sears veneer blade blade obtain able Sears stores has kerf about 1/16 inch So figured rib would takes inch plus hair thus 2-in rib unit would yield 14 15 ribs Since required 71 ribs six units yielded total 86 gave some spares came handy because some handling damage Now rib unit glue-up need top part upper surface form block lower part lower surface form block Place together shown Fig 7 attach suitable stops top block ends prevent fore aft movement dowel system would also work well Make dummy spars long enough project out side blocks Locate spars fixed side stops guides loose pieces shown Fig 7-A will need loose piece spar location removed proper truss piece inserted gluing Begin assembly clamping form blocks together surface sheets place will helpful place temporary spacer about 30% chord position keep surfaces fully separated Use ps during glue-up operation first pieces glued adjacent spars Once set remove spars should noted glues like Hot Stuff etc used mindful can penetrate balsa rib sheets may become part form block happening could disturb whole day same applies dummy spar Use material like Saran Wrap guard against unwanted joints Insert remaining truss sheets proper places voila its finished looks something like Fig 8 dried remove rib unit inspect internal glue joints Make certain joints solid Continue next rib unit glue-up proceed cut-off operationthe fun part couple ways cut off ribs band saw fence clamped place works very well however band saw gives rougher cut table saw plus band saw narrower kerf means ribs per rib unit table saw probably effective larger ribs table saw presents minor roadblock needs elim inated before cut standard blade insert has slot about blade comes through moves fence 1/16 inch blade cut rib being cut will break swept down crack sort work made up several wood inserts various blades Soft aluminum may also used August 198023 Fig 1 r b unt complete wth truss sheets glued place sothatfinished ribs may cut off Airfoil used n Ilustrat ons s Curtiss C72 found Curtiss Fledgling Fig 4 next step make surface sheet form blocks about 2 wide thickness about twice height airfoil system minimum length equal sections chord plus 11/2 added end Youll need study text point Fig 5 White pine ideal forthe job other woods may used ung srlesempIase isee Text lay out shape block Leading trailing edges must same distance block ends Insert new insert blank place carefully crank up running submerged blade cuts up insert makes its own slot insert can cut strips against fence paper thin See Fig 9 Make couple test cuts waste stock establish thickness rib desired proceed slice em off Occasionally may knock out truss piece due poor glue area pushing unit through too fast Move slowly carefully best results significant attribute built-up rib low weight Fledgling ribs averaged 30 grams solid rib same dimensions weighed 120 grams ratio 4 Fig 10 shows Fledglings lower wing root Fig 11 shows Fledgling rib unit lower wing 5-in chordofa Hawker Fury MK forcomparison Built-up ribs have fore aft compressive load capacity solid rib because just isnt much wood built-up planning use highly loaded covering such silk wise use solid rib 6 8 ribs occasional compression member between spars Ia full-scale practice procedure making ribs described above great big wing chords 5 6 inches up whatever salary will permit Smaller chords can built simpler method dont have big power tools dispos al Its great flat-bot tom sections especially want light structure Its method favored Fulton Hungerford case think may exercise genius producing magnifi cent wheels also mas ter model building inno vator Assuming have airfoil section laid out truss work established cut flat-bottom surface sheet sheet glue truss sheets have cut length See 5 TOP 0 LWR D REAR SPAR FRONT SPAR LOOSE PIECELOOSE PIECE IN PLACE TO LOCATE REAR SPAR FIG 7-A Fig 7 TopFor final glue-up need top part upper surface block lower part lower surface form block Stops B C D stop fore aft movement form blocks Above Details Fig 7A show loose pieces locate front rear spars 24 Model Aviation Fig 6 Note block foreground clamped together lower rib sheet place IOCk background forms rib upper sheet Grooves cut across face internal blocks Fig 4 speed up dry-out surface sheets Cuts made band sawsee text dimensions Left Fig 8First pieces glued adjacent spars removed Instant glues can penetrate balsa may glue surface sheets form blocks Saran Wrap protects against unwanted joints Below Fig 9Slicing off ribs table saw Carefully read instructions about various types saws jigging etc Wood soft alum inum inserts under rib pile prevent sliced-off rib being swept down crack saw table surface Procedures clearly described JJOTTHE 93UILT-UP III KUefl Fig 12 again wise number edge razor blade rib unit isnt too thick avoid errors choice use X-Acto longer blade thin piece dry cut bend over top sheet having shim stock used metal straightedge very just amply covered truss edges glue useful slice-off operaton Just careful dont pre-bend top surface keep blade vertical _________________ sheet truss work will adequately hold So much couple ways built-up shape Undercamber can easily made ribs Fm certain interested modelers will take pinning down bottom surface sheet over method extend twist bend idea form series wood pieces suit own inventive urges Thats Cutting ribs off achieved single- achieve progress idea spawns another 1 4- Fig 12 smaller chord wings big power tools available method can useddeveloped Fulton Hungerford flat-bottom sheet glue truss sheets cut length dry bend over top sheet truss edges just amply covered glue undercambered sections pin down bottom surface sheet over form series wood pieces August 198025 Top Fig 10The completed lower rib root Fledglings ribs weighs 30 grams Fig 11 below Fledgling rib unit lower wing 5-in chord Hawker Fury MK 1 shown comparison seems work consider goal properly built airplane