I I Editors note two-part article reviewed technical content noted modeler engineer Gil Morris Per review modifications have made original text author provided copy review asked consider revising text declined appropriate have included Morris comments italics presented allow reader form own judgments intended polarize discussion Please see Haught Cornerfor full discussion presentation I I II I g liLd study full scale aircraft structural design fascinating Take Bleriots cross channel monoplane its fuselage consisted four wooden longerons wooden crossmembers whole thing being wire braced Covering fabric fact aft fuselage left uncovered wing two wooden spars ribs fabric covering wire braced provided strength yet flexible torsion since lateral control wing warping Tail surfaces also wood fabric covering wire bracing Under impetus WW developments power plants aerodynamics structure rapid Early designers found drag reduction man datory improve performance take advantage greater engine power Fuselages became rounded oval cross-section retained same four-longeron load-bearing structures steel tubing formers stringers fabric covered providing external nonload-bearing shape Biplane wingswhich per mitted interplane bracing provide light yet strong structuresbecame popular drag high part tail surfaces outlined steel tubing flat surfaced fabric covered wire braced latter stages WW Germans developed rounded July1994 33 Authors original Osprey designed according principles presented Flies tail-dragger twin floats Srucur D.sign - L14 TIC MARKS x SOFT RUBBER SQUARE FIGURE nWThTFFWTFVrmTrvm - UiiijjjjjjjjjjjjjJjjjjJfl COMPRESSION FIGURE 3 all-plywood fuselage plywood skin provided low-drag external shape also absorbed structural loads thus locating material far neutral axis possible light yet strong stress-skinned structure achieved Fokker DVIII high-wing monoplane introduced cantilever wing too wooden structure plywood skinned much greater thickness contemporary biplane wings Other struts holding wing above fuselage no drag-producing external bracing stress-skinned As Allied air forces found Fokker DVIII formidable adversary Lockheed US de Havilland Great Britain produced plywood stress-skinned aircraft during 1930s Lindberghs Lockheed Sirius classic example WW lIthe deHavilland Mosquito outstanding wooden aircraft four-longeron fuselage externally braced wings metal-tube tail surfaces survive such aircraft Beech Staggerwing Piper Cub ultralights -What followed gradual swing all-metal stress-skinned aircraft structures Today aircraft produced quantity design Piper Beech Cessna Boeing McDonnell Douglas Lockheed examples 1970s use composite material came prominence pioneered German glider manufacturers Burt Rutan VariEze LongEze finally spectacular Voyager Beech Starship canard outstanding example Fiberglass epoxy foam carbon boron fibers Aramid Nomexall replacing metalbecame popular particularly sportplane field under stimulus Experimental Aircraft Association aircraft provide outstanding performance modest horsepower structures follow sound engineering principle locating material structures far neutral axis possible Now what neutral axis business about nodding acquaintance tension compression torsion/shear bending leverage will serve introduction Visualize piece rubber vertical lines spaced inch apart Figure 1 Figure 2 rubber under tension vertical lines spread apart rubber thins cross-section Figure 3 rubber under compressionthe opposite tension vertical lines move closer another cross-section thickens Figure 4 illustrates torsion shear ends rubber being twisted opposite directions rubber partially cut through edges cut would move apart Figure 4 Shear loads induced torsion twisting Bending illustrated Figure 5 lines move apart outer side bend come closer inner side upper edge under tension lower under compression Take hard look Figure 6 two rubber strips being bent together Note lower edge upper piece being compressed immediately below upper edge lower piece under tension opposing forces exerted along contact line between upper lower rubbers neutral axis piece rubber rather two neutral axis would under shear Bending thus combination tension compression shear July1994 35 TENSION FIGURE 2 SHEAR FIGURE 4 TEN SI ON N FIGURE 5 TENSION COMPRESSION SHEARNEUTRAL SURFACE FIGURE 6 Morris neutral axis intersected neutral surface neutral axis cross-section piece rubber rage portrayed Figure 7 lever shown resting fulcrum force 3 pounds B balanced force 1 pound engineering terms force 3 pounds lever foot long produces moment 3 foot-pounds does force 1 pound lever 3 feet long longer lever fulcrum point lower force needed achieve balance smaller cross-section area material needed resist force Morris fulcrum neutral axis would off-center section symmetrical modulus elasticity material side different other side assume simplicity [we] discussing symmetrical sections uniform materials composites example carbon side balsa other course would have off-center neutral axis might represented lever re 8 shows end view rubber strip lever arm neutral axis center cross-section area shown Figure 8B same cross-section areas have separated tensile compressive areas have separated joined vertical shear web increase bending strength proportional increase length levers Shear loads sustained web neutral axis Figure 8C shows greater separation top bottom flanges increases leverage permitting beam same strength 8B considerable reduction cross-section reduction material weight Figure 9A shows solid round rod rearranging same cross section area form cylinder Figure 9B torsional bending strengths improved proportionally increase length lever arms measured neutral axis Editors note Author reviewer disagree Morris says lever arm 9B shown inch long order comparable 9A correctly shown 25 inch lever arm resultant stress force should shown 7 inch long bending strength 9B tubular member 378 3 LBSI LB 4FT FT3FTA times strong round member neering principle increased strength material should located greatest possible distance neutral axis given strength locating material results least material consequently least weight Part II will consider application principle model aircraft structural design 436 Model Aviation 4B 4 3FT/LBFULCRUM3FT/LB LEVERAGE FIGURE 7 LEVERTOP FLANGES ARM NEUTRAL AXIS BEAMSC OTTOM FLANGES FIGURE 8 2 /8 IN LEVER ARM N LEVER ARM EUTRAL AIS /8 IN ROUNDB MEMBER TUBULARMEMBER FIGURE 9
Edition: Model Aviation - 1994/07
Page Numbers: 33, 35, 36
I I Editors note two-part article reviewed technical content noted modeler engineer Gil Morris Per review modifications have made original text author provided copy review asked consider revising text declined appropriate have included Morris comments italics presented allow reader form own judgments intended polarize discussion Please see Haught Cornerfor full discussion presentation I I II I g liLd study full scale aircraft structural design fascinating Take Bleriots cross channel monoplane its fuselage consisted four wooden longerons wooden crossmembers whole thing being wire braced Covering fabric fact aft fuselage left uncovered wing two wooden spars ribs fabric covering wire braced provided strength yet flexible torsion since lateral control wing warping Tail surfaces also wood fabric covering wire bracing Under impetus WW developments power plants aerodynamics structure rapid Early designers found drag reduction man datory improve performance take advantage greater engine power Fuselages became rounded oval cross-section retained same four-longeron load-bearing structures steel tubing formers stringers fabric covered providing external nonload-bearing shape Biplane wingswhich per mitted interplane bracing provide light yet strong structuresbecame popular drag high part tail surfaces outlined steel tubing flat surfaced fabric covered wire braced latter stages WW Germans developed rounded July1994 33 Authors original Osprey designed according principles presented Flies tail-dragger twin floats Srucur D.sign - L14 TIC MARKS x SOFT RUBBER SQUARE FIGURE nWThTFFWTFVrmTrvm - UiiijjjjjjjjjjjjjJjjjjJfl COMPRESSION FIGURE 3 all-plywood fuselage plywood skin provided low-drag external shape also absorbed structural loads thus locating material far neutral axis possible light yet strong stress-skinned structure achieved Fokker DVIII high-wing monoplane introduced cantilever wing too wooden structure plywood skinned much greater thickness contemporary biplane wings Other struts holding wing above fuselage no drag-producing external bracing stress-skinned As Allied air forces found Fokker DVIII formidable adversary Lockheed US de Havilland Great Britain produced plywood stress-skinned aircraft during 1930s Lindberghs Lockheed Sirius classic example WW lIthe deHavilland Mosquito outstanding wooden aircraft four-longeron fuselage externally braced wings metal-tube tail surfaces survive such aircraft Beech Staggerwing Piper Cub ultralights -What followed gradual swing all-metal stress-skinned aircraft structures Today aircraft produced quantity design Piper Beech Cessna Boeing McDonnell Douglas Lockheed examples 1970s use composite material came prominence pioneered German glider manufacturers Burt Rutan VariEze LongEze finally spectacular Voyager Beech Starship canard outstanding example Fiberglass epoxy foam carbon boron fibers Aramid Nomexall replacing metalbecame popular particularly sportplane field under stimulus Experimental Aircraft Association aircraft provide outstanding performance modest horsepower structures follow sound engineering principle locating material structures far neutral axis possible Now what neutral axis business about nodding acquaintance tension compression torsion/shear bending leverage will serve introduction Visualize piece rubber vertical lines spaced inch apart Figure 1 Figure 2 rubber under tension vertical lines spread apart rubber thins cross-section Figure 3 rubber under compressionthe opposite tension vertical lines move closer another cross-section thickens Figure 4 illustrates torsion shear ends rubber being twisted opposite directions rubber partially cut through edges cut would move apart Figure 4 Shear loads induced torsion twisting Bending illustrated Figure 5 lines move apart outer side bend come closer inner side upper edge under tension lower under compression Take hard look Figure 6 two rubber strips being bent together Note lower edge upper piece being compressed immediately below upper edge lower piece under tension opposing forces exerted along contact line between upper lower rubbers neutral axis piece rubber rather two neutral axis would under shear Bending thus combination tension compression shear July1994 35 TENSION FIGURE 2 SHEAR FIGURE 4 TEN SI ON N FIGURE 5 TENSION COMPRESSION SHEARNEUTRAL SURFACE FIGURE 6 Morris neutral axis intersected neutral surface neutral axis cross-section piece rubber rage portrayed Figure 7 lever shown resting fulcrum force 3 pounds B balanced force 1 pound engineering terms force 3 pounds lever foot long produces moment 3 foot-pounds does force 1 pound lever 3 feet long longer lever fulcrum point lower force needed achieve balance smaller cross-section area material needed resist force Morris fulcrum neutral axis would off-center section symmetrical modulus elasticity material side different other side assume simplicity [we] discussing symmetrical sections uniform materials composites example carbon side balsa other course would have off-center neutral axis might represented lever re 8 shows end view rubber strip lever arm neutral axis center cross-section area shown Figure 8B same cross-section areas have separated tensile compressive areas have separated joined vertical shear web increase bending strength proportional increase length levers Shear loads sustained web neutral axis Figure 8C shows greater separation top bottom flanges increases leverage permitting beam same strength 8B considerable reduction cross-section reduction material weight Figure 9A shows solid round rod rearranging same cross section area form cylinder Figure 9B torsional bending strengths improved proportionally increase length lever arms measured neutral axis Editors note Author reviewer disagree Morris says lever arm 9B shown inch long order comparable 9A correctly shown 25 inch lever arm resultant stress force should shown 7 inch long bending strength 9B tubular member 378 3 LBSI LB 4FT FT3FTA times strong round member neering principle increased strength material should located greatest possible distance neutral axis given strength locating material results least material consequently least weight Part II will consider application principle model aircraft structural design 436 Model Aviation 4B 4 3FT/LBFULCRUM3FT/LB LEVERAGE FIGURE 7 LEVERTOP FLANGES ARM NEUTRAL AXIS BEAMSC OTTOM FLANGES FIGURE 8 2 /8 IN LEVER ARM N LEVER ARM EUTRAL AIS /8 IN ROUNDB MEMBER TUBULARMEMBER FIGURE 9
Edition: Model Aviation - 1994/07
Page Numbers: 33, 35, 36
I I Editors note two-part article reviewed technical content noted modeler engineer Gil Morris Per review modifications have made original text author provided copy review asked consider revising text declined appropriate have included Morris comments italics presented allow reader form own judgments intended polarize discussion Please see Haught Cornerfor full discussion presentation I I II I g liLd study full scale aircraft structural design fascinating Take Bleriots cross channel monoplane its fuselage consisted four wooden longerons wooden crossmembers whole thing being wire braced Covering fabric fact aft fuselage left uncovered wing two wooden spars ribs fabric covering wire braced provided strength yet flexible torsion since lateral control wing warping Tail surfaces also wood fabric covering wire bracing Under impetus WW developments power plants aerodynamics structure rapid Early designers found drag reduction man datory improve performance take advantage greater engine power Fuselages became rounded oval cross-section retained same four-longeron load-bearing structures steel tubing formers stringers fabric covered providing external nonload-bearing shape Biplane wingswhich per mitted interplane bracing provide light yet strong structuresbecame popular drag high part tail surfaces outlined steel tubing flat surfaced fabric covered wire braced latter stages WW Germans developed rounded July1994 33 Authors original Osprey designed according principles presented Flies tail-dragger twin floats Srucur D.sign - L14 TIC MARKS x SOFT RUBBER SQUARE FIGURE nWThTFFWTFVrmTrvm - UiiijjjjjjjjjjjjjJjjjjJfl COMPRESSION FIGURE 3 all-plywood fuselage plywood skin provided low-drag external shape also absorbed structural loads thus locating material far neutral axis possible light yet strong stress-skinned structure achieved Fokker DVIII high-wing monoplane introduced cantilever wing too wooden structure plywood skinned much greater thickness contemporary biplane wings Other struts holding wing above fuselage no drag-producing external bracing stress-skinned As Allied air forces found Fokker DVIII formidable adversary Lockheed US de Havilland Great Britain produced plywood stress-skinned aircraft during 1930s Lindberghs Lockheed Sirius classic example WW lIthe deHavilland Mosquito outstanding wooden aircraft four-longeron fuselage externally braced wings metal-tube tail surfaces survive such aircraft Beech Staggerwing Piper Cub ultralights -What followed gradual swing all-metal stress-skinned aircraft structures Today aircraft produced quantity design Piper Beech Cessna Boeing McDonnell Douglas Lockheed examples 1970s use composite material came prominence pioneered German glider manufacturers Burt Rutan VariEze LongEze finally spectacular Voyager Beech Starship canard outstanding example Fiberglass epoxy foam carbon boron fibers Aramid Nomexall replacing metalbecame popular particularly sportplane field under stimulus Experimental Aircraft Association aircraft provide outstanding performance modest horsepower structures follow sound engineering principle locating material structures far neutral axis possible Now what neutral axis business about nodding acquaintance tension compression torsion/shear bending leverage will serve introduction Visualize piece rubber vertical lines spaced inch apart Figure 1 Figure 2 rubber under tension vertical lines spread apart rubber thins cross-section Figure 3 rubber under compressionthe opposite tension vertical lines move closer another cross-section thickens Figure 4 illustrates torsion shear ends rubber being twisted opposite directions rubber partially cut through edges cut would move apart Figure 4 Shear loads induced torsion twisting Bending illustrated Figure 5 lines move apart outer side bend come closer inner side upper edge under tension lower under compression Take hard look Figure 6 two rubber strips being bent together Note lower edge upper piece being compressed immediately below upper edge lower piece under tension opposing forces exerted along contact line between upper lower rubbers neutral axis piece rubber rather two neutral axis would under shear Bending thus combination tension compression shear July1994 35 TENSION FIGURE 2 SHEAR FIGURE 4 TEN SI ON N FIGURE 5 TENSION COMPRESSION SHEARNEUTRAL SURFACE FIGURE 6 Morris neutral axis intersected neutral surface neutral axis cross-section piece rubber rage portrayed Figure 7 lever shown resting fulcrum force 3 pounds B balanced force 1 pound engineering terms force 3 pounds lever foot long produces moment 3 foot-pounds does force 1 pound lever 3 feet long longer lever fulcrum point lower force needed achieve balance smaller cross-section area material needed resist force Morris fulcrum neutral axis would off-center section symmetrical modulus elasticity material side different other side assume simplicity [we] discussing symmetrical sections uniform materials composites example carbon side balsa other course would have off-center neutral axis might represented lever re 8 shows end view rubber strip lever arm neutral axis center cross-section area shown Figure 8B same cross-section areas have separated tensile compressive areas have separated joined vertical shear web increase bending strength proportional increase length levers Shear loads sustained web neutral axis Figure 8C shows greater separation top bottom flanges increases leverage permitting beam same strength 8B considerable reduction cross-section reduction material weight Figure 9A shows solid round rod rearranging same cross section area form cylinder Figure 9B torsional bending strengths improved proportionally increase length lever arms measured neutral axis Editors note Author reviewer disagree Morris says lever arm 9B shown inch long order comparable 9A correctly shown 25 inch lever arm resultant stress force should shown 7 inch long bending strength 9B tubular member 378 3 LBSI LB 4FT FT3FTA times strong round member neering principle increased strength material should located greatest possible distance neutral axis given strength locating material results least material consequently least weight Part II will consider application principle model aircraft structural design 436 Model Aviation 4B 4 3FT/LBFULCRUM3FT/LB LEVERAGE FIGURE 7 LEVERTOP FLANGES ARM NEUTRAL AXIS BEAMSC OTTOM FLANGES FIGURE 8 2 /8 IN LEVER ARM N LEVER ARM EUTRAL AIS /8 IN ROUNDB MEMBER TUBULARMEMBER FIGURE 9