The next time local hobby shop out prop need consider taking few hours make yourself U John Vant-Haaff Editors note beginners project Please study text thoroughly certain fully understand techniques involved before attempting carve props note disclaimermodelers have carved own props yearsbut feel extra word caution order I$ AKING YOUR OWN PROPELLERS can challenging rewarding fun can handy particularly large difficult-to-get props unusual pitches Its also nice able make own laminated antique scale propeller its handy able make prop just ran out ofone doesnt happen hobby shop shelf need part same principles apply model props full-size propellers theories terms math can pretty heavy reading appears some oversimplification its because want encourage would otherwise give up before start thereby missing out gratifying oftenoverlooked part hobby Making propellers maynot everyone can hang long enough try will intriguing addictive need healthy curiosity little ambition few basic tools piece wood bit time Once have prop blank rectangular piece wood slightly larger finished product will necessary pitch gauges can easily have 18-inch prop couple coats dope ready fly three hourswithout raising drop sweat brow Its instant allbut its bad either TOOLS AND MATERIALS will need some basic tools materials pencil good straightedge prefer steel ruler compass drill small saw knife sanding block set square will also need piece wood large enough make propeller first propellers made just simple tools worked quite satisfactorily have elaborate tools prop balancer will find valuable assets mandatory Propeller material can range handy scrap wood will cost virtually nothing something will have buy supplier specializes exotic wood Birch maple black walnut spruce particularly Sitka good piece fir will job Other woods can used well especially laminated props example have used mahogany creates very nice-looking finished product Regardless wood type try select pieces straight tightly grained possible kiln-dried First growth preferable though its always easy find case wood should clearie free knots checks small cracks fractures Carefully inspect end grain cracks too Its entirely possible fair amount wood may have cut off ends particular piece before clear wood found few moments spent carefully inspecting wood can avoid wasted time effort carving bad piece wood well preventing potentially hazardous situation should prop fail SPECIFICATIONS Determine props diameter pitch number blades prop typeleft- right-handed rotation pusher tractor example will 14 x 6 right-handed tractortype propeller 14-inch propeller used blank 141/8 inches long 1/8 inches wide blank 5/s-inch thick /2-inch works just well hub 1 inches diameter widest portion blade would considered thin prevented having cut across thegrain could tend weaken blade somewhat radical blade shape used laminating blank should June1993 27 Above Propeller blank profile patterns first set saw marks has made using card stock pitch gauges guide Below Spruce-and-black-walnut-laminated prop polyurethane-covered foil tip scale effect considered because adds strength blade also recommend laminating unusual blade designs such scimitar-shaped profiles because curved shape tends cut across grain see Figure 1 number blades desired will dictate whether solid piece wood should used whether blank must laminated Generally two-bladed prop single-bladed prop counterbalance can solid laminated prop three blades must laminated exception multiple blades bolted together machined hub PITCH GAUGES See Figure 2 graph may drawn fullsize particular scale provided plotted measurements maintain scale full-size drawing less likely produce errors therefore recommended Determine number stations per blade Stations may placed using either percentage distance hub inches percentage formula % x r x 628 smooth root transition accom plished using stations area Dont have station hub suitably sized sheet paper floor large props draw baseline equal slightly circumference circle described radius equal prop 14-inch propeller requires paper 6/2 x 44/2 inches end paper prefer left end draw perpendicular line slightly longer desired pitch case slightly six inches long Label intersection pitch line baseline 0 origin have used eight stations illustration last blank station tip laid out drawn across end thec formula determining theI position eachI station c convenience ations 1 2 3 may use c Oat from0 imference &299431257 628 x r used one- Oatfrom Center indies 2 inch stations except #2 1 / inches plotted baseline indicated Figure 2 Measurements station shown drawing Mark appropriate point props pitch Pin case six inches Some tools used rough out shape prop shown top photo elaborate tools can useful required produce satisfactory props lower left laminated prop blank bottom blade completed opposite blade progress position P draw lines intersect stations baseline forms series overlapping triangles should duplicated carefully thin sheet aluminum press plate stiff card stock gauge should marked see Figure 3 appropriate gauge used station Notice triangle closest root origin very steep last very shallow actual size gauges will determined width depth blade gauges should large enough fit conveniently slots should protrude above blanks surface past end easy reference making gauges little larger required same gauges may used same station points larger props additional gauges required would larger props extra stations THE PROP BLANK prop blanks opposite sides should close parallel possible adjacent sides should right angles Time taken effort spent will make layout process easier accurate will make props efficiency balance predictable prefer use least four laminations two-bladed prop although two-bladed props can also made single piece wood pieces laminated should smooth uniform size thickness Find heavy end piece arrange pieces blade weights roughly equalso balancing prop will difficult Check end grain lamination arrange prior gluing per Figure 1 Store propblank woodeven kiln-driedat room temperature least 24 hours before gluing good marine glue should used bond laminations have used UF 109 Arrowlight Resorcinol great success used Resorcinol several full-size propellers built because time best all-round glue highly rated 28 Model Aviation 1 End View blank showing typical arrangement laminations Fig 2 C x R inches station point on each half prop blank Full-size graph gauge patterns reduces chances error 4 5 6 78 168825142143377144 3 67 US Navy So have available tend use others circumstances may dictate another choice doubt use good marine glue application would avoid using epoxy glue have seen epoxy delaminate particularly after has sustained shock though epoxy strong some variables beyond manufacturers control such surface preparation moisture content latter extremely critical can greatly affect ultimate strength joint Wipe woods surface damp rag before brushing light layer glue particularly resin-type glue used Brush glue evenly piece Clamp assembled blank securely least 24 hours longer possible blank should clamped tightly evenly solid straightedge such good piece angle iron clamps practical Small blanks can clamped vise has soft jaws avoid marking surface blank provided jaws cover length blank Care should taken tighten clamps slowly evenly sequence prevent shifting out alignment Keep blank parallel square blank dry use old knife chisel screwdriver remove glue has squeezed out joints jointer can true up blank nicely using very little wood Sand away excess glue before using jointerit will easier jointer blades Whether use solid laminated blank always make little larger little longer finished product allow machining trimming blank now has desired length width thickness Its time carve finish propeller Fig 4 Use stiff cardstock thin aluminum profile label future reference use LAYOUT Pin center halfblade pattern profile center point propeller Fig 5 blank see Figure 4 will top surface prop blank blank profile should have centerlines drawn reference Lay centerline pattern centerline blank draw blade outline Swing pattern l8O match patteru blank centerlines draw outline opposite blade prop hub needs slightly larger prop boss backing plate engine Remove profile pattern Place point compass pinprick center blank Divide blade centerline convenient equal spacesthe number divisions arbitrary Use square project spaces around sides block shown Figure 5 Now its apparent important have Fig 3blankasclosetoaperfect rectangle possible Because props natural tendency flex forward running front side prop tip should lower top hub see Figure 6 particularly noticeable laminated props wide long strip wood will flex close center blank viewed front back would case tip located closer top front blank thus giving strength flexing occurs static run-ups rapid acceleration deceleration Very little flexing occurs during constant-speed run because propeller pulling itself through air static run prop held place force air pulled rhrough it unable thread itself through air Trailing Blade profile pattern pinned blank Derived old Blankblade own design CUTTING AND DRILLING prevent splintering blank center hole drilled clamp blank backup scrap wood drill press table available have reamer drill center hole slightly undersize dont have reamer drill hole its finished size case hole should small enough prop will fit securely balancers shaft after blades completed Cut blade shape band saw scroll saw hand saw Cut just outside blade line outline can sanded its final shape CARVING THE BACK Clamp blank vise sand profile shape down line Place piece scrap wood side blank prevent scratches vise Remove saw marks keep blade edge close square top possible Repeat opposite blade Use square project station marks top blade down leading trailing edges blank see Figure 7 Join vertical marks station corresponding marks across bottom blank youre keeping face prop flat draw line about /s top see Figure 6A cutting slots back side dont cut below line like drop tip down somewhat shown Figure 6B June1993 29 Bottom Pitch gaugeTE resting saw CutApprox finished -- shape station Pitch gauge example L E drop ft used-Top#2@1h Approx Ia top face block14x6Mark & keep Add subtract appropriate amountfor next time dropping raising tip Bottom side ISee comments articIel back side gauge should parallel L E cut @ 9O surfaceL E example 14-inch prop mark about /16 down tip fair within 1/ top roughly first third blade root see Figure 6B 18-inch prop drop tip about 5A6 nineinch prop about 5A2 amount isnt Fig 6 critical building curve thinning out last two-thirds blade helps increase performance Make saw cuts bottom side blank per pitch gauges developed station see Figure 3 careful wrong cut wrong place means throwing blank away starting over Glancing finished prop helps keep touch whats required Carefully chisel excess wood depth saw cuts sand flat Always work grain against roughing out back blade start sharp chisel keep flat side up work gently hub toward first saw cut After carving down first1/4 . ores3/32ifl cut work tip toward root ondesiredor Suit leading edge half blade Remem ber prop still upside down Working tip toward root gently chisel trailing edge portion down toward saw cut point wood will appear somewhat terraced Finish rasping filing sanding 100-grit paper until saw marks disappear Repeat second blade Briefly stated what have done lay Out drill cut shape carve back side blade What left carve front side sand smooth balance finish desired shape front side blades begin root removing wood trailing edge toward high point smooth fashion Leave enough wood finish shaping sanding Remember always work grain against deviation finish sanding front side crosshatch form oblique sanding direction may used achieve uniform surface remove too much wood gouge out piece prevents attaining uniform blade shape will have start over use filler correct carving mistakes Such material can become deadly projectile separates surface blade high rpm Gently sand forward side blade high point leading edge Clark Y shape round leading edge As noted earlier taper thickness blade toward tip BALANCING Balance propeller being careful remove material within first 40% Fig 7Blank outline before drilling & cutting Leading edge BLADE FRONT Remove blank vise turn over blade tapered now Figure 6 Keep top square edges easy reference Generally speaking blade cross section will approximate Clark Y airfoil shape high point roughly third chord Use pencil mark high point root tip blade Depending characteristics wish achieve high point can constant may vary 33% first third blade 24% second third little 15% last third Figure 8 can simply copy prop have hand Bear mind 10000 rpm tip 14-inch prop will traveling slightly over 416 mph look wing J-3 Cub uses Clark Y airfoil look wing aircraft flies about 400 mph will notice considerable difference airfoil shape same aerodynamic principles apply prop also apply wing prop effect vertically rotating wing lifts aircraft forward radius possible since least efficient portion propeller have careful choosing making blank shaping blades uniformly balance wont far off FINISH AND FLYING Finish propeller Topclear dope Varathane clear epoxy protect blades absorbing water protect general wear tear Two three very light coats takesbe judicious Check props balance again before useyou may have add extra finish blade rebalance 8 1/31/31/3 15%Of29%of33%of chordchordchord Chord -High point ret hne ifi~~ii7Now youre ready fly may seem like lot work once patterns gauges made takes about three hours complete 18-inch prop Smaller props take less time finishing can take long like have used props right off bench finish worked fine Once have made three four props will develop own shortcuts techniques Youll pleased well props work youll begin enjoy making process isnt reallyfast does get easier after youve made few recommend marking hub diameter pitch flight box will soon have assortment unknown propellers Have funand soft landings Flying Dutchman odel Aviation raight blade 1/8 C Draw appropriate reference line before making saw cuts back side blade B Curved drop tipped blade 1/8 . C %ef Taper off shaded area top side keep flat & square LE & TE Project station lines down leading edge trailing edge faces after drilling cutting out Continue station line across bottom Fig High Pt ref edge riTIik4 ref typSaw cuts saw cuts accurate per gauges LE ref line trailing edge contour formed automatically finishing back side blade
Edition: Model Aviation - 1993/06
Page Numbers: 27, 28, 29, 30
Edition: Model Aviation - 1993/06
Page Numbers: 27, 28, 29, 30
The next time local hobby shop out prop need consider taking few hours make yourself U John Vant-Haaff Editors note beginners project Please study text thoroughly certain fully understand techniques involved before attempting carve props note disclaimermodelers have carved own props yearsbut feel extra word caution order I$ AKING YOUR OWN PROPELLERS can challenging rewarding fun can handy particularly large difficult-to-get props unusual pitches Its also nice able make own laminated antique scale propeller its handy able make prop just ran out ofone doesnt happen hobby shop shelf need part same principles apply model props full-size propellers theories terms math can pretty heavy reading appears some oversimplification its because want encourage would otherwise give up before start thereby missing out gratifying oftenoverlooked part hobby Making propellers maynot everyone can hang long enough try will intriguing addictive need healthy curiosity little ambition few basic tools piece wood bit time Once have prop blank rectangular piece wood slightly larger finished product will necessary pitch gauges can easily have 18-inch prop couple coats dope ready fly three hourswithout raising drop sweat brow Its instant allbut its bad either TOOLS AND MATERIALS will need some basic tools materials pencil good straightedge prefer steel ruler compass drill small saw knife sanding block set square will also need piece wood large enough make propeller first propellers made just simple tools worked quite satisfactorily have elaborate tools prop balancer will find valuable assets mandatory Propeller material can range handy scrap wood will cost virtually nothing something will have buy supplier specializes exotic wood Birch maple black walnut spruce particularly Sitka good piece fir will job Other woods can used well especially laminated props example have used mahogany creates very nice-looking finished product Regardless wood type try select pieces straight tightly grained possible kiln-dried First growth preferable though its always easy find case wood should clearie free knots checks small cracks fractures Carefully inspect end grain cracks too Its entirely possible fair amount wood may have cut off ends particular piece before clear wood found few moments spent carefully inspecting wood can avoid wasted time effort carving bad piece wood well preventing potentially hazardous situation should prop fail SPECIFICATIONS Determine props diameter pitch number blades prop typeleft- right-handed rotation pusher tractor example will 14 x 6 right-handed tractortype propeller 14-inch propeller used blank 141/8 inches long 1/8 inches wide blank 5/s-inch thick /2-inch works just well hub 1 inches diameter widest portion blade would considered thin prevented having cut across thegrain could tend weaken blade somewhat radical blade shape used laminating blank should June1993 27 Above Propeller blank profile patterns first set saw marks has made using card stock pitch gauges guide Below Spruce-and-black-walnut-laminated prop polyurethane-covered foil tip scale effect considered because adds strength blade also recommend laminating unusual blade designs such scimitar-shaped profiles because curved shape tends cut across grain see Figure 1 number blades desired will dictate whether solid piece wood should used whether blank must laminated Generally two-bladed prop single-bladed prop counterbalance can solid laminated prop three blades must laminated exception multiple blades bolted together machined hub PITCH GAUGES See Figure 2 graph may drawn fullsize particular scale provided plotted measurements maintain scale full-size drawing less likely produce errors therefore recommended Determine number stations per blade Stations may placed using either percentage distance hub inches percentage formula % x r x 628 smooth root transition accom plished using stations area Dont have station hub suitably sized sheet paper floor large props draw baseline equal slightly circumference circle described radius equal prop 14-inch propeller requires paper 6/2 x 44/2 inches end paper prefer left end draw perpendicular line slightly longer desired pitch case slightly six inches long Label intersection pitch line baseline 0 origin have used eight stations illustration last blank station tip laid out drawn across end thec formula determining theI position eachI station c convenience ations 1 2 3 may use c Oat from0 imference &299431257 628 x r used one- Oatfrom Center indies 2 inch stations except #2 1 / inches plotted baseline indicated Figure 2 Measurements station shown drawing Mark appropriate point props pitch Pin case six inches Some tools used rough out shape prop shown top photo elaborate tools can useful required produce satisfactory props lower left laminated prop blank bottom blade completed opposite blade progress position P draw lines intersect stations baseline forms series overlapping triangles should duplicated carefully thin sheet aluminum press plate stiff card stock gauge should marked see Figure 3 appropriate gauge used station Notice triangle closest root origin very steep last very shallow actual size gauges will determined width depth blade gauges should large enough fit conveniently slots should protrude above blanks surface past end easy reference making gauges little larger required same gauges may used same station points larger props additional gauges required would larger props extra stations THE PROP BLANK prop blanks opposite sides should close parallel possible adjacent sides should right angles Time taken effort spent will make layout process easier accurate will make props efficiency balance predictable prefer use least four laminations two-bladed prop although two-bladed props can also made single piece wood pieces laminated should smooth uniform size thickness Find heavy end piece arrange pieces blade weights roughly equalso balancing prop will difficult Check end grain lamination arrange prior gluing per Figure 1 Store propblank woodeven kiln-driedat room temperature least 24 hours before gluing good marine glue should used bond laminations have used UF 109 Arrowlight Resorcinol great success used Resorcinol several full-size propellers built because time best all-round glue highly rated 28 Model Aviation 1 End View blank showing typical arrangement laminations Fig 2 C x R inches station point on each half prop blank Full-size graph gauge patterns reduces chances error 4 5 6 78 168825142143377144 3 67 US Navy So have available tend use others circumstances may dictate another choice doubt use good marine glue application would avoid using epoxy glue have seen epoxy delaminate particularly after has sustained shock though epoxy strong some variables beyond manufacturers control such surface preparation moisture content latter extremely critical can greatly affect ultimate strength joint Wipe woods surface damp rag before brushing light layer glue particularly resin-type glue used Brush glue evenly piece Clamp assembled blank securely least 24 hours longer possible blank should clamped tightly evenly solid straightedge such good piece angle iron clamps practical Small blanks can clamped vise has soft jaws avoid marking surface blank provided jaws cover length blank Care should taken tighten clamps slowly evenly sequence prevent shifting out alignment Keep blank parallel square blank dry use old knife chisel screwdriver remove glue has squeezed out joints jointer can true up blank nicely using very little wood Sand away excess glue before using jointerit will easier jointer blades Whether use solid laminated blank always make little larger little longer finished product allow machining trimming blank now has desired length width thickness Its time carve finish propeller Fig 4 Use stiff cardstock thin aluminum profile label future reference use LAYOUT Pin center halfblade pattern profile center point propeller Fig 5 blank see Figure 4 will top surface prop blank blank profile should have centerlines drawn reference Lay centerline pattern centerline blank draw blade outline Swing pattern l8O match patteru blank centerlines draw outline opposite blade prop hub needs slightly larger prop boss backing plate engine Remove profile pattern Place point compass pinprick center blank Divide blade centerline convenient equal spacesthe number divisions arbitrary Use square project spaces around sides block shown Figure 5 Now its apparent important have Fig 3blankasclosetoaperfect rectangle possible Because props natural tendency flex forward running front side prop tip should lower top hub see Figure 6 particularly noticeable laminated props wide long strip wood will flex close center blank viewed front back would case tip located closer top front blank thus giving strength flexing occurs static run-ups rapid acceleration deceleration Very little flexing occurs during constant-speed run because propeller pulling itself through air static run prop held place force air pulled rhrough it unable thread itself through air Trailing Blade profile pattern pinned blank Derived old Blankblade own design CUTTING AND DRILLING prevent splintering blank center hole drilled clamp blank backup scrap wood drill press table available have reamer drill center hole slightly undersize dont have reamer drill hole its finished size case hole should small enough prop will fit securely balancers shaft after blades completed Cut blade shape band saw scroll saw hand saw Cut just outside blade line outline can sanded its final shape CARVING THE BACK Clamp blank vise sand profile shape down line Place piece scrap wood side blank prevent scratches vise Remove saw marks keep blade edge close square top possible Repeat opposite blade Use square project station marks top blade down leading trailing edges blank see Figure 7 Join vertical marks station corresponding marks across bottom blank youre keeping face prop flat draw line about /s top see Figure 6A cutting slots back side dont cut below line like drop tip down somewhat shown Figure 6B June1993 29 Bottom Pitch gaugeTE resting saw CutApprox finished -- shape station Pitch gauge example L E drop ft used-Top#2@1h Approx Ia top face block14x6Mark & keep Add subtract appropriate amountfor next time dropping raising tip Bottom side ISee comments articIel back side gauge should parallel L E cut @ 9O surfaceL E example 14-inch prop mark about /16 down tip fair within 1/ top roughly first third blade root see Figure 6B 18-inch prop drop tip about 5A6 nineinch prop about 5A2 amount isnt Fig 6 critical building curve thinning out last two-thirds blade helps increase performance Make saw cuts bottom side blank per pitch gauges developed station see Figure 3 careful wrong cut wrong place means throwing blank away starting over Glancing finished prop helps keep touch whats required Carefully chisel excess wood depth saw cuts sand flat Always work grain against roughing out back blade start sharp chisel keep flat side up work gently hub toward first saw cut After carving down first1/4 . ores3/32ifl cut work tip toward root ondesiredor Suit leading edge half blade Remem ber prop still upside down Working tip toward root gently chisel trailing edge portion down toward saw cut point wood will appear somewhat terraced Finish rasping filing sanding 100-grit paper until saw marks disappear Repeat second blade Briefly stated what have done lay Out drill cut shape carve back side blade What left carve front side sand smooth balance finish desired shape front side blades begin root removing wood trailing edge toward high point smooth fashion Leave enough wood finish shaping sanding Remember always work grain against deviation finish sanding front side crosshatch form oblique sanding direction may used achieve uniform surface remove too much wood gouge out piece prevents attaining uniform blade shape will have start over use filler correct carving mistakes Such material can become deadly projectile separates surface blade high rpm Gently sand forward side blade high point leading edge Clark Y shape round leading edge As noted earlier taper thickness blade toward tip BALANCING Balance propeller being careful remove material within first 40% Fig 7Blank outline before drilling & cutting Leading edge BLADE FRONT Remove blank vise turn over blade tapered now Figure 6 Keep top square edges easy reference Generally speaking blade cross section will approximate Clark Y airfoil shape high point roughly third chord Use pencil mark high point root tip blade Depending characteristics wish achieve high point can constant may vary 33% first third blade 24% second third little 15% last third Figure 8 can simply copy prop have hand Bear mind 10000 rpm tip 14-inch prop will traveling slightly over 416 mph look wing J-3 Cub uses Clark Y airfoil look wing aircraft flies about 400 mph will notice considerable difference airfoil shape same aerodynamic principles apply prop also apply wing prop effect vertically rotating wing lifts aircraft forward radius possible since least efficient portion propeller have careful choosing making blank shaping blades uniformly balance wont far off FINISH AND FLYING Finish propeller Topclear dope Varathane clear epoxy protect blades absorbing water protect general wear tear Two three very light coats takesbe judicious Check props balance again before useyou may have add extra finish blade rebalance 8 1/31/31/3 15%Of29%of33%of chordchordchord Chord -High point ret hne ifi~~ii7Now youre ready fly may seem like lot work once patterns gauges made takes about three hours complete 18-inch prop Smaller props take less time finishing can take long like have used props right off bench finish worked fine Once have made three four props will develop own shortcuts techniques Youll pleased well props work youll begin enjoy making process isnt reallyfast does get easier after youve made few recommend marking hub diameter pitch flight box will soon have assortment unknown propellers Have funand soft landings Flying Dutchman odel Aviation raight blade 1/8 C Draw appropriate reference line before making saw cuts back side blade B Curved drop tipped blade 1/8 . C %ef Taper off shaded area top side keep flat & square LE & TE Project station lines down leading edge trailing edge faces after drilling cutting out Continue station line across bottom Fig High Pt ref edge riTIik4 ref typSaw cuts saw cuts accurate per gauges LE ref line trailing edge contour formed automatically finishing back side blade
Edition: Model Aviation - 1993/06
Page Numbers: 27, 28, 29, 30
The next time local hobby shop out prop need consider taking few hours make yourself U John Vant-Haaff Editors note beginners project Please study text thoroughly certain fully understand techniques involved before attempting carve props note disclaimermodelers have carved own props yearsbut feel extra word caution order I$ AKING YOUR OWN PROPELLERS can challenging rewarding fun can handy particularly large difficult-to-get props unusual pitches Its also nice able make own laminated antique scale propeller its handy able make prop just ran out ofone doesnt happen hobby shop shelf need part same principles apply model props full-size propellers theories terms math can pretty heavy reading appears some oversimplification its because want encourage would otherwise give up before start thereby missing out gratifying oftenoverlooked part hobby Making propellers maynot everyone can hang long enough try will intriguing addictive need healthy curiosity little ambition few basic tools piece wood bit time Once have prop blank rectangular piece wood slightly larger finished product will necessary pitch gauges can easily have 18-inch prop couple coats dope ready fly three hourswithout raising drop sweat brow Its instant allbut its bad either TOOLS AND MATERIALS will need some basic tools materials pencil good straightedge prefer steel ruler compass drill small saw knife sanding block set square will also need piece wood large enough make propeller first propellers made just simple tools worked quite satisfactorily have elaborate tools prop balancer will find valuable assets mandatory Propeller material can range handy scrap wood will cost virtually nothing something will have buy supplier specializes exotic wood Birch maple black walnut spruce particularly Sitka good piece fir will job Other woods can used well especially laminated props example have used mahogany creates very nice-looking finished product Regardless wood type try select pieces straight tightly grained possible kiln-dried First growth preferable though its always easy find case wood should clearie free knots checks small cracks fractures Carefully inspect end grain cracks too Its entirely possible fair amount wood may have cut off ends particular piece before clear wood found few moments spent carefully inspecting wood can avoid wasted time effort carving bad piece wood well preventing potentially hazardous situation should prop fail SPECIFICATIONS Determine props diameter pitch number blades prop typeleft- right-handed rotation pusher tractor example will 14 x 6 right-handed tractortype propeller 14-inch propeller used blank 141/8 inches long 1/8 inches wide blank 5/s-inch thick /2-inch works just well hub 1 inches diameter widest portion blade would considered thin prevented having cut across thegrain could tend weaken blade somewhat radical blade shape used laminating blank should June1993 27 Above Propeller blank profile patterns first set saw marks has made using card stock pitch gauges guide Below Spruce-and-black-walnut-laminated prop polyurethane-covered foil tip scale effect considered because adds strength blade also recommend laminating unusual blade designs such scimitar-shaped profiles because curved shape tends cut across grain see Figure 1 number blades desired will dictate whether solid piece wood should used whether blank must laminated Generally two-bladed prop single-bladed prop counterbalance can solid laminated prop three blades must laminated exception multiple blades bolted together machined hub PITCH GAUGES See Figure 2 graph may drawn fullsize particular scale provided plotted measurements maintain scale full-size drawing less likely produce errors therefore recommended Determine number stations per blade Stations may placed using either percentage distance hub inches percentage formula % x r x 628 smooth root transition accom plished using stations area Dont have station hub suitably sized sheet paper floor large props draw baseline equal slightly circumference circle described radius equal prop 14-inch propeller requires paper 6/2 x 44/2 inches end paper prefer left end draw perpendicular line slightly longer desired pitch case slightly six inches long Label intersection pitch line baseline 0 origin have used eight stations illustration last blank station tip laid out drawn across end thec formula determining theI position eachI station c convenience ations 1 2 3 may use c Oat from0 imference &299431257 628 x r used one- Oatfrom Center indies 2 inch stations except #2 1 / inches plotted baseline indicated Figure 2 Measurements station shown drawing Mark appropriate point props pitch Pin case six inches Some tools used rough out shape prop shown top photo elaborate tools can useful required produce satisfactory props lower left laminated prop blank bottom blade completed opposite blade progress position P draw lines intersect stations baseline forms series overlapping triangles should duplicated carefully thin sheet aluminum press plate stiff card stock gauge should marked see Figure 3 appropriate gauge used station Notice triangle closest root origin very steep last very shallow actual size gauges will determined width depth blade gauges should large enough fit conveniently slots should protrude above blanks surface past end easy reference making gauges little larger required same gauges may used same station points larger props additional gauges required would larger props extra stations THE PROP BLANK prop blanks opposite sides should close parallel possible adjacent sides should right angles Time taken effort spent will make layout process easier accurate will make props efficiency balance predictable prefer use least four laminations two-bladed prop although two-bladed props can also made single piece wood pieces laminated should smooth uniform size thickness Find heavy end piece arrange pieces blade weights roughly equalso balancing prop will difficult Check end grain lamination arrange prior gluing per Figure 1 Store propblank woodeven kiln-driedat room temperature least 24 hours before gluing good marine glue should used bond laminations have used UF 109 Arrowlight Resorcinol great success used Resorcinol several full-size propellers built because time best all-round glue highly rated 28 Model Aviation 1 End View blank showing typical arrangement laminations Fig 2 C x R inches station point on each half prop blank Full-size graph gauge patterns reduces chances error 4 5 6 78 168825142143377144 3 67 US Navy So have available tend use others circumstances may dictate another choice doubt use good marine glue application would avoid using epoxy glue have seen epoxy delaminate particularly after has sustained shock though epoxy strong some variables beyond manufacturers control such surface preparation moisture content latter extremely critical can greatly affect ultimate strength joint Wipe woods surface damp rag before brushing light layer glue particularly resin-type glue used Brush glue evenly piece Clamp assembled blank securely least 24 hours longer possible blank should clamped tightly evenly solid straightedge such good piece angle iron clamps practical Small blanks can clamped vise has soft jaws avoid marking surface blank provided jaws cover length blank Care should taken tighten clamps slowly evenly sequence prevent shifting out alignment Keep blank parallel square blank dry use old knife chisel screwdriver remove glue has squeezed out joints jointer can true up blank nicely using very little wood Sand away excess glue before using jointerit will easier jointer blades Whether use solid laminated blank always make little larger little longer finished product allow machining trimming blank now has desired length width thickness Its time carve finish propeller Fig 4 Use stiff cardstock thin aluminum profile label future reference use LAYOUT Pin center halfblade pattern profile center point propeller Fig 5 blank see Figure 4 will top surface prop blank blank profile should have centerlines drawn reference Lay centerline pattern centerline blank draw blade outline Swing pattern l8O match patteru blank centerlines draw outline opposite blade prop hub needs slightly larger prop boss backing plate engine Remove profile pattern Place point compass pinprick center blank Divide blade centerline convenient equal spacesthe number divisions arbitrary Use square project spaces around sides block shown Figure 5 Now its apparent important have Fig 3blankasclosetoaperfect rectangle possible Because props natural tendency flex forward running front side prop tip should lower top hub see Figure 6 particularly noticeable laminated props wide long strip wood will flex close center blank viewed front back would case tip located closer top front blank thus giving strength flexing occurs static run-ups rapid acceleration deceleration Very little flexing occurs during constant-speed run because propeller pulling itself through air static run prop held place force air pulled rhrough it unable thread itself through air Trailing Blade profile pattern pinned blank Derived old Blankblade own design CUTTING AND DRILLING prevent splintering blank center hole drilled clamp blank backup scrap wood drill press table available have reamer drill center hole slightly undersize dont have reamer drill hole its finished size case hole should small enough prop will fit securely balancers shaft after blades completed Cut blade shape band saw scroll saw hand saw Cut just outside blade line outline can sanded its final shape CARVING THE BACK Clamp blank vise sand profile shape down line Place piece scrap wood side blank prevent scratches vise Remove saw marks keep blade edge close square top possible Repeat opposite blade Use square project station marks top blade down leading trailing edges blank see Figure 7 Join vertical marks station corresponding marks across bottom blank youre keeping face prop flat draw line about /s top see Figure 6A cutting slots back side dont cut below line like drop tip down somewhat shown Figure 6B June1993 29 Bottom Pitch gaugeTE resting saw CutApprox finished -- shape station Pitch gauge example L E drop ft used-Top#2@1h Approx Ia top face block14x6Mark & keep Add subtract appropriate amountfor next time dropping raising tip Bottom side ISee comments articIel back side gauge should parallel L E cut @ 9O surfaceL E example 14-inch prop mark about /16 down tip fair within 1/ top roughly first third blade root see Figure 6B 18-inch prop drop tip about 5A6 nineinch prop about 5A2 amount isnt Fig 6 critical building curve thinning out last two-thirds blade helps increase performance Make saw cuts bottom side blank per pitch gauges developed station see Figure 3 careful wrong cut wrong place means throwing blank away starting over Glancing finished prop helps keep touch whats required Carefully chisel excess wood depth saw cuts sand flat Always work grain against roughing out back blade start sharp chisel keep flat side up work gently hub toward first saw cut After carving down first1/4 . ores3/32ifl cut work tip toward root ondesiredor Suit leading edge half blade Remem ber prop still upside down Working tip toward root gently chisel trailing edge portion down toward saw cut point wood will appear somewhat terraced Finish rasping filing sanding 100-grit paper until saw marks disappear Repeat second blade Briefly stated what have done lay Out drill cut shape carve back side blade What left carve front side sand smooth balance finish desired shape front side blades begin root removing wood trailing edge toward high point smooth fashion Leave enough wood finish shaping sanding Remember always work grain against deviation finish sanding front side crosshatch form oblique sanding direction may used achieve uniform surface remove too much wood gouge out piece prevents attaining uniform blade shape will have start over use filler correct carving mistakes Such material can become deadly projectile separates surface blade high rpm Gently sand forward side blade high point leading edge Clark Y shape round leading edge As noted earlier taper thickness blade toward tip BALANCING Balance propeller being careful remove material within first 40% Fig 7Blank outline before drilling & cutting Leading edge BLADE FRONT Remove blank vise turn over blade tapered now Figure 6 Keep top square edges easy reference Generally speaking blade cross section will approximate Clark Y airfoil shape high point roughly third chord Use pencil mark high point root tip blade Depending characteristics wish achieve high point can constant may vary 33% first third blade 24% second third little 15% last third Figure 8 can simply copy prop have hand Bear mind 10000 rpm tip 14-inch prop will traveling slightly over 416 mph look wing J-3 Cub uses Clark Y airfoil look wing aircraft flies about 400 mph will notice considerable difference airfoil shape same aerodynamic principles apply prop also apply wing prop effect vertically rotating wing lifts aircraft forward radius possible since least efficient portion propeller have careful choosing making blank shaping blades uniformly balance wont far off FINISH AND FLYING Finish propeller Topclear dope Varathane clear epoxy protect blades absorbing water protect general wear tear Two three very light coats takesbe judicious Check props balance again before useyou may have add extra finish blade rebalance 8 1/31/31/3 15%Of29%of33%of chordchordchord Chord -High point ret hne ifi~~ii7Now youre ready fly may seem like lot work once patterns gauges made takes about three hours complete 18-inch prop Smaller props take less time finishing can take long like have used props right off bench finish worked fine Once have made three four props will develop own shortcuts techniques Youll pleased well props work youll begin enjoy making process isnt reallyfast does get easier after youve made few recommend marking hub diameter pitch flight box will soon have assortment unknown propellers Have funand soft landings Flying Dutchman odel Aviation raight blade 1/8 C Draw appropriate reference line before making saw cuts back side blade B Curved drop tipped blade 1/8 . C %ef Taper off shaded area top side keep flat & square LE & TE Project station lines down leading edge trailing edge faces after drilling cutting out Continue station line across bottom Fig High Pt ref edge riTIik4 ref typSaw cuts saw cuts accurate per gauges LE ref line trailing edge contour formed automatically finishing back side blade
Edition: Model Aviation - 1993/06
Page Numbers: 27, 28, 29, 30
The next time local hobby shop out prop need consider taking few hours make yourself U John Vant-Haaff Editors note beginners project Please study text thoroughly certain fully understand techniques involved before attempting carve props note disclaimermodelers have carved own props yearsbut feel extra word caution order I$ AKING YOUR OWN PROPELLERS can challenging rewarding fun can handy particularly large difficult-to-get props unusual pitches Its also nice able make own laminated antique scale propeller its handy able make prop just ran out ofone doesnt happen hobby shop shelf need part same principles apply model props full-size propellers theories terms math can pretty heavy reading appears some oversimplification its because want encourage would otherwise give up before start thereby missing out gratifying oftenoverlooked part hobby Making propellers maynot everyone can hang long enough try will intriguing addictive need healthy curiosity little ambition few basic tools piece wood bit time Once have prop blank rectangular piece wood slightly larger finished product will necessary pitch gauges can easily have 18-inch prop couple coats dope ready fly three hourswithout raising drop sweat brow Its instant allbut its bad either TOOLS AND MATERIALS will need some basic tools materials pencil good straightedge prefer steel ruler compass drill small saw knife sanding block set square will also need piece wood large enough make propeller first propellers made just simple tools worked quite satisfactorily have elaborate tools prop balancer will find valuable assets mandatory Propeller material can range handy scrap wood will cost virtually nothing something will have buy supplier specializes exotic wood Birch maple black walnut spruce particularly Sitka good piece fir will job Other woods can used well especially laminated props example have used mahogany creates very nice-looking finished product Regardless wood type try select pieces straight tightly grained possible kiln-dried First growth preferable though its always easy find case wood should clearie free knots checks small cracks fractures Carefully inspect end grain cracks too Its entirely possible fair amount wood may have cut off ends particular piece before clear wood found few moments spent carefully inspecting wood can avoid wasted time effort carving bad piece wood well preventing potentially hazardous situation should prop fail SPECIFICATIONS Determine props diameter pitch number blades prop typeleft- right-handed rotation pusher tractor example will 14 x 6 right-handed tractortype propeller 14-inch propeller used blank 141/8 inches long 1/8 inches wide blank 5/s-inch thick /2-inch works just well hub 1 inches diameter widest portion blade would considered thin prevented having cut across thegrain could tend weaken blade somewhat radical blade shape used laminating blank should June1993 27 Above Propeller blank profile patterns first set saw marks has made using card stock pitch gauges guide Below Spruce-and-black-walnut-laminated prop polyurethane-covered foil tip scale effect considered because adds strength blade also recommend laminating unusual blade designs such scimitar-shaped profiles because curved shape tends cut across grain see Figure 1 number blades desired will dictate whether solid piece wood should used whether blank must laminated Generally two-bladed prop single-bladed prop counterbalance can solid laminated prop three blades must laminated exception multiple blades bolted together machined hub PITCH GAUGES See Figure 2 graph may drawn fullsize particular scale provided plotted measurements maintain scale full-size drawing less likely produce errors therefore recommended Determine number stations per blade Stations may placed using either percentage distance hub inches percentage formula % x r x 628 smooth root transition accom plished using stations area Dont have station hub suitably sized sheet paper floor large props draw baseline equal slightly circumference circle described radius equal prop 14-inch propeller requires paper 6/2 x 44/2 inches end paper prefer left end draw perpendicular line slightly longer desired pitch case slightly six inches long Label intersection pitch line baseline 0 origin have used eight stations illustration last blank station tip laid out drawn across end thec formula determining theI position eachI station c convenience ations 1 2 3 may use c Oat from0 imference &299431257 628 x r used one- Oatfrom Center indies 2 inch stations except #2 1 / inches plotted baseline indicated Figure 2 Measurements station shown drawing Mark appropriate point props pitch Pin case six inches Some tools used rough out shape prop shown top photo elaborate tools can useful required produce satisfactory props lower left laminated prop blank bottom blade completed opposite blade progress position P draw lines intersect stations baseline forms series overlapping triangles should duplicated carefully thin sheet aluminum press plate stiff card stock gauge should marked see Figure 3 appropriate gauge used station Notice triangle closest root origin very steep last very shallow actual size gauges will determined width depth blade gauges should large enough fit conveniently slots should protrude above blanks surface past end easy reference making gauges little larger required same gauges may used same station points larger props additional gauges required would larger props extra stations THE PROP BLANK prop blanks opposite sides should close parallel possible adjacent sides should right angles Time taken effort spent will make layout process easier accurate will make props efficiency balance predictable prefer use least four laminations two-bladed prop although two-bladed props can also made single piece wood pieces laminated should smooth uniform size thickness Find heavy end piece arrange pieces blade weights roughly equalso balancing prop will difficult Check end grain lamination arrange prior gluing per Figure 1 Store propblank woodeven kiln-driedat room temperature least 24 hours before gluing good marine glue should used bond laminations have used UF 109 Arrowlight Resorcinol great success used Resorcinol several full-size propellers built because time best all-round glue highly rated 28 Model Aviation 1 End View blank showing typical arrangement laminations Fig 2 C x R inches station point on each half prop blank Full-size graph gauge patterns reduces chances error 4 5 6 78 168825142143377144 3 67 US Navy So have available tend use others circumstances may dictate another choice doubt use good marine glue application would avoid using epoxy glue have seen epoxy delaminate particularly after has sustained shock though epoxy strong some variables beyond manufacturers control such surface preparation moisture content latter extremely critical can greatly affect ultimate strength joint Wipe woods surface damp rag before brushing light layer glue particularly resin-type glue used Brush glue evenly piece Clamp assembled blank securely least 24 hours longer possible blank should clamped tightly evenly solid straightedge such good piece angle iron clamps practical Small blanks can clamped vise has soft jaws avoid marking surface blank provided jaws cover length blank Care should taken tighten clamps slowly evenly sequence prevent shifting out alignment Keep blank parallel square blank dry use old knife chisel screwdriver remove glue has squeezed out joints jointer can true up blank nicely using very little wood Sand away excess glue before using jointerit will easier jointer blades Whether use solid laminated blank always make little larger little longer finished product allow machining trimming blank now has desired length width thickness Its time carve finish propeller Fig 4 Use stiff cardstock thin aluminum profile label future reference use LAYOUT Pin center halfblade pattern profile center point propeller Fig 5 blank see Figure 4 will top surface prop blank blank profile should have centerlines drawn reference Lay centerline pattern centerline blank draw blade outline Swing pattern l8O match patteru blank centerlines draw outline opposite blade prop hub needs slightly larger prop boss backing plate engine Remove profile pattern Place point compass pinprick center blank Divide blade centerline convenient equal spacesthe number divisions arbitrary Use square project spaces around sides block shown Figure 5 Now its apparent important have Fig 3blankasclosetoaperfect rectangle possible Because props natural tendency flex forward running front side prop tip should lower top hub see Figure 6 particularly noticeable laminated props wide long strip wood will flex close center blank viewed front back would case tip located closer top front blank thus giving strength flexing occurs static run-ups rapid acceleration deceleration Very little flexing occurs during constant-speed run because propeller pulling itself through air static run prop held place force air pulled rhrough it unable thread itself through air Trailing Blade profile pattern pinned blank Derived old Blankblade own design CUTTING AND DRILLING prevent splintering blank center hole drilled clamp blank backup scrap wood drill press table available have reamer drill center hole slightly undersize dont have reamer drill hole its finished size case hole should small enough prop will fit securely balancers shaft after blades completed Cut blade shape band saw scroll saw hand saw Cut just outside blade line outline can sanded its final shape CARVING THE BACK Clamp blank vise sand profile shape down line Place piece scrap wood side blank prevent scratches vise Remove saw marks keep blade edge close square top possible Repeat opposite blade Use square project station marks top blade down leading trailing edges blank see Figure 7 Join vertical marks station corresponding marks across bottom blank youre keeping face prop flat draw line about /s top see Figure 6A cutting slots back side dont cut below line like drop tip down somewhat shown Figure 6B June1993 29 Bottom Pitch gaugeTE resting saw CutApprox finished -- shape station Pitch gauge example L E drop ft used-Top#2@1h Approx Ia top face block14x6Mark & keep Add subtract appropriate amountfor next time dropping raising tip Bottom side ISee comments articIel back side gauge should parallel L E cut @ 9O surfaceL E example 14-inch prop mark about /16 down tip fair within 1/ top roughly first third blade root see Figure 6B 18-inch prop drop tip about 5A6 nineinch prop about 5A2 amount isnt Fig 6 critical building curve thinning out last two-thirds blade helps increase performance Make saw cuts bottom side blank per pitch gauges developed station see Figure 3 careful wrong cut wrong place means throwing blank away starting over Glancing finished prop helps keep touch whats required Carefully chisel excess wood depth saw cuts sand flat Always work grain against roughing out back blade start sharp chisel keep flat side up work gently hub toward first saw cut After carving down first1/4 . ores3/32ifl cut work tip toward root ondesiredor Suit leading edge half blade Remem ber prop still upside down Working tip toward root gently chisel trailing edge portion down toward saw cut point wood will appear somewhat terraced Finish rasping filing sanding 100-grit paper until saw marks disappear Repeat second blade Briefly stated what have done lay Out drill cut shape carve back side blade What left carve front side sand smooth balance finish desired shape front side blades begin root removing wood trailing edge toward high point smooth fashion Leave enough wood finish shaping sanding Remember always work grain against deviation finish sanding front side crosshatch form oblique sanding direction may used achieve uniform surface remove too much wood gouge out piece prevents attaining uniform blade shape will have start over use filler correct carving mistakes Such material can become deadly projectile separates surface blade high rpm Gently sand forward side blade high point leading edge Clark Y shape round leading edge As noted earlier taper thickness blade toward tip BALANCING Balance propeller being careful remove material within first 40% Fig 7Blank outline before drilling & cutting Leading edge BLADE FRONT Remove blank vise turn over blade tapered now Figure 6 Keep top square edges easy reference Generally speaking blade cross section will approximate Clark Y airfoil shape high point roughly third chord Use pencil mark high point root tip blade Depending characteristics wish achieve high point can constant may vary 33% first third blade 24% second third little 15% last third Figure 8 can simply copy prop have hand Bear mind 10000 rpm tip 14-inch prop will traveling slightly over 416 mph look wing J-3 Cub uses Clark Y airfoil look wing aircraft flies about 400 mph will notice considerable difference airfoil shape same aerodynamic principles apply prop also apply wing prop effect vertically rotating wing lifts aircraft forward radius possible since least efficient portion propeller have careful choosing making blank shaping blades uniformly balance wont far off FINISH AND FLYING Finish propeller Topclear dope Varathane clear epoxy protect blades absorbing water protect general wear tear Two three very light coats takesbe judicious Check props balance again before useyou may have add extra finish blade rebalance 8 1/31/31/3 15%Of29%of33%of chordchordchord Chord -High point ret hne ifi~~ii7Now youre ready fly may seem like lot work once patterns gauges made takes about three hours complete 18-inch prop Smaller props take less time finishing can take long like have used props right off bench finish worked fine Once have made three four props will develop own shortcuts techniques Youll pleased well props work youll begin enjoy making process isnt reallyfast does get easier after youve made few recommend marking hub diameter pitch flight box will soon have assortment unknown propellers Have funand soft landings Flying Dutchman odel Aviation raight blade 1/8 C Draw appropriate reference line before making saw cuts back side blade B Curved drop tipped blade 1/8 . C %ef Taper off shaded area top side keep flat & square LE & TE Project station lines down leading edge trailing edge faces after drilling cutting out Continue station line across bottom Fig High Pt ref edge riTIik4 ref typSaw cuts saw cuts accurate per gauges LE ref line trailing edge contour formed automatically finishing back side blade
