Lofting Techniques

Fr TECH U Roy Day Suppose want design Sport Scale airplane original thats bit different finm box wing Say youd like design airplane oval cross-section fuselage tapered wings Furthermore dont have computer Computer Aided Drafting CAD capability No problem simple techniques have use years long before advent computer CAD programs method called lofting Lofting used hundreds years ago ship designers lay out hulls applies equally well aircraft design Lofting technique drawing family shapes will result smooth outside form can used generate formers crosssection fuselage ribs tapered wing can also used design cowls canopies design Scale model scratch starting place three-view drawing full-scale airplane Unless lucky three-views give airplane outlines maybe two three fuselage cross-sections will need draw remainder fonners well ribs tapered wing Follow steps shown see easy Fuselage From three-view draw side view top view fuselage size airplane want build Assuming have couple cross-sections fuselage threeview draw Fuselage Reference Line FRL widest point fuselage side view Figure 1 Depending shape fuselage may may coincide thrustline Figure 1 shows case FRL slightly below thrustline top view November1999 85 Authors PZL-P38 Polish twin fighter bomber designed using lofting techniques described article Figure 1 56789 1234 Typical Top Side Views Fuselage Line Art Jill Ann Cavanaugh 5 6 7 Figure2a --1FRL 8765 8 Horizontal Vertical Measurements Stations Aft Station 4 7 6 5 4 6 5 Figure 2b Fuselage Cross-Sections Aft Cockpit Station 4 outline should same FRLthat widest part fuselage use crutch method build can build upper lower half fuselage over top view Assume given two cross-sections three-view firewall cockpit location stations 1 4 Figure 1 will also need formers wing leading edge trailing edge leading edge stabilizer others complete fuselage give skin/covering smooth contour example fuselage shown nine stations including rudder post stations drawn side top views shown Figure 1 Now ready draw fuselage cross-sections will give us formers stations indicated Figure 1 Draw axes shown Figure 2A composed vertical center line FRL Copy cross-section 4 three-view shown Figure 2A Plot horizontal widths fuselage top view station aft station 4 FRL Plot vertical dimensions measuring FRL side view fuselage Draw smooth curves through points follow shape cross-section station 4 resulting cross-sections shown Figure 2B Use same procedure generate cross-sections stations forward station 4 shown Figure 3 Using lofting technique have generated necessary former shapes give us smooth fuselage outline Because formers regular shapes its hard draw other half have match heres easy way Make template half former flip over draw other half Now have symmetrical former like SeeTempTM material making templates Youll need 34 Figure 3 ______FRL Fuselage Cross-Sections Forward Cockpit Station 4 Line Dividing Line 8 Equal Segments Figure 4 Root Rib Tip Rib Chord Line Lofting Ribs Tapered Wing 86 Model Aviation lates anyway draw formers balsa plywood build model Tapered Wing Ribs Lay down chord line ribs Draw root rib place tip rib determined wing taper Figure 4 make method easy space ribs equally along span Divide vertical horizontal space between root tip ribs number ribs nine case Heres little trick dividing arbitrary length line number equal parts problem divide line eight equal parts see Figure 5 Draw line B acute angle line Divide line B convenient eight segments Connect point 9 line B point X line Draw lines point line B parallel line 9-X will divide line required eight equal segments method used divide horizontal vertical spaces between tip root ribs Figure 4 Using French curve ship curve draw remaining ribs spars can also located shown Figure 4 50 spar notches can cut ribs Notice no washout indicated will introduced building Day 11709 Magruder Ln Rockville MD 20852 STEFAN GASPARINS C02 MOTORSVisit http/Iblacksheepsquadroncoml write Blackaheep Squadron 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