ForeandAft CO HOW TO WEIGHT-AND-BALANCE measurements full-scale aircraft required after manufacture periodically thereafter depending use aircraft major repairs modifications completed resultant ______________________ empty weight center gravity CG becomes starting point pilot properly load aircraft fuel passengers cargo remain within center-of-gravity limits dictated designer aircraft fore-andaft CG concern article trend toward larger models actual weight-and-balance measurements can accomplished using same procedures formulas used full-scale aircraft procedure requires least good scale weight capability least 1A weight aircraft sensitive bubble level steel scale carpenters square review terms used procedure might helpful refer illustration #1 measurements made arbitraiy fixed point called datum datum early aircraft usually firewall leading edge wing opened possibility error calculations Any point forward datum negative number aft positive number Adding multiplying positive negative numbers created confusion engineers now use arbitrary point somewhere front aircraft measurements positive arm name various distances measured computations arm multiplied weight distance results moment measurements jack point full-scale aircraft hard point will receive hydraulic jack model main wheel center and/or tail wheel/skid center use three points weight measurements points must measured accurately possible datum Weight scale reading observedremember subtract nonaircraft weight called tare scale such support blocks wheel chocks etc resultant computed ECG Empty Center Gravity ultimate reason whole procedure actually arm aft datumit shows fore-and-aft CG model recommend make simple drawing similar illustration #1 establish datum point somewhere front aircraft Put aircraft large table level aircraft spirit level FIND IT U Dick Eimert Refer drawing determine level area top cabin top edge engine mounts etc Use carpenters square similar device clamped table flush table edge datum record distance ILLUSTRATION #1from vertical point nose wheel axle tail wheel axle/skid note 2350drawingMeasurebacktothe main wheel axles should same both main wheels now have necessary distances arms necessary computations actual weights can measured scale negates requirement three calibrated scales Support model wheel/skid center scale use books wood blocks shims etc under remaining wheels level aircraft longitudinally laterally Note use engine mounts level aircraft remember remove level place engine cowl back position before taking weight measurement Take weight reading note drawing Use procedure other two weight measurements being very careful duplicate leveling procedures formula used calculations can worked simple calculator have used Lotus spreadsheet program computer full-scale model aircraft weight-and-balance computations See illustration #2 formula computations WRIGHT & BALANCE COMPUTATIONS ILLUSTRATION #2 ARM INSCALE OZTARENET NT MAIN WHEEL RIGHT MAIN WHEEL LEFT TOTAL MAIN WHEELS NOSE/TAIL WHEEL 5 2750 27 50 925 5775 5325 22SO 005775 005325 111 00 002250 TOTAL AIRCRAFT WRIGHT 13350 FORMULA -ARM X TOTAL NT B X WT B - ECO TOTAL AIRCRAFT WEIGHT EXAMPLE 2750 X 11100 X 2250 2442 13350 WEIGHTARMMOMENT AIRCRAFT NT AS WEIGHED133502442326093 REMOVE BATTERY AT 2600 INSTALL BATTERY AT 2100 NEW ECG AFTER BATTERY CHO AIRCRAFT WRIGHT ADD BALLAST AT 900 NEW ECO AFTER BALLAST CHO 700 700 13390 13250 600 13950 260019200 210014700 322963 2406NOT ACCEPTARLE 2406322563 9005400 327963 2351ACCEPTABLE ECO DESIRED EMPTY WEIGHT CENTER OF GRAVITY 2350 FROM DRAWING ALT B TAIL WHL/SKID NT & ARM WEIGHT & UATAbP CHART Ii---- ECO ARM --- DESIRED ECO IJL1LJ NT B HOSENT BOTH MAIN WHEELS ARM ----4 2750 NOTE ARMS SHOWN ARE FOR EXAMPLE ONLY 44 Model Aviation LAGE JIG STATIONS Provides solid support accurate building Rugged 7ply aircraft plywood Construction Three sizes available Standard torfuse up 7-1/2 wide Jumbo tuse up 10 wide Giant Scale fuse up 15 wide Use building board base mount Uni-St rut Guide Rails versatile set-up Contains hardware & instructions including Uni-Strut information Box 4 Standard Jig Stations $2195 Box 4 Jumbo Jig Stations $2395 Box 4 Giant Scale Jig Stations $3895 2 Five Ft Guide Rails & Mounting Nuts $2295 GATOR MORE GATOR PRODUCTS MV-i Typhoon Nats FAI Winner Plans Parts available 909 1000 22 1140 versions Plug-in Wing Tube & Socket Sets 7/16 5/8 7/8 1-1/2 dia Special Lengths Order Plug-in Wing Adjusters 4-pack Adjust Both WIng Panels Plug-in Adjustable Stab Kits Micro-Adjustment Both Stab Panels Soft-N-Safe Engine Mounts 120 91 60 size engines Feather Lite Glass Cloth 7 oz Close Weave Fast Filling Lightest Finished Weight 3713 Pompano Drive Pensacola FL 32514 Phone 904 494-0203 Clit /MasterCard Welcomed J/L Products VISA $4 50 per tern 5&H F ties dens add B Tax Backplate engine mount Throttle linkage standard Adjustable velocity stack optimum carburettor performance Standard muffler really muffles 25 Cu 30 HP 65H x60W x 60L Weight 45 pounds Chrome plated cylinder bore desired ECU usually noted drawings model aircraft model can use data supplied full-scale aircraft Measure distance point datum record drawing desired ECU After final ECU determined can shift ballast such adding battery ballast necessary achieve desired CU Ballast can added empty weight chart multiplied its arm get baltast moment added weighed moment divide new moment new weight will give new ECU tocation computerized chart especially useful because can see resultant ECU add change preferable shift location required equipment such battery rather add ballast Illustration #2 includes fictitious weights arms illustration substitute actual readings own measurements can also see change ECU add fuel other variable cargo Measure datum center tank multiply weight fuel moment fuel Insert data chart compute resultant ECU change fuel tanks full-scale aircraft generatty placed near center gravity fuel burn has little effect balance models tank forward ECU weight and-batance measurements should conducted empty tank Adding fuel will result forward shift ECU nose down acceptable ECU should never allowed shift aft desired position above procedure complicated models foreand-aft center gravity can found greater accuracy other method Reviewers note model flying CU location importanttoo far forward aft has bad consequences reliable plan will specify Otherwise new design must determined formula flight tests discussed Making Scate Model Airplanes Fly available Aircraft Data Box 763576 Dallas TX 753 763576 SASE info Eimert 8 Overbrook Dr Monsey NY 10952 46 Model Aviation odsczgapssjcaf Ihaiw ra//yIiin o lie power ts PRECISION FIBERGLASS PROD CO Hundreds cowls radial cowls & wheelpants Strong lightweight one-piece construction Exact duplicate manufacturers original Phone orders information call 423-984-0828 Send $100 catalog $200 Outside US 9am -6 pm EDT 3 2805 Big Bend Dr ville TN 37803
Edition: Model Aviation - 1997/11
Page Numbers: 44, 46
ForeandAft CO HOW TO WEIGHT-AND-BALANCE measurements full-scale aircraft required after manufacture periodically thereafter depending use aircraft major repairs modifications completed resultant ______________________ empty weight center gravity CG becomes starting point pilot properly load aircraft fuel passengers cargo remain within center-of-gravity limits dictated designer aircraft fore-andaft CG concern article trend toward larger models actual weight-and-balance measurements can accomplished using same procedures formulas used full-scale aircraft procedure requires least good scale weight capability least 1A weight aircraft sensitive bubble level steel scale carpenters square review terms used procedure might helpful refer illustration #1 measurements made arbitraiy fixed point called datum datum early aircraft usually firewall leading edge wing opened possibility error calculations Any point forward datum negative number aft positive number Adding multiplying positive negative numbers created confusion engineers now use arbitrary point somewhere front aircraft measurements positive arm name various distances measured computations arm multiplied weight distance results moment measurements jack point full-scale aircraft hard point will receive hydraulic jack model main wheel center and/or tail wheel/skid center use three points weight measurements points must measured accurately possible datum Weight scale reading observedremember subtract nonaircraft weight called tare scale such support blocks wheel chocks etc resultant computed ECG Empty Center Gravity ultimate reason whole procedure actually arm aft datumit shows fore-and-aft CG model recommend make simple drawing similar illustration #1 establish datum point somewhere front aircraft Put aircraft large table level aircraft spirit level FIND IT U Dick Eimert Refer drawing determine level area top cabin top edge engine mounts etc Use carpenters square similar device clamped table flush table edge datum record distance ILLUSTRATION #1from vertical point nose wheel axle tail wheel axle/skid note 2350drawingMeasurebacktothe main wheel axles should same both main wheels now have necessary distances arms necessary computations actual weights can measured scale negates requirement three calibrated scales Support model wheel/skid center scale use books wood blocks shims etc under remaining wheels level aircraft longitudinally laterally Note use engine mounts level aircraft remember remove level place engine cowl back position before taking weight measurement Take weight reading note drawing Use procedure other two weight measurements being very careful duplicate leveling procedures formula used calculations can worked simple calculator have used Lotus spreadsheet program computer full-scale model aircraft weight-and-balance computations See illustration #2 formula computations WRIGHT & BALANCE COMPUTATIONS ILLUSTRATION #2 ARM INSCALE OZTARENET NT MAIN WHEEL RIGHT MAIN WHEEL LEFT TOTAL MAIN WHEELS NOSE/TAIL WHEEL 5 2750 27 50 925 5775 5325 22SO 005775 005325 111 00 002250 TOTAL AIRCRAFT WRIGHT 13350 FORMULA -ARM X TOTAL NT B X WT B - ECO TOTAL AIRCRAFT WEIGHT EXAMPLE 2750 X 11100 X 2250 2442 13350 WEIGHTARMMOMENT AIRCRAFT NT AS WEIGHED133502442326093 REMOVE BATTERY AT 2600 INSTALL BATTERY AT 2100 NEW ECG AFTER BATTERY CHO AIRCRAFT WRIGHT ADD BALLAST AT 900 NEW ECO AFTER BALLAST CHO 700 700 13390 13250 600 13950 260019200 210014700 322963 2406NOT ACCEPTARLE 2406322563 9005400 327963 2351ACCEPTABLE ECO DESIRED EMPTY WEIGHT CENTER OF GRAVITY 2350 FROM DRAWING ALT B TAIL WHL/SKID NT & ARM WEIGHT & UATAbP CHART Ii---- ECO ARM --- DESIRED ECO IJL1LJ NT B HOSENT BOTH MAIN WHEELS ARM ----4 2750 NOTE ARMS SHOWN ARE FOR EXAMPLE ONLY 44 Model Aviation LAGE JIG STATIONS Provides solid support accurate building Rugged 7ply aircraft plywood Construction Three sizes available Standard torfuse up 7-1/2 wide Jumbo tuse up 10 wide Giant Scale fuse up 15 wide Use building board base mount Uni-St rut Guide Rails versatile set-up Contains hardware & instructions including Uni-Strut information Box 4 Standard Jig Stations $2195 Box 4 Jumbo Jig Stations $2395 Box 4 Giant Scale Jig Stations $3895 2 Five Ft Guide Rails & Mounting Nuts $2295 GATOR MORE GATOR PRODUCTS MV-i Typhoon Nats FAI Winner Plans Parts available 909 1000 22 1140 versions Plug-in Wing Tube & Socket Sets 7/16 5/8 7/8 1-1/2 dia Special Lengths Order Plug-in Wing Adjusters 4-pack Adjust Both WIng Panels Plug-in Adjustable Stab Kits Micro-Adjustment Both Stab Panels Soft-N-Safe Engine Mounts 120 91 60 size engines Feather Lite Glass Cloth 7 oz Close Weave Fast Filling Lightest Finished Weight 3713 Pompano Drive Pensacola FL 32514 Phone 904 494-0203 Clit /MasterCard Welcomed J/L Products VISA $4 50 per tern 5&H F ties dens add B Tax Backplate engine mount Throttle linkage standard Adjustable velocity stack optimum carburettor performance Standard muffler really muffles 25 Cu 30 HP 65H x60W x 60L Weight 45 pounds Chrome plated cylinder bore desired ECU usually noted drawings model aircraft model can use data supplied full-scale aircraft Measure distance point datum record drawing desired ECU After final ECU determined can shift ballast such adding battery ballast necessary achieve desired CU Ballast can added empty weight chart multiplied its arm get baltast moment added weighed moment divide new moment new weight will give new ECU tocation computerized chart especially useful because can see resultant ECU add change preferable shift location required equipment such battery rather add ballast Illustration #2 includes fictitious weights arms illustration substitute actual readings own measurements can also see change ECU add fuel other variable cargo Measure datum center tank multiply weight fuel moment fuel Insert data chart compute resultant ECU change fuel tanks full-scale aircraft generatty placed near center gravity fuel burn has little effect balance models tank forward ECU weight and-batance measurements should conducted empty tank Adding fuel will result forward shift ECU nose down acceptable ECU should never allowed shift aft desired position above procedure complicated models foreand-aft center gravity can found greater accuracy other method Reviewers note model flying CU location importanttoo far forward aft has bad consequences reliable plan will specify Otherwise new design must determined formula flight tests discussed Making Scate Model Airplanes Fly available Aircraft Data Box 763576 Dallas TX 753 763576 SASE info Eimert 8 Overbrook Dr Monsey NY 10952 46 Model Aviation odsczgapssjcaf Ihaiw ra//yIiin o lie power ts PRECISION FIBERGLASS PROD CO Hundreds cowls radial cowls & wheelpants Strong lightweight one-piece construction Exact duplicate manufacturers original Phone orders information call 423-984-0828 Send $100 catalog $200 Outside US 9am -6 pm EDT 3 2805 Big Bend Dr ville TN 37803