RELATIVEHUMIDITY 80000 04404 4 4 80 60 e540 20 30 40 5060 70 80 90 100 ItO 120 130 940 DRY-BULB TEMPERATURE DEG F till- CONTENT CHART authors atmospherics field kit consisting sting psychro meter calculator barometer Because good bad engine days generalized appreciation atmospheric conditions wilt help operate engine efficiently An understanding weather affects engine performance can lead efficient engine operation OVER THE YEARS times have modelers come conclusion old reliable sport engine has gone over hill deduction usually comes after varnish has removed cylin der wall piston plugs changed filters checked screws tightened needle valve assemblies examined success bringing back lost power Before sending mill back Clarence some freshening might well take stock elements day engine goes sour sky heavily overcast temperature well SOs promised summer storm moving area deteriorating weather conditions reduced air den sity could well cause reduction power overheating us dont recog nize symptoms Its costing us Everyone complains about weather nobody ever does anything about certain degree true statement other hand understanding weather affects engine perform ance will lead efficient engine op eration small two-stroke cycle semidiesels exceptionsophisticated air pumps require air large quan tities develop power useful chanical energy needed vehicles Air gas has freedom expand contract flows about earths surface same air contains about Effects David Gierke Atmospheho Condtbms oH Emgme Performamce part five vital combustion ele ment oxygen Air affected number factors either increases de creases availability oxygen engines cylinder individuals world high performance motor sports serious laboratory experimentation condition air air density great impor tance specific just much can air density affect engine performance Per sonally have experienced engine power difference 25% day next engine producing two horsepower excellent conditions reduction could much 1/2 horse power under poor conditions oxygen unavailable en gines consumption fuel must reduced order maintain proper air-to-fuel ratio reduction flow fuel through system given period time must result reduction power now know air its con dition has direct bearing upon engines perform Lets look specific factors observe affect air density begin should ex plained air density refers weight per given volume other words high density atmospheric condition means air molecules packed tightly together thus contain oxygen per cubic foot Temperature As temperature gas increases does its molecular activ ity molecules nitrogen four parts oxygen part moving about greater vibrating patterns effect moves further apart reduces density air decreases engine performance Pressure Refers force exerted weight atmosphere square inch earths surface unit area standard measure pressure sea level 2992 inches mercury hg approx 147 lbs per square inch known standard pressure travel mile-high city Den ver Cob air pressure would great ly reduced standard pressure about 24 inches Hg Actually atmos pheric pressure reduced about inch per 1000 foot above sea level al 10000 feet significant power loss would experienced altitudes Air pressure forces air engine 10 Model Aviation greater air pressure greater pressure differential exists between engines crankcase atmosphere pressure differential results great er air volume entering engine Im proved air volume generally increases cylinder packing volumetric efficiency Humidity Water Vapor nature air has ability absorb great quan tities water hold extended periods time amount water absorbed air directly related airs temperature illustrate point air can hold about ten times much water 900F possibly could 300F water molecules tend push oxygen nitrogen molecules further apart decreasing element density thus reducing engine power output review may stated fol lowing atmospheric conditions neces sary maximum engine performance High atmospheric pressure 2 Low air temperature 3 Low humidity Two methods will discussed concern ing handle newly acquired knowledge about weather First will Rule Thumb Method Secondly will Technical Method based upon weather instrumentation Rule Thumb Method What good bad engine day largely depends upon further discus sion relationship between air pressure water vapor content total air pressure determined barometer always sum normal air compo nents pressure exerted water vapor particularly important high temperature days potential large quantities water vapor being pres ent significant barometer may falsely high conditions high humidity because have previously mentioned water vapor reduces element density 0 ob tain representative air pressure readout water vapor pressure must subtracted barometer reading As can see importance accu rate weather instrumentation prime concern determination engine power potential temperature air low below 600F effect water vapor pressure minimal can gener ally disregarded Rule Thumb determination air density Listening radio television weather forecast can give some clue engine performance can also lead serious miscalcu lations shall see later Typical Forecast Temperature SOT 2 Barometer 3000 Hg rising 3 Relative humid ity 70% Rule Thumb Analysis Temperature low below stand ard 600F showing good density 2 Pressure high above standard 2992 Hg getting better should improve pressure differential between engine atmosphere good sign 3 Since air temperature low amount water may enter air low will affect baro metric readout great degree Overall Analysis better average engine perform ance day basis analysis should standard air conditions include Temperature 600F 2 Air pressure 2992 Hg sea level 3 0% humidity Any condition lowers tem perature less 600F raises barometer above 2992 Hg low humidity should considered Good engine day important factor affecting air character barometric pressure followed tempera ture finally humidity Humidity plays dual role reduces element air density giving barometer false ly high readout term relative humidity very mis leading term generally leads great confusion trying determine rule thumb air condition instru mentation method shall see later far superior Another Typical Forecast I Temperature 900F 2 Barometric pressure 2915 Hg 3 Relative humidity 70% Rule Thumb Analysis Temperature relatively high well above standard Poor air density 2 Baro metric pressure below standard will significantly affected high vapor pressure accompanies elevated temperature 3 Humidity quite high January 1976 11 some sling psychrometers theres scale gives percent relative humiditymay applied chart left determine moisture content terms grains water/pound dry air Right Rick Paine uses tachometer determine engine operating within desired power range Changing pitch and/or diameter will force engine operate desired speed range start laboratory dynamometer test authors reaction fan brake absorption unit Factors involved engine performance temperature pressure humidity water vapor Atmospheric Conditions air temperature involved Low density importantly water pressure will reduce actual barometric pressure reading Overall Analysis poor engine day Much less standard day high temperature con dition difficult pinpoint using ruleof-thumb method because water vapor effect following illustrates relative humidity has nothing actual water vapor weight atmosphere first example air temperature 500F relative humidity 70% actual water vapor weight deter mined use tables 38 grains water vapor per pound dry air 2 second example air temperature 900F relative humidity again 70% case however actual water vapor weight 142 grains per pound dry air represents increase over 350% rule thumb method can useful no other means available deter condition air pro duction power Some conclusions may drawn con cerning what may done retrieve some lost engine performance power due poor weather conditions virtu ally no way recall lost engine power due atmospheric density/pressure re duction exceptions Addition supercharger B Careful manipula tion oxygen liberating chemicals such nitromethane fuel supercharger impractical addition nitro usually doesnt work cause other limiting engine design fea tures such cooling capacity engine compression ratio etc. also probably already using can best procedure make engine run maximum its capability existing conditions proper rpm places engine within its operation al power band thus making its Student Gary Pajak slings psychrometer preparation dynamometer test lab Comparative engine tests meaningless un less atmospheric variable eliminated results Engines performing models must live existing conditions Prescriptions given article adjust factors governing en gine performance need arises power potential Example has determined poor engine day exists engine rpm down 12200 its normal 12900 following procedure might persued 1 Increase nitromethane content slightly ie 10 12% 2 Run engine observe rpm Sometimes speed will increase othertimes engine will simply overheat 3 If overheating occurs reduce size load prop easily ac complished reducing pitch ie Change 11-7 3/4 11-7 idea force engine operate its designed power range 4 Occasionally combination re duced load increased nitromethane content will improve performance case sure watch overheating drop raw fuel cylinder head should smoke burn away merely evaporate 5 Gb-plug heat range will sometimes make difference changing nitro methane contents ie Using certain Fox plugs makes cylinder removes heat quickly certain K&B plugs Similarly gb-plugs have indi vidual heat ranges Generally thing remember increased nitro content cylinders must cooled effectively called cool cold plug removes heat quicker Conversely hot plug retains cylinder heat Check Plug Heat Range 1 booster battery place plug check engine rpm tachometer 2 Remove booster bat tery note engine rpm Example #1 Plug hot rpm12500 Plug cool rpm12300 rpm drop 200 Example #2 Plug hot rpm12500 Plug cool rpm 12400 rpm dropl00 27 W02030E 30 25 24 23 22 21 S 6 5 4050 60 10606000 11000 30 DRY BULB TEMPERATURE F VAPOR PRESSURE CHART SHTL 3 U George Baynes using pocket aling psychrometer Kent Landefelds Cosmic Wind racer background Both rule thumb scientific interpretations forecasts explained BASE LINE RECORDSRI 2 61O N88 aDATE7774By DAVE DIEDDE IN rnNW -J NGINE PORE V-ACORIP RIDS SAN BE6SANDIND NN 46N0 -JZ6-N UWNtPROPPLUGFUELCOMPCOMMENTSGROUNDTIME NCCRATIORPM 9667562 2048 6/O7ONNL65%57000724500LOS 24 09 0 7DNA60%SF0BEFFEN20700P32 20 407086 L60% SF0GOOD21200126 8O7OSOL60%0030072460035 6107EDO DO60%ODDCOOLED24900COD 2 POD DO00%NFDDOLD00700CDO 666 L60%003COOL211063D 9667562 2048 9I~ D86 L60%070BASE LINE21200 An important segment laboratory determination engine perfor mance effective elimination atmospheric variable hp correction factor temperature pressure wet-and-dry bulb temperature being recorded Joe Frontera student teacher working author Power Technology Lab local high school first case rpm drop indicated cool cold plug particular oper ation determined because combustion process deteriorated engine would normally operate rela tively low cylinder head temperatures condition second case rpm reduction less still showing cool plug warmer example #1 other experiments may find plugs offer little no rpm loss plug may too hot con ditions ideal situation cases find plug delivers slight rpm drop removing booster 100 rpm loss too great fire may go out especially during idle mode operation visual method categorizing glo plugs observe relative thickness wire Generally larger wire diameters dictate colder plugs must re-emphasize no pro cedure will probably work restore lost engine power due poor atmospheric con ditions Some power may restored carefully adjusting compression ratio upward cases other racing just too impractical seriously considered important consider ation operate engine within its designed speed range power band terms power band may useful consult Peter Chinns torque horse power curves particular engine cases peak horsepower curve slightly beyond rpm scale type engine wants operate As mentioned earlier common pitfall concerning weather forecasts radio TV centers about corrected baro metric pressures relay pressures corrected sea level done purposes air navigation used inform general public weather changes regard altitude number years ago Denver radio announcer relayed barometric pressure being 29600 Hg could After contacting Denver weather de partment informed pres sure corrected reference purposes use portable aneroid barometer sure calibrate station pressure available local weather people uncorrected barometric pressure Please aware unless live sea level announced pressures mile off An Area Further Research Great concentrations water vapor seem have dramatic effect upon engines 272 Ii hi C hi n I6 Ir hi 0 hi 0 t Ihi 2 682B2 fueled high percentages alcohol ie FAI fuel effect alcohol engines per form rather poorly conditions Usually compression ratio must re duced order stop air/fuel mixture detonating combustion cham ber Reducing compression ratio un fortunately reduces power Several individuals studying phenomenon viewpoint actual water vapor weight present air along dew point temperatures barometric pres sures What anything can done control alcohol engines performance condi tions high humidity Will carburetor cylinder head designs help prob lem Only further research time will tell continued page 68 31 3 SIlT 4 January 1976 13 28 . ON BAROMETRIC PRESSURE INHG MERCURY BAROMETER 2992 Pt MG STANDARD CONDITIONS AT SEA LEVEL jJAPOUR PRESSURE 000 IN HG LTEMPERATURE 60 DES F anoernnwrO CORRECTION FACTOR CHART x DAVE LINSTRUMS STARSTREAM 0 ULTRA SIMPLE CONSTRUCTION ALL BALSA AND PLY PARTS MACHINE OR DIE CUT 48 INCH WINGSPAN AUTO-RUDDER CONTROL FULL SIZE ILLUSTRATED STEP BY STEP PLAN FLYING INSTRUCTIONS WINNER OF THE FAI/CIAMINCLUDED INTERNATIONAL DESIGN $1195 COMPETITION FOR YOUTH GLIDEF IDWEST PRODUCTS CO 400 South Indiana StHobartIndiana 46342 RC Sport/Van Putte continued page 18 Fig 1 shows what happens ground track airplane turn varying wind conditions load factor held con stant level coordinated turn load factor directly related bank angle aircraft very simple equation Load Factor X Cosine Bank Angle ll 3600 turn shown demonstrate what hap pens both downwind upwind turn figure can also used visualize what happens during turns wind make seem dangerous Consider first airplane going downwind starts 1800 turn pilot notes airplane going fur ther downwind desires increases bank angle load factor What may happen next pilot will continue increase bank angle until airplane stalls out crashes what about airplane going upwind starts 1800 turn pilot banks airplane comfortable no-wind bank angle discovers heading relative speed airplane suddenly changing much rapidly expected loses orientation over-rolls airplane ground Neither maneuver inherently dangerous lack understanding about what air plane will wind can severely unsettle pilot particularly beginner lowspeed trainer airplane since effects wind greater slower airplanes two things remember flying wind 1 Increase bank angle over normal amount turn downwind heading made Gradually reduce bank angle airplane swings wind 2 Decrease bank angle no-wind amount turn upwind heading made Gradually increase bank angle airplane comes around downwind Try it works Next month Ill present some wind effects vertical maneuvers last few weeks have testing new product called PoweR/Charge SP Systems Marietta Ga combined nickel-cadmium battery discharger-charger field tester havent made com prehensive test unit seems advertised have used batteries two radio systems old questionable airborne pack cases PoweR/Charge progressively increased discharge time indicating increased capacity Especially striking capacity increase old battery pack After initial charge old 475-ma pack should have discharged least 2 hours 10 minutes first discharge lasted 1 hour 40 minutes second dis charge 2 hours 4 minutes third dis charge lasted 2 hours 20 minutes Subsequent discharges pack hovered around 2 hours 30 minutes Similar less startling capacity increases occurred other battery packs tested future com prehensive review will published Have seen new book beginners called Basics Radio Control Modeling Fred Marks co-authors book Model Aviation editor Bill Winter Fred town couple weeks ago business pre sented copy review remarkably well done piece work book includes chapters tools materials radio equipment engines airplanes boats cars other models like way its written photography has quality often seen model publications address 12 Connie Dr Shalimar Fla 32579 FF Duration/Meuser continued page 43 can purchased $695 can buy individual parts unit accommodates Forster 29 O&R 23 K&B Torpedo primarily flying parts nicely polished unit makes attractive display too Weight 294 gramsa thin hair over ounceand overall length 2 info write Jim 1442 N Fruit Ave Fresno CA 93728 Call Papers National Free Flight Society soliciting papers 1976 NFFS Symposium held 1976 Nats Papers will published 1976 Symposium vol ume whether author able present paper personally Nats Papers should cover some aspect science art free-flight models including technical studies practical design engineering applied models new unusual model aircraft developments historical items Both indoor outdoor freeflight modeling developments included Please send proposed papers Ray Harlan 15 Happy Hollow Rd Wayland Mass 01778 Send title proposed paper together abstract 200 words or complete paper available considered ab stracts should submitted Feb 15 1976 Book Review A ero -Modeller Annual 1975-76 review general model aviation book free-flight column Well well skip RC CL stuff judge solely its free-flight content sign times perhaps first Annual Ive seen paperback price has doubled two years UK price trans lates $450 what actual USA price will remains seen Compared what get money buy say $600 worth magazines imagine will judge worth money drawings A P Lloyd usual top quality Most model plans have appeared other publications would have subscribe magazine news letter world have seen before plans count includes 17 FAI-class models smattering others Most articles original about dozen directly related free flight including series three finishing overview Pennyplane activity world-wide plenty plans Dave Lin strum photo-story covering dozen unusual engines such Elf flat-six rotary valve four-stroke Dooling turned 28000 rpm cover other John Daddy Warbucks Pond himself complete Old-Timer course SAM 01 license plate address 4200 Gregory St Oakland Calif 94619 66 Model Aviation
Edition: Model Aviation - 1976/01
Page Numbers: 10, 11, 12, 13, 66
RELATIVEHUMIDITY 80000 04404 4 4 80 60 e540 20 30 40 5060 70 80 90 100 ItO 120 130 940 DRY-BULB TEMPERATURE DEG F till- CONTENT CHART authors atmospherics field kit consisting sting psychro meter calculator barometer Because good bad engine days generalized appreciation atmospheric conditions wilt help operate engine efficiently An understanding weather affects engine performance can lead efficient engine operation OVER THE YEARS times have modelers come conclusion old reliable sport engine has gone over hill deduction usually comes after varnish has removed cylin der wall piston plugs changed filters checked screws tightened needle valve assemblies examined success bringing back lost power Before sending mill back Clarence some freshening might well take stock elements day engine goes sour sky heavily overcast temperature well SOs promised summer storm moving area deteriorating weather conditions reduced air den sity could well cause reduction power overheating us dont recog nize symptoms Its costing us Everyone complains about weather nobody ever does anything about certain degree true statement other hand understanding weather affects engine perform ance will lead efficient engine op eration small two-stroke cycle semidiesels exceptionsophisticated air pumps require air large quan tities develop power useful chanical energy needed vehicles Air gas has freedom expand contract flows about earths surface same air contains about Effects David Gierke Atmospheho Condtbms oH Emgme Performamce part five vital combustion ele ment oxygen Air affected number factors either increases de creases availability oxygen engines cylinder individuals world high performance motor sports serious laboratory experimentation condition air air density great impor tance specific just much can air density affect engine performance Per sonally have experienced engine power difference 25% day next engine producing two horsepower excellent conditions reduction could much 1/2 horse power under poor conditions oxygen unavailable en gines consumption fuel must reduced order maintain proper air-to-fuel ratio reduction flow fuel through system given period time must result reduction power now know air its con dition has direct bearing upon engines perform Lets look specific factors observe affect air density begin should ex plained air density refers weight per given volume other words high density atmospheric condition means air molecules packed tightly together thus contain oxygen per cubic foot Temperature As temperature gas increases does its molecular activ ity molecules nitrogen four parts oxygen part moving about greater vibrating patterns effect moves further apart reduces density air decreases engine performance Pressure Refers force exerted weight atmosphere square inch earths surface unit area standard measure pressure sea level 2992 inches mercury hg approx 147 lbs per square inch known standard pressure travel mile-high city Den ver Cob air pressure would great ly reduced standard pressure about 24 inches Hg Actually atmos pheric pressure reduced about inch per 1000 foot above sea level al 10000 feet significant power loss would experienced altitudes Air pressure forces air engine 10 Model Aviation greater air pressure greater pressure differential exists between engines crankcase atmosphere pressure differential results great er air volume entering engine Im proved air volume generally increases cylinder packing volumetric efficiency Humidity Water Vapor nature air has ability absorb great quan tities water hold extended periods time amount water absorbed air directly related airs temperature illustrate point air can hold about ten times much water 900F possibly could 300F water molecules tend push oxygen nitrogen molecules further apart decreasing element density thus reducing engine power output review may stated fol lowing atmospheric conditions neces sary maximum engine performance High atmospheric pressure 2 Low air temperature 3 Low humidity Two methods will discussed concern ing handle newly acquired knowledge about weather First will Rule Thumb Method Secondly will Technical Method based upon weather instrumentation Rule Thumb Method What good bad engine day largely depends upon further discus sion relationship between air pressure water vapor content total air pressure determined barometer always sum normal air compo nents pressure exerted water vapor particularly important high temperature days potential large quantities water vapor being pres ent significant barometer may falsely high conditions high humidity because have previously mentioned water vapor reduces element density 0 ob tain representative air pressure readout water vapor pressure must subtracted barometer reading As can see importance accu rate weather instrumentation prime concern determination engine power potential temperature air low below 600F effect water vapor pressure minimal can gener ally disregarded Rule Thumb determination air density Listening radio television weather forecast can give some clue engine performance can also lead serious miscalcu lations shall see later Typical Forecast Temperature SOT 2 Barometer 3000 Hg rising 3 Relative humid ity 70% Rule Thumb Analysis Temperature low below stand ard 600F showing good density 2 Pressure high above standard 2992 Hg getting better should improve pressure differential between engine atmosphere good sign 3 Since air temperature low amount water may enter air low will affect baro metric readout great degree Overall Analysis better average engine perform ance day basis analysis should standard air conditions include Temperature 600F 2 Air pressure 2992 Hg sea level 3 0% humidity Any condition lowers tem perature less 600F raises barometer above 2992 Hg low humidity should considered Good engine day important factor affecting air character barometric pressure followed tempera ture finally humidity Humidity plays dual role reduces element air density giving barometer false ly high readout term relative humidity very mis leading term generally leads great confusion trying determine rule thumb air condition instru mentation method shall see later far superior Another Typical Forecast I Temperature 900F 2 Barometric pressure 2915 Hg 3 Relative humidity 70% Rule Thumb Analysis Temperature relatively high well above standard Poor air density 2 Baro metric pressure below standard will significantly affected high vapor pressure accompanies elevated temperature 3 Humidity quite high January 1976 11 some sling psychrometers theres scale gives percent relative humiditymay applied chart left determine moisture content terms grains water/pound dry air Right Rick Paine uses tachometer determine engine operating within desired power range Changing pitch and/or diameter will force engine operate desired speed range start laboratory dynamometer test authors reaction fan brake absorption unit Factors involved engine performance temperature pressure humidity water vapor Atmospheric Conditions air temperature involved Low density importantly water pressure will reduce actual barometric pressure reading Overall Analysis poor engine day Much less standard day high temperature con dition difficult pinpoint using ruleof-thumb method because water vapor effect following illustrates relative humidity has nothing actual water vapor weight atmosphere first example air temperature 500F relative humidity 70% actual water vapor weight deter mined use tables 38 grains water vapor per pound dry air 2 second example air temperature 900F relative humidity again 70% case however actual water vapor weight 142 grains per pound dry air represents increase over 350% rule thumb method can useful no other means available deter condition air pro duction power Some conclusions may drawn con cerning what may done retrieve some lost engine performance power due poor weather conditions virtu ally no way recall lost engine power due atmospheric density/pressure re duction exceptions Addition supercharger B Careful manipula tion oxygen liberating chemicals such nitromethane fuel supercharger impractical addition nitro usually doesnt work cause other limiting engine design fea tures such cooling capacity engine compression ratio etc. also probably already using can best procedure make engine run maximum its capability existing conditions proper rpm places engine within its operation al power band thus making its Student Gary Pajak slings psychrometer preparation dynamometer test lab Comparative engine tests meaningless un less atmospheric variable eliminated results Engines performing models must live existing conditions Prescriptions given article adjust factors governing en gine performance need arises power potential Example has determined poor engine day exists engine rpm down 12200 its normal 12900 following procedure might persued 1 Increase nitromethane content slightly ie 10 12% 2 Run engine observe rpm Sometimes speed will increase othertimes engine will simply overheat 3 If overheating occurs reduce size load prop easily ac complished reducing pitch ie Change 11-7 3/4 11-7 idea force engine operate its designed power range 4 Occasionally combination re duced load increased nitromethane content will improve performance case sure watch overheating drop raw fuel cylinder head should smoke burn away merely evaporate 5 Gb-plug heat range will sometimes make difference changing nitro methane contents ie Using certain Fox plugs makes cylinder removes heat quickly certain K&B plugs Similarly gb-plugs have indi vidual heat ranges Generally thing remember increased nitro content cylinders must cooled effectively called cool cold plug removes heat quicker Conversely hot plug retains cylinder heat Check Plug Heat Range 1 booster battery place plug check engine rpm tachometer 2 Remove booster bat tery note engine rpm Example #1 Plug hot rpm12500 Plug cool rpm12300 rpm drop 200 Example #2 Plug hot rpm12500 Plug cool rpm 12400 rpm dropl00 27 W02030E 30 25 24 23 22 21 S 6 5 4050 60 10606000 11000 30 DRY BULB TEMPERATURE F VAPOR PRESSURE CHART SHTL 3 U George Baynes using pocket aling psychrometer Kent Landefelds Cosmic Wind racer background Both rule thumb scientific interpretations forecasts explained BASE LINE RECORDSRI 2 61O N88 aDATE7774By DAVE DIEDDE IN rnNW -J NGINE PORE V-ACORIP RIDS SAN BE6SANDIND NN 46N0 -JZ6-N UWNtPROPPLUGFUELCOMPCOMMENTSGROUNDTIME NCCRATIORPM 9667562 2048 6/O7ONNL65%57000724500LOS 24 09 0 7DNA60%SF0BEFFEN20700P32 20 407086 L60% SF0GOOD21200126 8O7OSOL60%0030072460035 6107EDO DO60%ODDCOOLED24900COD 2 POD DO00%NFDDOLD00700CDO 666 L60%003COOL211063D 9667562 2048 9I~ D86 L60%070BASE LINE21200 An important segment laboratory determination engine perfor mance effective elimination atmospheric variable hp correction factor temperature pressure wet-and-dry bulb temperature being recorded Joe Frontera student teacher working author Power Technology Lab local high school first case rpm drop indicated cool cold plug particular oper ation determined because combustion process deteriorated engine would normally operate rela tively low cylinder head temperatures condition second case rpm reduction less still showing cool plug warmer example #1 other experiments may find plugs offer little no rpm loss plug may too hot con ditions ideal situation cases find plug delivers slight rpm drop removing booster 100 rpm loss too great fire may go out especially during idle mode operation visual method categorizing glo plugs observe relative thickness wire Generally larger wire diameters dictate colder plugs must re-emphasize no pro cedure will probably work restore lost engine power due poor atmospheric con ditions Some power may restored carefully adjusting compression ratio upward cases other racing just too impractical seriously considered important consider ation operate engine within its designed speed range power band terms power band may useful consult Peter Chinns torque horse power curves particular engine cases peak horsepower curve slightly beyond rpm scale type engine wants operate As mentioned earlier common pitfall concerning weather forecasts radio TV centers about corrected baro metric pressures relay pressures corrected sea level done purposes air navigation used inform general public weather changes regard altitude number years ago Denver radio announcer relayed barometric pressure being 29600 Hg could After contacting Denver weather de partment informed pres sure corrected reference purposes use portable aneroid barometer sure calibrate station pressure available local weather people uncorrected barometric pressure Please aware unless live sea level announced pressures mile off An Area Further Research Great concentrations water vapor seem have dramatic effect upon engines 272 Ii hi C hi n I6 Ir hi 0 hi 0 t Ihi 2 682B2 fueled high percentages alcohol ie FAI fuel effect alcohol engines per form rather poorly conditions Usually compression ratio must re duced order stop air/fuel mixture detonating combustion cham ber Reducing compression ratio un fortunately reduces power Several individuals studying phenomenon viewpoint actual water vapor weight present air along dew point temperatures barometric pres sures What anything can done control alcohol engines performance condi tions high humidity Will carburetor cylinder head designs help prob lem Only further research time will tell continued page 68 31 3 SIlT 4 January 1976 13 28 . ON BAROMETRIC PRESSURE INHG MERCURY BAROMETER 2992 Pt MG STANDARD CONDITIONS AT SEA LEVEL jJAPOUR PRESSURE 000 IN HG LTEMPERATURE 60 DES F anoernnwrO CORRECTION FACTOR CHART x DAVE LINSTRUMS STARSTREAM 0 ULTRA SIMPLE CONSTRUCTION ALL BALSA AND PLY PARTS MACHINE OR DIE CUT 48 INCH WINGSPAN AUTO-RUDDER CONTROL FULL SIZE ILLUSTRATED STEP BY STEP PLAN FLYING INSTRUCTIONS WINNER OF THE FAI/CIAMINCLUDED INTERNATIONAL DESIGN $1195 COMPETITION FOR YOUTH GLIDEF IDWEST PRODUCTS CO 400 South Indiana StHobartIndiana 46342 RC Sport/Van Putte continued page 18 Fig 1 shows what happens ground track airplane turn varying wind conditions load factor held con stant level coordinated turn load factor directly related bank angle aircraft very simple equation Load Factor X Cosine Bank Angle ll 3600 turn shown demonstrate what hap pens both downwind upwind turn figure can also used visualize what happens during turns wind make seem dangerous Consider first airplane going downwind starts 1800 turn pilot notes airplane going fur ther downwind desires increases bank angle load factor What may happen next pilot will continue increase bank angle until airplane stalls out crashes what about airplane going upwind starts 1800 turn pilot banks airplane comfortable no-wind bank angle discovers heading relative speed airplane suddenly changing much rapidly expected loses orientation over-rolls airplane ground Neither maneuver inherently dangerous lack understanding about what air plane will wind can severely unsettle pilot particularly beginner lowspeed trainer airplane since effects wind greater slower airplanes two things remember flying wind 1 Increase bank angle over normal amount turn downwind heading made Gradually reduce bank angle airplane swings wind 2 Decrease bank angle no-wind amount turn upwind heading made Gradually increase bank angle airplane comes around downwind Try it works Next month Ill present some wind effects vertical maneuvers last few weeks have testing new product called PoweR/Charge SP Systems Marietta Ga combined nickel-cadmium battery discharger-charger field tester havent made com prehensive test unit seems advertised have used batteries two radio systems old questionable airborne pack cases PoweR/Charge progressively increased discharge time indicating increased capacity Especially striking capacity increase old battery pack After initial charge old 475-ma pack should have discharged least 2 hours 10 minutes first discharge lasted 1 hour 40 minutes second dis charge 2 hours 4 minutes third dis charge lasted 2 hours 20 minutes Subsequent discharges pack hovered around 2 hours 30 minutes Similar less startling capacity increases occurred other battery packs tested future com prehensive review will published Have seen new book beginners called Basics Radio Control Modeling Fred Marks co-authors book Model Aviation editor Bill Winter Fred town couple weeks ago business pre sented copy review remarkably well done piece work book includes chapters tools materials radio equipment engines airplanes boats cars other models like way its written photography has quality often seen model publications address 12 Connie Dr Shalimar Fla 32579 FF Duration/Meuser continued page 43 can purchased $695 can buy individual parts unit accommodates Forster 29 O&R 23 K&B Torpedo primarily flying parts nicely polished unit makes attractive display too Weight 294 gramsa thin hair over ounceand overall length 2 info write Jim 1442 N Fruit Ave Fresno CA 93728 Call Papers National Free Flight Society soliciting papers 1976 NFFS Symposium held 1976 Nats Papers will published 1976 Symposium vol ume whether author able present paper personally Nats Papers should cover some aspect science art free-flight models including technical studies practical design engineering applied models new unusual model aircraft developments historical items Both indoor outdoor freeflight modeling developments included Please send proposed papers Ray Harlan 15 Happy Hollow Rd Wayland Mass 01778 Send title proposed paper together abstract 200 words or complete paper available considered ab stracts should submitted Feb 15 1976 Book Review A ero -Modeller Annual 1975-76 review general model aviation book free-flight column Well well skip RC CL stuff judge solely its free-flight content sign times perhaps first Annual Ive seen paperback price has doubled two years UK price trans lates $450 what actual USA price will remains seen Compared what get money buy say $600 worth magazines imagine will judge worth money drawings A P Lloyd usual top quality Most model plans have appeared other publications would have subscribe magazine news letter world have seen before plans count includes 17 FAI-class models smattering others Most articles original about dozen directly related free flight including series three finishing overview Pennyplane activity world-wide plenty plans Dave Lin strum photo-story covering dozen unusual engines such Elf flat-six rotary valve four-stroke Dooling turned 28000 rpm cover other John Daddy Warbucks Pond himself complete Old-Timer course SAM 01 license plate address 4200 Gregory St Oakland Calif 94619 66 Model Aviation
Edition: Model Aviation - 1976/01
Page Numbers: 10, 11, 12, 13, 66
RELATIVEHUMIDITY 80000 04404 4 4 80 60 e540 20 30 40 5060 70 80 90 100 ItO 120 130 940 DRY-BULB TEMPERATURE DEG F till- CONTENT CHART authors atmospherics field kit consisting sting psychro meter calculator barometer Because good bad engine days generalized appreciation atmospheric conditions wilt help operate engine efficiently An understanding weather affects engine performance can lead efficient engine operation OVER THE YEARS times have modelers come conclusion old reliable sport engine has gone over hill deduction usually comes after varnish has removed cylin der wall piston plugs changed filters checked screws tightened needle valve assemblies examined success bringing back lost power Before sending mill back Clarence some freshening might well take stock elements day engine goes sour sky heavily overcast temperature well SOs promised summer storm moving area deteriorating weather conditions reduced air den sity could well cause reduction power overheating us dont recog nize symptoms Its costing us Everyone complains about weather nobody ever does anything about certain degree true statement other hand understanding weather affects engine perform ance will lead efficient engine op eration small two-stroke cycle semidiesels exceptionsophisticated air pumps require air large quan tities develop power useful chanical energy needed vehicles Air gas has freedom expand contract flows about earths surface same air contains about Effects David Gierke Atmospheho Condtbms oH Emgme Performamce part five vital combustion ele ment oxygen Air affected number factors either increases de creases availability oxygen engines cylinder individuals world high performance motor sports serious laboratory experimentation condition air air density great impor tance specific just much can air density affect engine performance Per sonally have experienced engine power difference 25% day next engine producing two horsepower excellent conditions reduction could much 1/2 horse power under poor conditions oxygen unavailable en gines consumption fuel must reduced order maintain proper air-to-fuel ratio reduction flow fuel through system given period time must result reduction power now know air its con dition has direct bearing upon engines perform Lets look specific factors observe affect air density begin should ex plained air density refers weight per given volume other words high density atmospheric condition means air molecules packed tightly together thus contain oxygen per cubic foot Temperature As temperature gas increases does its molecular activ ity molecules nitrogen four parts oxygen part moving about greater vibrating patterns effect moves further apart reduces density air decreases engine performance Pressure Refers force exerted weight atmosphere square inch earths surface unit area standard measure pressure sea level 2992 inches mercury hg approx 147 lbs per square inch known standard pressure travel mile-high city Den ver Cob air pressure would great ly reduced standard pressure about 24 inches Hg Actually atmos pheric pressure reduced about inch per 1000 foot above sea level al 10000 feet significant power loss would experienced altitudes Air pressure forces air engine 10 Model Aviation greater air pressure greater pressure differential exists between engines crankcase atmosphere pressure differential results great er air volume entering engine Im proved air volume generally increases cylinder packing volumetric efficiency Humidity Water Vapor nature air has ability absorb great quan tities water hold extended periods time amount water absorbed air directly related airs temperature illustrate point air can hold about ten times much water 900F possibly could 300F water molecules tend push oxygen nitrogen molecules further apart decreasing element density thus reducing engine power output review may stated fol lowing atmospheric conditions neces sary maximum engine performance High atmospheric pressure 2 Low air temperature 3 Low humidity Two methods will discussed concern ing handle newly acquired knowledge about weather First will Rule Thumb Method Secondly will Technical Method based upon weather instrumentation Rule Thumb Method What good bad engine day largely depends upon further discus sion relationship between air pressure water vapor content total air pressure determined barometer always sum normal air compo nents pressure exerted water vapor particularly important high temperature days potential large quantities water vapor being pres ent significant barometer may falsely high conditions high humidity because have previously mentioned water vapor reduces element density 0 ob tain representative air pressure readout water vapor pressure must subtracted barometer reading As can see importance accu rate weather instrumentation prime concern determination engine power potential temperature air low below 600F effect water vapor pressure minimal can gener ally disregarded Rule Thumb determination air density Listening radio television weather forecast can give some clue engine performance can also lead serious miscalcu lations shall see later Typical Forecast Temperature SOT 2 Barometer 3000 Hg rising 3 Relative humid ity 70% Rule Thumb Analysis Temperature low below stand ard 600F showing good density 2 Pressure high above standard 2992 Hg getting better should improve pressure differential between engine atmosphere good sign 3 Since air temperature low amount water may enter air low will affect baro metric readout great degree Overall Analysis better average engine perform ance day basis analysis should standard air conditions include Temperature 600F 2 Air pressure 2992 Hg sea level 3 0% humidity Any condition lowers tem perature less 600F raises barometer above 2992 Hg low humidity should considered Good engine day important factor affecting air character barometric pressure followed tempera ture finally humidity Humidity plays dual role reduces element air density giving barometer false ly high readout term relative humidity very mis leading term generally leads great confusion trying determine rule thumb air condition instru mentation method shall see later far superior Another Typical Forecast I Temperature 900F 2 Barometric pressure 2915 Hg 3 Relative humidity 70% Rule Thumb Analysis Temperature relatively high well above standard Poor air density 2 Baro metric pressure below standard will significantly affected high vapor pressure accompanies elevated temperature 3 Humidity quite high January 1976 11 some sling psychrometers theres scale gives percent relative humiditymay applied chart left determine moisture content terms grains water/pound dry air Right Rick Paine uses tachometer determine engine operating within desired power range Changing pitch and/or diameter will force engine operate desired speed range start laboratory dynamometer test authors reaction fan brake absorption unit Factors involved engine performance temperature pressure humidity water vapor Atmospheric Conditions air temperature involved Low density importantly water pressure will reduce actual barometric pressure reading Overall Analysis poor engine day Much less standard day high temperature con dition difficult pinpoint using ruleof-thumb method because water vapor effect following illustrates relative humidity has nothing actual water vapor weight atmosphere first example air temperature 500F relative humidity 70% actual water vapor weight deter mined use tables 38 grains water vapor per pound dry air 2 second example air temperature 900F relative humidity again 70% case however actual water vapor weight 142 grains per pound dry air represents increase over 350% rule thumb method can useful no other means available deter condition air pro duction power Some conclusions may drawn con cerning what may done retrieve some lost engine performance power due poor weather conditions virtu ally no way recall lost engine power due atmospheric density/pressure re duction exceptions Addition supercharger B Careful manipula tion oxygen liberating chemicals such nitromethane fuel supercharger impractical addition nitro usually doesnt work cause other limiting engine design fea tures such cooling capacity engine compression ratio etc. also probably already using can best procedure make engine run maximum its capability existing conditions proper rpm places engine within its operation al power band thus making its Student Gary Pajak slings psychrometer preparation dynamometer test lab Comparative engine tests meaningless un less atmospheric variable eliminated results Engines performing models must live existing conditions Prescriptions given article adjust factors governing en gine performance need arises power potential Example has determined poor engine day exists engine rpm down 12200 its normal 12900 following procedure might persued 1 Increase nitromethane content slightly ie 10 12% 2 Run engine observe rpm Sometimes speed will increase othertimes engine will simply overheat 3 If overheating occurs reduce size load prop easily ac complished reducing pitch ie Change 11-7 3/4 11-7 idea force engine operate its designed power range 4 Occasionally combination re duced load increased nitromethane content will improve performance case sure watch overheating drop raw fuel cylinder head should smoke burn away merely evaporate 5 Gb-plug heat range will sometimes make difference changing nitro methane contents ie Using certain Fox plugs makes cylinder removes heat quickly certain K&B plugs Similarly gb-plugs have indi vidual heat ranges Generally thing remember increased nitro content cylinders must cooled effectively called cool cold plug removes heat quicker Conversely hot plug retains cylinder heat Check Plug Heat Range 1 booster battery place plug check engine rpm tachometer 2 Remove booster bat tery note engine rpm Example #1 Plug hot rpm12500 Plug cool rpm12300 rpm drop 200 Example #2 Plug hot rpm12500 Plug cool rpm 12400 rpm dropl00 27 W02030E 30 25 24 23 22 21 S 6 5 4050 60 10606000 11000 30 DRY BULB TEMPERATURE F VAPOR PRESSURE CHART SHTL 3 U George Baynes using pocket aling psychrometer Kent Landefelds Cosmic Wind racer background Both rule thumb scientific interpretations forecasts explained BASE LINE RECORDSRI 2 61O N88 aDATE7774By DAVE DIEDDE IN rnNW -J NGINE PORE V-ACORIP RIDS SAN BE6SANDIND NN 46N0 -JZ6-N UWNtPROPPLUGFUELCOMPCOMMENTSGROUNDTIME NCCRATIORPM 9667562 2048 6/O7ONNL65%57000724500LOS 24 09 0 7DNA60%SF0BEFFEN20700P32 20 407086 L60% SF0GOOD21200126 8O7OSOL60%0030072460035 6107EDO DO60%ODDCOOLED24900COD 2 POD DO00%NFDDOLD00700CDO 666 L60%003COOL211063D 9667562 2048 9I~ D86 L60%070BASE LINE21200 An important segment laboratory determination engine perfor mance effective elimination atmospheric variable hp correction factor temperature pressure wet-and-dry bulb temperature being recorded Joe Frontera student teacher working author Power Technology Lab local high school first case rpm drop indicated cool cold plug particular oper ation determined because combustion process deteriorated engine would normally operate rela tively low cylinder head temperatures condition second case rpm reduction less still showing cool plug warmer example #1 other experiments may find plugs offer little no rpm loss plug may too hot con ditions ideal situation cases find plug delivers slight rpm drop removing booster 100 rpm loss too great fire may go out especially during idle mode operation visual method categorizing glo plugs observe relative thickness wire Generally larger wire diameters dictate colder plugs must re-emphasize no pro cedure will probably work restore lost engine power due poor atmospheric con ditions Some power may restored carefully adjusting compression ratio upward cases other racing just too impractical seriously considered important consider ation operate engine within its designed speed range power band terms power band may useful consult Peter Chinns torque horse power curves particular engine cases peak horsepower curve slightly beyond rpm scale type engine wants operate As mentioned earlier common pitfall concerning weather forecasts radio TV centers about corrected baro metric pressures relay pressures corrected sea level done purposes air navigation used inform general public weather changes regard altitude number years ago Denver radio announcer relayed barometric pressure being 29600 Hg could After contacting Denver weather de partment informed pres sure corrected reference purposes use portable aneroid barometer sure calibrate station pressure available local weather people uncorrected barometric pressure Please aware unless live sea level announced pressures mile off An Area Further Research Great concentrations water vapor seem have dramatic effect upon engines 272 Ii hi C hi n I6 Ir hi 0 hi 0 t Ihi 2 682B2 fueled high percentages alcohol ie FAI fuel effect alcohol engines per form rather poorly conditions Usually compression ratio must re duced order stop air/fuel mixture detonating combustion cham ber Reducing compression ratio un fortunately reduces power Several individuals studying phenomenon viewpoint actual water vapor weight present air along dew point temperatures barometric pres sures What anything can done control alcohol engines performance condi tions high humidity Will carburetor cylinder head designs help prob lem Only further research time will tell continued page 68 31 3 SIlT 4 January 1976 13 28 . ON BAROMETRIC PRESSURE INHG MERCURY BAROMETER 2992 Pt MG STANDARD CONDITIONS AT SEA LEVEL jJAPOUR PRESSURE 000 IN HG LTEMPERATURE 60 DES F anoernnwrO CORRECTION FACTOR CHART x DAVE LINSTRUMS STARSTREAM 0 ULTRA SIMPLE CONSTRUCTION ALL BALSA AND PLY PARTS MACHINE OR DIE CUT 48 INCH WINGSPAN AUTO-RUDDER CONTROL FULL SIZE ILLUSTRATED STEP BY STEP PLAN FLYING INSTRUCTIONS WINNER OF THE FAI/CIAMINCLUDED INTERNATIONAL DESIGN $1195 COMPETITION FOR YOUTH GLIDEF IDWEST PRODUCTS CO 400 South Indiana StHobartIndiana 46342 RC Sport/Van Putte continued page 18 Fig 1 shows what happens ground track airplane turn varying wind conditions load factor held con stant level coordinated turn load factor directly related bank angle aircraft very simple equation Load Factor X Cosine Bank Angle ll 3600 turn shown demonstrate what hap pens both downwind upwind turn figure can also used visualize what happens during turns wind make seem dangerous Consider first airplane going downwind starts 1800 turn pilot notes airplane going fur ther downwind desires increases bank angle load factor What may happen next pilot will continue increase bank angle until airplane stalls out crashes what about airplane going upwind starts 1800 turn pilot banks airplane comfortable no-wind bank angle discovers heading relative speed airplane suddenly changing much rapidly expected loses orientation over-rolls airplane ground Neither maneuver inherently dangerous lack understanding about what air plane will wind can severely unsettle pilot particularly beginner lowspeed trainer airplane since effects wind greater slower airplanes two things remember flying wind 1 Increase bank angle over normal amount turn downwind heading made Gradually reduce bank angle airplane swings wind 2 Decrease bank angle no-wind amount turn upwind heading made Gradually increase bank angle airplane comes around downwind Try it works Next month Ill present some wind effects vertical maneuvers last few weeks have testing new product called PoweR/Charge SP Systems Marietta Ga combined nickel-cadmium battery discharger-charger field tester havent made com prehensive test unit seems advertised have used batteries two radio systems old questionable airborne pack cases PoweR/Charge progressively increased discharge time indicating increased capacity Especially striking capacity increase old battery pack After initial charge old 475-ma pack should have discharged least 2 hours 10 minutes first discharge lasted 1 hour 40 minutes second dis charge 2 hours 4 minutes third dis charge lasted 2 hours 20 minutes Subsequent discharges pack hovered around 2 hours 30 minutes Similar less startling capacity increases occurred other battery packs tested future com prehensive review will published Have seen new book beginners called Basics Radio Control Modeling Fred Marks co-authors book Model Aviation editor Bill Winter Fred town couple weeks ago business pre sented copy review remarkably well done piece work book includes chapters tools materials radio equipment engines airplanes boats cars other models like way its written photography has quality often seen model publications address 12 Connie Dr Shalimar Fla 32579 FF Duration/Meuser continued page 43 can purchased $695 can buy individual parts unit accommodates Forster 29 O&R 23 K&B Torpedo primarily flying parts nicely polished unit makes attractive display too Weight 294 gramsa thin hair over ounceand overall length 2 info write Jim 1442 N Fruit Ave Fresno CA 93728 Call Papers National Free Flight Society soliciting papers 1976 NFFS Symposium held 1976 Nats Papers will published 1976 Symposium vol ume whether author able present paper personally Nats Papers should cover some aspect science art free-flight models including technical studies practical design engineering applied models new unusual model aircraft developments historical items Both indoor outdoor freeflight modeling developments included Please send proposed papers Ray Harlan 15 Happy Hollow Rd Wayland Mass 01778 Send title proposed paper together abstract 200 words or complete paper available considered ab stracts should submitted Feb 15 1976 Book Review A ero -Modeller Annual 1975-76 review general model aviation book free-flight column Well well skip RC CL stuff judge solely its free-flight content sign times perhaps first Annual Ive seen paperback price has doubled two years UK price trans lates $450 what actual USA price will remains seen Compared what get money buy say $600 worth magazines imagine will judge worth money drawings A P Lloyd usual top quality Most model plans have appeared other publications would have subscribe magazine news letter world have seen before plans count includes 17 FAI-class models smattering others Most articles original about dozen directly related free flight including series three finishing overview Pennyplane activity world-wide plenty plans Dave Lin strum photo-story covering dozen unusual engines such Elf flat-six rotary valve four-stroke Dooling turned 28000 rpm cover other John Daddy Warbucks Pond himself complete Old-Timer course SAM 01 license plate address 4200 Gregory St Oakland Calif 94619 66 Model Aviation
Edition: Model Aviation - 1976/01
Page Numbers: 10, 11, 12, 13, 66
RELATIVEHUMIDITY 80000 04404 4 4 80 60 e540 20 30 40 5060 70 80 90 100 ItO 120 130 940 DRY-BULB TEMPERATURE DEG F till- CONTENT CHART authors atmospherics field kit consisting sting psychro meter calculator barometer Because good bad engine days generalized appreciation atmospheric conditions wilt help operate engine efficiently An understanding weather affects engine performance can lead efficient engine operation OVER THE YEARS times have modelers come conclusion old reliable sport engine has gone over hill deduction usually comes after varnish has removed cylin der wall piston plugs changed filters checked screws tightened needle valve assemblies examined success bringing back lost power Before sending mill back Clarence some freshening might well take stock elements day engine goes sour sky heavily overcast temperature well SOs promised summer storm moving area deteriorating weather conditions reduced air den sity could well cause reduction power overheating us dont recog nize symptoms Its costing us Everyone complains about weather nobody ever does anything about certain degree true statement other hand understanding weather affects engine perform ance will lead efficient engine op eration small two-stroke cycle semidiesels exceptionsophisticated air pumps require air large quan tities develop power useful chanical energy needed vehicles Air gas has freedom expand contract flows about earths surface same air contains about Effects David Gierke Atmospheho Condtbms oH Emgme Performamce part five vital combustion ele ment oxygen Air affected number factors either increases de creases availability oxygen engines cylinder individuals world high performance motor sports serious laboratory experimentation condition air air density great impor tance specific just much can air density affect engine performance Per sonally have experienced engine power difference 25% day next engine producing two horsepower excellent conditions reduction could much 1/2 horse power under poor conditions oxygen unavailable en gines consumption fuel must reduced order maintain proper air-to-fuel ratio reduction flow fuel through system given period time must result reduction power now know air its con dition has direct bearing upon engines perform Lets look specific factors observe affect air density begin should ex plained air density refers weight per given volume other words high density atmospheric condition means air molecules packed tightly together thus contain oxygen per cubic foot Temperature As temperature gas increases does its molecular activ ity molecules nitrogen four parts oxygen part moving about greater vibrating patterns effect moves further apart reduces density air decreases engine performance Pressure Refers force exerted weight atmosphere square inch earths surface unit area standard measure pressure sea level 2992 inches mercury hg approx 147 lbs per square inch known standard pressure travel mile-high city Den ver Cob air pressure would great ly reduced standard pressure about 24 inches Hg Actually atmos pheric pressure reduced about inch per 1000 foot above sea level al 10000 feet significant power loss would experienced altitudes Air pressure forces air engine 10 Model Aviation greater air pressure greater pressure differential exists between engines crankcase atmosphere pressure differential results great er air volume entering engine Im proved air volume generally increases cylinder packing volumetric efficiency Humidity Water Vapor nature air has ability absorb great quan tities water hold extended periods time amount water absorbed air directly related airs temperature illustrate point air can hold about ten times much water 900F possibly could 300F water molecules tend push oxygen nitrogen molecules further apart decreasing element density thus reducing engine power output review may stated fol lowing atmospheric conditions neces sary maximum engine performance High atmospheric pressure 2 Low air temperature 3 Low humidity Two methods will discussed concern ing handle newly acquired knowledge about weather First will Rule Thumb Method Secondly will Technical Method based upon weather instrumentation Rule Thumb Method What good bad engine day largely depends upon further discus sion relationship between air pressure water vapor content total air pressure determined barometer always sum normal air compo nents pressure exerted water vapor particularly important high temperature days potential large quantities water vapor being pres ent significant barometer may falsely high conditions high humidity because have previously mentioned water vapor reduces element density 0 ob tain representative air pressure readout water vapor pressure must subtracted barometer reading As can see importance accu rate weather instrumentation prime concern determination engine power potential temperature air low below 600F effect water vapor pressure minimal can gener ally disregarded Rule Thumb determination air density Listening radio television weather forecast can give some clue engine performance can also lead serious miscalcu lations shall see later Typical Forecast Temperature SOT 2 Barometer 3000 Hg rising 3 Relative humid ity 70% Rule Thumb Analysis Temperature low below stand ard 600F showing good density 2 Pressure high above standard 2992 Hg getting better should improve pressure differential between engine atmosphere good sign 3 Since air temperature low amount water may enter air low will affect baro metric readout great degree Overall Analysis better average engine perform ance day basis analysis should standard air conditions include Temperature 600F 2 Air pressure 2992 Hg sea level 3 0% humidity Any condition lowers tem perature less 600F raises barometer above 2992 Hg low humidity should considered Good engine day important factor affecting air character barometric pressure followed tempera ture finally humidity Humidity plays dual role reduces element air density giving barometer false ly high readout term relative humidity very mis leading term generally leads great confusion trying determine rule thumb air condition instru mentation method shall see later far superior Another Typical Forecast I Temperature 900F 2 Barometric pressure 2915 Hg 3 Relative humidity 70% Rule Thumb Analysis Temperature relatively high well above standard Poor air density 2 Baro metric pressure below standard will significantly affected high vapor pressure accompanies elevated temperature 3 Humidity quite high January 1976 11 some sling psychrometers theres scale gives percent relative humiditymay applied chart left determine moisture content terms grains water/pound dry air Right Rick Paine uses tachometer determine engine operating within desired power range Changing pitch and/or diameter will force engine operate desired speed range start laboratory dynamometer test authors reaction fan brake absorption unit Factors involved engine performance temperature pressure humidity water vapor Atmospheric Conditions air temperature involved Low density importantly water pressure will reduce actual barometric pressure reading Overall Analysis poor engine day Much less standard day high temperature con dition difficult pinpoint using ruleof-thumb method because water vapor effect following illustrates relative humidity has nothing actual water vapor weight atmosphere first example air temperature 500F relative humidity 70% actual water vapor weight deter mined use tables 38 grains water vapor per pound dry air 2 second example air temperature 900F relative humidity again 70% case however actual water vapor weight 142 grains per pound dry air represents increase over 350% rule thumb method can useful no other means available deter condition air pro duction power Some conclusions may drawn con cerning what may done retrieve some lost engine performance power due poor weather conditions virtu ally no way recall lost engine power due atmospheric density/pressure re duction exceptions Addition supercharger B Careful manipula tion oxygen liberating chemicals such nitromethane fuel supercharger impractical addition nitro usually doesnt work cause other limiting engine design fea tures such cooling capacity engine compression ratio etc. also probably already using can best procedure make engine run maximum its capability existing conditions proper rpm places engine within its operation al power band thus making its Student Gary Pajak slings psychrometer preparation dynamometer test lab Comparative engine tests meaningless un less atmospheric variable eliminated results Engines performing models must live existing conditions Prescriptions given article adjust factors governing en gine performance need arises power potential Example has determined poor engine day exists engine rpm down 12200 its normal 12900 following procedure might persued 1 Increase nitromethane content slightly ie 10 12% 2 Run engine observe rpm Sometimes speed will increase othertimes engine will simply overheat 3 If overheating occurs reduce size load prop easily ac complished reducing pitch ie Change 11-7 3/4 11-7 idea force engine operate its designed power range 4 Occasionally combination re duced load increased nitromethane content will improve performance case sure watch overheating drop raw fuel cylinder head should smoke burn away merely evaporate 5 Gb-plug heat range will sometimes make difference changing nitro methane contents ie Using certain Fox plugs makes cylinder removes heat quickly certain K&B plugs Similarly gb-plugs have indi vidual heat ranges Generally thing remember increased nitro content cylinders must cooled effectively called cool cold plug removes heat quicker Conversely hot plug retains cylinder heat Check Plug Heat Range 1 booster battery place plug check engine rpm tachometer 2 Remove booster bat tery note engine rpm Example #1 Plug hot rpm12500 Plug cool rpm12300 rpm drop 200 Example #2 Plug hot rpm12500 Plug cool rpm 12400 rpm dropl00 27 W02030E 30 25 24 23 22 21 S 6 5 4050 60 10606000 11000 30 DRY BULB TEMPERATURE F VAPOR PRESSURE CHART SHTL 3 U George Baynes using pocket aling psychrometer Kent Landefelds Cosmic Wind racer background Both rule thumb scientific interpretations forecasts explained BASE LINE RECORDSRI 2 61O N88 aDATE7774By DAVE DIEDDE IN rnNW -J NGINE PORE V-ACORIP RIDS SAN BE6SANDIND NN 46N0 -JZ6-N UWNtPROPPLUGFUELCOMPCOMMENTSGROUNDTIME NCCRATIORPM 9667562 2048 6/O7ONNL65%57000724500LOS 24 09 0 7DNA60%SF0BEFFEN20700P32 20 407086 L60% SF0GOOD21200126 8O7OSOL60%0030072460035 6107EDO DO60%ODDCOOLED24900COD 2 POD DO00%NFDDOLD00700CDO 666 L60%003COOL211063D 9667562 2048 9I~ D86 L60%070BASE LINE21200 An important segment laboratory determination engine perfor mance effective elimination atmospheric variable hp correction factor temperature pressure wet-and-dry bulb temperature being recorded Joe Frontera student teacher working author Power Technology Lab local high school first case rpm drop indicated cool cold plug particular oper ation determined because combustion process deteriorated engine would normally operate rela tively low cylinder head temperatures condition second case rpm reduction less still showing cool plug warmer example #1 other experiments may find plugs offer little no rpm loss plug may too hot con ditions ideal situation cases find plug delivers slight rpm drop removing booster 100 rpm loss too great fire may go out especially during idle mode operation visual method categorizing glo plugs observe relative thickness wire Generally larger wire diameters dictate colder plugs must re-emphasize no pro cedure will probably work restore lost engine power due poor atmospheric con ditions Some power may restored carefully adjusting compression ratio upward cases other racing just too impractical seriously considered important consider ation operate engine within its designed speed range power band terms power band may useful consult Peter Chinns torque horse power curves particular engine cases peak horsepower curve slightly beyond rpm scale type engine wants operate As mentioned earlier common pitfall concerning weather forecasts radio TV centers about corrected baro metric pressures relay pressures corrected sea level done purposes air navigation used inform general public weather changes regard altitude number years ago Denver radio announcer relayed barometric pressure being 29600 Hg could After contacting Denver weather de partment informed pres sure corrected reference purposes use portable aneroid barometer sure calibrate station pressure available local weather people uncorrected barometric pressure Please aware unless live sea level announced pressures mile off An Area Further Research Great concentrations water vapor seem have dramatic effect upon engines 272 Ii hi C hi n I6 Ir hi 0 hi 0 t Ihi 2 682B2 fueled high percentages alcohol ie FAI fuel effect alcohol engines per form rather poorly conditions Usually compression ratio must re duced order stop air/fuel mixture detonating combustion cham ber Reducing compression ratio un fortunately reduces power Several individuals studying phenomenon viewpoint actual water vapor weight present air along dew point temperatures barometric pres sures What anything can done control alcohol engines performance condi tions high humidity Will carburetor cylinder head designs help prob lem Only further research time will tell continued page 68 31 3 SIlT 4 January 1976 13 28 . ON BAROMETRIC PRESSURE INHG MERCURY BAROMETER 2992 Pt MG STANDARD CONDITIONS AT SEA LEVEL jJAPOUR PRESSURE 000 IN HG LTEMPERATURE 60 DES F anoernnwrO CORRECTION FACTOR CHART x DAVE LINSTRUMS STARSTREAM 0 ULTRA SIMPLE CONSTRUCTION ALL BALSA AND PLY PARTS MACHINE OR DIE CUT 48 INCH WINGSPAN AUTO-RUDDER CONTROL FULL SIZE ILLUSTRATED STEP BY STEP PLAN FLYING INSTRUCTIONS WINNER OF THE FAI/CIAMINCLUDED INTERNATIONAL DESIGN $1195 COMPETITION FOR YOUTH GLIDEF IDWEST PRODUCTS CO 400 South Indiana StHobartIndiana 46342 RC Sport/Van Putte continued page 18 Fig 1 shows what happens ground track airplane turn varying wind conditions load factor held con stant level coordinated turn load factor directly related bank angle aircraft very simple equation Load Factor X Cosine Bank Angle ll 3600 turn shown demonstrate what hap pens both downwind upwind turn figure can also used visualize what happens during turns wind make seem dangerous Consider first airplane going downwind starts 1800 turn pilot notes airplane going fur ther downwind desires increases bank angle load factor What may happen next pilot will continue increase bank angle until airplane stalls out crashes what about airplane going upwind starts 1800 turn pilot banks airplane comfortable no-wind bank angle discovers heading relative speed airplane suddenly changing much rapidly expected loses orientation over-rolls airplane ground Neither maneuver inherently dangerous lack understanding about what air plane will wind can severely unsettle pilot particularly beginner lowspeed trainer airplane since effects wind greater slower airplanes two things remember flying wind 1 Increase bank angle over normal amount turn downwind heading made Gradually reduce bank angle airplane swings wind 2 Decrease bank angle no-wind amount turn upwind heading made Gradually increase bank angle airplane comes around downwind Try it works Next month Ill present some wind effects vertical maneuvers last few weeks have testing new product called PoweR/Charge SP Systems Marietta Ga combined nickel-cadmium battery discharger-charger field tester havent made com prehensive test unit seems advertised have used batteries two radio systems old questionable airborne pack cases PoweR/Charge progressively increased discharge time indicating increased capacity Especially striking capacity increase old battery pack After initial charge old 475-ma pack should have discharged least 2 hours 10 minutes first discharge lasted 1 hour 40 minutes second dis charge 2 hours 4 minutes third dis charge lasted 2 hours 20 minutes Subsequent discharges pack hovered around 2 hours 30 minutes Similar less startling capacity increases occurred other battery packs tested future com prehensive review will published Have seen new book beginners called Basics Radio Control Modeling Fred Marks co-authors book Model Aviation editor Bill Winter Fred town couple weeks ago business pre sented copy review remarkably well done piece work book includes chapters tools materials radio equipment engines airplanes boats cars other models like way its written photography has quality often seen model publications address 12 Connie Dr Shalimar Fla 32579 FF Duration/Meuser continued page 43 can purchased $695 can buy individual parts unit accommodates Forster 29 O&R 23 K&B Torpedo primarily flying parts nicely polished unit makes attractive display too Weight 294 gramsa thin hair over ounceand overall length 2 info write Jim 1442 N Fruit Ave Fresno CA 93728 Call Papers National Free Flight Society soliciting papers 1976 NFFS Symposium held 1976 Nats Papers will published 1976 Symposium vol ume whether author able present paper personally Nats Papers should cover some aspect science art free-flight models including technical studies practical design engineering applied models new unusual model aircraft developments historical items Both indoor outdoor freeflight modeling developments included Please send proposed papers Ray Harlan 15 Happy Hollow Rd Wayland Mass 01778 Send title proposed paper together abstract 200 words or complete paper available considered ab stracts should submitted Feb 15 1976 Book Review A ero -Modeller Annual 1975-76 review general model aviation book free-flight column Well well skip RC CL stuff judge solely its free-flight content sign times perhaps first Annual Ive seen paperback price has doubled two years UK price trans lates $450 what actual USA price will remains seen Compared what get money buy say $600 worth magazines imagine will judge worth money drawings A P Lloyd usual top quality Most model plans have appeared other publications would have subscribe magazine news letter world have seen before plans count includes 17 FAI-class models smattering others Most articles original about dozen directly related free flight including series three finishing overview Pennyplane activity world-wide plenty plans Dave Lin strum photo-story covering dozen unusual engines such Elf flat-six rotary valve four-stroke Dooling turned 28000 rpm cover other John Daddy Warbucks Pond himself complete Old-Timer course SAM 01 license plate address 4200 Gregory St Oakland Calif 94619 66 Model Aviation
Edition: Model Aviation - 1976/01
Page Numbers: 10, 11, 12, 13, 66
RELATIVEHUMIDITY 80000 04404 4 4 80 60 e540 20 30 40 5060 70 80 90 100 ItO 120 130 940 DRY-BULB TEMPERATURE DEG F till- CONTENT CHART authors atmospherics field kit consisting sting psychro meter calculator barometer Because good bad engine days generalized appreciation atmospheric conditions wilt help operate engine efficiently An understanding weather affects engine performance can lead efficient engine operation OVER THE YEARS times have modelers come conclusion old reliable sport engine has gone over hill deduction usually comes after varnish has removed cylin der wall piston plugs changed filters checked screws tightened needle valve assemblies examined success bringing back lost power Before sending mill back Clarence some freshening might well take stock elements day engine goes sour sky heavily overcast temperature well SOs promised summer storm moving area deteriorating weather conditions reduced air den sity could well cause reduction power overheating us dont recog nize symptoms Its costing us Everyone complains about weather nobody ever does anything about certain degree true statement other hand understanding weather affects engine perform ance will lead efficient engine op eration small two-stroke cycle semidiesels exceptionsophisticated air pumps require air large quan tities develop power useful chanical energy needed vehicles Air gas has freedom expand contract flows about earths surface same air contains about Effects David Gierke Atmospheho Condtbms oH Emgme Performamce part five vital combustion ele ment oxygen Air affected number factors either increases de creases availability oxygen engines cylinder individuals world high performance motor sports serious laboratory experimentation condition air air density great impor tance specific just much can air density affect engine performance Per sonally have experienced engine power difference 25% day next engine producing two horsepower excellent conditions reduction could much 1/2 horse power under poor conditions oxygen unavailable en gines consumption fuel must reduced order maintain proper air-to-fuel ratio reduction flow fuel through system given period time must result reduction power now know air its con dition has direct bearing upon engines perform Lets look specific factors observe affect air density begin should ex plained air density refers weight per given volume other words high density atmospheric condition means air molecules packed tightly together thus contain oxygen per cubic foot Temperature As temperature gas increases does its molecular activ ity molecules nitrogen four parts oxygen part moving about greater vibrating patterns effect moves further apart reduces density air decreases engine performance Pressure Refers force exerted weight atmosphere square inch earths surface unit area standard measure pressure sea level 2992 inches mercury hg approx 147 lbs per square inch known standard pressure travel mile-high city Den ver Cob air pressure would great ly reduced standard pressure about 24 inches Hg Actually atmos pheric pressure reduced about inch per 1000 foot above sea level al 10000 feet significant power loss would experienced altitudes Air pressure forces air engine 10 Model Aviation greater air pressure greater pressure differential exists between engines crankcase atmosphere pressure differential results great er air volume entering engine Im proved air volume generally increases cylinder packing volumetric efficiency Humidity Water Vapor nature air has ability absorb great quan tities water hold extended periods time amount water absorbed air directly related airs temperature illustrate point air can hold about ten times much water 900F possibly could 300F water molecules tend push oxygen nitrogen molecules further apart decreasing element density thus reducing engine power output review may stated fol lowing atmospheric conditions neces sary maximum engine performance High atmospheric pressure 2 Low air temperature 3 Low humidity Two methods will discussed concern ing handle newly acquired knowledge about weather First will Rule Thumb Method Secondly will Technical Method based upon weather instrumentation Rule Thumb Method What good bad engine day largely depends upon further discus sion relationship between air pressure water vapor content total air pressure determined barometer always sum normal air compo nents pressure exerted water vapor particularly important high temperature days potential large quantities water vapor being pres ent significant barometer may falsely high conditions high humidity because have previously mentioned water vapor reduces element density 0 ob tain representative air pressure readout water vapor pressure must subtracted barometer reading As can see importance accu rate weather instrumentation prime concern determination engine power potential temperature air low below 600F effect water vapor pressure minimal can gener ally disregarded Rule Thumb determination air density Listening radio television weather forecast can give some clue engine performance can also lead serious miscalcu lations shall see later Typical Forecast Temperature SOT 2 Barometer 3000 Hg rising 3 Relative humid ity 70% Rule Thumb Analysis Temperature low below stand ard 600F showing good density 2 Pressure high above standard 2992 Hg getting better should improve pressure differential between engine atmosphere good sign 3 Since air temperature low amount water may enter air low will affect baro metric readout great degree Overall Analysis better average engine perform ance day basis analysis should standard air conditions include Temperature 600F 2 Air pressure 2992 Hg sea level 3 0% humidity Any condition lowers tem perature less 600F raises barometer above 2992 Hg low humidity should considered Good engine day important factor affecting air character barometric pressure followed tempera ture finally humidity Humidity plays dual role reduces element air density giving barometer false ly high readout term relative humidity very mis leading term generally leads great confusion trying determine rule thumb air condition instru mentation method shall see later far superior Another Typical Forecast I Temperature 900F 2 Barometric pressure 2915 Hg 3 Relative humidity 70% Rule Thumb Analysis Temperature relatively high well above standard Poor air density 2 Baro metric pressure below standard will significantly affected high vapor pressure accompanies elevated temperature 3 Humidity quite high January 1976 11 some sling psychrometers theres scale gives percent relative humiditymay applied chart left determine moisture content terms grains water/pound dry air Right Rick Paine uses tachometer determine engine operating within desired power range Changing pitch and/or diameter will force engine operate desired speed range start laboratory dynamometer test authors reaction fan brake absorption unit Factors involved engine performance temperature pressure humidity water vapor Atmospheric Conditions air temperature involved Low density importantly water pressure will reduce actual barometric pressure reading Overall Analysis poor engine day Much less standard day high temperature con dition difficult pinpoint using ruleof-thumb method because water vapor effect following illustrates relative humidity has nothing actual water vapor weight atmosphere first example air temperature 500F relative humidity 70% actual water vapor weight deter mined use tables 38 grains water vapor per pound dry air 2 second example air temperature 900F relative humidity again 70% case however actual water vapor weight 142 grains per pound dry air represents increase over 350% rule thumb method can useful no other means available deter condition air pro duction power Some conclusions may drawn con cerning what may done retrieve some lost engine performance power due poor weather conditions virtu ally no way recall lost engine power due atmospheric density/pressure re duction exceptions Addition supercharger B Careful manipula tion oxygen liberating chemicals such nitromethane fuel supercharger impractical addition nitro usually doesnt work cause other limiting engine design fea tures such cooling capacity engine compression ratio etc. also probably already using can best procedure make engine run maximum its capability existing conditions proper rpm places engine within its operation al power band thus making its Student Gary Pajak slings psychrometer preparation dynamometer test lab Comparative engine tests meaningless un less atmospheric variable eliminated results Engines performing models must live existing conditions Prescriptions given article adjust factors governing en gine performance need arises power potential Example has determined poor engine day exists engine rpm down 12200 its normal 12900 following procedure might persued 1 Increase nitromethane content slightly ie 10 12% 2 Run engine observe rpm Sometimes speed will increase othertimes engine will simply overheat 3 If overheating occurs reduce size load prop easily ac complished reducing pitch ie Change 11-7 3/4 11-7 idea force engine operate its designed power range 4 Occasionally combination re duced load increased nitromethane content will improve performance case sure watch overheating drop raw fuel cylinder head should smoke burn away merely evaporate 5 Gb-plug heat range will sometimes make difference changing nitro methane contents ie Using certain Fox plugs makes cylinder removes heat quickly certain K&B plugs Similarly gb-plugs have indi vidual heat ranges Generally thing remember increased nitro content cylinders must cooled effectively called cool cold plug removes heat quicker Conversely hot plug retains cylinder heat Check Plug Heat Range 1 booster battery place plug check engine rpm tachometer 2 Remove booster bat tery note engine rpm Example #1 Plug hot rpm12500 Plug cool rpm12300 rpm drop 200 Example #2 Plug hot rpm12500 Plug cool rpm 12400 rpm dropl00 27 W02030E 30 25 24 23 22 21 S 6 5 4050 60 10606000 11000 30 DRY BULB TEMPERATURE F VAPOR PRESSURE CHART SHTL 3 U George Baynes using pocket aling psychrometer Kent Landefelds Cosmic Wind racer background Both rule thumb scientific interpretations forecasts explained BASE LINE RECORDSRI 2 61O N88 aDATE7774By DAVE DIEDDE IN rnNW -J NGINE PORE V-ACORIP RIDS SAN BE6SANDIND NN 46N0 -JZ6-N UWNtPROPPLUGFUELCOMPCOMMENTSGROUNDTIME NCCRATIORPM 9667562 2048 6/O7ONNL65%57000724500LOS 24 09 0 7DNA60%SF0BEFFEN20700P32 20 407086 L60% SF0GOOD21200126 8O7OSOL60%0030072460035 6107EDO DO60%ODDCOOLED24900COD 2 POD DO00%NFDDOLD00700CDO 666 L60%003COOL211063D 9667562 2048 9I~ D86 L60%070BASE LINE21200 An important segment laboratory determination engine perfor mance effective elimination atmospheric variable hp correction factor temperature pressure wet-and-dry bulb temperature being recorded Joe Frontera student teacher working author Power Technology Lab local high school first case rpm drop indicated cool cold plug particular oper ation determined because combustion process deteriorated engine would normally operate rela tively low cylinder head temperatures condition second case rpm reduction less still showing cool plug warmer example #1 other experiments may find plugs offer little no rpm loss plug may too hot con ditions ideal situation cases find plug delivers slight rpm drop removing booster 100 rpm loss too great fire may go out especially during idle mode operation visual method categorizing glo plugs observe relative thickness wire Generally larger wire diameters dictate colder plugs must re-emphasize no pro cedure will probably work restore lost engine power due poor atmospheric con ditions Some power may restored carefully adjusting compression ratio upward cases other racing just too impractical seriously considered important consider ation operate engine within its designed speed range power band terms power band may useful consult Peter Chinns torque horse power curves particular engine cases peak horsepower curve slightly beyond rpm scale type engine wants operate As mentioned earlier common pitfall concerning weather forecasts radio TV centers about corrected baro metric pressures relay pressures corrected sea level done purposes air navigation used inform general public weather changes regard altitude number years ago Denver radio announcer relayed barometric pressure being 29600 Hg could After contacting Denver weather de partment informed pres sure corrected reference purposes use portable aneroid barometer sure calibrate station pressure available local weather people uncorrected barometric pressure Please aware unless live sea level announced pressures mile off An Area Further Research Great concentrations water vapor seem have dramatic effect upon engines 272 Ii hi C hi n I6 Ir hi 0 hi 0 t Ihi 2 682B2 fueled high percentages alcohol ie FAI fuel effect alcohol engines per form rather poorly conditions Usually compression ratio must re duced order stop air/fuel mixture detonating combustion cham ber Reducing compression ratio un fortunately reduces power Several individuals studying phenomenon viewpoint actual water vapor weight present air along dew point temperatures barometric pres sures What anything can done control alcohol engines performance condi tions high humidity Will carburetor cylinder head designs help prob lem Only further research time will tell continued page 68 31 3 SIlT 4 January 1976 13 28 . ON BAROMETRIC PRESSURE INHG MERCURY BAROMETER 2992 Pt MG STANDARD CONDITIONS AT SEA LEVEL jJAPOUR PRESSURE 000 IN HG LTEMPERATURE 60 DES F anoernnwrO CORRECTION FACTOR CHART x DAVE LINSTRUMS STARSTREAM 0 ULTRA SIMPLE CONSTRUCTION ALL BALSA AND PLY PARTS MACHINE OR DIE CUT 48 INCH WINGSPAN AUTO-RUDDER CONTROL FULL SIZE ILLUSTRATED STEP BY STEP PLAN FLYING INSTRUCTIONS WINNER OF THE FAI/CIAMINCLUDED INTERNATIONAL DESIGN $1195 COMPETITION FOR YOUTH GLIDEF IDWEST PRODUCTS CO 400 South Indiana StHobartIndiana 46342 RC Sport/Van Putte continued page 18 Fig 1 shows what happens ground track airplane turn varying wind conditions load factor held con stant level coordinated turn load factor directly related bank angle aircraft very simple equation Load Factor X Cosine Bank Angle ll 3600 turn shown demonstrate what hap pens both downwind upwind turn figure can also used visualize what happens during turns wind make seem dangerous Consider first airplane going downwind starts 1800 turn pilot notes airplane going fur ther downwind desires increases bank angle load factor What may happen next pilot will continue increase bank angle until airplane stalls out crashes what about airplane going upwind starts 1800 turn pilot banks airplane comfortable no-wind bank angle discovers heading relative speed airplane suddenly changing much rapidly expected loses orientation over-rolls airplane ground Neither maneuver inherently dangerous lack understanding about what air plane will wind can severely unsettle pilot particularly beginner lowspeed trainer airplane since effects wind greater slower airplanes two things remember flying wind 1 Increase bank angle over normal amount turn downwind heading made Gradually reduce bank angle airplane swings wind 2 Decrease bank angle no-wind amount turn upwind heading made Gradually increase bank angle airplane comes around downwind Try it works Next month Ill present some wind effects vertical maneuvers last few weeks have testing new product called PoweR/Charge SP Systems Marietta Ga combined nickel-cadmium battery discharger-charger field tester havent made com prehensive test unit seems advertised have used batteries two radio systems old questionable airborne pack cases PoweR/Charge progressively increased discharge time indicating increased capacity Especially striking capacity increase old battery pack After initial charge old 475-ma pack should have discharged least 2 hours 10 minutes first discharge lasted 1 hour 40 minutes second dis charge 2 hours 4 minutes third dis charge lasted 2 hours 20 minutes Subsequent discharges pack hovered around 2 hours 30 minutes Similar less startling capacity increases occurred other battery packs tested future com prehensive review will published Have seen new book beginners called Basics Radio Control Modeling Fred Marks co-authors book Model Aviation editor Bill Winter Fred town couple weeks ago business pre sented copy review remarkably well done piece work book includes chapters tools materials radio equipment engines airplanes boats cars other models like way its written photography has quality often seen model publications address 12 Connie Dr Shalimar Fla 32579 FF Duration/Meuser continued page 43 can purchased $695 can buy individual parts unit accommodates Forster 29 O&R 23 K&B Torpedo primarily flying parts nicely polished unit makes attractive display too Weight 294 gramsa thin hair over ounceand overall length 2 info write Jim 1442 N Fruit Ave Fresno CA 93728 Call Papers National Free Flight Society soliciting papers 1976 NFFS Symposium held 1976 Nats Papers will published 1976 Symposium vol ume whether author able present paper personally Nats Papers should cover some aspect science art free-flight models including technical studies practical design engineering applied models new unusual model aircraft developments historical items Both indoor outdoor freeflight modeling developments included Please send proposed papers Ray Harlan 15 Happy Hollow Rd Wayland Mass 01778 Send title proposed paper together abstract 200 words or complete paper available considered ab stracts should submitted Feb 15 1976 Book Review A ero -Modeller Annual 1975-76 review general model aviation book free-flight column Well well skip RC CL stuff judge solely its free-flight content sign times perhaps first Annual Ive seen paperback price has doubled two years UK price trans lates $450 what actual USA price will remains seen Compared what get money buy say $600 worth magazines imagine will judge worth money drawings A P Lloyd usual top quality Most model plans have appeared other publications would have subscribe magazine news letter world have seen before plans count includes 17 FAI-class models smattering others Most articles original about dozen directly related free flight including series three finishing overview Pennyplane activity world-wide plenty plans Dave Lin strum photo-story covering dozen unusual engines such Elf flat-six rotary valve four-stroke Dooling turned 28000 rpm cover other John Daddy Warbucks Pond himself complete Old-Timer course SAM 01 license plate address 4200 Gregory St Oakland Calif 94619 66 Model Aviation