Simplified Proof Loading

By William E. Brown, EAA 10669 Capt., USAF APO 9247, New York, N.Y.

INTRODUCTION BROWN-JODEL D-9FG The following sequence illustrates the steps which NACA 23012 were taken to static test the modified folding wing of my Spa. Chord 47'/<" Jodel D-9 e severa n lighth I . f o t l in-flight structural fail- Chord 39H" ures which have taken e past place informatioth th ,n i e n shoulf intereso e b do anyon t t e buildin n originaa g r o l modifyin provea g n design originalito N . s claimedi y e th , methods having been lifted from a number of sources and simplified where possible to suit the test undertaken. De- tails of the test have not been described and emphasis has been placee analyticath n do l procedure b y thao ma s e t i t applied to other . Stations 4 -vw-2 W- W-W- 3l p Ti 6 8 W-W- W- W-57 e tesTh t describe undertakes - dwa en n para a f s no a t FIG. I —WING LAYOUT 12-28-64 gineering special-problems cours takine Unim a th e I t -ga versity of Missouri. I am indebted to Richard N. Pugh, 2. Gross Weight my instructor e interesth r fo ,t e projectaketh d n i nan t Maximum design-gross s weighuseIbs5 r 57 wa .dfo f o t assistance th e give carryinn ni teste th t . gou all calculations. single-spaJodee a s Th ha l r cantilever win. g 1) (se g eFi 3. Drag Effects Only the box itself was tested (see Fig. 2). Primary Airfoil drag effects were ignored in the test. This was interest was in verifying strength of the wing-folding felt to be justified, since it is small compared to the modification. If the test were applied to a two-spar wing, lift. t i woul e necessarb d o computt y e loath e d divisio- be n 4. Center of Pressure Effects twee e sparnth s (see Refr Refo . 2 .4) . The twisting moments on the wing were ignored. This thin I s case e entirth , e wing would e testehavb o t ed is valid for the airfoil in question (NACA 23012) which and the weights hung over the spars by straps or some has little center of pressure movement, but would not other means. l al e vali b r fo d , especially e oldesomth f ro e ones. 5. Effects LOADING ASSUMPTIONS The wing was tilted 12 deg. for the test to simulate e entirTh e validit tesy an te assump f th restyo n o s - e angle winth th f attact o ea g k givin e maximuth g m tions made. Onl f thesi y e carefullar e y verifiede th n ca , lift coefficient. test represen e conditionth t s mean wa o represent t t ti s . 6. Effects of Wing Weight With thi n mindi s e loadinth , g assumptionse th use n i d e winTh g weigh tt involveitselno s i f n creatini d ga tese describedar t e b . t Rememberno y ma r o , they ma y beam load on the spar. Wing weight was subtracted valid for another type of test and should be carefully ex- from the gross weight to obtain the net weight carried amined before the e applieyar anotheo dt r airplanee Th . winge byth . Wing weigh estimates wa t d usin gweigha t assumptions made were: of 1.35 Ibs. per sq. ft. for cantilever (Ref. 2). 1. Load Factor This proved to be very close to the actual wing weight s chose wa loaA s suitabla G nd 4 facto4. o t ef o r whe e winnth g components were weighed later. demonstrate basic airworthines e winth f g o s (CAR Gross wt. = GW = 575 Ibs. utility category) e win s designe. .Th G gwa 9 r dfo Wetted Wing Area/Semi-span = A = 47.84 ft.2

TABLE 1 — LOAD SUMMARY p Ti 8 W- 7 W- 6 W- 5 W- 4 W- 3 W- 2 W- Station ] W- s

AREA TOTAL WETTED BETWEEN 6 19 5.73 483 387 WING ARF>, STATIONS 576 6 19 6.19 9.08 (FT/') 47.84 ft .'

FRACTION OF C,. REMAINING 1 0 1.0 1 0 1.0 1.0 1.0 046 0.38 AFTER LOSSES EFFECTIVE TOTAL EFFECTIVE WETTED = WETTED WING AREA AREA 5.76 6 19 6.19 908 6.19 573 222 7 4 1 BETWEEN STATIONS 42.83 ft.'

NET WING 521 521 521 521 521 521 521 521 LOADING LBS /FT'

SPAR LOAD LBS/G 30.0 32.2 322 473 322 30.0 116 7.7

BAGS NEEDED . BrowE . nW 2-l5Lb 2-16 Lb 2-16 Lb 3 16 Lb 2-16Lb. 2-. 1 5Lb M2Lb l-8Lb PER G 12-28-64

6 1 NOVEMBER 1965 12 percent was applied from Station W-8 to the tip and percen4 t from o StatioW-8t 7 . ThesW- n e reductions e arbitrarar d represenan y t besa t t gueso what s a ts e win effece tipTh ge th washou. t th alsta os thinha t s t s thiignorede tipbu th wa s, o t fro8 . mW- 9. Load Concentration at the Ribs A distributed loadin s use wa o gsimplift d y sand bag- ging. In the actual wing, loads are concentrated at the ribs.

FIG. 2 The spar with the maximum 4.4 G load ap- plied t thia . s .in loadingDeflectio 6 3. tips e .th swa t na

1.3x = 64.Estimate 55 A Ibs= . W d = Win . gWt Net Load Carrie r Semi-spadPe N = n N= y 2=(GW Ibs./W 3 %(575— )22 G 64.= — 5) 7. Tip Effects FIG6 Spa. r center sectio mountes a ne fuselage th o t d . e lifTh t coefficien s assumei t e halveb o t dd froa m t beeye nplywoot e fronaddee no Th th d r reao o tdt ha r point one chord width from the tip (see Ref. 1). Station e spaoth f r box. ] W-7 was chosen as it lies 32 /4 in. from the tip which METHO COMPUTINF DO G BEAM LOADINGS has a chord of 29 25/32 in. The method applied in correcting for the tip and 8. Washout Effects washou t reduco effectt s e winwa eth s g are r calculafo a - The wing washout starts at Station W-7 and is a maxi- tion purposes. Thiwinw ne sg arecalles awa e effectiv dth e e tipth . t mu4 degFroa f .m o m NACA 23012 airfoil wetted wing areae winTh . g area reduction from Station dat e lifath t , (Refcoefficien3) . s determinewa t e b o dt W-7 to W-8 was 50 percent for tip loss and 4 percent for reduced a maximum of 12 percent at the tip. The full washout, or a total of 54 percent. From Station W-7 to e tip 2 e reductioth 1 th ,percen0 losp d 5 ti s an sr nwa fo t percen r washoutfo t 2 percent6 a tota, f o l . Effective wetted are s the percena6 wa n4 fro 8 mW- t Statioo t 7 nW- of actual area. Effective wetted area from Statio8 W- n thes percen8 wa n3 p toti t actual area. The total effective area was then tabulated and the net wing loading determined. Net weight carried per semi-span Net wing Effective wetted wing area per semi-span = loading t loadinne s thee gwa Th n multiplie e effectivth y b d e wing area between stations to determine the load carried be abovy Th eac . e G he wincalculation r th par pe f g o t s showe ar winTable n ni th . Refegr e1 layout fo Figo 1 t r . . FIG. 3 The method of taking deflection readings. The fron reaand tr readin averageis g determinto d inthe e- STATIC TEST METHOD cremen f deflectioo t n after each increas loadn i e . spae mountes (seg ji Th wa er a ) usin Fig5 n de o . gth same attachment bolts that attace fuse th e spa th -ho t r lage. The jig attachment was made identical to the fuse- lag teso attachmene t th t t portio e spa th wels a rf s no a l the spar itself. After calculation of the load carried between each station per G, sand bags were prepared to permit adding G 4 loadina e weight 3. t th , ge G go 4 t s 2. sequenc , G 1 f eo and 4.4 G. Some large bags were used, but 15 Ib. bags were the easiest to handle. The biggest job is sacking the sand. A set of deflection measurements was taken at five points along the wing. Five foot sticks were attached to the wing (see Figs. 3 and 4), and front and rear readings were averaged to measure deflections. A shakedown run thed wawine an nth s gG mad 1 unloaded o et . This served to remove slack in the jig and fittings. A set of zero de- flection readings was then taken and subsequently taken t eaca h loading e deflectioTh . s alsowa n taken afte- un r loading from the maximum load. This served to deter- e spa mountes Th a r e tes FIG4 th t . n di jig .2 1 Not e eth mine if any permanent damage was done to the wing. The deg. mounting angle and the sticks used to take the de- illustrations show various stages of the test. flection readings. CONCLUSIONS A simple static test as described can serve to demon- FIG. 5 Front view of the spar as mounted in the test rig. strate the basic airworthiness of a design. This will greatly e winTh g fold fitting e visible dihedrasar th t a e l break. (Continued on bottom of next page)

SPORT AVIATION 17 Have Film - - . II By George Anneand Gruenberger

WERE E looking forwar r tri Hawaiio ou pt o dt , when In San Francisco, George went soaring at Les Ar- W we rea e n articlJanuara dth n i e y 1965 issuf o e nolds' fiel Fremontn i d unusuan a , d wherha l e experieh - SPORT AVIATION written by W. A. and Muriel Reynolds. ence. As he took off in a glider, the tow rope broke at They claimed there was no private flying on the island. 300 ft. Looking for a place to set down, he made a forced Georg d beeha e n corresponding with ColBurm Sa . - landing down wind, south of the airport. Getting back to gess e presidenth ,e Hawaith f o ti chapter o saidwh , that the field, and using another glider, he got into the air, e seveoth f n members x wersi , e building planes. Non- this time with no further trouble. He also used Mike memberA EA s were proud owner f homebuiltso s , too. Duffy's facilitie t Calistoga s a (northwes Francisco)n Sa f o t , Was ther r wasn'o e t there private flying e intendeW ? d wher wene eh t soaring with Roger Sherron Pan-Aa , m cap- to find out. tain. We left Milwauke Februarn o e t 10:0a 3 y2 0 P.Mn .i This dinner meeting took Embere placth t ea s Restau- one of the worst blizzards of the year. Because it was tak- rant in San Leandro, with popular Gus Caballo presiding. o lonmiless w o covefe t gg in o ,s r Georg s gettinwa e g Noel Becar was one of the members, among the 60 attend- worried. Before we left, he had contacted various chap- ing, that George had looked forward to meeting. ters acrosmeetingp u e viewe countr t th th s se r - fo o st y Finally, after traveling 2,600 miles across the United e latesth f to 196Fly-Ig A in 4EA n film. This storm could States, we were only one day and 2,400 miles from our upset our schedule. Fortunately, conditions started to im- original destination t I too. k foud one-halan r f houry b s prove after Tulsa, and we arrived in Amarillo on the jet; flying high over clouds all the way. As we got closer, 25th. the clouds broke, and in the distance below was Honolulu. Havin e evening th o plann gr e callefo sw , d Paul It's true Pacifie th , s bluei c deea ; p blue whic s almosi h t n Halei s Corners d n wertouci an t , eh ge tol wito t d h unbelievable. Ted Heller. He is a former B-24 pilot, and director of The days are warm, the nights are cool, and the peo- Marketing and Redistribution at Amarillo AFB. Thanks ple are charming; so friendly and happy. The beach boys lie MuseuA toF-8n a t TedfighterEA 4 s je e mha th , , cut-away on the beach all day, strumming ukuleles, with time out t enginesje , instruments, mock-ups mand an , y other items. for surf boarding. Coconuts lie in the streets — unwanted. We spent an enjoyable evening with him and his wife Lush vegetation cover e wholth s e island; orchids grow talking abou wha— t t else? EAA. wild. Wha paradisea t ! In order to keep our date in Phoenix on the 27th, It's a fact that there's not much private flying yet. we drove 660 miles the following day, and reached Globe, What flying there is, has to be shared at Honolulu's air- Ariz., a little mining town of 7,000 inhabitants. port wite e commerciamilitarth th h d an y l planest bu , The next day, getting to Phoenix with time to spare, many private plane e basear s d hereafted An .r seeine gth e chapteth r president, John Krupa d Georgan , e looket a d enthusiastic job Sam and the other members are doing, homebuilts in the area. Later, John, his wife, Joan, and t i won' e lonb t g before homebuilts will becomg bi a e his sons, Daren, Adrian and Barry, took us out for an par f Hawaiiao t n flying. excellent dinner e Municipath ; o t the n no l Airport, where Rex Newma d Wendelan n l Davenport e botar ho wh , the film was to be shown in a large meeting hall. There workin a coupl n g o f Volmerso e , were amonper0 4 e - gth was an audience of about 60 people, and since there were sons presene dinneth t a tr meeting, whic s helt wa a hd so many late arrivals decideds wa t i popula,y b , r demand, e GreeTh n Turtle. Chapter Presiden Burgesm n i Sa ts wa s re-ruo t filme nth . charge of the proceedings. Our nex s Vegast agaiLa showind n i An . ns Georggwa e looke t homebuiltsa d , this time with Chapter President While in Hawaii, George took advantage of an oppor- Rollen Caler. That evening, 40 people attended the din- tunity to fly with Herman Brandt in one of his fleet of ner meeting, which was held at Swankey's at Henderson, immaculate UC78's e alsH . o saile a catamara n i d n owned 10 miles from Las Vegas. Staying at the Tropicana, we by Woody Brown, former sailplane champion. sae fabulouwth s Folies Bergere aftee meetingth r . We must have visited Honolul t jusa e urigh th t t While in Los Angeles for three days, we visite insecto n d raio d n snan w durinsa time r e stayd gou W . an , friend d too an sa guidek d tour through Universal City. the members told us they had perfect flying weather We saw a few famous television and movie stars, and yeae th r 'round. acted like typical small town hicks when Jimmy Stewart We are convinced that this is the only way to travel. waved at our group. meetingsp u film A t se EA ,prepard - n an Pac,a en p o ku et The Los Angeles meeting was held at Hawthorne joy yourself. How else could you meet so many wonder- Memoria Stity e effortd th Ra an s f o t o s le Centerdu d An . ful, friendly d interestinan , g u peopleattenyo e f th d(I ? Chapter President Harry Scott , a turn-outher s wa ef o t Fly-I t Rockfordna course)f o , . over 200 people including: John Thorp, Dorothy Smith, Our thanks, once again, to all those nice people who e MoranJo d manan , y others well know o EAAt n . mad trir pou e suc pleasanha t one. *

(Continued from preceding page) of Airplanes, September 1930, National Advisory Com- add to the peace of mind of the builder when test flight mitte r Aeronauticsefo . time comes. . SPOR2 T AVIATION, November 1963, pag , "Simpli12 e - Many simplifying assumptions are necessary, but these fied Wing Stress Analysi a Strut-Brace of s d Mono- nee t affec dno e validit e testh tth f the i te f careo yar y - plane." fully justifie appliedd dan . 3. RPT 824, Summary of Airfoil Data, National Advisory REFERENCES Committe r Aeronauticsefo . 1. TM 581, Load Assumptions for Calculating The Strength 4. Light Airplane Design . PazmanyL , , 1963.

18 NOVEMBER 196$