+ BULLETIN 1128, U. S. DEPARTMENT OF AGRICULTURE. 
rock elm* are sometimes used instead of white ash. Hickory,® so 
far, has been principally used for tail skids. The two finest woods 
for propellers are black walnut (Juglans nigra Linn.) and true 
mahogany (Swietenia mahagonit Jacq.), also known as Centrai 
American mahogany. Other species commonly used are yellow 
birch (Betula lutea Michx. f.), sweet birch (B. lenta Linn.), Afri- 
can mahogany (haya senegalensis A. Juss.), black cherry (Prunus 
serotina Ehrh.), hard maple, white oak, and yellow poplar. How- 
ever, a number of other woods are occasionally utilized, and in the 
future a wide variety of species will probably be admitted. Euro- 
pean designers even now are less exacting in this respect, sometimes 
using two species of wood in the same propeller, which on the 
whole is considered poor practice in this country. 
TABLE 1.—Distribution of wood in airplanes, showing the service requirements 
and the adaptation thereto of the different grades of the several species. 
Species of wood and quality designation (grade). 
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Main and center planes, ailerons, stabilizer, | | 
elevator, rudder, and fins: | | | 
Beams, solid:+: #6222. Vises. Seee ee A\A|A AS|EA || An |SAMIESS [5c2 si 
Beans :b0x sct beh tpn edhe eee oe ee A] AC) A ote A [ck | AIR |e te [ais 
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RGM G SUEEP Sse eee B, | BBB) | BUR ry BeieBy (== sa peat esse 
Panel blocks— lene essed fad 
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orner DlOCKS 2223 4.252 2 = eee 
Spacer DlOCKS {oF eee a ee a C C Cc C C | C Cc; Cc C | Cc | Gc 
Reinforcing blocks...............2..-.- | ber toads] fea) 
Rib webs, solid. -.-- a eaScecc: soss-66- Bo BB | Bae feb) Bile eee oatees RSS esa 
Rib webs, compression (solid)-----........ A | -A A | PAT AAT DAMN ACS Suc hrs tte aoe ae See apa 
Conipression stlats=—-=se— eee Pea ees A Al SAM oa Pees WI Cd | Jo = = pa eee Ce ee ee 
Cap strips. --.----------------------------- AS (AS | ACS | Ae ess EAS e as otros eae jeeee)ose = s52e fe 
Trailing edge— hotell | | 
Straight .....-..-.-----------------.--- B-B: | BH. |- Bo Bo) BB |----]----|---2)--=- [2 
BGH bf sono saat: Sees eee eee ee poeta ee ase | ae oe peeps bs 2 bo eet || ey ;A;A] A) AS A 
Entering edge— | | : 
Sipe ses he so sek seco sees soess ise BB; B..... B| BB) Bi....|-.--|.... Fezadl 
Bente? 22.52 223 SCs Se PaaS I ee eee eee (esec tec Sted seed Ses ee: eg be - ar s  fov FEy © 
GHISSCLS: 2 ets Sek nes 228 wo oak See eseeee B) BBS Wiel 5 eee 3 a ene (Racal ee Sie tea en fs So poe 
Masts. / Act hcen tend Sete ee Neen armen A} AC ACTS sariiciae |e ae ee sme [est [Ss8at 
Strimpers. 0h esate Gee eee ee ose eee B|B|B B | Bot BoB Alc see|eece | eee ae 
iinterplane StMUtS= == pees eee ere eee AM AP ASS ee oe |e mesmo | regs A|A | A (epee 
- | = Center section Struts.” “2-5 55 =- aon. 3- ae = Acyl 2A. | PAGE tence elie ae eee OA ALS SAS] ae 
Fuselage: (St Shc samen | See Se eae | 
Longerons— | l | 
Straighta esses esa eee TAGE eR Ass Age Cae el oe eeyelesee faeces race 
‘Bente= sees eee PLES EAE, Sa Peer) aed ee pede LN See [obs Bale AS OAS ee 
- §truts, vertical, and horizontal— | | | | | bone 
Higirstress 226.52 5.057) ee eee A}A|) Alo) | A PASPAC PB Ba Re Be 
TOWESDLESS tas ren eee ee eee BiB yt Bo.) Bol Bri BaRB ies sisoe eases figs 
Situts, diagonals. s2ea) = see eee eee Beebe brees| B By Ba Bales eee ee 
Supports; hédvy--- /2.2----2-8-. 33.8812: A | ASTAS | 2 5| A AS As) AS) GAS) Ae eee 
UIP POEES, Ho tts oe res oe eee ee ee BBB.) BB. | B-| BB | Ba Sees eee 
Brace blocks 27 eos ch ee BB BBs 1B) Be | BB pe eee 
Stifloners . s8375 se 27-4 -b -a esata eee ee BolsBr) BB Bs Bas | Bee ose lee | shee 
Cleats Oe oa. oe eee ee cet Se eee ee ae eee ie | sl eee Bees eseeleze-/ C | C1 CLC 
Purrilig stfips<: s-2-2--i2252- 20-2 ae ee- =|] 2B Ba BB] Bs | Te | Bere eealeeeet eee 
Rloor and seat bGards:-c-52---e5- eee eee ie Gul a CAG GAG |) Ca Cae = se eee jee. 
Gradlesiats:-=- iets se eee eee | GC aa GC) CC: | Cree ee ee eee 
BSOAE RAILS Sos! 25-0. pene Pees ee fe 1 ATES less) pAnc | <A-:} CA tetas [eee | 3 chaos 
TAY POSbs ool = te cieie nee ene Seneca AS ACG Arr Sed etic os ee (eee She se a NE ea ea 
Se UE L4G a So ee ose eco Sse Slate: [Et sspeeeclee alee. | sive) SSE [| Acs AL peAS ears A: 
Landing chassis: 
SUTutse - c2he2k sess cides cle slemiae wr asin~ cena YA AC Ar es a ose AAA eA ~| AS A Aaa 
Stream lining ¢ 2242) = pees eee C;C|c};c)c;c | Gal: <leAes see Bes erie 
“Rock elm includes rock elm (Ulmus racemosa Thomas) and the more dense stock of 
both white elm (U. americana Linn.) and slippery elm (U. pubescens Walt.). 
©The true hickories include mockernut hickory (Hicoria alba (Linn.) Br.), shcllbark 
hickory (H. laciniosa (Michx. f.) Sarg.), pignut hickory (H. glabra (Mill.) Br.), and shag- 
bark hickory .(H. ovata (Mill.) Br.). 
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