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FLIGHT, July 6, 193c).

T h e ma m win g s p ar h a s tu b u la rbooms and channe l- sec t ionbraces The jo in t be tween innerspar portion and the wing r ibad jacent to the fuse lage is madeon the neutra l ax is and not a tthe f langes.

(Left) Details ofspar cons truc t ion :The spar has doubletube booms in theinner por t ion andsingle tube in theoute r .(Right) The inner main sparpasses th rough the enginenacelle , and supports it , andthe spar of the outer wingportion is bolted to it insidethe nacelle covering

lo n g e r o n s , r e s u l t in g f r o m th e s e o f f s et s ,a r e p r o b a b l y q u i t e n e g l i g i b l e . C e r t a i n l yf r o m a m a n u f a c t u r i n g p o i n t o f v i e w t h ea r r a n g e m e n t i s m u c h s i m p l e r t h a n t h a tu s e d in th e W e l le s l e y .I t is n o t , h o we v e r , i n th e g e n e r a ls c h e m e o n l y t h a t t h e W e l l i n g t o nfuse lage d if fe r s f rom tha t o f the

W e l l e s l e y . T h e d e t a i l s t h e m s e l v e s h a v eb e e n s imp l i f i e d c o n s id e r a b l y . Re f e r e n c eh a s a l r e a d y b e e n m a d e t o t h e s i m p l ea t t a c h m e n t o f t h e g e o d e s i e s t o t h e t u b u l a r l o n g e r o n s . A t t h e c r o ss - o v e r p o i n t s ,a l s o , a d i f f e r e n t ty p e o f jo in t h a s b e e na d o p t e d . W h e r e t h e t w o b a r s c r o s s o n ea n o t h e r , t h e y a r e " h a l v e d t o g e t h e r , " a sw e s h o u l d h a v e s a i d i n t h e o l d d a y s of w o o d c o n s t r u c t i o n ,a n d t h e j o i n t is m a d e b y " b u t t e rf l i es " r a t h e r l i k e w i n gn u t s a t r i g h t a n g l e s t o o n e a n o t h e r , a n d h a v i n g a b o l tt h r o u g h t h e i r c e n t r e s : t h e r e a r e g u s s e t p l a t e s o n t h e o u t s i d e . T h e s k e t c h o n p a g e d s h o w s t h e a r r a n g e m e n t . T h eg e o d e s ie s th e m s e lv e s a r e of d i f f e r e n t f o r m , w i th ' ' h o l lo w -b a c k e d ' ' c h a n n e l s e c t io n s in p la c e of th e p la in s t r a ig h t -b a c k e d c h a n n e l s o f th e W e l le s l e y .I t ma y b e r e c o l l e c te d th a t in th e W e l le s l e y o n e of th ep r o b l e m s w a s t o p r o v i d e s u f fi c ie n t s t r e n g t h i n t h e s p a rf r a me s to r e s i s t t h e v e r y h ig h c o n c e n t r a t e d s t r e s s e s t r a n s mi t t e d fr o m th e s p a r f la ng es . I n f a c t , t h e s e f r a m e s h a d tob e s o s u b s t a n t i a l t h a t t h e y w e i g h e d a s m u c h a s t h e w h o l eo f th e r e s t o f th e f u s e la g e . I n th e W e l l in g to n a mo s t in g e n i o u s a r r a n g e m e n t h a s b e e n a d o p t e d w h e r e b y t h e l o a d si n t h e s p a r f ra m e s a r e g r e a t l y r e d u c e d , s o t h a t t h e f r a m e sc a n b e m a d e m u c h l i g h t e r t h a n t h e y w o u l d o t h e r w i s e b e .

(Below) Serratedplate joints are usedwhere the double -tube booms of thespar join the s ingle-tube booms of theoute r wing por t ion .

l o u n d e r s t a n d t h e i d e a i t i s n e c e s s a r yto e x p la in th a t th e w in g is o f th e th r e e -s p a r t y p e , w i t h a s i n g l e s p a r a t t h em a x i m u m d e p t h o f t h e w i n g s e c t i o n ,a n d f r o n t a n d r e a r s p a r s o f m u c h s m a l l e rd e p t h a t t h e le a d i n g e d g e a n d t o w a r d st h e t r a i l i n g e d g e . T h e c e n t r a l s p a rp a s s e s r ig ht th r o u g h th e f u s e la g e( a c tu a l ly i t i s jo in e d o n th e c e n t r e - l in e )a n d " f lo a t s " in i t w i th o u t to u c h in g i t .T h e f r o n t a n d r e a r s p a r s a r e a t t a c h e dto th e s id e s o f th e f u s e la g e o r , mo r espec if ica l ly , to th e f langes of th e sparf r a me s b y a f o r m o f c a r d a n h in g e wh ic hg i v e s f r ee m o v e m e n t a b o u t a v e r t i c a la n d a h o r i z o n t a l a x i s . F r o m t h i s i tw i l l b e o b v i o u s t h a t t h e c e n t r a l s p a r ,w h i c h c a r r i e s t h e w i n g b e n d i n g l o a d s ,t r a n s m i t s n o s t r e s s e s to th e f u s e la g es t r u c t u r e d i r e c t .

T h e f r o n t a n d r e a r s p a r s , b e c a u s e o lt h e c a r d a n h i n g e s , c a n n o t t r a n s m i t c o m p r e s s iv e lo a d s a r i s in g f r o m l i f t , b u t o n lyc a u s e d b y w i n g d r a g , a n d w h i c h a r eT h e win g l i ft is t r a n s m i t t e d f r o m t h ece ntr a l spar to th e f ron t an d rea r sp ar roo t f it tings an dt h r o u g h t h e m t o t h e f u s e la g e . T h e j o i n t b e t w e e n m a i nc e n t r a l s p a r a n d win g r o o t r ib o c c u r s in th e c e n t r e o f th esec t ion , and n ot a t th e f langes, th e tu be of w hic h , in f ac t ,c r o s s e s t h o s e o f t h e s p a r w i t h o u t t o u c h i n g t h e m .A l t h o u g h t h e s p a r f r a m e s h a v e b e e n r e l i e v e d of l o a d sin th e ma t t e r ju s t d e s c r ib e d , th e y s t i l l h a v e to b e o f f a i r lys u b s t a n t i a l c o n s t r u c t i o n , a s t h e y d o t r a n s m i t t h e e n t i r ewin g l i f t t o th e f u s e la g e , a n d a l s o s e r v e a s th e b a s i s f o rl o c a t i n g t h e w h o l e f u s e l a g e s t r u c t u r e . H o w t h e w i n g r o o tf it tings a r e a t ta ch ed to th e f langes of th es e f ra m es , an dh o w th e g e o d e s ie s o f th e f u s e la g e p a n e l s a r e s e c u r e d tot h e m , i s s h o w n i n o u r s k e t c h e s . S h e e t - m e t a l p l a t e s a r ef ir st r ive ted to th e f lang es of th os e geo des i es w hi ch c ro sst h e s p a r f r a m e s , a n d t h e p l a t e s a r e t h e n b o l t e d t o t h e f r a m e s

t h o s e w h i c h a r er e l a t i v e l y s m a l l .