- size ▁wind ▁tunnel . ▁ ▁While ▁at ▁Lang ley , ▁the ▁DM 1 ▁under w ent ▁significant ▁changes . ▁The ▁original ▁design ▁used ▁air fo ils ▁of ▁very ▁thick ▁section , ▁especially ▁the ▁vertical ▁stabil izer , ▁which ▁ran ▁all ▁the ▁way ▁to ▁the ▁nose ▁of ▁the ▁aircraft ▁and ▁served ▁double ▁duty ▁as ▁the ▁co ck pit . ▁For ▁high ▁speed ▁flight , ▁th icker ▁air fo ils ▁are ▁known ▁to ▁have ▁very ▁high ▁drag , ▁which ▁proved ▁to ▁be ▁true ▁on ▁the ▁DM 1 . ▁The ▁design ▁was ▁progress ively ▁modified ▁in ▁an ▁effort ▁to ▁lower ▁drag . ▁One ▁of ▁the ▁first ▁changes ▁was ▁to ▁remove ▁the ▁large ▁vertical ▁stabil izer ▁and ▁replace ▁it ▁with ▁one ▁of ▁much ▁smaller ▁size ▁in ▁a ▁more ▁conventional ▁layout , ▁and ▁adding ▁a ▁normal ▁co ck pit ▁can opy ▁taken ▁from ▁a ▁Lock he ed ▁P - 8 0 ▁Sho oting ▁Star . ▁Further ▁work ▁introduced ▁sharp ▁extensions ▁along ▁the ▁leading ▁edge ▁of ▁the ▁wing , ▁which ▁had ▁the ▁side - effect ▁of ▁showing ▁periodic ▁generation ▁of ▁very ▁large ▁vor tex es ▁over ▁the ▁wing . ▁The ▁significance ▁of ▁this ▁effect ▁would ▁not ▁be ▁fully ▁understood ▁until ▁the ▁ 1 9 5 0 s . ▁ ▁The ▁DM 1 ▁influenced ▁design ▁of ▁the ▁Con v air ▁delta ▁f igh ters ▁such ▁as ▁XP - 9 2 , ▁X F - 9 2 A , ▁X F Y , ▁F 2 Y , ▁F - 1 0 2 ▁and ▁F - 1 0 6 . ▁After