( ( ( Drive ( only ( fast enough ) ) ) ( to ( ( create ( a ( small ( bow wave ) ) ) ) ( in ( front ( of ( the vehicle ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB Drive) (ADVP (RB only) (RB fast) (RB enough)) (S (VP (TO to) (VP (VB create) (NP (DT a) (JJ small) (NN bow) (NN wave)) (PP (IN in) (NP (NP (NN front)) (PP (IN of) (NP (DT the) (NN vehicle))))))))) (. .)))
Drive only fast enough to create a small bow wave in front of the vehicle.
(ROOT (S (NP (DT A) (NN bow) (NN wake)) (VP (VBZ is) (VP (VBN created) (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NN wave) (NN source)) (VP (VBZ moves) (ADVP (RBR faster)) (PP (IN than) (NP (DT the) (NN wave) (NN propagation) (NN speed)))))))) (. .)))