ability , ▁especially ▁considering ▁the ▁length ▁of ▁the ▁bla de . ▁That ▁leaves ▁fib re - re in for ced ▁compos ites , ▁which ▁have ▁high ▁strength ▁and ▁st iff ness ▁and ▁low ▁density , ▁as ▁a ▁very ▁attract ive ▁class ▁of ▁materials ▁for ▁the ▁design ▁of ▁wind ▁tur b ines . ▁ ▁Wood ▁and ▁canvas ▁s ails ▁were ▁used ▁on ▁early ▁wind m ills ▁due ▁to ▁their ▁low ▁price , ▁avail ability , ▁and ▁ease ▁of ▁manufact ure . ▁Sm aller ▁bl ades ▁can ▁be ▁made ▁from ▁light ▁met als ▁such ▁as ▁al umin ium . ▁These ▁materials , ▁however , ▁require ▁frequent ▁maintenance . ▁Wood ▁and ▁canvas ▁construction ▁limits ▁the ▁air fo il ▁shape ▁to ▁a ▁flat ▁plate , ▁which ▁has ▁a ▁relatively ▁high ▁ratio ▁of ▁drag ▁to ▁force ▁captured ▁ ▁( low ▁aer od ynamic ▁efficiency ) ▁compared ▁to ▁solid ▁air fo ils . ▁Const ruction ▁of ▁solid ▁air fo il ▁designs ▁requires ▁inf lex ible ▁materials ▁such ▁as ▁met als ▁or ▁compos ites . ▁Some ▁bl ades ▁also ▁have ▁incorpor ated ▁light ning ▁conduct ors . ▁ ▁New ▁wind ▁tur bine ▁designs ▁push ▁power ▁generation ▁from ▁the ▁single ▁meg aw att ▁range ▁to ▁up wards ▁of ▁ 1 0 ▁meg aw att s ▁using ▁larger ▁and ▁larger ▁bl ades . ▁A ▁larger ▁area ▁effectively ▁increases ▁the ▁tip - speed ▁ratio ▁of ▁a ▁tur bine ▁at ▁a ▁given ▁wind ▁speed , ▁thus ▁increasing ▁its ▁energy ▁extra ction . ▁Computer - a ided ▁engineering ▁software ▁such ▁as ▁Hyper S izer ▁(