Prop blade failure is more and more common as prop rpm increases. I witnessed at least three props throw blades at last year's LA SAWs, all props were hardened but were spining in excess of 45,000 rpm. The problem seems to be blades which are thinned to much, brittle metal after hardening, and high rpm. The vibration is tremendous. Stronger metal is the most likely solution, although lower rpm could help extend current BeCu prop life. Many seem to believe that extreme rpm is needed to achieve high speeds, yet I was able to get my old 12-NiMH cell-powered riggers into the 90s with rpm under 40,000. A prop with 3.5" of pitch (v947 etc) spinning just 40,000 rpm will push a good rigger to 110+ mph.
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