Mike, you might want to ask Joe about that. The key is the blade bolts. They bend on overspeed, according to Joe Howard. Metal or plastic grips have no bearing on the issue either, which I just learned. Depends on the weight of the blades, the symmetry, airfoil, etc.
Let me tell a story.
Lama Benzine. Damaged the 725 benzine blades because of tail failure. In a pinch so I bought some V-Blades. It flew on them, I had to increase the head speed way up or it wouldn't hold. I even tried overhaul. It made it better, but still not right. Changed gearing, still not right.
Well a very good friend gave me a set of Joe Howard's heavy lifters, in 780's (I had a set of 800's but they were the cause of my failure above, too long and wiped out the tail rotor). Anyhow back to the saga.
So I checked the balance on them, perfect, slapped on some red paint stripes, rechecked the balance, and bolted them up. Dropped my head speed from 1500 t0 1300 right up front, knowing I had the 90:18 gears in. Now before it would climb, but more like me walking up a hill instead of a 10 year old running up the hill.
Man this thing climbs like a fricking rockett. So far I have experimentally lifted 5 pounds and flown around with it, couldn't tell it was there.
The Benzines don't like 3D blades.
My benzines and my turbine love these heavy lift blades. They have a spot of washout at the tips, sound like a real heli, and fly like on rails. Buy yourself an early Xmas present/
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