I'm really not a big "fan" of MT's cheezy wooden propellers. They call them "Natural Composite" but it's really just densified/compressed wood with a thin fiberglass wrapping. Here's an example of what you can expect from in-service damage, a Jetstream 41 recently hit a bird, shed a blade, and it shot right through the passenger cabin. The hilarious thing is that the government investigation called it a "survivable accident" because no one happened to be seated in the row that it shot through. <a href="https://avherald.com/h?article=4f2a35e6" rel="nofollow">https://avherald.com/h?article=4f2a35e6</a><p>I was involved in the evaluation of proposed repairs to a Beechcraft Bonanza with a 3 bladed MT prop that taxied into a vinyl traffic cone at idle speed. The Beech shed two prop blades, bent the engine mount and firewall. There was a slight cut in the traffic cone, but it was returned directly to revenue service.
Somewhat related thread [0] from last month about the "tipless" Sharrow MX-1 prop [1] which achieves efficiency gains of between 9-15% over comparable 3-blade propeller designs. They started out working on an aircraft propeller but pivoted to a watercraft prop.<p>0: <a href="https://news.ycombinator.com/item?id=33949895" rel="nofollow">https://news.ycombinator.com/item?id=33949895</a><p>1: <a href="https://www.mby.com/gear/sharrow-mx-1-tipless-propeller-110120" rel="nofollow">https://www.mby.com/gear/sharrow-mx-1-tipless-propeller-1101...</a>
For reference on more or less blades, aviation stack exchange has some great discussions on this subject. One of my favorites<p><a href="https://aviation.stackexchange.com/questions/23009/what-are-the-advantages-of-more-than-4-propeller-blades" rel="nofollow">https://aviation.stackexchange.com/questions/23009/what-are-...</a>
Props with high blade count substantially reduce noise for drones as well<p><a href="https://youtu.be/1nk74KEIc2c?t=138s" rel="nofollow">https://youtu.be/1nk74KEIc2c?t=138s</a>
As a former aircraft owner, I immediately began to calculate the costs of doing on overhaul on those props. My three bladed props would need an overhaul at least every 2000 hours. There is also a time minimum as well if you don't reach the hours before the time interval. It seemed like the engines and the props would hit overhaul hours around the same time, usually hitting me with a bill well over $10,000.<p>I wonder what the cost will be on dual, 11-blade adjustable pitch props? It makes my eyes water and feel thankful I am not the owner/operator of such an aircraft.<p>Perhaps it all makes sense given the fuel consumption and speed improvements?
I'd imagine that, just like in other industries, there are tons of metrics (or counter-metrics) that are also important. Some that come to mind are efficiency, noise, vibration, cost, maintenance, stall characteristics, RPM requirements, weight, etc etc. From some fiddling with RC quads, I remember that increasing the number of blades does increase thrust, but at the cost of efficiency and several other parameters.
Kind of related: Do the same efficiency dynamics that apply to wind turbines apply to a fan providing propulsion? I.e. if a one-bladed fan is the most efficient for capturing wind, would it also be the most efficient airplane propeller or boat propeller? Obviously efficiency isn't the only consideration, but I am curious and I expect there's going to be some fan experts in this thread...
Seems like this 11 blade propeller -- might make a great rear propeller for the Celera 500L:<p><a href="https://ottoaviation.com/" rel="nofollow">https://ottoaviation.com/</a>
for those wondering...<p><a href="https://www.reddit.com/r/AskEngineers/comments/g39s6s/is_there_a_reason_that_fans_always_have_an_odd/" rel="nofollow">https://www.reddit.com/r/AskEngineers/comments/g39s6s/is_the...</a>