Two Blades Vs Three Blades
Join Date: Mar 2002
Location: where eva the plane is broken down
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Imho,without getting into E=MC......2 blades=greater cruise speed,slower roc,more vibration(especially once nicked a few times) & less ground clearance. 3blades=greater roc,slower cruise speed,less vibration,better grd clearance.this applies to most lighties,eg c182,c206-210(early models),mooneys,lance & cherokee 6,arrows etc. Price was normally about the same(3-4 yrs ago)$14-20,000 au$,dep on a/c type.Meat bombers with C182s usually have 3 bladers to get up quicker.Only economical once fitted prop out of hrs tho. PI 
Join Date: Mar 2000
Location: QLD, Australia
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Magnim has got it.
2 blade = speed
3 blade = acceleration
You will find exactly the same on boats
Less blades = more speed
More blades = more acceleration or pulling power.
However at altitude where the air gets thin you need big blades and/or more of them.
Big blades are a significant drag at lower altitudes.
3 blade = acceleration
You will find exactly the same on boats
Less blades = more speed
More blades = more acceleration or pulling power.
However at altitude where the air gets thin you need big blades and/or more of them.
Big blades are a significant drag at lower altitudes.
Just better ground clearance!!
OK jarjar, I'll buy that.
I have sometimes been misunderstood by trying to represent 10 pages of theory in only a few lines of text here.
enicalyth raised another important subject, especially for aerobatic aeroplanes. A composite 3 blade prop has much lower polar moment of inertia than a 2 blade metal one. A lot easier on the crankshaft flange when doing lomcevaks, flat spins and snap rolls. At least double the price though.
I have sometimes been misunderstood by trying to represent 10 pages of theory in only a few lines of text here.
enicalyth raised another important subject, especially for aerobatic aeroplanes. A composite 3 blade prop has much lower polar moment of inertia than a 2 blade metal one. A lot easier on the crankshaft flange when doing lomcevaks, flat spins and snap rolls. At least double the price though.
The gyroscopic/Pfactor force is noticably less with the 3 blade prop on my 185 than it was with the 2 blade prop of the same diameter. in my practical experience, i think that only the climb is better with the 3 blade prop.
all this is on a C185 300hp.
all this is on a C185 300hp.
