|
Fixed pitch
With this (fixed) propeller the blades
are fixed and cannot move (except rotate), thus propeller blade
angle is fixed (but the blade angle changes from the root to the tip as
explained above). It can be seen that there is also one RPM / airspeed
combination where the propeller is
operating at its optimum angle of attack and produces its maximum thrust. On all other
airspeeds (or conditions of flight) there is less thrust available from
the propeller. In
other words, its effective angle of attack depends on RPM and
airspeed.
some rule of thumb equations for relating HP and prop
diameter, I found cruising the internet.
Two-blade: d = 22 x fourth
root of (HP)
Three-blade: d = 18 x fourth root of
(HP)
Using these two relationships (no ideal how valid the
relationship - for one thing no indication of the effect of chord which we have
found to be considerable) here are some of the blade dimensions that result
| 2 blade |
|
|
3 blade |
| HP |
D inches |
|
D inches |
| 150 |
76.99 |
|
62.99 |
| 160 |
78.24 |
|
64.02 |
| 170 |
79.44 |
|
65 |
| 180 |
80.58 |
|
65.93 |
| 190 |
81.68 |
|
66.83 |
| 200 |
82.73 |
|
67.69 |
| 210 |
83.75 |
|
68.52 |
| 220 |
84.73 |
|
69.32 |
| 230 |
85.68 |
|
70.1 |
|