Correlating Propeller Performance
with Kt/Kq Multipliers
A HydroComp Technical Report
Report 101
Product link: NavCad,
SwiftCraft,
PropExpert
The AU
and MAU (modified AU) propellers are a series of aerofoil
blade section propellers popular in Japan and the Far East. The
basic geometry of the series is quite similar to the Wageningen
BSeries developed at NSMB.
Unlike
the Bseries, the thrust and torque performance has never been
developed into polynomial expressions for the calculation of Kt
and Kq. It is possible to adequately predict the performance of
the AU/MAU series through the use of Kt and Kq multipliers.
Kt and Kq multipliers shift the predicted curves for the chosen
series (Bseries in this case), to make them closer to what is
expected from the actual propeller (AU/MAU). HydroComp has identified
that to predict AU/MAU series performance:
 Series:
Bseries
 Kt
multiplier: 1.07
 Kq
multiplier: 1.07
 Use
suitable scale corrections and options as for the Bseries
A
plot of actual AU/MAU performance compared to multipliercorrected
Bseries performance is shown below. This was performed at model
scale for a 5bladed propeller with 0.80 expanded area ratio and
pitch/diameter ratio of 0.80. The multiplier was chosen to minimize
the error in the range of the maximum efficiency. The calculation
tended to overpredict (less than 4%) below the point of maximum
efficiency, and underpredict above.
