After trying to get a technical description of the ROV's propellers from Graupner, and having no answer. I decided to make some research related to the propellers that are being used for the OpenRov Project.
Real tests, if duly performed, are quite a good way for knowing how the props behave. But ...for a general knowledge, and for extrapolating the results to other conditions, the parameters of the propeller must be well known.
As many of you surely know, there is a couple of standarized propeller series, which properties are well known and tested. Those standard series, provide statistical results, obtained from hundreds of channel tests, performed under many different conditions, allowing for very accurate predictions.
Propeller calculations can be accurately made from curves and/or polynomial series, that represent the joint of the statistical results.
After some research and comparison with real propellers we have at our yard, the GRAUPNER 2308/65 and related family, has resulted to belong to the GAWN-KCA series, or .. skewed Gawn-Burril series.
The pic below, belongs to the a series "mother propeller", where the radius=1, pitch=1.5 radius, and Ae/Ao=0.5
All linear measurements are given as a radius fraction.
For other P/D (Pitch/Diameter), or areas, just start from the expanded measurements, or enter the GAWN series polynomial data.
For the seek of clarity, a DraftSight .dwg is attached.KCA.DWG
Dont hersitate asking for any explanation, or pointing any correction.