Hatz Biplane Association

Hi all,

Rotec aerosport has the following performance chart for several conditions and 3 different tried props. Our final prop is a German MT prop with 2050mm (81") dia and 1200mm (47") pitch.

Link:

http://www.rotecaerosport.com/wp-conten ... arison.pdf

Feel fre to ask any questions you may have!

Hans & Sam, H.C.78, Switzerland

Hans,
I'm curious about the choice of prop diameter (81"). Both Rotec and the Hatz plans specify 84", what was it that brought you to 81"? Was there a reason NOT to use 84" diameter?

Hi Doug,
Sorry for delay!
Well, the proposal of a 81"diameter of the MT prop came from Gerd Muehlbauer himself. He told us that he has the "FAR " license for this max. diameter for a 150HP engine turning at max. 2450 Rpm. I think, this is also many for noise reason or whatever! You know, we in Switzerland don't have the same rules as you have (one says, that a homebuild is much more difficult to license in Switzerland than in USA)!
First, we wanted to order a St. Croix prop, but then we feared, that we might get acceptance difficulties with our BAZL (Swiss FAA).
We and especially propellor specialists know, that different brand props with same dia and pitch may have a complete different behaviour, so it is possible, that e.g. a Culver prop with 83 or 84" dia and more pitch than we have works just fine on the Rotec 3600.
For us it is very difficult to make major changes (a prop is considered a major change) after receipt of a permit to fly, so it might take some time until we need a new prop and then we might make a change based on fellow Rotec Hatz experiences.
I'm sorry not be able to give you a better answer, but ourselfes, we are happy with our engine/prop results. We have good cruise (almost 100Mph at 2100 Rpm) and good climb (depending on actual load).

Best regards
Hans & Sam, H.C.78, Switzerland

Thanks Hans. That's good info. So if I understand you correctly, the choice of prop length had more to do with the ability to get it accepted by the licensing authorities in Switzerland than it did with any performance issues. Correct?

Thanks for the detailed info Hans, this is good stuff.

Dear Doug,

That's absolutlyi correct. MT didn't want to build a larger dia prop for this engine.

I sent you an email concerning a new member by name of Francesco from Italy. Didn't you receive it, which is your correct email address?

Best regards
Hans

Hi Hans, yes I got your email (you have the correct email address). We've been away on vacation (after OSH) and I'm just now getting caught up on things.