Tower height?

XXavier

Member
This may be of some help. It is a page from 'Flugphysik der Tragschrauber' (Duda/Seewald):

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The formula giving the optimal distance is: hU = rmBl ·kBl


Where:

rmBl is the distance between the point where the prolongations of the blades meet at the rotor head and the center of mass of a blade (CGBl)

and:

kBl is the conicity, in radians.

In the example of the book (an MBO rotor) that distance hU is 12cm. In your case it is probably different. Just insert your numbers and see what happens...

Good luck...
 
Last edited:

Gyro28866

David McCutchen
Hello Bobby:
I have a set of 27' Dragonwings on my Dominator.
I will get by the airfield and get some measurements and post them here for you.
 

AirCommandPilot

Just a fledgeling
XXavier;n1139510 said:
Thanks XXavier, but that just adds more questions.

My issue is I have a single place Air Command with a heavy Subaru EA82. With my 200 lbs of weight added to the 635 lbs of machine, and 25' SkyWheels I'm not getting the climb performance I would like (during the summer). Last winter the thing would rise in the air like an elevator. I'm getting around 435 lbs of thrust in the heat, and was getting 455 lbs during the winter.
My guess is I need a 27' rotor to make up for the weight. I might have access to borrow a set of 27' Dragon Wings from a two place dominator to test out my 'guess', but I would have to use taller tower plates on my head. I'm just trying to figure out where my teeter bolt needs to be if I get to test the 27' rotor.
I don't know the specifics of the Dragon wing e.g. the blade CG and Blade weight. This info should already be out here. I just haven't been able to find it.
 

AirCommandPilot

Just a fledgeling
Gyro28866;n1139521 said:
Hello Bobby:
I have a set of 27' Dragonwings on my Dominator.
I will get by the airfield and get some measurements and post them here for you.
Thanks David. Would it matter if mine is a single place? Your Dominator is tandem right? Or would it just be about the weight?
 

XXavier

Member
AirCommandPilot;n1139524 said:
Thanks XXavier, but that just adds more questions.

My issue is I have a single place Air Command with a heavy Subaru EA82. With my 200 lbs of weight added to the 635 lbs of machine, and 25' SkyWheels I'm not getting the climb performance I would like (during the summer). Last winter the thing would rise in the air like an elevator. I'm getting around 435 lbs of thrust in the heat, and was getting 455 lbs during the winter.
My guess is I need a 27' rotor to make up for the weight. I might have access to borrow a set of 27' Dragon Wings from a two place dominator to test out my 'guess', but I would have to use taller tower plates on my head. I'm just trying to figure out where my teeter bolt needs to be if I get to test the 27' rotor.
I don't know the specifics of the Dragon wing e.g. the blade CG and Blade weight. This info should already be out here. I just haven't been able to find it.
I hope you may solve the problem soon, but (it seems to me) it may be a problem of thrust available, and not of rotor size. Perhaps a different propeller (or a different pitch, if adjustable) could be of help... Good luck...
 

AirCommandPilot

Just a fledgeling
My thrust is only 30 lbs less than one of our AR1s with a 912. The my weight is similar to the AR1 yet it can carry another person and fly just fine. The two differences are the rotor diameter and the drag. Not much I can do about the drag without a total redesign, but I can change the rotor. If it doesn't help, I know what I need to do.
Another example is the early RAF with the same engine as me would fly two people, but I think it has a 30' rotor. Am I thinking wrong here?
 
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