Hanuman Airfoil

[RickH]

Is there anybody out there who can tell me the Airfoil designation of the airfoil section used on the X-Air Hanuman IE Clark Y, Naca --- , Eppler 748 (tho I think it would be unlikely to be Eppler of any kind)

 

Regards

 

RickH

 

 

[Head in the clouds]

Given the type of wing construction, it's not likely to be any particular section. Wings built using tubular front and rear spars with compression tubes and internal wire bracing are generally known as 'ladder-wings'. I'm not all that familiar with the Hanuman but I think it has battens in pockets in the upper surface of the fabric like a Drifter or Thruster wing. Those battens are not rigid like a wing rib and so they change their curvature a fair bit according to the position of the Cp which moves around according to the angle of attack (alpha). Because of that the airfoil shape doesn't stay constant.

 

Also - that type of wing generally doesn't have lower surface battens so the lower surface changes camber according to the wing loading and the fabric tension, so in effect the whole wing camber is constantly changing and also never likely to be exactly the same from one aircraft to the next which is why people often say one Drifter flies quite differently from another.

 

If you're wanting to know the airfoil section so that you can do some lift calcs or similar you could probably use something around the 0.8x the Cl of a Clark Y but modified in your software for the appropriate thickness ratio (a Clark Y is only about 11.7% IIRC). BUT - although you might get 0.8x the Cl you would probably be more in the region of 1.2x the drag (or more) due to the higher camber of the ladder-wing's foil caused by the undercamber of the lower surface. There's a lot of guesswork involved with that kind of wing construction and mainly because of the difficulty in getting the fabrics really tight.

 

 

[RickH]

Given the type of wing construction, it's not likely to be any particular section. Wings built using tubular front and rear spars with compression tubes and internal wire bracing are generally known as 'ladder-wings'. I'm not all that familiar with the Hanuman but I think it has battens in pockets in the upper surface of the fabric like a Drifter or Thruster wing. Those battens are not rigid like a wing rib and so they change their curvature a fair bit according to the position of the Cp which moves around according to the angle of attack (alpha). Because of that the airfoil shape doesn't stay constant.Also - that type of wing generally doesn't have lower surface battens so the lower surface changes camber according to the wing loading and the fabric tension, so in effect the whole wing camber is constantly changing and also never likely to be exactly the same from one aircraft to the next which is why people often say one Drifter flies quite differently from another.

 

If you're wanting to know the airfoil section so that you can do some lift calcs or similar you could probably use something around the 0.8x the Cl of a Clark Y but modified in your software for the appropriate thickness ratio (a Clark Y is only about 11.7% IIRC). BUT - although you might get 0.8x the Cl you would probably be more in the region of 1.2x the drag (or more) due to the higher camber of the ladder-wing's foil caused by the undercamber of the lower surface. There's a lot of guesswork involved with that kind of wing construction and mainly because of the difficulty in getting the fabrics really tight.

Cheers mate

 

I get your point about the changing Profile although the Hanuman does have lower wing battens which are curved to help with the profile as well as the upper battens. Interesting that you picked the Clark Y to compare as this is the reason for the inquiry, I've done most of my flight training in a Hanuman but my bird is a little single seat job with a Clark Y and as yet I have not flown it although the first flight is about to happen fairly soon and whilst my Instructor says they should be fairly similar and whilst by no means any disrespect to my Instructor (not only is he greatly experienced but also a good friend and knows my machine) I am simply interested in any comments re possible similarities or other.

 

Regards

 

RickH

 

 

[facthunter]

The factors you are discussing will show up as pitch.trim change with airspeed change. It's quite amazing how much this varies from plane to plane. ( To me anyhow). It could be a critical factor if the CofG is well back and your elevators aren't very effective, or the horizontal stabilised not at the right riggers angle. There can be pitch instability. I'm sure HITC can elaborate on this. nev

 

 

[RickH]

CofG range for my machine is 25% to 35% chord ( I assume that this is due to this being same as the center of pressure range for this particular airfoil) as per design specs and with me and full fuel it is currently

 

set to about 27.5% of chord (this position chosen as I figured it's better to err on the side of to far forward as opposed to the alternative of to far aft). Horizontal stabilizer is also set as per design specs IE parallel to top longeron and the main airfoil is set at 2.5 degrees to top longeron again as per design specs. Thrust line of of prop is inline with top longeron. Initial ground runs seem to indicate control surfaces are at least as responsive as on the Hanuman. The machine being discussed is the one in the photo used as my avatar. ie single seat, midwing powered by 110hp Hirth. Allup weight is 334kg.

 

RickH

 

 

[facthunter]

You are aware of all the essentials. Nev