Woooo Hoooooo!!!!

[Mithrandir]

Hey check it out.... I got the first thread!!!! Sweet!!!!

So I got an aerodynamic question....

What Aero Properties make for a nice Harriering model?????


Anyone?????

[wildhare]

A thick airfoil with rounded leading edge (not sharp).

Large ailerons that get close to the fuselage to catch air blast from the propellor.

Large elevators that are in the propwash.

A rudder that is not obstructed by elevators when viewed from the bottom/front.

A harrier is flown at high angle of attack very slowly. The only control you get is from the propwash so you want control surfaces that will react to the propwash and a wing that does not stall abruptly.

Look at a Cap for tail layout that really works.

TF

[madmax]

HA! Great reply Tom, and great topic Mike!

[OverTemp]

	Quote:
	A thick airfoil with rounded leading edge (not sharp).

I have to disagree... both of my JTEC 35% planes harrier exceptionally well... rock solid... and both have very sharp leading edges. I much prefer that for snaps.

[snap a saurus]

A combination of things, large size fuse, huge control surfaces, a lot of throw, the right airfoil and a good pilot.fg57

[hillmanr2]

	Quote: Originally Posted by snap a saurus
	a good pilot.fg57

[damien]

I often wonder how much the airfoil actually affects harriers, the two easiest planes to harrier i have flown are a shockflyer and a SPAD, both have no airfoil. I also have the electric phoenix models yak54 which has a very thin, sharp wing and it harriers very well.

[SargeNZ]

From what I have read the flat wings that shockie types use help the airflow to break away uniformly from the wing surface, apparently this is good thing but I get lost during the explanation

If your plane suffers from wing rock in harrier, a little up spoileron mixed into elevator on a switch can usually soften it or kill it completley.

[TRuss]

A sharper thinner airfoil will transition into stall better than a thicker one. Look at the latest 3D parkflyers. Besides growing in size the next most noticeable difference are thinner airfoils. I think the Extreme Flight Extra has pretty much started this. I did a some research on this early in the year and I as result of what I learned, I totally expected this to happen. It has a lot to do with the viscocity of the air relative to an aircrafts size. This is where Reynolds numbers come from. The smaller and slower the aircraft the stickier the air becomes and the more likely that laminar flow totally breaks up into hysterisis, where the flow over the surfaces just does whatever, making sudden transisitions to stalled, to laminar and back. The best thing that we can do, is to introduce a turbulent flow. It's not as good as laminar, but we can still control it and make it go where we want.

So, what I started to figure out, what works for a full scale aircraft will not necesarily work for a scaled down model. Notice how thick the airfoil is, especially at the root of a full scale aerobat. So, as the model gets smaller I am likely to lean towards the thinner airfoil being the best all around performer. On a larger model like a 40%er maybe something in between. As for performing the harrier, I don't think that airfoil shape matters too much. The thinner sharper leading edge will break into the stall more easily, but once there the airfoil is doing nothing. It's stalled. At this point we are relying on propwash which is very turbulent, and it should make it over the surfaces regardless of airfoil shape. Again, I like thinner sharper airfoils, but keep in mind that I am no kind of expert on the subject.

As for what you need for a good harriering machine. I'd say, a light wingloading, a longer tail moment and large control surfaces with plenty of throw.

[EddieWeeks]

I think what is more important than airfoil is the Platform (this is the shadow the wing makes) Long wings with short cords are the worst. Another term is
Aspect ratio.. At low RN airfoils don't work very well at all and any harrier is
at very low RN.

[paffy]

I want data, measurements, wind tunnel results !