What software are you guy's using?

[Mithrandir]

it has been my experiance that planes with thick, blunt & round leading edges on the wings don't harrier very well....

Why are you using an airfoil that is such a Fatty?

[rcpilot82]

I have a few skeeters with an airfoil like that. they don't do high alpha worth a crap. but are still fun planes. The hobby lobby reflex nailed the airfoil in my opinion.

[esc]

Hi guy's,

When the drawings are finished the ailerons will be shown to be constructed of balsa strip and fillets. I will probably re-model them anyway as I created them as a one piece extrusion for expediency sake. At the moment the drawing does not reflect the real construction. I may create them in pieces or fake it on the 2-D drawing.

The wing section is typical of those used by Precision Aerobatics for their "Electric Shock" and several other planes I can think of. You are right that a blunt aerofoil section has some pecularities but it also generates lots of lift for slow speed maneuvres. All aerofoil sections are a compromise and this may not be the best one in the end. If the prototype does not perform as well as it might I will adjust it or re-design the wing if necessary.

One other thing blunt sections tend to do is tip stall (that can be compensated for with the wing tip design) and this may be what caused your harrier problems. My wingtips will change before I let rcpilot82 have the drawings.

Thank you for your comments, keep them coming.

Dave

[Wojcigitty]

Ever flown a PA Addiction? Thick wing, rock-solid harriers if you get the angle right.

YouTube - Cody - Freestyle RC

There is more to it than the thickness of the airfoil. The depth of stall, angle of attack, aspect ratio, and CG are all big players. I agree though, I have flown many fun-fly planes that absolutely sucked in a harrier. You might try increasing the chord and decreasing the span to improve harrier performance.

[Mithrandir]

the max Cl of a thick section is not much more then a thin section...
the thin section... or more specifically... the sharper leading edge causes a more
distinct and abrupt seperation then a blunt leading edge... so in the instance of a harrier... the top of the wing seperates, and stays seperated.... the blunt leading edge has a stall line that meanders across the cord of the airfoil so the lift also changes.... and it is this action that combines with wing rock to cause more wing rock....

at least this is what was 'splained to me by Hanno Prettner at the St. Louis Huckfest in 1994

[esc]

Nice flying Wojcigitty.

No I haven't got one of those but I have an electric shock. The Addiction is on my list of planes to build sometime in the future :-)

Note the wing tips - I think they may help to prevent tip stalling and I am contemplating changing my design to something similar.

Truth is someone has to build my plane to find out if it flies well or not, everything else is just speculation. it's not etched in stone yet and given enough reason I will change it.

Dave

[rcpilot82]

HeHe.... I am A guinia Pig!

[Wojcigitty]

	Quote: Originally Posted by esc
	Nice flying Wojcigitty. No I haven't got one of those but I have an electric shock. The Addiction is on my list of planes to build sometime in the future :-) Note the wing tips - I think they may help to prevent tip stalling and I am contemplating changing my design to something similar. Truth is someone has to build my plane to find out if it flies well or not, everything else is just speculation. it's not etched in stone yet and given enough reason I will change it. Dave

Dave,

Thanks for the kind words.

I would be hesitant about the wing tips. One thing that I have noticed on airplanes with wingtips like this (Addiction, Harrier 46, Flip, Sudokhoi) is that high-alpha KE gets really weird and squirrely. In KE, when the plane is rolled slightly on its back, it will roll that way (further towards its back). Conversely, when it's rolled towards the gear, it keeps rolling in that way too. You can't mix it out, you have to stay on top of it. Other than that little quirk, the Addiction is a perfect 3D monster. I'll try to get some more video where I'm doing more than hovers and harriers. There are reports of the Flip and Diablotin becoming more stable and well-behaved in KE after chopping the wing tips off.

I would build your profile with flat wing tips, and you can try another version with Addiction-style tips to check their effect.

[esc]

Hey, Wojcigitty - you are more than welcome, credit where it's due.

Re: the wing tips - Blast! - I did an Autodesk training course yesterday on advanced surfacing and was looking forward to putting my newly gained knowledge into some fancy wing tips :-(

Certainly the way the tips are drawn is the simplest easiest to achieve an end result which may in the long run prove to be the most efficacious solution.

I will finish the drawings off and then it's over to Mr. Guinea Pig himself (rcpilot82) to tell us all the results - no pressure! :-)

Dave

[esc]

Hi Guys,

I have got the new wing tip designed thanks to the training course - something must have sunk into my old dense brain

I am going to show both the flat version and this one on the plan so rcpilot82 can take his choice of which to try.

[esc]

Oops, sorry the image didn't upload. I'll try again:

Dave

[rcpilot82]

looks cool, ought to be fun!!

[esc]

She is finally finished!

Rcpilot82 if you could PM me your email address I will send you the two files, one PDF in colour and one AutoCAD 2007 version.

Please note that you will have to plot the AutoCAD file in sections as it is too large for the print area you said you could do in one go. However the important sections, like side and plan elevations will fit at 1:1 in one piece without problem.

Regards,

Dave

[esc]

For those of you that would like to see the finished drawing attached is a 600 dpi res. pdf file.

Regards,

Dave

[rcpilot82]

PM Sent. thanks!!