Aerodynamic modifications

[Curt_B]

Re: Aerodynamic modifications

We had the same tips as Dago. They were the upswept/reverse horton... Whatever you call them. They had pretty bad spillover from the bottom of the wing that caused almost reverse airflow in the last 4-6 inches of the aileron.

Found some time to look. Confused Dago with Red Barron, maybe because they're both, 'red'. Dago looks like they sported the same tips throughout.

Dago/ original PM tips are pretty bad.


Dago could have been faster. The sharp corner buys separation with the laminar airfoil section, and would also cause separation for a conventional section. They should have blended the vertical end plate in with a generous surface curvature like is seen on blended winglets. The 45 degree scarf is still a good idea, but having the end follow the upper surface curvature on the aft end of the airfoil, like Red Barron, is not. Original winglets had the same sharp corner that compromised their performance.

Wing tip vortices cause induced drag by some definitions, but they also cause flow disturbances and 3D boundary layer build-up on the wing upper surface as seen in the picture.

A couple of ways around that is to thin the tip and delete the aft surface as seen on stock Cubs, or minimize the wing tip chord as is found on soaring birds. Soaring birds also get the wingtip vortex out of the plane of the wing. Birds that fly through bushes and trees have low aspect ratio wings and the tip chord is long to get the wing loading down for maneuver in tight spaces.

The Formula guys have figured it out with tips that come to a point at the trailing edge. That fast biplane does the same essentially, and they even applied the idea to the prop tips.

Boeing's new airplane models minimize tip chord and the vortex is out of the wing plane due to wing deflection at 1g. They also sweep the tip because the shock wave wants to unsweep at the tip.

Anybody know how we got from Red Barron type tips to Voodoo/Strega tips?

[CJAM427]

Re: Aerodynamic modifications

Found some time to look. Confused Dago with Red Barron, maybe because they're both, 'red'. Dago looks like they sported the same tips throughout.

Dago/ original PM tips are pretty bad.
[ATTACH=CONFIG]20376[/ATTACH]

Dago could have been faster. The sharp corner buys separation with the laminar airfoil section, and would also cause separation for a conventional section. They should have blended the vertical end plate in with a generous surface curvature like is seen on blended winglets. The 45 degree scarf is still a good idea, but having the end follow the upper surface curvature on the aft end of the airfoil, like Red Barron, is not. Original winglets had the same sharp corner that compromised their performance.

Wing tip vortices cause induced drag by some definitions, but they also cause flow disturbances and 3D boundary layer build-up on the wing upper surface as seen in the picture.[ATTACH=CONFIG]20375[/ATTACH]

A couple of ways around that is to thin the tip and delete the aft surface as seen on stock Cubs, or minimize the wing tip chord as is found on soaring birds. Soaring birds also get the wingtip vortex out of the plane of the wing. Birds that fly through bushes and trees have low aspect ratio wings and the tip chord is long to get the wing loading down for maneuver in tight spaces.

The Formula guys have figured it out with tips that come to a point at the trailing edge. That fast biplane does the same essentially, and they even applied the idea to the prop tips.

Boeing's new airplane models minimize tip chord and the vortex is out of the wing plane due to wing deflection at 1g. They also sweep the tip because the shock wave wants to unsweep at the tip.

Anybody know how we got from Red Barron type tips to Voodoo/Strega tips?

That's awesome to hear "Dago could have been faster" -Gives me goosebumps!!!
There was a thread on here a while back about the wingtip evolution, I'll see if I can dig it up...

Curt, I had a thought the other day about afterbody drag.
Like you said jets have a big hole at the rear end that helps eliminate it -If you could somehow cut a hole in the back of a P-51 (like at the bottom of the rudder) as an exit for cooling fluids, etc. This would be on a scoopless 'stang. -Kind of like Rare Bear's current setup with the stinger...

[Curt_B]

Re: Aerodynamic modifications

That's awesome to hear "Dago could have been faster" -Gives me goosebumps!!!
There was a thread on here a while back about the wingtip evolution, I'll see if I can dig it up...

Curt, I had a thought the other day about afterbody drag.
Like you said jets have a big hole at the rear end that helps eliminate it -If you could somehow cut a hole in the back of a P-51 (like at the bottom of the rudder) as an exit for cooling fluids, etc. This would be on a scoopless 'stang. -Kind of like Rare Bear's current setup with the stinger...

The wing tip thing would be a great add. We've already added the strakes as a data inclusion.

The jets have an opportunity to reduce the fuselage close-out angle with the big hole and high mass flow. The RearBear low energy exhaust pipe at the back end has the benefit of keeping the boundary layer undisturbed if it exhausted somewhere on the side of the airframe - so in that sense it's good. As long as the weight of running more pipe back there isn't too severe. If you make the hole even bigger, say to handle a radiator boil-off on the Mustang somehow, then you'd still have the stock fuselage close-out angle. Good thinking though, with enough ideas, every now and then a gem sees the light.

[CJAM427]

Re: Aerodynamic modifications

The wing tip thing would be a great add. We've already added the strakes as a data inclusion.

The jets have an opportunity to reduce the fuselage close-out angle with the big hole and high mass flow. The RearBear low energy exhaust pipe at the back end has the benefit of keeping the boundary layer undisturbed if it exhausted somewhere on the side of the airframe - so in that sense it's good. As long as the weight of running more pipe back there isn't too severe. If you make the hole even bigger, say to handle a radiator boil-off on the Mustang somehow, then you'd still have the stock fuselage close-out angle. Good thinking though, with enough ideas, every now and then a gem sees the light.

Back to the drawing board then as they say! Haha

I haven't found it yet, but I'll have more time to look for the wing tip thread tomorrow

[Lockheed Bob]

Re: Aerodynamic modifications

I'm sure all have noticed how the "Ghost" had the boiloff coming off the fuselage side. I wonder if that affected the aerodynamics at racing speed?

[Curt_B]

Re: Aerodynamic modifications

I'm sure all have noticed how the "Ghost" had the boiloff coming off the fuselage side. I wonder if that affected the aerodynamics at racing speed?

Think I'll refrain from talking about Ghost specifics, if someone else has a comment, that'd be good. Haven't noticed any aero guys here though, unless they haven't joined to comment yet. Or you can pm me.

[CJAM427]

Re: Aerodynamic modifications

I'm sure all have noticed how the "Ghost" had the boiloff coming off the fuselage side. I wonder if that affected the aerodynamics at racing speed?

I have always wondered the same thing, but then the question comes up: where would you have it come out?

[CJAM427]

Re: Aerodynamic modifications

Here's one thread on Dago's wingtips.

http://www.aafo.com/hangartalk/showthread.php?7763-i-have-a-good-dago-red-qustion

Still haven't found the evolution one yet... If I remember right though, it went something like Jeannie or Stiletto had a certain type of wing tip that everyone else copied. Then someone else debuted the up-swept tips and someone copied those... Something like that...

[Curt_B]

Re: Aerodynamic modifications

Here's one thread on Dago's wingtips.

http://www.aafo.com/hangartalk/showthread.php?7763-i-have-a-good-dago-red-qustion

Still haven't found the evolution one yet... If I remember right though, it went something like Jeannie or Stiletto had a certain type of wing tip that everyone else copied. Then someone else debuted the up-swept tips and someone copied those... Something like that...

Great stuff. Seems like the sport is full of leaders and followers - but that's true of all kinds of racing. I like the anodized prop instead of paint. What they didn't realize is that paint has a thickness that contributes to the airfoil thickness at the tip, which is bad. The paint thickness is small, but so is the propeller tip thickness, so the addition is felt as decreased prop efficiency.

The method of testing leaves a lot to be desired. If anybody can come up with pictures of those wingtips tried on Dago, that would be good.

[CJAM427]

Re: Aerodynamic modifications

Great stuff. Seems like the sport is full of leaders and followers - but that's true of all kinds of racing. I like the anodized prop instead of paint. What they didn't realize is that paint has a thickness that contributes to the airfoil thickness at the tip, which is bad. The paint thickness is small, but so is the propeller tip thickness, so the addition is felt as decreased prop efficiency.

The method of testing leaves a lot to be desired. If anybody can come up with pictures of those wingtips tried on Dago, that would be good.

That's for sure... Speaking of props what's your opinion on the best P-51 prop?

I have no idea where to find those pics of Dago, Bruce Lockwood, or maybe Bucky D, or Neal Nurmi would be my best guess as to someone with those photos...

[Curt_B]

Re: Aerodynamic modifications

That's for sure... Speaking of props what's your opinion on the best P-51 prop?

I have no idea where to find those pics of Dago, Bruce Lockwood, or maybe Bucky D, or Neal Nurmi would be my best guess as to someone with those photos...

That'd be good if they'd chip-in. The cuff works best to absorb the extra power I'd imagine - and also to feed the inlet. He mentioned something about reprofiling the blades, so can't comment without seeing what was done. The best current prop would be the one they're using now.

[CJAM427]

Re: Aerodynamic modifications

That'd be good if they'd chip-in. The cuff works best to absorb the extra power I'd imagine - and also to feed the inlet. He mentioned something about reprofiling the blades, so can't comment without seeing what was done. The best current prop would be the one they're using now.

Yes it would be!

Awesome! Thanks for your insight!

[John]

Re: Aerodynamic modifications

That'd be good if they'd chip-in. The cuff works best to absorb the extra power I'd imagine - and also to feed the inlet. He mentioned something about reprofiling the blades, so can't comment without seeing what was done. The best current prop would be the one they're using now.

Speaking of prop cuffs, it seems Rare Bear's 3 blade should be better than the 4 blade due to the formers very nicely designed cuffs.(by the way, who designed and built the cuffs for the modified P-3 3 blade that was once used on the Bear?)

Also, what was your opinion of the Risky Business wing tips during the days it was raced at Reno?

[Wild Bill Kelso]

Re: Aerodynamic modifications

Speaking of prop cuffs, it seems Rare Bear's 3 blade should be better than the 4 blade due to the formers very nicely designed cuffs.(by the way, who designed and built the cuffs for the modified P-3 3 blade that was once used on the Bear?)

Also, what was your opinion of the Risky Business wing tips during the days it was raced at Reno?

California Propeller if I remember correct.

[BD4Flyer01]

Re: Aerodynamic modifications

Let me rewind and ask a question about this post on page 6 of this thread:

"......Rear Bear. Pretty sure they know what they're up against and have heard about a new, extended leading edge designed to decrease the t/c of the root section and smooth the upper surface curvature changes to mitigate compressibility drag. A good way to smooth out the area rule would be by shaping the canopy, if they haven't already."

Please tell me what "t/c" means in that sentence? I know it's probably obvious, but it's driving me crazy!

Noticed that some Bonanzas have a similar sharp edged wedge at the wing root, which I am told is to enhance stall warning.

Thank you for a terrific thread, I am learning a lot.