For you speed mod types

Found this today. It is intended for transport category equipment but I thought you speed-guys might be interested. Probably not alot to gain with a 200 mph RV, might even be draggier but it looks interesting.
Obviously, they are channeling the wing tip vortices.



Link:

http://www.gizmag.com/minix-wing-tip-vortex-aircraft-aerodynamics/15526/picture/116756/

Interesting to be sure. Claims to be better at tip vortex reduction than blended winglets.

There's a gent up in Canada that is contemplating a blended winglet for small GA airplanes, and the RV is on his list. I spoke to him, but it requires replacing the outer wing rib with his rib design that accepts the structural support for the winglet. Not sure I'd want to go that far, as I'd want to be able to swap tips dependent on the mission, and my gut says winglets just might impact aerobatic capability .

This design looks as though it could be designed somewhat plug and play, with little to no structural mods (perhaps...but that is total speculation...who knows what aerodynamic wing bending/twisting forces would be applied throughout the entire flight envelope).

Something to keep an eye on to see if it gains any traction and lives up to expectations.

Looks cool though, and that's worth a knot or two!

Cheers,
Bob

FWIW, Bob....

...several years ago, someone was making winglets for our Air Tractors claiming improved airflow and less intense vortices that impact our chemical spray pattern.

It didn't take long for Air Tractor to warn any owners that their spar life would take a 40% hit if they installed them! My 8000 hour spar (Which I've replaced) would then become a 4800 hour spar

Best,

Don't get me started!

Ah come on guys, don't EVEN get me started......

pierre smith said:

...several years ago, someone was making winglets for our Air Tractors claiming improved airflow and less intense vortices that impact our chemical spray pattern.

It didn't take long for Air Tractor to warn any owners that their spar life would take a 40% hit if they installed them! My 8000 hour spar (Which I've replaced) would then become a 4800 hour spar

Best,

Click to expand...

Pierre, its those unintended consequences that concern me as well. Reshaping tips to find lower drag/higher speed is one thing. Adding things that radically change the characteristics or create unwanted aerodynamic forces is quite another!

scsmith said:

Ah come on guys, don't EVEN get me started......

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Steve, please go ahead...always good to hear the view from the Aero Engineer's seat. I know winglets are optimized for high and fast (as in jet high/fast), and this tip says 6% at .8 mach. The likelyhood of either being effective at RV speeds is likely low, and the design strength consequences could be high. No intent here to use either, but always willing to learn from the discussion.

It looks innovative and kinda neat at one look. OK, it also looks like one of the new beer bottle swirl tops that supposedly makes the brew pour faster too.

But interested to hear your thoughts...and still looking for the magic wingtip (OBTW, have talked to many racers, and no one has really found the magic tip...lots of theories, some increased speeds...but no clear "perfect" tip).

Thoughts? Starter button pushed!

Cheers,
Bob

rvmills said:

Thoughts? Starter button pushed!

Cheers,
Bob

Click to expand...

When they say it is 5 times more effective than winglets my BS dial goes up. The APB winglets retrofitted to the B-757 gain at least 4 1/2% according American Airlines and they are not just a bolt on deal. The last 10 ft of the wing planks get cut off and replaced. Also, the spars get beefed from the pylons to the tip to handle the additional bending moments. The $1.2m cost for them gets paid back in less than a year in fuel savings. Originally they were only going to mod 22 or so of them, but now are doing the fleet.

If winglets are only for high speeds then why do the latest gliders have them for performance? It certainly isn't to look cool. check out http://www.dg-flugzeugbau.de/leistung-e.html for one manufacturer's opinions on how to increase performance.

Why would you want to put a deer whistle on your wingtips?

dhammer said:

When they say it is 5 times more effective than winglets my BS dial goes up. The APB winglets retrofitted to the B-757 gain at least 4 1/2% according American Airlines and they are not just a bolt on deal. The last 10 ft of the wing planks get cut off and replaced. Also, the spars get beefed from the pylons to the tip to handle the additional bending moments. The $1.2m cost for them gets paid back in less than a year in fuel savings. Originally they were only going to mod 22 or so of them, but now are doing the fleet.

If winglets are only for high speeds then why do the latest gliders have them for performance? It certainly isn't to look cool. check out http://www.dg-flugzeugbau.de/leistung-e.html for one manufacturer's opinions on how to increase performance.

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Hammer,

My BS flag was pegged when reading the article as well...why I mentioned to watch and see if it lives up to expectations. For something to be that revolutionary is very unique, especially when we often see something "new", only to find aerodynamic research from the early 20th century that already has tested and debunked or dis-proven a theory or modification. So I'm with ya!

I also fly wingletted jets (737's in my case) at work, and concur with you...no easy bolt-on mod. But as you said, the fuel savings are phenomenal. Could it work for speed with an RV...dunno, but its fun to contemplate.

SARL chairman Mike Thompson did some flat plate add-ons to his flat wingtips that were like a fence above the top skin at the outer edge. They loaded up his ailerons and made roll forces uncomfortably high, so they were pitched.

Bob Axsom and I have been playing with flat tips as well, and all three of us are still contemplating testing flat plate fence-like add-ons that fair to the wing top before they get back to the aileron...either above the wing only, or above and below the wing (think A-320-like tips, but a bit more curved). Wish we had a wind tunnel, and AVC and OSH are on our radars before this type of project. But it's all in the spirit of experimentation and innovation...with a keen eye to safety...none of us want to experiment with no regard for risk!

I probably bit a little hard on this thread, but when things like this pop up, its a chance to gain wisdom from the group during discussion. And honestly, it also falls in the category of "education and entertainment"!

David Paule said:

Why would you want to put a deer whistle on your wingtips?

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David,

I thought of the whistle-factor too! The only reason I can think of is to sound like a Corsair!

Of course, noise probably means drag, right!

All in good fun!

Cheers,
Bob

Probably be cool with a smoke canister attached!

Actually, I have seen something similar before. A French Aero Eng instructor built a homebuilt and put round tube wing tips on it. He claimed an efficiency gain from it. I posted a link to it years ago on one of Bob Axsom's threads, but can't locate it now.

Looking up Minix looks like it is a French company. I wonder if it is the same guy and if he has optimized his design?

An interesting comment here, post #16.
http://www.oshkosh365.org/ok365_Dis...d=147&id=1235&forumid=175&topicid=3339&page=1

Keep in mind that at high density altitudes induced drag becomes one of the premier things. Induced drag decreases with span-squared, while parasite drag goes up with area. These new long, triangular tips that you are now seeing on the new Boeings only increase area at half the rate that span increases so there is a net overall drag decrease. That's what Jim Smith's triangular tips did is give him slightly more speed above 7000'-8000' dalt but much improved take-off and landing. He has some photos of tufts on the tips just prior to stall and they're straight back. 'Course, roll-rate is down. 'Can't have everything!

Paul,

How are Jim's top speeds impacted by his triangular tips at sea level, or at lower DA's? And by much improved TO and LND, do you mean shorter distances?, lower stall and landing speeds?, both? other? Thanks!

Cheers,
Bob

Data, I need Data

As an engineer I require proof (data) to convince me of a new widget. Since there is a lack of data (actually I saw no data since flow traces do not indicate drag reduction especially since the wetted area and interference drag term will go way up) I doubt it actually reduces drag. Since the article has only speculation, I am free to speculate myself and I would guess it is higher drag.

rvmills said:

OK, it also looks like one of the new beer bottle swirl tops that supposedly makes the brew pour faster too.

Click to expand...

I can test a beer bottle flow many times and actually have many times in my youth.

rvmills said:

But interested to hear your thoughts...and still looking for the magic wingtip (OBTW, have talked to many racers, and no one has really found the magic tip...lots of theories, some increased speeds...but no clear "perfect" tip).

Click to expand...

What he said!

This ain't no speed mod for an RV, since RV's have next to zippo induced drag at max speed. If it were a problem, they wouldn't have been given such stubby wings.

Andy_RR said:

This ain't no speed mod for an RV, since RV's have next to zippo induced drag at max speed. If it were a problem, they wouldn't have been given such stubby wings.

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That's true at lower altitudes, but as you get above 7-8k, those stubby wings start really getting with the induced drag. For x-country at 14k'-15k' dalt, you'll find that you will have to fly at a much higher nose-up attitude. Here's some formulae to calculate your induced drag area, Ai, in sq.ft.
Q=(IAS, mph X 22 /15) X rho / 2
Ai=W^2 / (Q^2 X S^2 X pi X e)
where rho=.00237689; W=weight, lb; S=span, ft.; e, Oswald efficiency,=0.81 for typical RV wingtips.
Note that neither wing area nor aspect ratio are in the formula. I first became aware of the higher RV induced drag when I had Jim Smith do tests with the Elippse prop that I loaned him. I saw that his speed dropped off much faster with altitude than does my own plane. With his it was about 1.1%/1000', whereas on my plane it runs about 0.6%/1000'; that's quite a difference, 83% greater! I was curious why this was taking place and as soon as I did the math the induced drag reared its ugly head. That is why I recommended to Jim that he make the triangular tips to use whenever he went on a long x-country at high dalt and weight. I also told him that if he was to compete in the SARL races at low altitude to minimize wing area by using very short tips, such as has been tested by Bob Axsom. As you point out, at low altitude induced drag is minimal when running full out. However, it does show up again in slow flight or takeoff and landing.
And sorry, Bob, I don't have those numbers as Jim, because of rainy weather soaking his field, hasn't been able to do a full series of TAS vs dalt. As far as takeoff and landing speed, Jim noted that he got back the shorter take-off run on his grass field that he lost due to his three-blade Elippse prop that has lower static and low-speed thrust during the initial part of the take-off run. So that part of it is purely subjective.

rvmills said:

...There's a gent up in Canada that is contemplating a blended winglet for small GA airplanes...

Click to expand...

My understanding is that "Blended Winglet" is a trademarked term used by Aviation Partners to refer to their patented technology for smoothly lofting the transitional area between the wing and the winglet blade.

Minix at Oshkosh

Did anyone see these at Oshkosh......... more importantly did anyone but them and fit them.

Apparently the designer has done testing with them on an RV4 and 7 and claims significant improvements. I have been to his website but its not well structured and difficult to find specific information about the performance on RVs.