The difference between winglets and higher a/r

[stanislavz]

Simple question. Two planforms. One - square wing, area 8m2 1m chord with winglets, and other one is 9 m2, but 20% of span is tapered. Like Strojnik wings or w10 Tailwind. Total weigh or area is similar.

But - will wing with winglets will be less sensite to air turbulences ? And be more structural efficient ? . In simplifacation I see a winglet as a way to make us close to infinite a/r ?

 

[wsimpso1]

Sat through a presentation by Barnaby Wainfan at OSH where the takeaways I got were:

• A well designed and executed winglet is the same as more span to efficiency/altitude performance and to loads in the structure;
• If you can fit more span in your hangar and on your ramp, you are still in design phase, and you want more efficiency/climb/altitude capability, just go with more span.
• Do know that adding properly designed winglets, no matter their length or angle, are the same to structural loads - the wings are loaded as if the span were bigger. You can safely add winglets only if you can safely at span...
• The reason some jetliner designs use winglets is more span won't fit within infrastructure, but winglets will.

Going a little deeper, this engineer knows that wing extensions beyond the ailerons reduces roll control effectiveness. I suspect same is true with wing tip extensions that go up too. Who wants less effective ailerons?

If we want the climb, altitude, and efficiency benefits, and can fit it physically and structurally, this engineer thinks we can make a better airplane by making the span bigger and carry ailerons out until you have to end them because you are in the contour of your chosen wing tip shape.

Billski

 

[stanislavz]

Sat through a presentation by Barnaby Wainfan at OSH where the takeaways I got were:

• A well designed and executed winglet is the same as more span to efficiency/altitude performance and to loads in the structure;
• If you can fit more span in your hangar and on your ramp, you are still in design phase, and you want more efficiency/climb/altitude capability, just go with more span.
• Do know that adding properly designed winglets, no matter their length or angle, are the same to structural loads - the wings are loaded as if the span were bigger. You can safely add winglets only if you can safely at span...
• The reason some jetliner designs use winglets is more span won't fit within infrastructure, but winglets will.

Going a little deeper, this engineer knows that wing extensions beyond the ailerons reduces roll control effectiveness. I suspect same is true with wing tip extensions that go up too. Who wants less effective ailerons?

If we want the climb, altitude, and efficiency benefits, and can fit it physically and structurally, this engineer thinks we can make a better airplane by making the span bigger and carry ailerons out until you have to end them because you are in the contour of your chosen wing tip shape.

Billski

Agree and thank you. One small remark - will gust load see more wing-span, but will ignore winglets ?

 

[blane.c]

Sat through a presentation by Barnaby Wainfan at OSH where the takeaways I got were:

• A well designed and executed winglet is the same as more span to efficiency/altitude performance and to loads in the structure;
• If you can fit more span in your hangar and on your ramp, you are still in design phase, and you want more efficiency/climb/altitude capability, just go with more span.
• Do know that adding properly designed winglets, no matter their length or angle, are the same to structural loads - the wings are loaded as if the span were bigger. You can safely add winglets only if you can safely at span...
• The reason some jetliner designs use winglets is more span won't fit within infrastructure, but winglets will.

Going a little deeper, this engineer knows that wing extensions beyond the ailerons reduces roll control effectiveness. I suspect same is true with wing tip extensions that go up too. Who wants less effective ailerons?

If we want the climb, altitude, and efficiency benefits, and can fit it physically and structurally, this engineer thinks we can make a better airplane by making the span bigger and carry ailerons out until you have to end them because you are in the contour of your chosen wing tip shape.

Billski

Any thoughts on ailerons on the winglets like these? Nenadović biplane

 

[Jay Kempf]

There is no general winglet design that can be applied to a random wing. First you need aspect ratio to exploit so a Hershey bar at AR5 is not going to see any benefit. Before winglets multi-taper spans with some sweep leading into the wingtip were all the rage. Winglets build on that sort of worrying about efficiency. If you are using HP to get your efficiency then a winglet isn't going to help.

Second, there are winglets and then there are winglets. An airliners winglet has only one purpose at only one point in the performance envelope and that is at best fuel efficiency cruise at max cargo load. Any other design point and they aren't helping. Certainly span and gate spacing is a factor.

For gliders you have two design points where they have to work and you hope to have them working through all the speeds between these two points if you're good. First is just above stall with some camber changing flaps engaged. And I mean just above stall. Ailerons need to work and the winglets need to be helping you get the best L/D you can at that slow speed. The other speed is your fast cruise between lift. There you want the winglets to either disappear or reduce induced drag as much as is possible. So sweep and twist and base incidence in the two configurations have to be taken into account so that the AOA in both is what it needs to be to accomplish the goal of drag reduction. That is a level that no one should ever try to go to trying to clean up a Thorp T-18 for best cruise fuel efficiency as the gains are non-existent.

Winglet design isn't trivial AT ALL. Rearranging a planform is way more low hanging fruit. Careful twist management is even lower hanging fruit.

 

[BBerson]

If you have significant sweep then winglets serve double function adding vertical stabilizer area.
When Burt gave up sweep did he give up on winglets?

 

[wsimpso1]

Burt Rutan's swept wings had vertical stabilizers on the end of them. They had to go someplace, might as well help with 8nduced drag. Most of these designs had a rudder in them too, but the Defiant did not.

 

[Jay Kempf]

Any thoughts on ailerons on the winglets like these? Nenadović biplane

Thoughts? Yeah, box wings are mostly terrible ideas. The idea is there is some structural and configuration advantage. But the drag side is mostly horrible. Biplanes are mostly horrible when it comes to drag.

Why is Lionheart so fast compared to other biplanes...?

 

[wsimpso1]

Thoughts? Yeah, box wings are mostly terrible ideas. The idea is there is some structural and configuration advantage. But the drag side is mostly horrible. Biplanes are mostly horrible when it comes to drag.

Why is Lionheart so fast compared to other biplanes...?

No struts and no wires and enough stagger to keep the wings out of each other’s way aerodynamically.

 

[Jay Kempf]

Exactly, a box wing wasn't on the list of optimization choices...

 

[fly2kads]

Winglet design isn't trivial AT ALL.

I have a couple of winglet design papers by Dr. Mark D. Maughmer and one of his grad students. They make very clear that it's really easy to make things worse with a poorly designed winglet.

 

[Peterfyg]

In sailplanes winglets are held too improve aileron response, putting it crudely acting as fences limitin transverse flow across the outer end of the ailerons. Tip extensions often make things worse. This may not be as significant at lower aspect ratios. Sailplane winglet design is clearly complex, on roughl ,3rd generation now

 

[WonderousMountain]

Simple question, - will wing with winglets will be less sensite to air turbulences ? And be more structural efficient ?

First answer, It depends?
Okay so I don't really know, having an extra 1/8th to react air currents might be noticeable. On the other hand having vert surface could add drift and affect holding heading slightly.

More efficient, let's cover that.

Sooo... Short span -stubby- aircraft do benefit from tip fences,
the better direction for a winglet is down, but that goes against ground clearance, also, the more complex structures are rarely built & wouldn't be expected on a homebuilt plane. Compared to our Strojnik example I doubt you will have appreciable gains; outboard taper is more effective than AR alone, efficiency @AoA increase, during takeoff banking or low cruise manueving is worse for no taper.

However, take note, at fast cruise, A.K.A normal sport plane operating range with lift coefficient 1/4 or less parasite drag, surface friction dominates and drag due to circulation is small fraction of F*D to maintain airspeed.

You did not specify winglet height, and taking the common build,
theory shows pretty good data for something like 1M verticals.
Flaps should not lose effectiveness, but the mass will take
effort to accelerate, which again, is not ideal in sport planes.

As far as structure goes, what I found in stubby, is that my
aerostructure was basically extended for the stablets, and
I would wager increasing area or span considerably easier
than using tip fences. Of course, vert surface was sought.

 

[blane.c]

Thoughts? Yeah, box wings are mostly terrible ideas. The idea is there is some structural and configuration advantage. But the drag side is mostly horrible. Biplanes are mostly horrible when it comes to drag.

Why is Lionheart so fast compared to other biplanes...?

What if speed isn't the goal? What if the aerodynamic efficiency you are striving for is lower, much lower airspeed? Say 120kph (75mph) VNE now you are talking a different kettle of fish aren't you? So a Nenadovic' (or I like to think Neanderthal) type of wing is more efficient to this flight regime than to faster flight? The Fieseler Storch and later Helio Courier Had leading edge slats, the early model Storch's had weird wing stalling problems about 120mph but later models and the Couriers fixed it by retracting the slats. It is likely that the Nenadovic' wing will have weird stalling problems at higher speeds? It is unlikely it will achieve these speeds except it is in a steep dive? Considering a low powered design.

There are a lot of compromises in aviation to consider.

But the ailerons on the (for sake of argument) winglets of the AS-37 seem to work according to a flight report and require little or no rudder input because of the angle in which the are affixed. So this seems a simple way to simplify adverse aileron yaw?

 

[Bille Floyd]

...
Before winglets multi-taper spans with some sweep leading into the wingtip were all the rage. Winglets build on that sort of worrying about efficiency.
...

Looks like the German designer of the Atos I have ; he
Incorporated all of that !!!

I'm going to get rid of the control frame, pilot, and wires
to get even more efficiency ; place the pilot in a clean pod.

What if speed isn't the goal? What if the aerodynamic efficiency you are striving for is lower, much lower airspeed?
...

Yes Blane , the VNE on this glider is under 60-mph ; so I believe
the designer, "Was" looking to max out efficiency with his design ?

Bille

 

[blane.c]

Has anybody tried the pod on a tether?

 

[Vigilant1]

General observations:
- "Winglets are hard to get right" agrees with all I've read.
- Winglets can add effective span and may be preferable if span is constrained (e. g. Gate spacing at airports)
- If the wings are to be removable or foldable, winglets will be a pain in the neck.
- Winglets could have marketing advantages ("cool," "advanced", "efficient"). Have a wind tunnel study ready for extra credit.

 

[User27]

General observations:
- Winglets can add effective span and may be preferable if span is constrained (e. g. Gate spacing at airports)

Also gliders are constrained by class rules (Standard, 15m, 18m, 20m) so winglets give increased effective span while remaining legal. Makes packing the wings into a trailer a real pain - many vertical parts have to be removable which just makes the tip manufacture more complicated.
I wonder if the tips on aircraft such as the Pioneer 400 are more for the marketing department than anything else?

 

[stanislavz]

Ok.. so back to some facts. Yes, it really look winglets are mo to be cool, than something that is right and easy to design. If you can afford extra span - just do it.

Top argument against winglet - if you have removable wings, it will be harder to handle them with winglets.

On glider thing - i did read, they got extra handicap point for having winglets ? Do the must be working for kind of span-enhacener.

 

[stanislavz]

And this one approach - vortex splitter ? Easy to do and test, and it works like virtual span extender, adding according yo one aerodynamist a one point to glide ratio for ga in sub 200 mph region.