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Old Oct 19, 2005, 08:12 AM
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Wing end plates

Does anyone know anything about wing end plates, their dimensions and their effect on a wing having an aspect ratio of 8?
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Old Oct 19, 2005, 11:05 AM
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Punta Gorda, FL
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The wing end plates have too much weight and drag is for most kinds of planes. With large end plates the weight and drag are very bad. With small end plates the weight and drag are small and less bad.

Use a tapered wing platform to keep the tips light and maneuverable in most planes. The end plates slow the roll rate. The tapered wing planform gives it a better strength to weight ratio. The mimimum drag wing comes from a elliptical lift distribution. See:
http://aero.stanford.edu/WingCalc.html

When the end plates distort the wing elliptical lift distribution and increase the basic wing drag plus the end plates drag themselves.
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Old Oct 19, 2005, 12:27 PM
Lift is cheap - Drag sucks
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Socorro, NM
Joined Jul 2004
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As Ollie points out tip plates are not considered a good general solution.

The question is - solution for what? If you want a compact airplane with an AR of 4:1 tip plates will reduce drag during take off landing and cruise. You might be better off to invest the weight and effort in increased span but if your goal is 'compact' then tip plates will work for you.

I'm not sure there is any advantage above 6:1 AR. Winglets work, but notice that they have a gentle transition to vertical in order to avoid hot spots.

The most practical coverage I have seen on the topic is Alex Strojnik "Laminar Aircraft Design". He has a web site. Strojnik also discusses straight line taper planforms that approximate an elipse.
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Old Oct 19, 2005, 11:33 PM
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The latest issue of Quiet Flyer magazine has a very interesting arcticle about winglets. The author is a respected airfoil designer and makes comparisons among several full-size sailplanes as well as models.

Keith
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Old Oct 20, 2005, 09:36 AM
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While I agree with everything said so far, in some most cases endplates actually increase aileron effectiveness. In some cases with very low AR wings, endplates increase L/D at high lift coefficients.

F-80's roll a lot nicer with tip tanks installed, and the effect is even better on T-33's with their permanently installed tip tanks. The increased aileron effectiveness more than makes up for the increased roll moment.

Tip tanks on an F-104 results in less E-bleed in hard turns and better control at low speeds. Even wingtip missiles have a small positive effect on the 104. The only good thing about clean wingtips on an F-104 is a slightly better acceleration rate.
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Old Oct 20, 2005, 10:31 AM
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Endplates and winglets are different animals.
Different purposes entirely.
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Old Oct 20, 2005, 01:29 PM
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Sparky paul

Could you please elaborate on the difference between end plates and winglets?
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Old Oct 20, 2005, 02:28 PM
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Endplates are a method of controlling flow on low-aspect ratio wings.
Winglets do something different on high aspect ratio wings by extending the span. They work best at a single speed.. on full-scales that's the cruise speed.
They don't add as much drag when off-point as endplates do for all points.
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Old Nov 06, 2005, 05:10 AM
717
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If you're talking end plates and winglets you're trying to reduce induced drag. Conversely, devices for accomplishing this increase parasite drag. 8:1 aspect ratio sounds like a glider-type aircraft.

Good info I found on this subject:

Reducing induced drag
Points of interest from this link:

- The most powerful design feature for reducing induced drag is a long wingspan.

- Long wingspans at low AOA and low altitudes increase parasite drag more then they offset induced drag.

- Small end plates installed on some aircraft are virtually useless. The tip-tanks installed on many planes do reduce induced drag one or two percent, but they increase the parasite drag much more than that.

- Winglets produce a forward thrust vector which offsets the induced drag vector.

- In summary, Winglets should only be installed on aircraft, which will routinely fly at high altitude and or large angles of attack (this fits the profile of a long range jet airliner, or a long range corporate jet, gliders, as well as high altitude spy planes such as the U2, but not most light aircraft.)
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Old Nov 06, 2005, 02:07 PM
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So. Cal.
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Thanks for the link.

I always wondered about drooped wingtips. I put some of them on my balsa slope gliders only because they looked better that way.

Dart
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Old Nov 17, 2005, 04:48 AM
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Quote:
Originally Posted by kamcoman
The latest issue of Quiet Flyer magazine has a very interesting arcticle about winglets. The author is a respected airfoil designer and makes comparisons among several full-size sailplanes as well as models.

Keith
I just read that article about WINGLETS. It is tricky business. The last paragraph is most relevant. It is a quote from the winglet expert Mark Maughmer, who says that it is easier to screw up the performance of a sailplane by adding winglets and the articles author adds that is truer for models.

The articles's author makes the ascertion throughout the article that there are several factors involved in the proper design of winglets, based on PSU research, and that low Re behavior is key to selecting an airfoil suited for winglets. You only want seperation to occur at the stall of the main wing or the advantage is lost. I would assume that since the reynolds at the tip for a model is going to be much lower than full scale, the airfoil would be very HLG like, since those airfoils are optimized for low Re, but his airfoil doesnt look HLG like. The airfoil the author uses on winglets on models looks alot like a cross between an RAF32 and an Eppler 387. He has used his winglet airfoil on the main wing as well.
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Old Nov 17, 2005, 09:24 AM
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"I just read that article about WINGLETS. It is tricky business. The last paragraph is most relevant. It is a quote from the winglet expert Mark Maughmer, who says that it is easier to screw up the performance of a sailplane by adding winglets and the articles author adds that is truer for models."

Well said, ElectoStorch!
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Old Nov 24, 2005, 12:15 AM
making it up as i go.
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Stillwater, Oklahoma, United States
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yea, winglets can work, if you run a full cfd solution.... electrostorch is right, you will screw up the flow if done improperly. winglets have the effect of adding 70% of their height to the span of the wing. this is obviously for reasonable heights. dont expect to put a foot tall winglet on there and have an 8 inch gain in span

endplates are pretty much the same thing, they are just there to distort the formation of vortices off the wing, neither should aerodynamically influence your roll rate much.... (unless your ailerons continue all the way to the tip, in which case it could make a VERY small difference) the addition of mass on the tips of your wing will have a greater influence on your rates. so if you do it... MAKE IT LIGHT

both methods are general techniques for increasing the span effeciency toward the tips of the wing. but if you want a more effecient wing.... just increase AR to get it, much less draggy.
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