Winglets ? (moved)

Discussion in 'Scratchbuilding!' started by lucyf-18, Feb 1, 2010.

  1. lucyf-18

    lucyf-18 Rookie

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    Anyone think that winglets would make a difference? Or maybe just look cool.
    [​IMG]
     
  2. Dredogol

    Dredogol M0DERATOR - (aka "Dred")

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    There's actually a purpose to those winglets. :)

    Without them, wingtip vortices cause unnecessary drag and reduced wingtip performance (quicker wingtip stalling)
    With them, you redirect the wingtip vortices to be more "efficient" and allow better aileron control (less wingtip stalling)

    Sorry for the bad wording... :p
     
  3. Aviation nerd

    Aviation nerd Rookie

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    yup, he is right, i usually put winglets on my planes for that reason, in a better wording they provide more lift with a smaller wing and longer flight times because of their efficiancy.they also increase yaw stability. i even put winglets on my wild hawk! :D
     
  4. D_Thissen

    D_Thissen Rookie

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    yup they look cool too!:cool:
     
  5. PecanGrower

    PecanGrower Rookie

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    I'll throw my 2 cents in again.

    Short answer: I think winglets will decrease the performance of most conventional RC airplanes (ie. not flying wings, or large delta wings).

    Long answer: The advantages of winglets are noted in the previous posts. The issue is that winglets like the one in your picture are much more aerodynamically complicated than they look. There is a very complex relationship between the efficiency you gain by reducing tip vortices, and the efficiency you lose from parasitic drag.

    Take a look at these two modern Cessna aircraft.

    [​IMG]

    [​IMG]

    Why didn't Cessna put winglets on them? Are they not smart enough to know that winglets will make the plane more efficient?

    Don't count on Cessna's lack of engineering for multi-million dollar aircraft. The most likely reason is that winglets are not practical for this application. When someone buys a corporate jet, fuel usage can be a significant consideration. If Cessna could significantly increase the fuel efficiency by putting simple winglets on that Citation X, they would.

    Now look at this new composite aircraft from Cessna.

    [​IMG]

    It has winglets, kinda sorta, but they aren't just two vertical pieces of wing. They are precisely shaped (and very small) to improve the flight characteristics of this airplane.

    If you just cut some foam and glue it to your wingtip, I would expect you to actually decrease your performance 99 out 100 trials. It's possible that even that is overly optimistic.

    Bottom line that I'm trying to get across: Don't think that winglet design is simple just because it looks like a simple addition on large jet aircraft.
     
  6. D_Thissen

    D_Thissen Rookie

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    exactly, some aircraft will benefit from winglets, some dont. there are many different factors to consider, such as the wing design, the application for the aircraft (heavy lifting, cruising, etc)
     
  7. Cabledawg1

    Cabledawg1 Cadet

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    I allwayd wondered why some planes have it and some dont...much like I wonder why some planes have stall fences and some dont. I have noticed that planes that are more manuverable seem to have stall fences. But then again, commercial airliners have them as well.

    [​IMG]

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  8. D_Thissen

    D_Thissen Rookie

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    the vortex generators/stall strips help produce lift by not allowing the air to flow outward from wing root to wing tip. they force the air to stay attached to the wing in a laminar flow. They are usually attached on the wing where the air flow seperates from the wing and forces the air to flow over the wing. they are not installed on all aircraft for various reasons such as cost to develope, how much they affect the plane, or in other cases just there is no demand for them
     
  9. XSrcing

    XSrcing Rookie

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    This sounds like it would be a fun experiment. Try different designs of winglets on a shortened wing, and add stall fences along different sections.
     
  10. all4smallrc

    all4smallrc Airman

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    I wonder what vortex generators would do on an RC? I suppose the effort probably wouldn't be worth it though. Still, it would be interesting if someone tried it.
     
  11. Dredogol

    Dredogol M0DERATOR - (aka "Dred")

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    You have to be careful HOW you make them / put them on.

    They must be smooth and "curved" at the wingtips. If it is 90-degrees (perpendicular) you won't get the full benefits.
    Also, if they are too tall and the wingtips are too narrow, you'll have wingtip bending due to lack of reinforcement at the tips.

    Sure, this tech stuff won't KILL your plane, and the effects are minor.
    But... just some info you should know. :)
     
  12. XSrcing

    XSrcing Rookie

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  13. flycap93

    flycap93 Rookie

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    Could someone post some pictures of THEIR rc plane with winglets on it. Aviation nerd could you post some of your wildhawk winglets?:cool:


    Secondly, i have a cessna and i want it to be more stable at slower speeds, should i put vortex gen. or wing fence. I would really like to fly more stable at much slower speeds, so how would i go about doing it.
     
  14. all4smallrc

    all4smallrc Airman

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    Here's one I did. They didn't work very well though. Like some of you have said, I think mine is a case where they actually added more drag! I couldn't even get the thing to stay in the air for more than 30sec. I previously built a smaller one with just dihedral and no curved wingtips (see third pic) and it was FAST! I could fly that one on half throttle and it had roughly the same thrust/weight ratio as the larger one!
     

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  15. Cabledawg1

    Cabledawg1 Cadet

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    allforsmallrc, Im not sure if your model classifies as winglets. When I think of winglets, it looks something like a near vertical surface.
    [​IMG]
     
  16. ScottLott

    ScottLott Administrator

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    Winglets are NOT vertical stabilizers, as you mentioned CableDawg.
    [​IMG]
    The purpose of the "winglets" on designs like that are alot more about having a vertical stabilizer and alot less about creating and controlling lift. So in truth, I'm not sure those can even be considered winglets, but simply vertical stabilizers.

    FlyCap, if you want more control of your cessna at lower speeds get a digital radio like the DX6i and mix in "spoilerons". The spoilerons keep your control surfaces from stalling out at lower speeds by aligning with the airflow. This will be MUCH more effective than figuring out the physics of winglets. :)
     
  17. Cabledawg1

    Cabledawg1 Cadet

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    Scott, I never called winglets vertical stabilizers. I was just saying that the model in all4smallrc's picture did not look like winglets. The end of his wings dont have that typical vertical surface like you would normally see on a winglet.
     
  18. Sonicjet

    Sonicjet Rookie

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    Wow,Scott,that looks like a ton of work in that plane!
     
  19. all4smallrc

    all4smallrc Airman

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    But the plane in the picture you posted has wingtip vertical stabs. Those are not winglets. I suppose you could say that my plane has an extreme amount of tip dihedral, but they are pretty close to being able to be qualified as winglets. I do understand your point that winglets generally stick straight up and mine don't.
     
  20. flycap93

    flycap93 Rookie

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    Thanks scott i have a JR radio with mixing. So do I mix spolierons with elevator to counteract the pitching of the aircraft. I have the DYNAM CESSNA like Dave.:confused:
     
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