RCU Review: Balancing Upside Down!

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    Contributed by: Mike Buzzeo | Published: November 2005 | Views: 35787 | email icon Email this Article | PDFpdf icon

    "How To" Article by Mike Buzzeo (MinnFlyer) Email Me

    It seems that lately we have been getting a lot of questions asking if it is correct to balance a low wing plane upside-down. The simple answer to this is "Yes", but a more accurate answer would be "Usually, but not necessarily always". Once you understand the basic principle, you'll easily see why.

    Imagine that the image below is a wooden plank with two Pegs in it (One Red and one Green). If you were going to lift the plank by the Pegs, would you lift it from Peg "A" or "B"?

    The obvious answer is to lift it from Peg "A", because if you tried to lift it from Peg "B" it would probably rotate 180 degrees due to the fact that all of the weight is above the pivot point.

    Now, let's change the shape of those pegs to an airfoil shape. It's easy to see that the same rule applies. So in this case, you would still balance it by lifting at Peg "A" (Fig 1).

    But now, let's suppose that you decided to flip the plank upside down (Fig 2). In this case, you would now balance it from Peg "B" since the majority of the weight is below it.

    The next obvious conclusion that can be drawn is that in either case, the lower peg is not needed.

    Now if we just modify the graphics a bit, you can see why it is easier to balance a Low-Wing Plane Upside Down.

    Now let's look at when you CAN balance a Low-Wing Plane Right-Side-Up

    Now that you understand that it is easier to balance a plane when the Center Of Weight is below the point from which you are balancing it, you should be able to see that if a Low-Wing Plane has enough Dihedral, the Center Of Weight will be BELOW the wingtips. Therefore, on some models you CAN balance the plane Right-Side-Up if you balance at the Wingtips instead of next to the Fuselage.

    So the next time you're not sure which way is "Up", just think about these Illustrations. Good Luck!

    Comments on RCU Review: Balancing Upside Down!

    Posted by: koolkrabber47 on 11/19/2009
    that was a great example....it was very easy to understand.....can you please post a "how to" on lateral balaning???....side to side balancing, especially for a mid-wing 3d plane???....koolkrabber47....
    Posted by: MinnFlyer on 11/19/2009
    Already did: http://www.rcuniverse.com/magazine/article_display.cfm?article_id=84
    Page: 1


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