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Flapper What?


Flapper What?

Solo RTW racer (and former acrobatic pilot and flight instructor) Brad Van Liew sent us a little primer on wing terminology after he heard Clean refer to the trailing bits of the wing as ‘flaps.’ He writes:

There are a few mass-produced airplanes with things called ‘flaperons.’ In fact, if you are sitting on an Airbus 300 series as you fly home from San Diego it has them.  The control surface all the way at the end of the wing is the aileron and they go up and down like BMWO’s thingies.   On a plane, one aileron goes down to create more lift at the end of the wing and the other side aileron simultaneously displaces up to create drag and decrease lift which banks the plane into a turn.  Flaps only go down in slow flight conditions to increase lift and create drag to help manage speed.  They are closer to the fuselage and used halfway down for takeoff to add lift with minimal drag increase, and then on landing they are used all the way down to increase lift but also create big drag to help keep speed down while descending for landing.

So now the terminology debate evolves. The wing thing has a series of sort of ailerons cuz they displace both ways to increase the camber or “roundness” (and therefore lift) of the wing in either direction and the idea is not to create big increases of drag like a flap for landing.  But in many ways they are flaps too, at least in the sense that flaps are used for increased lift at takeoff.  So back to the Airbus, when you take off or land and look out the window to the aileron at the end of the wing, you’ll notice that it’s drooped around 30 degrees from its normal straight back position.  They both droop the same amount when the flaps are set to half flap down or more, which helps the flaps increase the overall lift of the wing. 

To me, the BMW wing control surface at the trailing edge would best be called flaperons, because they function as part lift-increasing device and part bi directional trim device, swinging both ways like ailerons.  To complicate things a bit more, there is one other type of flaperon that turns the plane simply by creating more drag on one side of the plane, essentially dragging it into a turn, but that description would not necessarily apply to this scenario.  

Ok so do with all this whatever you want – this is the super-simple Aerodynamics 101 version (it’s the old flight instructor in me) but at least when some geek private pilot that thinks he can dog fight Chuck Yeager to the dirt and knows basic aerodynamics which is about half covered in this email you can talk the talk.  The problem comes when Dirk Kramers tears the words apart –  which he won’t because he’s too nice a guy! But before you’re too sure that BMW will face a soft-sail opponent, remember that Dirk proudly wears an Alinghi logo, and last time I was in his garage I saw one of coolest wing-masted cats in the universe…

Nonetheless, there are a lot of minds turning on how to broaden the use of wing technology on the water now that we’re seeing what a nearly unlimited R&D program can come up with.  From my understanding, this is a very new take on wings with real applications.  The little cats are cool, but I never thought they could translate to this scale,  and with my limited knowledge of the wing DC used on Stars & Stripes, this is a whole new level that could be used in significantly more variable conditions.  Like offshore racing once someone figures out how to trim to neutral or reef it!

Check out more wing info in a great interview with wing designer Dimitri Despierres on Anarchist "Tribormat’s" blog.