You're putting a huge air dam under the plane. This is essentially the same as a gurney flap on the back of a stock car. While the flap itself isn't making downforce on the car, it's making the air under the wing, and quite a distance out to either side of the flap pack up, and provide greater differential pressure.
I wonder if the optimum position for a belly board is further back than where a flap would normally hinge. On Mon, Sep 15, 2014 at 12:40 PM, Mark Langford via KRnet < krnet at list.krnet.org> wrote: > Jeff Scott wrote: > > " A belly board generates lots of drag, but not lift" > > I thought this also, "common knowledge", I believe, and it may not be true > "lift" that the belly board generates, but something makes drops the stall > speed about 3 mph. I proved this a few weeks ago while calibrating my > stall > speed on a very calm morning with board up and board down. I did about > five > tests, and four yielded 3 mph, and one showed 2 mph. Maybe it's just a > "lift vector"...a reaction created by simply meeting the oncoming air at an > angle, or perhaps it changes AOA of the tail or whole airplane to lower > drag, but whatever it is, it unloads the wing enough to drop the stall > speed. I was surprised, but that's what the testing shows. It's also > interesting that your flaps are on par with the belly board regarding stall > speed improvement. > > To answer somebody else's question, it probably takes two to three times > the > effort to integrate the short "stock" flaps into the stub wings on a new > build as opposed to installing a belly board, but that factor could climb > dramatically if you're talking paint repair on an existing plane. > > Mark Langford, Harvest, AL > ML at N56ML.com > www.N56ML.com > > > > > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options >
