Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

patriot xl flap?

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Old 11-15-2004, 11:02 AM
  #1  
speedy1379
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Default patriot xl flap?

To flap or not to flap? That is the ?.

Any pros or cons to putting them on this bird?
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Old 11-15-2004, 12:15 PM
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bob27s
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Default RE: patriot xl flap?

From what I understand from folks, its worth installing them and using them.

Also.... for what its worth.....
Do not consider using mixed flapperons instead of the inboard flaps. From my experience trying this with the .40 size, its probably not a good idea

Bob
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Old 11-15-2004, 12:25 PM
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IFlySlowPlanes
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Default RE: patriot xl flap?

Any particular reason flaperons are a bad idea with this design? It seems to me that aerodynamically it shouldn't make too much of a diference either way (other than the flaperons option would theoretically slow down the plane even more because more of the wing would (I assume) be affected). I'm not being disrespectful....I really do want to understand since I'd like to build a Patriot XL over the winter. Thanks!
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Old 11-15-2004, 01:02 PM
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Default RE: patriot xl flap?

IFly......
no problem ..... its fairly simple.

The ailerons on the Patriot extend pretty much full span out toward the wing tips.

Deflecting the ailerons downward as they would be for flaps.......creates "wash in" out near the tip. Makes the wing very vulnerable to a tip stall. If anything, you want wash-out when flying at high alpha, low and slow. Flapperons create the opposite condition.

Making it worse, using flapperons, the plane will gladly ablidge you by slowing nicely so that tip stall can occure without warning on landing approach about the time you attempt to bring the nose up for a flair. I found the 40 size patriot landed much better without any flap effect. With the flapperons down, the landing angle could be steeper, but the landing speed had to be increased to prevent the tip stall. Ended up not a good trade-off.

Others may have had different experiences. These were mine.

On the big XL, since it includes inboard flaps, I might be tempted to set up a "crow" landing setup. Flaps way down, ailerons slightly up for landing (radio permitting) creating additional wash-out effect. In the past, this has provide some very nice nose-high landing ability on some of my other aircraft.

There are some full scale aircraft that do use full length TE flaps or flapperons..... but their design tends to change the airfoil/wing shape and camber so that they create the additional lift while retaining the handling qualties at high angles of attack.
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Old 11-15-2004, 01:04 PM
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Default RE: patriot xl flap?

I toyed with the idea of either using flaperons on my .40 sized patriot..however I think im going for inboard flaps operated via torque rods, and have the aileron servos in the wing. The flaps will be the same width as the aileron.... this sound ok??


Cheers
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Old 11-15-2004, 11:24 PM
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Flyboy Dave
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Default RE: patriot xl flap?

I have a plane with "crow", an Ultra Stick 40....forget about crow. Especially
with the Pat XL. When you are in crow, you lose almost all aileron action....
because they are up, and the flaps are down. Also you have mucho drag
because the flaps are way down....the plane sinks like a rock, and you have
no aileron control....all you have left is the rudder. [X(]

With the rudder, you can change the direction of flight somewhat, but it's still
sinking like a rock, with no ailerons....not a good idea.

However, with conventional flaps....we can slow the plane down, and still have
full aileron control....a good idea. Remember to set the flap/elevator trim. When
you hit the switch for full flaps, the plane will shoot straight up because of all
the extra lift, so the automatic elevator down trim will compensate for that.

Now, with a couple clicks of throttle on final approach to compensate for the extra
drag....we can slow her down, and grease her right in.

FBD.
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Old 11-16-2004, 10:11 AM
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Default RE: patriot xl flap?

You don't want a serious crow 'brake' mode like on a glider or as described on the ultra-stick instructions. As noted, the idea of that configuration is to make the plane fall from the sky..... kill all lift.

I set the plane for 50 deg down flaps, and about 2 or 3 deg up ailerons. Provides a slight reflex to the tip airfoil making it better behaved at higher angle of attack with slower airspeed. It in no way hinders aileron control, and if done right improves slow speed handling. Just helps makes the plane fly rock solid right to touchdown. (especially helpful for high wing loading). You will find that some of the ducted fan/turbine guys configure like this for landing.

However, on the XL, you probably won't need the reflex....... having the seperate inboard flaps is adquate. Setting up a 40 size patriot with inboard flaps would be nice. Although, Im not entirely sure its worth the weight and complexity. The plane flys and lands pretty well as is.
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