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Old Nov 01, 2012, 08:23 PM
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For every plane I have used Flaperons on, they pitch nose DOWN... thus need up elevator to offset that.
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Old Nov 01, 2012, 08:24 PM
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Originally Posted by Maxthrottle View Post
Oh boy! Here we go!
Flapperons...not needed, sorry Max couldnt help it . Im staying outta this discussion.
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Old Nov 01, 2012, 08:32 PM
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Originally Posted by Whiskey Whiskey View Post
LOL, you guys are hurting my head...

For my landing mix with flaps deployed, do I need to program in down eleveator or up elevator?

A majority of my flap experience, with gliders, has been down elevator...
Taileron Pitch up input. Glider need more down to counter the stab angle and fight the wings/flaps lift.

How much pitch up depends on your entry speed and deployment which is why there isn't a straight do this much answer cause I can't describe [re stall speed; I can only visualize it and work back my settings from there.

The flapperons are so close to neutral that at higher speed they create more down pitch but lift the model. At slower approach speeds its very little pitch moment acting more as drag and lift needing less pitch up input but remains necessary to hold the wing at a slight AoA. And this is where it again differs from a glider because you then hold that attitude but feather your throttle to control decent with only very little pitch input unless something goes awry.

I'm still working on the setting so nothing to share.
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Old Nov 01, 2012, 08:42 PM
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Huh? I never said they don't work... I said they DO. And they cause a pitch change, which is enough to be a nuisance.
Flaps are.... can be... quite different.....

Ailerons can only move some smallish angle (typically to 45deg max, if that), so they become a 'camber changing' device - mainly when in the downwards direction - in the upwards direction they become more of just an 'airflow killer', a spoileron, and also just pure airflow deflection 'upwards' = pressure downwards (not due to 'inverse lift' - like a flaperon did create more real Bernoulli based lift).

But flaps can move to a much larger angle, so when they go down, they crossover from a 'camber device' to an 'airflow killer, airbrake device', which also increases lift purely due the massive face they present to the airflow and thus they have large upwards direction force vectors then. And in all cases I have used them, large angles give the air braking, extra lift and MINOR (or no) pitch change by that angle. Though you would think they should also affect pitch, but something in the combination of factors means they don't.
eg P-51's (many/most warbirds) at 80deg landing flap angles, even Jumbo jets etc.

So as long as you make flaps that can go past the flaperon/'camber device' sort of angle (60deg+) (whilst those lower angles, and their resultant behaviours, are more useful for take-off), you will get that nice combination of effective lift increase (via "flat plane high AoA" resultant), drag increase, little to no pitch change.
But you had to pass through the lower angle ranges, and their more pronounced pitch change, to get to the high angle. Well, maybe not if you have 'instant reaction' switched servo channel.
I always use approx 6 seconds travel time to full flaps, and that is so slow that you auto-correct the short period of pitch change the lower angles present and then it is all back to 'normal' flight once they cross out of the 'camber device' range.

There is a weird (?) mixture of "real lift" (Bernoulli) and "a high AoA face" that occurs in wings and the overall shapes control surfaces can make in total out of them. eg you can make a plain flat (zero camber) wing and a plane will still "fly".... it will run almost purely off the "High AoA face" form of lift creation. Just like your hand makes your arm 'fly' (up, or down even) if you stick it out the window of a moving car. All you need is airspeed and a flat plane for a wing...

But anyway.... Su-35's don't have flaps......
Though if you could get the ailerons down to 60deg+ they would behave like them, and a nicer landing result.
I haven't checked, but it is probably not physically impossible to have them do that.... but it is such a docile landing plane anyway, there is no need for flaps OR flaperon/spoilerons. (I guess you might be landing on an aircraft carrier sometimes.)
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Old Nov 01, 2012, 08:42 PM
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Originally Posted by v8truckin View Post
Flapperons...not needed, sorry Max couldnt help it . Im staying outta this discussion.
I know bullets flying everywhere. We had a nice discussion in the Jet talk forum on flapperons or spoilerons. They don't work on all models because models usually deviate for scale or are not scale to begin with or were never designed for flapperons, just flaps.

I should add for WW not to attempt this if you don't have roll control in the tail. That is tail stabs as tailerons roll and pitch not just as it comes factory as stabilators pitch only.

I'm gonna stay out of this conversation myself. Even when the question is not should I or shouldn't I, there are so many who have this blanket it'll never work rule from using it on bad examples or setting it up incorrectly. I start asking such, then why does it work for the turbine guys flying scale models.

Oh good night Pete. You are going into one of those holes again that in short is explained in that it does work. All the issues you described are overcome and apply from FS to model. So little point in discussing your grappling with the subject.
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Old Nov 01, 2012, 08:48 PM
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Flap trim change is affected by two primary influences - the change in moment of the main airfoil (called the elevon effect around here), and the change in downwash impinging on the tailplane.

Purely considering lowering flap. Raising crow is simply the opposite.

Flap goes down, the main wing now has a (more) nose-down pitching moment. This is due to the elevon-type influence. I think most people understand this one. This requires back-stick to counter.

The other influence is a bit harder to understand, therefore less talked about.
The main wing creates downwash, so the tailplane is always in a slightly downward flow (compared to the freestream). If you lower flap, the amount of downwash is increased - that's a result of the extra lift (or the cause, take your pick). That means the tailplane now has more of a downward flow on it. The extra angle of attack on the tailplane means it produces a stronger tail down force, so pitches the nose up.

There is no hard and fast as to which influence wins. Some planes pitch up, some down.
Some become more stable with flap, some less. The hows and whys have caused some serious crew room discussion in the past, with no hard and fast answers!

Try it, and let us know. I'd love a bit of flap down for takeoff, and negative flap for stupid high alpha stuff

Edit: Oh, and Su35 does have flap.
Video:
Su-35 Crazy landing (0 min 22 sec)
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Old Nov 01, 2012, 08:50 PM
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I guess I won't be maidening this weekend. I plugged in the battery and one of BECs smoked... Look familiar?
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Old Nov 01, 2012, 08:51 PM
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I wonder why the real ones don't have flaps? Or do they?
F-22's do I am pretty sure.... flaps/elevons.
FBW could probably control TV and surfaces effectively enough to create a very slow landing speed anyway I guess(?).

Now that I think about it I MUST have pitch change at full flaps, but it is probably quite a bit less than at half flaps (for eg) and seeing it is all done slowly (6 seconds) your real-time adjustments to offset it are not noticeable.
Less pitch effect at large flap angles because, for eg, a 90deg face would give very little upwards force vectors, almost all horizontal force vector by then, but a 45deg face would be near the peak amount of upwards force vector you would pass through.
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Old Nov 01, 2012, 08:56 PM
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Crazy because it flew towards the crowd?
Or just unconventional in safety leeway terms - not of the crowd, but just the fact that a banking landing is much more demanding and risky than straight in.
Aeromodellers do that sort of stuff quite often !! LOL

Oh, they have flaps??? Well then I will have to add some.....
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Old Nov 01, 2012, 08:56 PM
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Originally Posted by Whiskey Whiskey View Post
I guess I won't be maidening this weekend. I plugged in the battery and one of BECs smoked... Look familiar?
Ouch! thats why i always pull the stock esc's if a kit isnt available. Although I think Max had a aftermarket hobbywing esc fail on his bench??? I could only imagine it happening in flight
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Old Nov 01, 2012, 09:03 PM
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Pete don't engage brain here. Just look at the landing pic and accept whats happening.

Note there isn't always a pronounced pitch up angle because the approach speeds are different in each photo.

No need to think angles that the flapperons are never deployed to etc etc
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Old Nov 01, 2012, 09:08 PM
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Fred, I might have explained myself badly...

Of course the F4C Yak was fiberglass, for somehing it weighed 25kg and used a Kerosene turbine...

I just mean this foam ultradetailed YAK is modeled after that one using the experience and effort set into the big one thanks to Vitaliy Robertus' Team.

Ehr, Max, did you just say Su-39?



Cheers!
Jandro.
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Old Nov 01, 2012, 09:14 PM
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Originally Posted by v8truckin View Post
Ouch! thats why i always pull the stock esc's if a kit isnt available. Although I think Max had a aftermarket hobbywing esc fail on his bench??? I could only imagine it happening in flight
That was my stupid that caused it and the becs weren't in use. I tend to pull the FW ESCs out and used them on a less demanding model like a prop job. But its getting such that it makes you start to wonder if they did some changes from their ESC supplier.

Two Euros recently went down in similar fashion, only it happened with them in the air. Total loss.
And with all of these BECs in parallel failing.... makes me wonder...

New ESCs and a external BEC.
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Old Nov 01, 2012, 09:20 PM
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Ehr, Max, did you just say Su-39?
Yes. What does everyone have against the Frog foot . Yak used a lot of its design in the 130. It was a great little close support attack aircraft. Didn't loiter like the A-10 but is was RUs counter part which was more closely based of the A-10 Fairchild competitor.
You're just stringing me along here right
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Old Nov 01, 2012, 09:23 PM
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Originally Posted by Maxthrottle View Post
That was my stupid that caused it and the becs weren't in use. I tend to pull the FW ESCs out and used them on a less demanding model like a prop job. But its getting such that it makes you start to wonder if they did some changes from their ESC supplier.

Two Euros recently went down in similar fashion, only it happened with them in the air. Total loss.
And with all of these BECs in parallel failing.... makes me wonder...

New ESCs and a external BEC.
lol! back to the olden days of the thread. Why i always frowned at the use of 2 internal bec on the esc's.

I do the same with the pulled stock esc's save em for a lesser model.
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