Is snap-flap benefical in thermal style flying?

[Jurgen]

Under snap-flap I mean chamber is coming in when pulled UP, and visa versa.
I understand usage for distance, speed and F3F style turns.
But for the slower flying speeds in thermal style flying (where often the chambering is already present by switching to thermal mode) I ask if extra chamber by snap-flap mixing is still productive. Are we not getting "over-chambering" the moment we pull hard in the termal turn?
Or should the servo be max-limited to avoid the over chamber?
All info very welcome, Jurgen.

[infopimp]

Second hand from a seasoned slermal pilot I was fortunate to have lessons from: in really light conditions some planes work better with the center section aileron control off except for camber. Curious to hear what people say... and which models they are basing their opinions on... thanks. -Steve

[Tuomo]

Some use snap-flap, so do well without it.

I use a couple millimeters of snap-flap only in launch mode. I feel it helps "snappy" elevator response at the moment of release. Maybe it just takes some flex off from flaps and ailerons.

Personally I try to do my flying with as stable wing trailing edge as possible. I do not change camber that ofter. With Aspire I often fly the whole flight with neutral trailing edge. Changing camber changes elevator trim, causing the flight being not so smooth -- so why bother with camber chamges if airfoil has broad enough speed envelope?

The only exception to this are thermal turns is rough and windy conditions. Maybe there is something wrong my flying, but airpeed generally tends to decrease when I enter the downwind phase of the circle, and increses when heading to wind. know what I mean? Offcourse I try to avoid this sort of DS-phenomena, happening more strongly at lower altitudes, but it is not allways so easy...

Snap flap could be a help there: little more camber when pulling around the downwind arc of a thermal turn. But then again, if you circle correctly and with constant airspeed (or lift coefficient, to be exact), it can be done (and should be done) with constant camber.

My 2 cents :)

[ThermalBuster]

Some pilots swear by it, some swear at it. Personally, I have tried it on several occasions and have not found it to be a benefit. But it may be more a matter of flying style than an absolute rule. I camber with the left stick as necessary (and sometimes more than necessary =:-0 ) to keep the wing camber matched to my speed.

I wouldn't say that those who use it are wrong but I would say that if you are not sure that its right for you, it will not be of benefit.

Hope this helps.

[trend.ab]

Dr. Drela's setup for the Supra (see attached) includes 3mm snap-flap on top of 3mm camber in thermal mode.
I am using this on my Supra and a similar setup on my other TD ships. Flying a turn requires increased lift, which is provided by the increased camber. To my understanding, a wing with a variable camber airfoil works more efficiently this way.
I find this especially helpful in low level turns, where the planes just are less stall sensible with the snap-flap. I even do this on the DLGs.
I know several people who fly great without snap-flap, so I do not think it is THE deciding factor in plane setup.

Beat