Flap question

[IanN]

I haven't had a 'plane with flaps yet, but a couple of future builds I'm considering may need them.

 

Is a simple  "on-off" switch (Futaba 6EX / Spektrum DS6) adequate, or are there major benefits from a proportional rotary control knob?

[Former Member]

[This posting has been removed]

[David Davis]

I have flaps fitted to the "works" Telemaster 40.

 

When it was first flown with Richard Golding's Spektrum Dx7 transmitter we had the option of three flap settings. Now that it is controlled by my Dx6 it only has two options, up or down.

 

The three position option was preferable but a rotary control knob would give you an infinite number of settings.

 

Watch the stall on full flap and slow flight.

[David perry 1]

But no one has answered the original question: is an on/off two position setting adequate? The answer, IanN, is yes. It is adequate.

 

I assume you want flaps for landing (shorten the landing distance and steepen the glide path, so make the setting greater than about 40 degrees.  A spitfire had 90, many light planes have about 50 degrees.

 

If you want it simply for fun then make it ground adjustable and enjoy seeing what different settings do for you.

 

HTH

 

David 

[Marko]

Hi lan I've put my flaps on ch5 on my 6exa for my chippie it works fine "on /off they are only set to 33% l didn't like the dial wheel for the flaps all l can say is try and see what you like to suit you! Hope this helps ............. Mark

[David Turner 5]

Flaps should have two positions ... ON  and  OFF .

 

Just like throttles.

 

Can't think why we need all this proportional rubbish. Bring back the old "bang-bang" sets, I say.

[ntsmith]

Answer as you wanted. Short and sweet and not drawn out with too much verbosity or repetitiveness.

Yes

[Biggles' Elder Brother - Moderator]

I agree that on/off is adequete for most models. However,....flaps really have at least two different functions - and using them that way can be fun.

 

Ideally you should set a small amount of flap, about 10 degrees, for take-off - this increases the wing camber and gives you more lift at low speeds and so shortens the take-off run.

 

When landing the flaps can do something different. By deploying more flap, about 40-50 degrees, you don't so much increase the camber as increase the drag. This helps you to decend steeper without gaining loads of unwanted speed.

 

So ideally three settings would be best - 0, 10, 40. The problem is if the model is quite small you will not really get the benefit and so might just settle for a "one-size-fits-all" approach. And so On/Off is fine. But if the model is larger and/or faster you may well benefit from the two different deployed positions to perform the two different roles. If you have a three position switch on your tranny it might be good to set the flaps to zero, ten and forty degrees on that. You could experiment a bit with the exact settings.

 

So, I suppose my conclusion would be, on/off is fine, three position has the potential for more fun - and with a larger model may actually be useful, but fully propo is not needed at all in my view.

 

BEB

Edited By Biggles' Elder Brother on 14/06/2010 11:33:02

[David Turner 5]

Posted by David Turner 5 on 14/06/2010 10:58:01:

Flaps should have two positions ... ON  and  OFF .

 

Just like throttles.

 

Can't think why we need all this proportional rubbish. Bring back the old "bang-bang" sets, I say.

 

 

I should have added,  "Said with heavy sarcasm."

 

I'd no more think of using two-position flaps than of venturing forth without my undergarments.

[A.A. Barry]

Ian M, when planning my W.Whirlwind, I reconstructed the whole wing frame, and not knowing the outcome of a 2 positional switch,,a rotary one was programed in, so that at a safe height , I could activate and control the varied amount of flap, to see the how the model behaved. as it turned out it was not neceassary, so if your model has already been tested with flaps then the 2/3 postional switch it should be more than adequate, ........happy flying

A.A.Barry

[A.A. Barry]

Pardon my humor, David Turner. "than of venturing forth without my undergarments."

are you scottish or morrish

Barry

[David Turner 5]

Neither sir. I am English.

 

As you may  know, Accident and Emergency Triage is conducted by initial reference to the patients' under-clothing.  That very fact was drummed into we boys at Junior School.

Hence, I would regard it as the height of folly to cross my own lintel unless suitably attired in freshly-laundered smalls.

 

So, too, with the operation of flying controls. Smooth and progressive is the best order of service.  I have yet to meet the aeroplane that benefitted from a coarse flying technique.

[James40]

Ian, what type of patch do you fly from ? If it's rough grass then two position flaps can be an advantage as you can select take off flap to give more lift without sacrificing too much airspeed. Landing flaps give both lift and airbrake function so you can slow right down. What I would recommend for a single position flap switch is a servo slowing widget, rapidly deploying a flap to 40' will give you quite a pitch change but a servo slow will reduce this greatly.

[IanN]

Our patch is quite well tended. Nice smooth green stuff. I hadn't considered slowing the servo

 

Interesting responses so far: I was expecting to hear that full proportional control was, if not mandatory, at least very highly desireable. On balance so far it seems like "on-off" is fine for most of you

 

 

 

 

 

 

 

 

 

[Stephen Grigg]

Yes on my complex Fun Cub,on off does it for me

[James40]

Ian,

Here's an example of what I mean Clicky  They work really well, you still might get some pitch change but it's easy to catch or mix in some down elevator on the TX.

 

Both my H9 Mustangs have two position flaps but to be honest I've only ever used flaps for landing so where it's a cool option to have, it's never been put into action.

[IanN]

11 squid sounds very reasonable

[Simon Chaddock]

IanN

It all depends on what you mean by "flaps".

Some planes have quite small flaps where the trim changes are small whereas others are much larger where applying full flap fast or at speed would create a big trim change and possibly overload the flap linkage.

As Eric said the Spits flaps were on/off and really more air brakes than lift producers whereas the F4U Corsair had big flaps with 4 or 5 settings. The Fiesler Storch on the other hand had "wind down" flaps - infinitely variable.

So if you have big effective flaps a multi setting or full proportional control is probably a good idea. It certainly gives plenty of scope for experimentation. 

 

[ntsmith]

The spitfire's flaps were virtualy airbrakes. They came down to 85degrees. If you try that angle with a model the trim change is suprisingly small. With say 40degrees there is a very large pitch change.
I just set mine to the full flap position so the answer is what I previously stated.
Simply yes.
More modern aircraft use them for take off, with vaying amounts as well as landing for extra lift. The Spitfire and other warbirds are exceptions. They were slippery and needed to have the drag increased so flaps on a warbird ususaly means airbrakes - and very effective at 85 degrees they are as well.


Posted by David perry 1 on 14/06/2010 08:10:00:

But no one has answered the original question: is an on/off two position setting adequate? The answer, IanN, is yes. It is adequate.

 

I assume you want flaps for landing (shorten the landing distance and steepen the glide path, so make the setting greater than about 40 degrees.  A spitfire had 90, many light planes have about 50 degrees.

 

If you want it simply for fun then make it ground adjustable and enjoy seeing what different settings do for you.

 

HTH

 

David 

 

[Yorkman]

I have a Dx6i and flaps on the York-with the mix function it is set up with 'up' ; 'takeoff' and 'landing' positions (about zero, 20 and 45 degrees) and works perfectly fine.

But the flaps on my ASW17 are infinitely variable (including a bit of negative) so they can be 'tuned' in light lift conditions-which isn't required for a power model (well, not normally!)

I can't see why infinitely variable flaps would be required on a power model.

[Pete B]

How did you do that, Yorkman? I'm flying an E-Flite Beaver with a Dx6i, with ailerons on separate channels and the flaps on the gear channel, with just one position (which I can alter between flights). I use a servo slow on the flaps.

If there's a way of using a mix to give me two position flaps, I'd love to know!

 

Pete

[Yorkman]

Posted by Pete B on 24/07/2010 12:27:23:

How did you do that, Yorkman? I'm flying an E-Flite Beaver with a Dx6i, with ailerons on separate channels and the flaps on the gear channel, with just one position (which I can alter between flights). I use a servo slow on the flaps.

If there's a way of using a mix to give me two position flaps, I'd love to know!

 

Pete

 Hi Pete

quote-

Mix 1

FLAP-FLAP ACT

RATE D +111% U -22%

SW MIX       TRIM INH

With that setup switching (I think-haven't flown it for a while!) the mix switch gives 'takeoff' flap, then switching 'flap' gives full flap. Of course, if you swich 'flap' first, it goes straight to full flap, so you don't....

(I may have got the switches reversed, but it will be obvious when you try!)

And the amount of flap is set by the % values in the mix.

If you're using the gear channel, then I imagine substituting 'gear' for 'flap' and using the 'gear' switch should work too. Let us know how you get on.

[Pete B]

Thanks for that, Yorkman! I'm going to have to put it on the back burner for now - too much else happening - but I'll get there eventually

 

Pete

[Martin Harris - Moderator]

Posted by Yorkman on 24/07/2010 11:56:57:

I have a Dx6i and flaps on the York-with the mix function it is set up with 'up' ; 'takeoff' and 'landing' positions (about zero, 20 and 45 degrees) and works perfectly fine.

But the flaps on my ASW17 are infinitely variable (including a bit of negative) so they can be 'tuned' in light lift conditions-which isn't required for a power model (well, not normally!)

I can't see why infinitely variable flaps would be required on a power model.

 

On various spam cans the flaps are driven by electric actuators and a slow transition would be appropriate.  However, real aeroplanes (well Chipmunks and Super Cubs at least) have much simpler direct linkages where the movement is to a detent position so a switched position would be nearer full size practice.

 

Full sized flapped gliders also have fixed positions and operating them in flight is a case of moving them from one position to the next in a swift but smooth movement as the positions are quite close together in the cockpit. As an example, the ASW20 had 5 positions - 2 negative settings for efficient high speed flight, neutral, thermalling and landing position (40egrees). A clever mechanical mixer also raised the ailerons in the positive settings to maintain effectiveness as the ailerons were designed to follow the flaps in the negative settings. I never flew an ASW17 but I'd imagine it used a similar system.

 

I ended up using a helicopter mix on my (old style) FF7 to take advantage of the 3 position switch and I'm firmly convinced the the Chippy handles better on take-off with the scale take-off setting of 15 degrees and is certainly rock steady on approach at the 30 degree setting. I use a side mounted slider switch now with my FF10 but still use the 2 end points and the beep in the middle to replicate the full size procedure.

 

So, I'd say that there's no right or wrong - a slow transition will help initially if the model has a large pitch change with flap but once you're used to it or have mixed appropriate elevator there's no problem either way.  However, I hate using a rotary control on top of the transmitter when flying someone else's model...

 

Edited By Martin Harris on 28/07/2010 14:23:43