Balooning with flaps

[Matt Watts]

Hello again!

I have flown my Easyglider several times, and I LOVE IT!! It's no wonder that so many people join this hobby (i wonder how many are waiting to come out of the closet?). Anyway, I've noticed that when I lower the flaps, instead of balooning upwards, it immediately noses downwards. As far as I can tell, I'm not bumping the right stick when reaching the flap dial, and before anyone asks, yes I have dialled in the flaps the right way and I know which position down is. Though not dangerous (at any less than three feet off the ground) it is kind of alarming, and is definately not going with what I've heard of models balooning upwards with flap application.

Eh wot? 

[Mike Hawkins]

When you apply down elevator, the lift of the tail increases and the nose goes down. When you apply flap the lift of the rear section of the wing increases, this being behind the CG will cause pitch down. The elevator has a longer moment, giving it more of an affect than flap. However the plane may lift depending on the way the wing generates lift, so for some planes they will balloon, others will pitch down. So if you can, mix in some up elevator to counteract the pitch down of flaps.

[Former Member]

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[iawnski]

 do you have you flaps or flaperons  on easy glider ,ie 2 servos in each wing/or just 1 servo in each wing/

[Paul Adams]

I don't think its as easy as that otherwise applying the same logic, some models would react in the oposite direction when applying ailerons. ie left aileron down, right aileron up would result in model banking to the left. I have also flown a number of flying wings and all have reacted with the model lifting its nose when the elevator moves up. 

My thoughts on why the model noses down is that when the flaps are deployed the main wing looses lift and as such can no longer support the weight of the model and hence the nose goes down. I would be interested to know if we are talking about separate flaps or flaperons, and what angle they are at when they are deployed.

[iawnski]

still  same do you have 2 servos in each wing ? or 1 in each wing ? then we can make a start

[Bob Cotsford]

I think it's a side effect of the flaps varying the downwash from the wing and how it hits the tailplane, combined with the way the centre of pressure moves backwards/forwards and the centre of drag moves  up/down for the particular configuration.  My Cessna has a strong nose-up tendancy with flaps, I think I've got something like 14% down ele mixed in for 45 degrees flap movement.

IIRC dropping the flaps down to 60 or 70 degrees or more still gives an increase in lift, but also a much greater increase in drag - the flaps would have to be very badly designed to decrease the wings lift.

[Peewhit]

I have an EG electric and I don't know if the model wing section is suitable for using flaps.

The glide angle (when trimmed appropriately) is sufficiently shallow without them, and there is no mention of using flaps in the insructions.

This machine will slope soar nicely in the lightest of winds without flaps.

The model is designed to use spoilerons (both ailerons up) for landing, and this requires 5mm of down elevator compensation (nearly half) to maintain level flight.

Applying the converse, surely the use of down flaps would require up elevator compensation?

I would forget using flaps and just trim in a bit of up elevator to give minimum sink when you need to.

[Mike Hawkins]

Here is some info on flaps at http://adg.stanford.edu/aa241/highlift/highliftintro.html. Halfway down it states "Flaps change the airfoil pressure distribution, increasing the camber of the airfoil and allowing more of the lift to be carried over the rear portion of the section", more lift at the rear portion will raise the rear portion relative to front, hence nose down. However the amount of lift has increased (dependant on attitude). If the nose down attitude provides less downward force than the lift increase, the aircraft will climb, climbing in a nose down attitude. If the extra lift is not greater than the nose down attitude it will decrease in altitude.

[Former Member]

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[Matt Watts]

Interesting. I'll try and find the spoileron mix on my 6EXA. The problem is, the hill I fly off isn't really straight. I try to land it down the path (I don't know why, it's a habit and it looks good) which goes downhill. This is usually futile as it refuses to drop, being a glider. I'ts odd, I only have 25% flaperon trim, which is activated proportionally by a dial instead of a switch. Spoilerons would definately come in handy - I can see the advantages in crow brakes!

[iawnski]

have you put flaps on this eg, as they dont come with flaps just ailerons

[Matt Watts]

No, I left the ailerons full length for use as flaperons.

[iawnski]

so why we talking flaps? when you dont have any

[Peewhit]

I Don't know how you manage to land your EG on a downhill path without using spoilerons.

Think mine would end up in the car park at the bottom of the hill!

I use a Futaba 6EX and have set the flap travel on the transmitter to give the recommended maximum up travel on both ailerons to act as spoilers.

Then set the flap dial to the position which gives neutral flap, and put on that little plastic flap dial lever with the lever pointing downwards so that it rests against the transmitter case.

Hence, the ailerons will not go any lower yet when you turn the lever/dial in the only direction possible to max, you get both ailerons on maximum up position - spoilers (or to be more correct, spoilerons).

Then set the programmable mix (I think you have only one) to give 5mm down elevator when the spoilers are at max.

The result when you activate the spoilers is that the aircraft remains in level flight, yet the glide angle steepens significantly which is ideal for accurately judging landing position.

Hope this helps,

Peter

[Matt Watts]

Brilliant, that's just what I need! Thanks.

By the way iawnski, flaperons are still technically flaps.... I think. Well, I mean, they are very similar, just a combo. Oh, you know what I mean!

Thanks all!

[iawnski]

byeeeeeeeeeeeeeee

[Tim Mackey]

Yep, flaperons are still flaps, but one word of caution - if the ailerons are full length, some models do not like having them used as flaperons - all sorts of weird behaviour occurs. I also have set spolierons on my ancient but refurbed Schizo, and this does not pitch up when they are deployed, so I dont mix in any down elevator trim.

On another model of mine, spoilerons actually caused a down pitch effect.

I think what I am saying is that different models will respond in different ways when you go altering the section of the wing..... on first flights, experiment at safe height and typical landing speed to assess the effect.

[Former Member]

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[Peewhit]

The EG is designed for spoilerons as a landing aid and not down flaps.

The Multiplex recommendation is both ailerons full up with 5mm of down elevator as compensation.

This set up works very well, and seems to be just what Matt wanted to do in the first place.

[iawnski]

matt spoilerons are up aileron ,,,,,,,,,,,,,,,, flaperon is down aileron ,,,,,,,,,,,,theres no flap cause you dont have any ,also flaperon is a bit prone to tip stalling ,,,,,,,,,,, im going to bed

[Matt Watts]

Right. I've programmed in spoilerons and was going to test it today but too windy to fly enjoyably. I just hope this doesn't hold out tomorrow.

[Peewhit]

Matt,

It will work fine, mine does!

[iawnski]

matt youll have no probs  ,mine does the same  enjoy

[Matt Watts]

It's funny, I had spoileron mix at 50%, but when I lowered the right aileron (using the aileron control) I got some rather disturbing clicking, as if the gears kept slipping. Naturally, I reduced it to 25%, and it's OK now. Still rather concerning though. Cause for worry?