terrymf

Would a wing that is fatter on the tip than at the root on the leading edge cause the plane to tip stall?

This is a Nitro models Funtana EP..flyes real nice unless your turning too slow and out of nowhere it stalls and falls. (both directions.)
I was looking the wing over earlyer and noticed the leading edge was larger at the tip than at the root. Maybe just a poorly built plane or maybe part of the design...I dont know.

Anyone have any ideas???

jaka

Hi!
In general a thick wing section would stall later than a thin wing section.
As for your model...Have you checked the wing so that it isn't warped. Using some " wash-out" in the tips is always good.
Stalling is also due to a too heavy airplane (high wing loading). So always use as light servos, batteries, wheels and all other things as possible.

terrymf

wing area is over 400 sq inchs..flying weight is 3 pounds..the wings seem straight and true, except the leading edge...the plane is balanced front to back and side to side..Im running hitech hs 85 metal gear servos all the way around

if you turn it like it was a jet it is fine...but just a little slow on the turns and she falls..


I have flown maybe 20 or 30 other planes including warbirds (that h9 p 51 pts trainer will tip stall pretty easy with the wing droops removed) and have never encontered anything to this extreme...guess I will just keep the speed up till the wheels are close to the ground...(which is hard to do if the battery runs low)

I thank you for your advice and welcome any more

Rodney

[quote]ORIGINAL: terrymf

Would a wing that is fatter on the tip than at the root on the leading edge cause the plane to tip stall?
No Just the opposite, it acts similar to washout only works when you are inverted as well. Back in the 60's, this was a common technique on pattern planes as it prevented or delayed tip stalls.

Avgeek

Hi I have a 10e yak 55 which does the same thing and put me off the model (i hung it up and ignored it) but it looks so good. then i read in a mag about mixing in spoiler (up on both ailerons) with up elevator and at about 15% (on my radio) the problem is almost completly gone! this seems to stop the tip stall by reducing lift at the tips. also taping the aileron hinge gaps helps but i assume that would have been done?

terrymf

Both sound like good ideas to me.
I have not sealed the hinges (my bad) and was unaware of the spoiler mixing...I will try both

I had thought about adding some material to the wing tips for more surface area and hopefully more lift, but as I am not an aircraft engineer I'm not sure how to go about it...maybe just buy some h9 wing droops like on the p 51 trainer...that wouldn't look too bad (ha ha)

I have also heard about washout and how to add it to a plane that you are building...but if the wing is already built..how would I tweak the tips for more washout???

JohnW

My Feedback: (6)

You can sometimes add a bit of washout to a built up wing (or straighten too) by twisting the wing and setting the twist with a heat gun.

All planes stall if you are going too slow. If in a turn, I can almost gaurentee it will roll during the stall becase one wing has higher camber than the other due to deflected ailerons. You sure you just weren't going too slow?

Ditto on the blunt leading edge, they generally stall softer than sharp leading edges. So, I'd guess a wing such as in your photo would stall at the root first.

terrymf

Lots of great ideas...I guess I have my work cut out...i will try these out as I am able until I can get some measure of control on this thing.

Thanks for all the input.

BillyGoat

Keep in mind that a "tip stall" is actually a spin or the beginning of one, so you need to look at what causes a plane to spin... One wing going fully stalled before the other.

First I suggest using an incidence meter to check incidence along the entire wing, from root to tip. I’m not a big fan of using wash out in a plane beyond advanced trainers because when inverted, washout now becomes wash in. Now you want to see a plane that really snaps over in a stall?

Also make sure that you’re not cross controlling in the turns (opposite rudder) either by mixing in the radio or inadvertently with the sticks. Lastly if the wing is straight and your coordinating rudder in your turns correctly, try moving the CG forward. This can help tame an incipient spin.

TexasAirBoss

My Feedback: (22)

I have a Cap232 that was/is a little tippy. I used reflex, which is raising both ailerons a couple of clicks. Acts like washout, especially with tapered wings. It helps alot.
The prefered geometry of modern aerobats is that they have tapered wings , but that the leading edge is straight with no sweep. Its important that there is no sweep and special care should be taken when assembling the wings.
And sometimes when you scale down a design, the wing tip is too tapered. When wing tip cords are around 6 inches or less, you can get a tippy airplane.
One more factor, the sharper the leading edge is, the higher the stall speed. So, in tapered wings, not only is the chord tapered, but the thickness of the foil gets thinner. This means the leading edge near the tip is sharper. So, its bound to have a higher stall speed.
Real airplanes beneift from the tapered wing by reducing the weight of the outboard wing which lessens the rotational inertia of the wings mass during manuevers, ie, the roll stops nice and crisply when you want it to and doesn't try to keep rotating. But models are already very light with low mass and don't really gain much benefit from this design, but you do notice the draw back.
So its a systemic design flaw. Various techniqies can minimize it . All will have some repracutions.

terrymf

Take a look at the picture below. it is not my exact plane but an ad from nitro models for the same plane. It does show the wingtip rather well which is what I want to bring to everyone's attention.

This ARF did not include the throw settings with the ..uh..manual....so I used the old "That Looks About Right"

Had to do some readjusting on the elevator and rudder but I never changed the aileron settings from what I had set originally..Then I got to looking at it yesterday.

Notice in the picture that the ailerons are almost half the cord width at the tip. And if that huge aileron is deflecting even a little too much..the wingtip and its available lift is cut almost in half..am I right???

I'm thinking a little less aileron deflection and a little more speed in the corners might be in order here..any suggestions?

I also have to agree that washout would affect inverted flight..what about stall strips at the root? anybody had any success with that?

I am learning a lot here...you guys are saving me (and hopefully others) a lot of headachs and bewilderment...Thank you!!

Rodney

The plane in the picture does illustrate at least one bad design features. It is best (from a flutter inducing point) to never extend the ailerons all the way to the tip, especially on an aerobatic model.

FILE IFR

Terry,

If I were you, I'd program 'Differential Alieron' into it. It's a great cure for the Adverse Yaw problem in a turn.

Set-up is super easy, but you'll need 2 channels to do this.

For the alieron that goes up, allow that particular alieron to go it's normal throw in the 'Up' dircetion.
For the alieron that goes down, allow that particular alieron to go ONLY a slight distance (1/3rd the normal distance) in the 'Down' direction.

Coordinated turns are a good thing to do too![8D]

terrymf

'Differential Alieron'

Now there is another concept that I have heard of but never even thought to try..exellent!!

Of course that might affect inverted flight but how bout this??? I could mix the 'Differential Alieron' in for a "take off and landing mix" and something more aggressive for higher alltitudes...(Im gonna need a new radio..when is christmas??)

I think that sounds great considering I have no intention of landing inverted anyway..although, with a narley tip stall, my fist landing turned inverted to about kneecap high and somehow I pulled it out and retried my approach. (with a really fast turn and moderately quick approach)

Fantastic ideas guys..and to think I had almost decided to give up on this little plane that flyes great high up but was tricky to land.


Rodney
it is hard to see in the picture but the ailerons are made with some thicker wood and are built fairly strong..unlike the elevator and rudder...It would take some doing to fludder the ailerons on this bird..I think..really dont wanna find out..

but I certainly get your point..I learned to fly on a Thunder Tiger Fun Tiger Extra (yeah I know..but no one ever told me that there was such a thing as a trainer)..the manual even said..not too fast or she will flutter...talk about sink or swim LOL

Lnewqban

Terrymf:

I believe the thicker airfoil at the wing tip provides better lift than the one at the root for the same angle of attack; however, it also makes the tip stalls at a lower AOA, or before the root.

You can verify this at:

http://www.grc.nasa.gov/WWW/K-12/airplane/foil4.html

The purpose is the same than the tappered wing, easy stalls at the wing tips for brilliant snap rolls and other aerobatics.

That is a good stall-spin caracteristic for aerobatics, but not for landings.

The use of aileron is dangerous for these type of models when landing; instead, a more straight approach should be tried and mostly the rudder should be used, avoiding heavy corrections close to the ground.

What happens is that when one aileron is dropped, it increases the AOA of the airfoil, and also increases the drag of that half wing, slowing it up.
Both things tend to push that half wing toward the stall angle or/and velocity, or beyond, causing the model to spin at low altitude.

I suggest:
1) To tape the hinge gap.
2) To adjust the throw of the aileron with abundant differential.
3) To install turbulators close to the wing tips.
4) To short the ailerons from the tips as much as possible.
5) Not to use ailerons during landings.

Regards!

daveopam

My Feedback: (9)

The H9 Funtana wing is done the same way. I don't know what it is supposed to do but many a Funtana 40 has snapped in.

David

terrymf

I understand what your saying except for in your suggestions..


3) To install turbulators close to the wing tip s.
4) To short the ailerons from the tip s as much as possible

Could you elaborate a little on these points?
What are tubulators?
By "short the ailerons" Do you mean to take away some of the aileron material at the tips?

and then..

5) Not to use ailerons during landings.

I only wish I were that good of a pilot..I know I would mess that one up.
I cant even do that on a h9 Alpha trainer (or a nextar, or a tower trainer or a (insert your easy to fly plane here)



daveopam

Nitro Models compare this bird to the h9 version....below is a quote from their website.

"And, like the Hangar 9 FuntanaS™ 3D performers, the NitroModels version flies like a dream with unlimited potential to perform any aerobatics an experienced electric pilot can conjure up."

Wish they would have said something about the landing being the most aerobatic thing the plane can do...LOL

Tired Old Man

My Feedback: (1)

Nobody has mention the CG in this thread. A nose heavy plane, even a light one with wings designed to delay a stall, is one that needs to be flown fast to prevent stalling. A nose heavy plane is one where the elevator is trying to hold up the nose due to the heavy moment arm at the front end. How to tell if that's a problem? One os to check the elevator trim after a landing. Iftheir is "up" elevator noted at the tail then it's nose heavy. Is it balanced per the instructions? If it is that does not mean it's balanced correctly. Many manufacturers provide a CG that's forward to make the plane more stable for beginners. Doing so makes it need to fly faster.

The amount of control deflection for the flying speed is also a critical factor in stalling a plane. Too much elevator deflection and the plane stalls at any speed. Too much aileron combined with too much elevator is another problem area. Just because we can pull a 40 degree deflection does not mean we should always do so.

The wing design itself is just fine and works well to delay the stall. Wing area is great for the weight. Look at "wash in", CG location, and surface deflection amounts (meaning heavy thumbs) as the probable cause. Bear in mind that every plane has a speed at which the plane will no longer fly, and fat wing planes generate a lot of frontal drag that makes them fall out of the sky at slow speeds once the engine stops.

terrymf

I have to agree and I feel like there is ...was to much throw on the ailerons at the beginning of this thread.

As far a the cg goes i only needed a couple of clicks on the maiden flight to get her to hold a level path. But it would not hurt to move the battery back..maybe 1/4 inch and try again. (way high in the sky)

There have been a lot of great suggestions so far (that I haven't gotten a chance to try yet), that is why I posted it here. I knew some of you have already been through this or something like it and I could greatly benefit from such experience. Beats the heck out of learning from the school of hard knocks.

da Rock

Not true actually.

The airfoil is symmetrical. With them, thickening them allows them to generate a greater max lift at a greater AOA before stalling. Earlier in this thread I think somebody mentioned that fact has been used in model designs for years and years to make tapered wings less apt to tip stall. It's been proven over and over.

With the wing you're looking at, the thicker tip is to help the outboard stall later than it would otherwise.

The airplanes pictured so far have all been designed to do slow speed 3D "flight". The huge ailerons are there to work at zero airspeed. And the designs all rig them to have large deflections. Everyone of those suckers are flown quite differently than "normal" models and fly "normal" flight with almost no stick movement. Or with large differential in the TX, or with dual rates that have extremely low low rates. And the airfoil progression designed into the wing was done to help deal with the Jeckyl/Hyde nature of those beasts by attempting to reduce tip stall.

BTW, tapered wings naturally stall farther out the wing. It's what they do naturally. So the designer's choice in airfoils on those planes was probably an attempt to reduce that tendency.

JohnW

My Feedback: (6)

Ditto with da Rock as per airfoil related to stall. Blunt leading edges and thick airfoils allow slower flight and soften stalls… hence nearly every funfly/3D type ship designed for slow flight uses them.

I can’t really tell from the OP’s picture in post #1, but it looks like maybe the airfoil at the tip isn’t any thicker, just the leading edge is more blunt, i.e. larger LE radius? This would soften the tip entry into stall compared to root, which is generally what you want to have happen if you are trying to avoid hard spin entry with stall. On some ships I've done the opposite to help a wing stall better, such as for snaps and spins, by taping something sharp to the LE. Pretty easy to try, just tape a piece of triangle stock to the LE of your wing at the root, or tip, etc. to see how a sharp leading edge changes stall.

jaka

Hi!
Thicker airfoil at the tips prevent the tips from stalling first.
But..How have you set up your plane. To fly well you should balance your plane so that the C of G is not too far forward...if it is you have to use too much elevator throw ...which will likely stall the plane when landing. A reasonable elevator throw on planes of this model is just 10 or 15 degrees up /down. That's just 2-3cm measured at the trailing edge of the elevator. Using as much as 30-45 degrees ...as you read about in magazines flying 3D planes is just used...when flying 3D! Not for landing.
Have you tried moving the C of G backwards and in the same time reducing the elevator throw???

Taping the gaps on all flying surfaces is mandatory if you want a good flying airplane! I use strips of Oracover (Ultracote in the US) on the underside of wing/ailerons and stab/elevator.

Then there is the most vital thing...Weight (Wing loading)! When building an aerobatic /3D model you must always build it as light as possible and use the lightest equipment possible.

Last: A Robart incident meter is a must if you suspect a wing to be twisted. Most of the time this could be fixed by using an iron or a warm air gun.

da Rock

Those wings often have no decrease in thickness from root to tip. They're almost always made with a straight, non-tapered spar. I don't believe I've ever seen one that increases so the tip is thicker. The decrease in chord from root to tip results in the tip airfoil having a thicker airfoil however. The thickness of the airfoil is considered to be it's percentage of the chord.

For example, if the airfoil at the root has a 12" chord and is 1" thick, it'll have a 8% thick airfoil. Keep the spar 1" thick to the tip where you have tapered the chord to 8" and the airfoil out there will be a 12.5% thick one.

terrymf

da Rock
jaka
JohnW

You guys have some incredable insight to this sort of thing. But I must resist the temptation to get carried away on this paticular aircraft. It only cost 85 bucks shipping and all for the ARF. But I am certainly paying attention because my other planes cost a lot more so I will head your advice .

I went back to a post by daveopam and made a device similar to his..only mine was cardboard. I used it to check the difference of the leading edge from root to tip on both wings..the tips are fatter on both wings but also..the two wings were different from each other as far as the leading edge goes. One root end was considerably thinner than the other. I dont see a way around that without replacing the wings with some that are...shall we say ...better. Can't expect precision for 85 bucks.

Anyway, it is a fun little plane once it is in the air and I am far from a 3d pilot so for the money I dont feel to bad and I can use some of the ideas layed out here on this thread to try and improve the landings. Best part is..no glow fuel cleanup at the end of the day. It does get a little dusty hanging on the wall but one flight and it becomes self cleaning.

I certainly would not recommend this model as a first electric (and it is not my first) but for the price it could be a decent 3rd or 4th.

da Rock

Bottom line ????

Don't sweat so hard over the measurements. You've put the model into perspective. It's a cheap model. Fly the sucker and THEN you'll know for sure what might or might not require fiddling.