Ultra stick 60, Quad Flaps. All I have set up right now are the flaps. If I drop them, what will happen? Does it slow the plane down? Or will it climb?

it increases the lifting power of ing by increasing airfoil, thus landing at low spead is easier/possible. some planes that require you to come in hot will land much slower with flaps (flaps unlike alirons both go down.) if they go up they are spoilers and reduce the lift as wel las slow the plane. hope this helps not sure what quad flaps are...

I think the quad flaps use the alirons with the flaps so you can have all 4 up to do a very short takeoff, or all 4 down to do a floating "Crow" landing. Correct me if I'm wrong. I'm building (messing up) my first ARF currently. An Ultra Stick 40 with flaps. - Joe

The intended function of wing flaps is to increase the decent angle without increasing airspeed. When using flaps for landing, you should slow the airplane to just above normal approach speed before deploying the flaps. This will help to prevent ballooning. The flaps will tend to cause the airplane to pitch up. Be ready to lower the nose slightly when you add the flaps. Flaps cause a lot of drag, so either a little more nose down or a sight power increase will be required.

Ok... I have a skybolt with flaperons When I deploy the flaps the plane dives to the ground.. Whats up with that? I figured them to balloon me a bit up wards.. Do you think I might be dropping them to far and need to not put them down that far? Maybe creating too much drag? I am new to the flap idea. I wanted to try them on one of my planed so I went out and made it possible. Now I hate flipping the switch because the plane gets very violent.

Assuming that you are using a computer radio, be sure to add some down elevator mix with the flaps on this plane, as without it the plane will balloon once you drop the flaps. Take the plane up 2 mistakes high, drop to < 1/4 throttle, wait for the plane to slow down and then "experiment" with the flaps to see just how much down elevator you need. On my Ultra-Stick 60, I have about 26% down elevator trim programmed in, but as the Ads say, "your results may vary".

NOVA,

I have the same plane as you have for your icon. I have my flaps set down at 45º. When I am flying at mid throttle and flip the switch, my plane climbs at a 45º angle and begins slowing. I haven't mixed the elevator yet, because the amount of down elevator varies depending on the speed of the plane. I haven't tried them on take off or landing. I haven't flown the plane a great deal and it already lands very slowly. Now that I don't have to worry about selling it any longer (an embarrasing story) I am going to give them a try the next time I fly. I will let you know.

The crow uses the same flap setting, but also flips the ailerons up. On my airplane, this also makes the plane pitch up, but slows it dramatically. In the crow mode, the only controls you have are rudder and elevator. This isn't a good picture (lost the other ones when I formatted the wrong HD) because you can't see the flaps, but you can see the ailerons in the crow position. It looks really cool on the ground, but takes some getting used to in the air.[8D]

Here is something I learned from a magazine that you may want to try. It works GREAT for me. I can use one had to hold the wing, and the other to plug in all the wing connections.

I used two pieces of 1/2 x 3/8 balsa, set the female (arguably male) connector on one piece, drew around the connector, removed the wood so it would sit completely down inside, and then screwed them together so they could be removed if necessary. The cut to width of the fuse, and ran screws into the ends from the outside. I labeled the connections from the wing with masking tape, and it works great--if I don't get the connections in backwards. In hopes of preventing this, I mounted them all in the same direction--all the black wires on the right.

Cougar,
That nose-down tendancy with your plane is no big deal.

Short coupled planes tend to nose-down when flaps are dropped, while planes with a longer tail moment will pitch up. It's possible to get a plane with just the right combination of CG, tail length and size, flap size and deflection etc etc, that it won't pitch at all when you hit the flaps.

So, when trying flaps for the first time, be sure to do it up high. It's hard to predict exactly what the effect will be on a given plane.

Thanks Montague,

I was thinking it was because of the wing chord (or whatever the width of the wing is called), and trying to move them forward. Now, I can just shorten the tail <if it ever "re-kitted" of course>

I've created a section on "High Lift Devices" on my web site (non-commercial and free) at http://homepage.mac.com/mikejames/rc...ite/index.html which includes info on flaps of different kinds, slats, spolers, leading edge devices, etc.. It includes various contributions from other RCU participants, so check it out.

By the way...
After I read Andy Lennon's book ("The Basics of RC Model Aircraft Design" ( http://www.rcstore.com/rs/general/li...id=8&catego=BO ) and tried his approach, it was proven to me that many of the pitching issues associated with flaps can be solved by increasing their chord to 30%. Of course, like on an actual aircraft, flaps shouldn't typically be deployed at high speed. If you wait until you've slowed down a bit for your landing approach, then apply the flaps, you'll have much less pitch up on deployment.

Anyway, flaps and all the other gadgets are fun, and can be challenging to build, if you choose a scale method. I think they add a lot to both the looks and performance of a model.

Happy flying!

Flaps have three different effects on the flightpath

1.Putting flaps down increases the lift of the wing which makes the plane rise so the tail does its job of pitching the plane up top get it straight into the airflow again. Putting flaps down also alters the relative rigging angle between wing and tail so again causing a nose up pitch.

2.Putting flaps down increases the camber of the wing. Camber causes a wing to pitch nose down, the more camber it has the more strongly it pitches nose down. This effect can be very strong and is the reason why some aircraft pitch nose down and dive when flap is lowered. This is how deltas and tailless aircraft fly, the “flap� has the same effect as an elevator in pitch, down flap is down elevator.

3.Putting flaps down increases the angle of the downwash. If the tail sits in the down wash such as on a high wing, low tail plane like a Cessna, the leverage it exerts can be stronger than the nose down effect from the wing’s camber so it pitches nose up. If the position of the tail relative to the wing is high enough such as a CAP then it feels no change to the downwash and the nose down pitch will dominate.

Wings always create a nose down pitch when flap is lowered, but if the tail is in the downwash it may balance or even overcome that and pitch up.

H

Before I started flying a glider 30+ years ago, I read a lot about aerodynamics and understood that lift was created because the top surface of the wing was longer than the bottom. Because more air moved over the top of the wing it created less pressure on top of the wing, than the bottom. That difference in pressure essentially sucked the wing upward, pulling the plane airplane with it by creating lift. As I learned more about jet airplanes and flight at mach speeds, I understood that most of the ability to fly was created by thrust and not lift. If a jet had a airfoil like the Wright Brothers, it would continue lift more and more as the speed increased. The result would make the jet very difficult to fly at high speed. I also heard many, many times from people in the industry, that even a rock would fly if given enough thrust. Hey, I threw a lot of rocks so that made sense to me.

When I first I started flying RC with my trainer, I believed that lowering a trailing surface on a wing (be it flap or aileron), increased the lift (as the theory of dynamics indicated) due to the air rushing faster over the top of the wing than the bottom. This difference in air pressure caused less pressure on top the wing than the bottom and, essentially, it sucking the wing upward. That made good sense to me because the trainer wing definitely had more surface on top, than on the bottom of the wing. So it made sense then, that as the aileron was lowered, the pressure on top increased, and "lifted" one wing more than the other. That explained that wing. But as I looked at the other wing, I realized that changing the angle of the aileron did NOT increase the length of the lower surface enough to explain the opposite effect on it. So, I and began to suspect something else was involved here.

However, when I got my second airplane (fourstar 60, with symmetrical wing) I found that the surfaces were the same on both the top and on the bottom. This took me back to previous "jet" theory--that it is thrust that makes if fly more than lift generated by the wing. When the aileron was defected down, it changed the length of the surfaces very little. Granted, it changed it some, but not enough to explain the significant increase in roll rate. This essentially, blew my whole belief in the theory of aerodynamics as I knew it. But, I didn't care, the fourstar flew great, and I was having fun.

When I finally got my first airplane with flaps (Ultrastick 60) I couldn't wait to try them out. After getting used to flying the new plane a while, it was time to try the flaps. I was flying straight and level at least 100' feet up, at a moderate speed and flipped the flap switch. I was expecting the plane to lift straight up, and/or slow down, but instead, the nose went up at a 45º angle and climbed rapidly. I was so surprised, I immediately turned the flaps off, and leveled the plane. Subsequent tries revealed that the plane needed a lot of down elevator in order to maintain level flight. I was very confused for a while, but then I realized that the flaps hadn't really created any "lift" as I knew it, but the result was actually caused by "push" from the air under the wing pushing up on downward deflected surfaces. Since the flaps were relatively closer to the CG than the tail, it began to make some sense, but not a lot.

I realize the "theory of aerodynamics" was developed by people much smarter than I, but I don't think the theory has the same effect on model airplanes as it does on full scale aircraft. My suspicion is that, the relative density of the air in relation to large aircraft verses small aircraft causes a much different effect on the two. The air is relatively more dense to a small airplane, than it is to a jumbo jet. There may be some residual effect due to gravity (and some momentum and inertia thrown in), but I think it is mainly the relative density of the air that we use to fly RC. I guess that is why Newton stated his "Law of Gravity" in a vacuum, because in reality, an apple and a feather don't fall at the same rate in the air we fly in. But then I believe tornadoes don't suck the air, they actually blow it--but that would be for a whole different forum.

Sorry this was so long! Retorts are welcome--unless they are about tornadoes, then please P.M. me so we don't get the tread off on a tangent :-)

Bumblebees, model planes and full size jumbos all fly in the same air density, there is no such thing as relative density. Viscosity has a magnified effect on very small flying things, a bee feels like air is treacle compared to what a jumbo jet feels.

Thrust has no part in wing lift, otherwise gliders would fall like a stone. An F-104 in level flight at Mach 2 is flying on its wing as much as a vintage glider doing 30knots. Vertical climbs are a different matter!

The reason your early lessons on wings and lift fell apart when you found symmetrical aerofoils was that those lessons were wrong, though it is a false explanation that is repeated on and on. See what NASA says about that longer top surface, and lift in general at www.grc.nasa.gov/WWW/K-12/airplane/short.html and look at the section entitled lift, especially the 3 incorrect theories of lift. Two air molecules that were separated at the leading edge simply do not have to meet up again at the trailing edge, and don't! And here's what the university academics have to say on the matter www.aa.washington.edu/faculty/eberhardt/lift.htm

Unfortunately people are brought up on the myths about lift (half-venturi, longer top surface, Bernoulli) for so many years that finding out that it is junk is a real shock and is hard for them to believe!

H

Of course they all fly in the same air. But that same density of air, effects each one differently.
If there is no such thing as "relative density" then how can the following have any validity?

What I meant by "relative density" is that if one were to calculate the ratio of the size of a molecule of air compared to the size of a bumble, then one could derive X. If one then calculated the size of a molecule of air compared to a RC airplane, one could derive Y. And the air molecule compared to the size of a jumbo jet would be Y. Therefore, X, Y, & Z would be the relative densities I was referring to. I'll admit I am not a mathematician or physisit, but it just seems like common sense to me.

I have seen many squirrels (not the flying kind) fall 40' from a tree onto the ground, and then run off seemingly unaffected. Granted there are other factors involved, but if a man fell 10' he's probably going to the hospital. My thinking is that if the molecules of air have a different impact (magnified) on very small things like bumble bees, then they should have a different impact on medium sized things than they do on extremely large things. Thus the effect of the density of the air, would be relative to the size of the object.

Perhaps
If there was no "thrust" involved, then the glider would remain on the runway wouldn't they?--unless a very strong wing came along? Even if the "thrust" is provided by a tow plane, it has to have thrust to overcome the drag.

While I see the reasoning here, if they are equal, then, if they were both sitting on the runway and a 30 knot wind came along, the F-104 would be lifted the same as the vintage glider, wouldn't it? Not to mention that mach 2 is achieved well above the flight envelope of the glider--another relative difference in density. (I wasn't aware that a F-104 could achieve that speed in level flight).

I REALLY appreciate you verifying that those lessons were wrong and the links! I have only read the first "wrong theory" http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html -- so far, but you can only imagine the feeling it gave me. On one hand, I have always thought that was B.S. on the other hand, I thought I was just not intellegent enough to understand them properly. I have always had a difficult time just accepting things because they are "accepted theories". It is definately a shock to me! I don't understand all I know about some things, but, fortunately, I have a enough common sense to get by

Thanks for you help HarryC

Density is a variable in the equation for lift, drag and reynolds number. But the value of density at any point in space and time is fixed for whatever object is in it. Whether you calculate the lift from a insect or from a jumbo you use the same value for density. The density value is not modified by the object you are doing the calculation for. The density is only changed by pressure and temperature, not by the object within the air. The fact that you get different values out of the calculations is due to different properties of the object, not the density of the air which remains a constant value. Therefore there is no such thing as relative density. Viscosity also remains a constant value but viscosity is a resistance to shearing by the object. Air viscosity and air momentum can oppose one another, when air is accelerated and curved around the upper surface of the wing its momentum wants to make it go in a straight line and detach from the curved surface whereas viscosity wants to keep the air attached to the surface. What happens depends on which has the greater force at any point. For example the stall occurs when momentum carrying the air away from the wing overcomes viscous forces trying to keep the air stuck to the wing, and the flow detaches from the surface. But small objects impart very little momentum to the air so the air's viscosity effects dominate over the opposing momentum. Thus the air has the same viscosity for any object but the counterbalancing momentum force that is created by the object can be very different depending upon the size of the object, so small objects feel all the viscosity and hardly any counterbalance which is why small objects feel as if viscosity is much greater.

While thrust of some form is required to give the glider height in the first place, it plays no part in the generation of lift. Lift is 1/2*density*V^2*Cl*A. There is no variable in that equation for thrust, it is not thrust that generates the lift. Thrust is needed to overcome drag in order to maintain V above zero but it is not the creator of lift from a wing. Thrust plays a part on holding up a plane if the aircraft is flying nose up such as in a climb, or a nose high landing approach, then the thrust vector is inclined upward and it provides some of the upward force but that is directly from the engine itself, that is upward thrust, not wing lift.

My point about the F-104 and the glider is that in level flight both rely on their wings to provide the lift, not some other object like the engine. Clearly they both develop different amounts of lift, each must produce the same as their weight and the F-104 can't produce enough at 30kts, but that doesn't alter the fact that when flying in level flight regardless of speed, or weight, or thrust, a plane uses its wing to fly and not engine thrust. Very few planes have more thrust than weight and would simply find it impossible to be airborne on thrust.

As any pilot knows, lift is created by money. The more money you have, the bigger the plane you can fly!

H

I agree that the density of the air is a constant (at a given altitude and barometric pressure) so I see where that doesn't change. I also see why you don't agree because I mis-stated what I meant. I was referring to the "ratio" between the density of air, and the size of the object. It only makes sense that, that "relationship" would vary.

I agree that an f-104 and a vintage glider both use wings to maintain flight. However, there is a big difference in how they use them

Like I said I am not a mathematician (can't even spell :-) but if thrust didn't play a major part in lift, then why does an f-104 have such a different airfoil and wing shape as the glider? While they both must move through the air, in order to create lift (or the air must be moved around the wing), the F-104 MUST move through air much more quickly than a glider in order to remain flying. Since a glider has no engine, and an F-104 has a very powerful one, thrust MUST be a factor.

Of course most airplanes use its wing to fly. The point I am trying to make is that they use wings much differently because of the thrust. Lift must be created by the wing to begin and maintain flight in most jet aircraft. An F-15 needs a wing (airfoil shape) to take off. But due to its thrust to weight ratio, after take-off, it is able to fly straight up and uses it's wing more for guidance and stability than for lift. As we have seen in the X-plane projects, airfoil shaped wings are not "required" to maintain straight and level flight. While it is true that most airplanes need airfoils to get airborn, once they are in the air, and if they have enough thrust, the airfoil is more of a hindrance than benefit above mach 1. And then, there are the flight characteristics of missiles. Thrust may not generate lift, but it sure has a big impact on flight.

I apologize for using incorrect terms and misleading from what I meant by what I was saying. Unfortunately, that happens all too often to many of us. If I had taken the time to write the messages "properly" the thread would have been lost. You are obviously a well learned individual (I suspect a professor of some sort) and I don't mean to "fly in the face" <pun intended> of sound principle. However, I think some "theories" should be thrown out the window. <more pun intended>

Aside from our differences on some aspects of flying, what happens when an RC airplane deploys its flaps? It it because of lift, or push? <big grin> Thanks. <to bad you live so far a way, it sounds like it would be great to sit down over a "pint" and get to the root of the problems of this world! :-). I do love a challenging discussion.

The reason the F-104 needs a big engine is for the big speed. Moving that body through the air at very high speeds creates a lot of drag, and that is what thrust overcomes. Try pushing the glider along at those speeds (assuming the structure could hold together) and it too will need an awful lot of thrust. Just draw yourself the standard 4 forces acting on an aeroplane (I am sure they will be shown somewhere on the NASA site) and you see that thrust opposes drag. Lift off the wing is always at 90 degrees to thrust so thrust can never contribute to wing lift. Thrust can contribute to the overall force holding the plane up such as when the aeroplane is inclined upwards but it is still at 90 degrees to the wing lift so it still plays no part in the creation of lift from the wing. In a perfectly vertical climb the wing is at its zero lift angle and produces no lift at all, only engine thrust opposes gravity, but that is not the same thing as lift from a wing. If during a vertical climb the wing is pulled to some positive angle of attack, its lift is not upwards but horizontal, as it is defined as being at 90 degrees to the wing. So by definition it is simply impossible that the thrust generates wing lift. A force of some sort is required to balance drag in order to maintain speed, and speed is required in order to generate lift, but that doesn't make that force the generator of lift. For example, where does a glider get the forward pointing thrust that balances drag? It has no engine to create thrust. It gets its energy, its fuel if you like, from trading height into speed but what creates that forward pointing thrust? Lift! The wing is actually angled slightly downwards so that the lift vector though still at 90 degrees to the wing is poining ever so slightly forward of the vertical. Then in comparison to the fixed orientation of the gravity vector, lift has a vertical and a horizontal component. That forward pointing horizontal component of lift is the thrust that balances drag. Since in any aeroplane in gliding mode the lift is the thrust, then to say that thrust creates lift would mean that lift would be creating lift. That's a circular argument, lift cannot be the creator of itself, so clearly it is false, lift/thrust does not create lift.

H

Again, I obviously used the wrong terms. Personally, my concern is with "flight" (the movement of an airplane through the air in a controlled manner) as a result of lift and thrust. I understand that thrust does NOT create lift. I can also understand how (given your explaination) thrust can not have an impact on lift. But the combination of (and the relationship between) lift and thrust, have a definate impact on flight. Sorry for the confusion.

Can you answer the question of how the flaps work in relation to flight, relative to RC?