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  #31  
Old 07-06-2007, 01:15 PM
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Aeronautical Side Note

Actually, the word torque is a misnomer (but it is a convenient catchall). The primary cause of "torque" is the spiral airflow that comes off of the prop. There are two other sources – the “P” factor and the pure torque of the engine – but they are small contributors.

If you held a streamer behind a spinning prop, you’d see a corkscrew path in the same direction as the prop rotation. This airflow strikes the left side of the fin and rudder (which is usually above the thrust line) and yaws the plane left. As the plane accelerates, the pitch of the corkscrew pattern gets straighter, so that the torque effect is greatest at low speed and high throttle.
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  #32  
Old 07-06-2007, 06:41 PM
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Saving your trim settings

As you are doing your flight tests and adjusting the trims on your controller, you need a way to permanently save the settings. Well the RF controller doesn't have digital trims that will be remembered between models. But the RF program does...

Here's how to save the settings:

Say you've just finished a test flight and had to put in a couple of clicks of right rudder. Before you reset the trim on your controller, open the plane in the editor. Go to the software radio for the channel(s) you added trim to.

At the bottom on the page for the channel is a number for the current value of the channel. Remember this number and zero your trim for the channel. The current value will go to zero (or very close to it). Now in the top field for trim, invert the sign and type the same number here. The display will round to the nearest whole number but your value will go into the system and be stored with the aircraft.
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  #33  
Old 07-06-2007, 08:35 PM
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The topics of pitch trim, getting a good glide, and correcting for torque effects have all been addressed. There are two more directional control issues that effect planes in the simulator. They go hand-in-hand with the trimming for torque effects, but there is no good way to address all issues simultaneously.

The first problem is known as cross-trim. The direction of the aircraft can be controlled by either the rudder or the ailerons, but these two control surfaces do not behave the same way. When a plane is cross-trimmed it also behaves differently turning left vs. right.

Let’s say the model has the rudder offset to the right to correct for the small yaw induced by adding left thrust to the engine. The ailerons will need to be trimmed left to fly in a straight line (in fact the plane will be crabbing to the right). When this plane is turned left it will tend to hang its nose “out of the turn” and may even tend to roll back to level flight. When turned to the right, however, this same model will tend to roll harder into the turn and even try to roll over into a spiral dive.

To correct the cross-trim, make left and right turns (with the same angle of bank) and adjust the rudder away from the direction of turn that the plane rolls into the turn. Every time you adjust the rudder, retrim the ailerons for level flight. When you think that you have it right, try a long glide at idle power as a fine-adjustment test. If the model wanders off to one side tweak the rudder trim to correct and retrim the ailerons again.
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  #34  
Old 07-06-2007, 08:45 PM
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The second directional control problem that effects planes in the simulator is known as adverse yaw.

This problem often gets worse at low speeds and high angles of attack, in other words - when you least want it. What happens is this: Say you want to apply right bank to exit a left turn. The desired result will be to lift the left wing and lower the right. Wings are not very heavy, but it does takes more energy to raise a wing than it does to lower one. The energy needed to raise the wing comes from drag. This means that the left wing that is being raised has more drag and it tries to yaw the plane in the wrong direction (i.e. adverse yaw).

There are three ways to correct adverse yaw. The first is to do what full-scale pilots do: always use rudder along with ailerons. It’s called a coordinated turn and it is a basic flying skill. While this is a skill most RC pilots would do well to learn, it is often too much for a novice to handle. The second thing is to couple the ailerons into the rudder. So that when right aileron is applied, right rudder is also. This can be done mechanically or with a programmable radio mix. Typically, full aileron throw only requires roughly one-quarter rudder. The third and preferred method is to use aileron differential. Some coordinated rudder may still be necessary during the steepest climbs, but a differential setting that is good for the entire flight profile can usually be found. Many full-scale aircraft are even manufactured to use differential ailerons. For example, a Piper Cub has nearly twice the aileron travel in the up direction.

A typical low-wing sport model usually needs the ailerons to move up about 20% more than they move down. A good starting point for high-wing trainers, however, is about 50%.

Aileron differential is easy to describe but may require a little effort to set up in a real RC plane (I'll cover this at the end of the thread). In simple terms, when you move the ailerons, the aileron that goes up must travel farther (in degrees) than the one that goes down. Modern radios can do this with programming if two servos are used for the ailerons. The mechanical method is to use creative offset linkages to control the ailerons.
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  #35  
Old 07-06-2007, 08:51 PM
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The test to see whether you need to add differential aileron throws is called a Dutch Roll.

Fly in a straight line away from yourself at a safe low altitude. Smoothly rock the plane from side to side, banking the plane at about 45° each way. Use as much aileron as you can while comfortably keeping up with the plane. One of three things will happen:

1) Axial Rolling. The plane will roll back and forth and the tail will point straight at you and not wiggle at all. That means the differential is perfect for level flight.

2) Adverse Yaw (typical). The model “duck walks”, with the tail wiggling right as you turn right. This means that the nose is going the wrong way and more differential or aileron-into-rudder coupling is needed.

3) Proverse Yaw (uncommon). The nose turns in the same way the plane banks. The tail swings out as if starting a sudden turn. This is not great for aerobatics, but it is perfectly acceptable for a trainer. It adds stability and control during all positive-G flight. If you decide to adjust it, reduce the differential or aileron-into-rudder coupling.

Retest the Dutch Roll test in a climb to uncover any adverse yaw problems that may require a lot of differential.
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Last edited by dhk79; 07-10-2007 at 01:51 PM.
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  #36  
Old 07-06-2007, 09:18 PM
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Quote:
Originally Posted by bobbaker
No offense sir, but your UltraStick really flies like poo-poo.
I own one and it flies no where near that. So why are you wasting your time posting this doodie?
I read through the entire damn thing and it don't help me out one ding, dang bit!

Regards,
Mr. Baker
Just saying something flies bad is not much help. You have to let someone know how it flies bad.

You say it doesn't fly like yours and that may or may not be a problem. I've owned three of them and think it's a pretty fair representation, but then the G3 model is set up the way my favorite real one was (overpowered with lots of extra control throw). When that plane was modeled over a year ago, there was a lot of discussion from other real UltraStick owners. Most felt the model was very accurate. Now if you would like an AV that matches yours more closely, maybe we can work something out.
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  #37  
Old 07-06-2007, 11:12 PM
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To set up differential ailerons in the sim, open the software radio section. The ailerons on this model are on channels 1 & 5. Note that you do need to have two ailerons servos in order to do this.

In the first picture the ailerons move symmetrically, up & down the same amount. Delete the inputs under each channel. Replace the simple inputs with complex inputs. Open the response graph and edit the end that corresponds to the aileron moving down (picture 2). Now in picture 3, you can see that the left aileron has moved down only half as much as the right one has moved up.

Note that this is an excessive amount of aileron differential for this particular plane, but I wanted the difference to be visible in the picture.
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Last edited by dhk79; 07-07-2007 at 12:50 AM.
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  #38  
Old 07-06-2007, 11:19 PM
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Quote:
Originally Posted by bobbaker
No offense sir, but your UltraStick really flies like poo-poo.
I own one and it flies no where near that. So why are you wasting your time posting this doodie?
I read through the entire damn thing and it don't help me out one ding, dang bit!

Regards,
Mr. Baker
Your such a lil' baby,go get your binky and shuuuut uuuup.
P.S POO Does Not Fly.
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  #39  
Old 07-06-2007, 11:22 PM
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Thank you for the tutorial DHK,i'm confused tho,i'm not sure how you line up/shape the fuse.
You were wright on the F-16,i went crazy with the weight!
I have gotten better now,try out the kingcat composite AV,it flys nice,really smooth too not crazy with speed,200mph,thats ok for jets! Bibplane and 200mph=What kinda turbine is in your turbo toucan!?!?
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  #40  
Old 07-06-2007, 11:59 PM
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That pretty much finishes the trim topics that can effect the simulator's physics. There are, however, some other problems that can have an affect on real RC aircraft. Most of these problems have their root in the construction of the airplane.

The first problem occurs mostly at low-speed and high angles of attack, and has probably contributed to more RC landing mishaps that all other causes combined. The problem is uneven aileron hinge gaps (this is not a problem in the simulator). It occurs very unpredictably, but when it occurs you often do not have time to recover (i.e. landing). It is better to fix this problem before it ever bites you and the fix is easy. Just seal the gaps between the ailerons and the wing, so that the higher pressure air from under the wing cannot pass through the gap. It only takes a couple of minutes to use tape or monocote to create the seal, before you take a bird out for its first flight. It's cheap insurance...

The second problem is lateral (side-to-side) balance. The instructions for most ARFs (and kits too) only tell you to balance the plane from end-to-end to set the CG, but the lateral balance is important too (especially if you want to do more than fly around in a level pattern). The lateral balance is only effected by gravity and so it does not change with airspeed, but it will cause the plane to roll towards the heavy side in “High-G” maneuvers (i.e. loops). The solution to keeping the plane balanced at all speeds is to have the aircraft weight balanced from side-to-side. The easiest way to do this is to take the prop off and suspend the plane from the prop shaft and a cord passed under a rudder hinge (use the hinge closest to, but above the aircraft center of mass). Add weight to the high side until you get the plane to balance.

The third problem is imperfect airfoils. These are tiny differences in airfoil shape (especially the rounding of the LE) that can require that the ailerons be trimmed to counteract. The aileron deflection and resulting airfoil shape will have different airspeed characteristics, so the required trim will change with airspeed. There is not much that can be done about this after the fact, so use care if you are building a kit.

The last problem is wing warps, even subtle ones. These also require aileron trim to counter and vary with airspeed. A warp will usually maintain its influence at very low speeds, however, while any aileron trim loses effectiveness. Some minor wing warps can be fixed, if the wing is covered in heat shrink covering. Have someone twist the wing in the opposite direction of the warp and small creases will appear in the covering. While the wing is being held, use a heat gun to shrink out the creases. As the covering cools, it will hold against the warp and hopefully flatten out the wing.
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Last edited by dhk79; 07-10-2007 at 01:55 PM.
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  #41  
Old 07-07-2007, 12:08 AM
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Quote:
Originally Posted by Blade Scraper
i'm confused tho,i'm not sure how you line up/shape the fuse.
The shape of the fuselage in the wire-frame actually comes from the 3D model, but the dimensions are the standard 3.9x49x3.9 that RF uses for all new fuselage sections. The wire-frame of a fuselage section will assume the shape of whatever 3D component is assigned to it. In the case of the fuselage this is the rootframe. To line it up, you just have to move its origin and size it to match the 3D image (just like any other component that you add in the editor).
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Last edited by dhk79; 07-10-2007 at 11:11 AM.
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  #42  
Old 07-07-2007, 12:13 AM
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OK, I think that pretty much wraps things up. This has been a compilation of RC tidbits I've collected over many years. I don't claim to know everything, in fact I am always adding to my data collection. Whenever I come across a new idea or suggestion, I write it down. So you've just been treated to what I could dredge out of the data barrow.

Many of the flight test interpretations are heavily plagiarized from a series of articles in Modern Aviation, called "Trimming from the Ground Up". I've adapted what they said for my own use, but they should receive the original credit.

Please feel free to ask questions or post comments. If you have a question about a particular step, please include the post #. Also if you have other tips or tricks that you'd like to share, please add them

You can tell this is a labor of love, I LOVE this sport...

Doug
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Last edited by dhk79; 07-10-2007 at 02:10 PM.
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  #43  
Old 07-07-2007, 09:18 AM
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One thing that I forgot to add was how to manually adjust real servo linkages to provide differential throws to ailerons. This is for those that do not have a computer radio that can do it for them.

This example will have the servo and the linkage on the bottom of the wing, such that the servo will push on the linkage to move the aileron up. If your plane has the servo/linkage on the bottom of the you'll have to reverse the servo arm.

This is a lot easier to show, that it is to explain. So here are three pictures. The first shows a wing that has flaps & aileron, but I'm going to add servos and linkages as if it had two sets of ailerons.

The second picture has one servo controlling both ailerons, a common setup for strip ailerons. Notice how the two "Z" bends are forward of the center line of the servo wheel? Having this offset will cause the servo to push more than it pulls and will give you differential throw.

The last picture is of one of two aileron servos that are on a "Y" cable to the same channel. Again the offset will provide more push than pull.

Again if you have a computer radio, it is easier to use two channels and let the radio do the work.
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Last edited by dhk79; 07-10-2007 at 02:12 PM.
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  #44  
Old 07-07-2007, 02:06 PM
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Quote:
Originally Posted by Blade Scraper
Your such a lil' baby,go get your binky and shuuuut uuuup.
P.S POO Does Not Fly.
Well, that wasn't very nice young man. You offended me.
...and yes, poo DOES fly when you blow it out your rear end!
Yes! I gotchya! How do you like me now?

As for the UltraStick, mister, the ding dang thing don't even hover!?!!?!
...let alone do a freakin' loop!

Regards,
Mr. Baker
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  #45  
Old 07-07-2007, 02:36 PM
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Quote:
Originally Posted by bobbaker
Well, that wasn't very nice young man. You offended me.
...and yes, poo DOES fly when you blow it out your rear end!
Yes! I gotchya! How do you like me now?

As for the UltraStick, mister, the ding dang thing don't even hover!?!!?!
...let alone do a freakin' loop!

Regards,
Mr. Baker
What kinda poo do you have,oh wait your ultra stick,never mind your poo does fly.
Quote:
Originally Posted by bobbaker
No one gives a rats ass.
I wasn't nice,my @ss
I got ya! BURNED!
Your kinda acting like little me,warbird,always has prob with every thing,when burned he goes nuts ect.

Last edited by Blade Scraper; 07-07-2007 at 02:42 PM.
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