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Old May 17, 2011, 11:32 AM
G_T
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Initial programming of a DLG

Hello everyone,

I had suggested a method of setup previously, but it took me a while to find it in searching. So I'm duplicating the info here in its own thread to make it easier to locate in the future. Perhaps some will find it useful, as setup questions frequently occur. Starts at next post.

Gerald

PS - See post 97 for a more at-the-field approach.
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Old May 17, 2011, 11:33 AM
G_T
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I'd probably tick off some people with my opinion on a good starting setup. I end up spending a fair bit of time at each contests reprogramming or adjusting people's setups. Then they fly them, and after a few flights I get a comment that the plane is a whole new plane, flying better and easier than ever before. I usually do 2-3 per contest, but it has been as many as 5 once.

Ok, so I guess it is time for me to tick some people off.

Part I
---------

Efficient throws for smooth flying:

Flaperons aileron function +/- 3/8".
Rudder +/- 1/2".
Elevator - determined by testing.

Aggressive throws for tree huggers:

Flaperons aileron function +/- 1/2".
Rudder up to +/- 1".
Elevator determined by testing.

That's the easy part.

Setup procedure:

Start with verifying all control linkages are tight and that the servos are up to the job. Note that a D-47 on rudder is NOT up to the job. I know, those that do it won't believe me... Just switch to something like an SM-22, JR-241, JR-285, etc, (and there are a number of other good choices and good compromises for space challanged installations). You will find your launch is straighter and higher. If you needed a rudder preset before, you won't now.

Verify that the desired travel range is accomplished through utilizing nearly all of the servo's travel range. If not, then the power at the control surface, and the precision at the control surface, are reduced. For our purposes, that power is worth more than the speed of travel.

Take the transmitter sticks and set their spring tension to the max. With soft springs, one CANNOT feel the location of the control surfaces with sufficient precision. Soft sticks sell radios. Stiff sticks win competitions. If the max is not high enough, get stiffer springs. They are available for pretty much any radio.

As a philosophy, disable every control on the transmitter that you do not intend to use. Functioning controls can get bumped...

Disable all exponential, all dual rates. Zero out all trims in all flight modes. Get rid of any differential. Zero out offsets for flight modes.

Have a program that supports flight modes for launch, speed, cruise, and float. There needs to be a launch preset switch that enables the launch mode. There needs to be a three position switch for selecting between speed, cruise, and float. Why a single three position switch? Less controls to fiddle with, so simpler operation. If it isn't simple it takes thought. If it takes thought, then you are not flying the plane.

That gets rid of the preliminaries. Now on to the plane setup.

Start with the flaperons. Set the flap stick (it IS on a stick, right??? It should be on a stick and ONLY on a stick) and set it at half stick. Now set the servo subtrims for these two servos to match their angle of droop. This can be seen clearly by looking from the back of the plane with the tail held high. Match them exactly. Wiggle the sticks to make sure.

Now move the stick back up. Adjust the servo travel limit in that direction so that the flaperons are even with each other. Now move the stick full down, and repeat for the other direction of servo travel.

Now when the flap stick is moved, these surfaces should exactly match each other's travel. I've yet to have someone hand me a plane to help program where this was the case.

Now with the stick back up at the top, set the aileron travel. On some radios, this is through setting the dual rate. Keep the dual rate settings the same for all flight modes and all switch positions, if you can't disable the switch.

When the aileron stick is moved to its limit, both ways, there should be no evidence of the travel being clipped off. If there is, then adjust settings to get rid of that. Clipping of aileron travel with the flaps up is NOT ALLOWED. Clipping of aileron travel with the flaps down is a feature, if you want it. It improves roll control in that state.

Now with the flaperons up, move the aileron stick. Observe the relative travel of the left and the right aileron. Do they travel equal distance? If not very very close, then adjust differential settings to get them to travel equally. Note this is a preliminary setting that gets finalized in testing. Call it the vanilla setup.

Now go to the rudder. Set the servo subtrim so the surface is centered. Adjust the endpoints so you get the desired travel range. This is at a minimum 12mm, regardless of rudder chord percentage. Yes, a funny result. If you want the analysis on this, look up one of my analysis threads. Actually, for an asymmetric airfoil vertical stabilizer, you want a few percent more travel in the "down" direction than in the "up" direction. 12mm away from the throwing blade and 13mm towards it, for instance. That would be a minimum travel setting. Realize that any travel beyond this level causes rapid increase in drag. It should be avoided in flight. HOWEVER, if one is playing tag with treelines, then in some instances drag may become a far lesser consideration to dodging a tree! So one may want to increase the travel beyond this level, but don't bother going beyond an inch. Just try not to use that extra travel except for emergencies, ok?

Now on to elevator. Set the downward travel to about as much as you can get. Don't jam the elevator into the boom (seen that a lot) but get what you can. At the top of the launch, the plane is flying pretty dead slow. It can take a lot of travel to plop the plane over to horizontal with authority. That's about the only thing we use down travel for!

Leave up travel where it was for the momemt. It will be tuned in during flying.

End Part 1.

Gerald
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Old May 17, 2011, 11:34 AM
G_T
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Part II
---------

Flying. Start with native speed mode (or cruise, or whatever has the flaperons even with the tab). Do some gentle hand tosses and get the elevator trimmed out. DO NOT use the elevator trim lever on the front of the transmitter. Use the servo centering in the programming.

Do enough of a toss to get a touch of altitude, and check that the plane is suitably stable. Gentle DL at an upwards angle, then guiding it with the elevator stick, is a good approach. Check stability via dive test or whatever you are comfortable with. Make preliminary adjustments to CG, and retrim the elevator centering in the programming to re-establish proper glide path. CG and elevator trim are interrelated.

Now that one flight mode is flying fine, set up some preliminary camber settings for the others. If one has no information on what to set up, then these guidelines may help:

Generally speaking, speed mode has the bottom of the wing in the back half relatively flat. One can check that with a straightedge or even a piece of paper. This setting is also usually optimal for launch.

Cruise mode generally has about 2 degrees or 2mm more down on the flaperons.

float setting generally has about 3 to 4 degrees down on the flaperons, from speed mode. 4 degrees for Zone, 3.5 for Edge, ... If in doubt, it is better to use a little less than a little more.

Note that the float setting is NOT the thermal setting! It is the setting you would use in dead air flying. One can tune it in with a stopwatch in the right conditions, carefully adjusting the camber and the associated elevator trim and doing many tests. Notice the experts out floating around slowly as the fog is burning off the field? Some of them are doing this, as well as looking for the best areas to float. FWIW, don't assume that the slowest you can fly is the best for min sink. It is not true for all DLGs.

Now fly the plane a little, setting the elevator trim in the flight modes to give reasonable glide speeds for these three camber settings.

For the surprising part of this, the speed difference between the float camber setting and the speed camber setting is on the order of 1M/s. That is all. Now one may CHOOSE to tune the speed setting to be faster than that, but one is giving up peak L/D to get it.

Speed should be tuned for its peak L/D, or at most very very slightly faster. If you want faster than that, use the stick! Peak L/D is peak distance coverage in dead air for a given altitude.

Cruise should be tuned for peak L/D generally speaking, but not faster.

Float should be tuned for min sink.

When these are trimmed, if one finds that the plane turns one way at float camber, but the other way at speed, then start looking for wing warps to remove.

Set up a launch preset that gives a reasonable rotation rate. It can be tuned using an altimeter, but realize the tuning will be somewhat dependent on the thrower and the wind speed, as well as the plane. I'm afraid there isn't one universal optimal setting.

Now get the plane up in the air, and into level hands-off flight. Now rock the ailerons rapidly back and forth. If the plane pitches down, then the aileron differential needs to be set so as to increase the down aileron travel and decrease the up aileron travel. If the plane pitches up, do the reverse. If the sticks are soft, then the pilot probably can't move the stick without bumping a touch of elevator so the results may be suspect.

If the pilot absolutely insists on aileron->rudder mixing, then set it up now. Watch the fuselage pointing direction, and rock the ailerons as before. The pointing direction should not change. If it changes, then adjust the mix and test again.

I am against that mix, as it is impossible for the mix to do the complete job and most who use the mix use it as a crutch rather than learning to use their other thumb. This holds them back as pilots. Some, however, do use their other thumbs and know how to compensate correctly for the mix to make coordinated turns. It is fine for them.

If you choose to fly rudderless, that's your problem, not mine

End Part II

Gerald

PS - I should probably throw something out there about differential but I don't really want to get into it. It is a dead horse as far as I'm concerned. Differential on ailerons can be considered to be a combination of a pure aileron input (can rock ailerons and plane doesn't pitch) and a camber change (which causes an associated pitch change).
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Old May 17, 2011, 11:37 AM
G_T
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Part III
----------

Elevator related stuff... This includes total up elevator travel (down is already set to the max of what you can get), elevator->camber mixing, camber->elevator mixing.

Look up "loop test". I wrote this up a while back. http://www.rcgroups.com/forums/showthread.php?t=1234569 Use that for getting elevator up travel and elevator->camber mix settings. It gets you in the ballpark fairly quickly with a little experience. It prevents one from setting up inefficient combinations which is perhaps more to the point.

Expect that the elevator->camber mix in the downward direction whould be less for float camber and for speed camber than for cruise camber. Expect that the mix should be symmetric for speed camber, but not necessarily for the others. I personally use symmetric for speed and cruise cambers, but have more up than down for float. Up for float matches up for cruise. It is a feel thing... and keeping the wing flying near-optimally.

In speed mode, the lift coefficients are lower. The changes in lift coefficients are smaller as one uses elevator, so the required changes in camber to keep the wing near optimal are also smaller.

In float mode, we are getting about as much lift out of the wing as we can efficiently achieve without making the wing way too difficult to fly well (and thereby costing all the performance increase and then some). So adding much more camber when one pulls up elevator becomes a minus. But decreasing camber more aggressively as one pushes the nose over and speeds up makes sense.

Cruise is somewhere in between.

For flap->elevator mix, one cannot use a linear mix and get it good enough. Sorry, that's the breaks. The reason is the travel of the flaps is too large. As the flaps start to be moved down, they are making a notable change to the angle of attack of the wing. But if the flaps were at, say, 90 degrees down, then they would be making no change to the angle of attack of the wing.

When we are setting the elevator response to the flaps, what we are really mostly doing is making the horizontal tail's angle of attack match the wing's angle of attack, over the range of travel of the flaps. Any other phenomenon is secondary and much smaller. So, one needs to have the elevator respond faster in the upper part of the flap travel than for the lower part of the flap travel.

In practice, a bilinear curve is sufficient to do the job. This is one where we specify 3 points. Two won't do. More is nice, perhaps, but not necessary at all. 3 with some smoothing is excellent.

Often people try to use the built-in mix for this. Then they run into subtle issues with some transmitters making it a whole lot more work.

I usually make my own mixer.

What you want is the ability to adjust this mixing ratio (upper and lower ratio) without having to adjust the elevator trim! Some of the built-in mixers assume the stick is in the center for neutral, and mess this up.

Set up the mixer, and adjust the ratios so that when one is in level flight, one can slowly move the flap stick over its range of travel and the plane behaves nicely. Nicely means maintaining a smooth steady glide, though the descent angle may increase a little as full flaps are used, and the speed then is slower.

If in the middle of the range, the plane pitches up, increase the mix in the middle. If around full flaps it pitches up, increase the mix at that end.

Now landing approaches should be a breeze.

End Part III and that's enough for now.

Gerald
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Old May 17, 2011, 11:38 AM
G_T
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I forgot to add something important on the transmitter setup. Set the trim step so that each click of a trim tab causes one minimal step motion of the servo. The default setting for most transmitters seems to be something around 4 steps for one click. A servo such as a JR285 can work with a step setting of 1, and a servo such as a JR185 can use a step setting of 2, for instance. Heck, a D-47 can use 3 if I recall correctly. This is most important for elevator and least important for rudder.

People seem to fail to realize that if they want to set their DLGs to a balance point near neutral, then precision of the elevator servo and linkage, and fine steps of trim, are critical to getting the best performance out of their plane. IF one doesn't have these things, then one shouldn't use a CG near neutral but instead should balance a little farther forward.

Gerald
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Old May 17, 2011, 01:47 PM
BenRoberto
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Thanks for re-posting your notes.

-- b
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Old May 17, 2011, 02:14 PM
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Thx, GT.
I was going to have you set up my Vandal and 8FG at IHLGF

Do you have any suggestion for a 4 servo wing?

How about rudderless?

Tai
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Old May 17, 2011, 02:19 PM
Jim C
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I read all of that and I am not ticked off.

That is similar effort and quality to another type of model trimming in the IMAC world by Peter G. It takes time to do so thanks for the effort.

Saying that, do not let my next comment tick you off!

The icing on the cake would be some videos of this being done on a glider. If you ever want to do that, let me know. I think it would be a fun project and I would be willing to help. Teaching for a living, I know that many people are visual learners. Seeing the changes in setup while you program the surfaces could clarify the verbiage.
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Old May 17, 2011, 02:39 PM
G_T
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Quote:
Originally Posted by tai626 View Post
Thx, GT.
I was going to have you set up my Vandal and 8FG at IHLGF

Do you have any suggestion for a 4 servo wing?

How about rudderless?

Tai
Sorry I couldn't make that event. It is getting difficult for me to make any events this year, unfortunately.

For a 4 servo wing, I would set up the inner flaperons' aileron travel to be roughly 1/3 of the outer flaperons' aileron travel. The exact choice would be based on the location of the control surface split. It should be close enough to optimal for most purposes. The useful range should be 1/4 to 1/2.

I would set up the outer flaperons' aileron travel limits to be a little above what you would use for normal flaperons.

The combination above will yield the same roll response that a flaperon wing generates.

Camber would be matched across the wing for each flight mode.

elevator->camber mix... That one could take some thought and some number crunching that I don't have the time for. Probably default to even across the wing, lacking the analysis.

Flaps, obviously lots of flaps for the inner flaperons. Or at least more flaps than for the outer flaperons! Otherwise, what's the point? I'd probably have them go down in sync to perhaps 10 degrees (stretching a float to the hand) but after that, have the outer flaperons reverse direction to end up slightly reflexed. Sort of a mild crow (or at least have them stop going down farther). This would necessitate having the servo neutrals be a bit different in installation as one would bias the inner flaperons for substantial down travel and little up travel, whereas the outer flaperons would be much closer to equal available travel up and down.

Gerald

PS - I'd probably then put the flap stick in the middle, as the location where the ailerons stop going down. Easy to keep track of where one is, that way. Upper part becomes floating, lower part becomes braking.
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Old May 17, 2011, 02:47 PM
G_T
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Quote:
Originally Posted by ShadowFalken View Post
I read all of that and I am not ticked off.

That is similar effort and quality to another type of model trimming in the IMAC world by Peter G. It takes time to do so thanks for the effort.

Saying that, do not let my next comment tick you off!

The icing on the cake would be some videos of this being done on a glider. If you ever want to do that, let me know. I think it would be a fun project and I would be willing to help. Teaching for a living, I know that many people are visual learners. Seeing the changes in setup while you program the surfaces could clarify the verbiage.
Certainly not ticked off... I'll consider it.

I have thought of doing something like Bruce's famous presentation to try to do the same thing with plane setup, but it is more difficult. Plane setup requires reprogramming transmitters and each installation will be a little different, transmitters are quite different, and usually some remedial work on the plane is required before even getting started. All this takes quite a bit of time.

Gerald
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Old May 17, 2011, 02:57 PM
agony sweetns the victory
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Thanks Gerald!

That's an excellent tutorial.
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Old May 17, 2011, 03:55 PM
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Originally Posted by atjurhs View Post
Thanks Gerald!

That's an excellent tutorial.
What he said!
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Old May 17, 2011, 05:36 PM
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Thanks Gerald, your excellent tutorial helped me immensely!
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Old May 17, 2011, 07:21 PM
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Quote:
Originally Posted by G_T View Post
Disable all exponential, all dual rates. Zero out all trims in all flight modes. Get rid of any differential. Zero out offsets for flight modes.
I assume that this is just for the initial setup phase, and later you go back in and expo, dual rates, etc...?
Quote:
Originally Posted by G_T View Post

When the aileron stick is moved to its limit, both ways, there should be no evidence of the travel being clipped off. If there is, then adjust settings to get rid of that. Clipping of aileron travel with the flaps up is NOT ALLOWED. Clipping of aileron travel with the flaps down is a feature, if you want it. It improves roll control in that state.
Could you elaborate a bit more on this clipping? Is this were you have a little bit of stick movement at the far ends where there is no corresponding movement of the ailerons? If so, what causes it and what settings do you adjust to get rid of it?

I'm new to this whole DLG thing so your taking the time to write out all these setup tips is greatly appreciated.

Thanks,

Paul Barros
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Old May 17, 2011, 08:33 PM
G_T
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Nope. No expo or dual rates. If one needs expo, then tighten the springs on the sticks. Expo softens the response around neutral, but loses control when off neutral by much. So if one sets expo on elevator for instance, then when in a thermal turn, the elevator response rate is now different (and asymmetric) compared to level flight. Why make things more complex and difficult?

Similarly for dual rates, when one suddenly decides to make a maneuver, do you have to hit a switch first? Which state is that switch in now?

Not having varying or changeable rates is simpler to learn.

Our planes really don't have a wide speed range, so there isn't even that justification for rate changes.

Clipping - That is running out of travel in a plane's control surface to support the motion input at the stick. That can be a feature or a problem, depending on how it is used. I often set up planes so that at the bottom of the flap travel, downward travel for ailerons is clipped but upwards travel is not. That greatly reduces the adverse yaw in this special case where additional down aileron travel does not increase lift but simply greatly increases drag. So in that case it is a feature.

But having an upwards motion of aileron stop before the stick reaches the limit would be a problem.

Gerald
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