|Sep 08, 2011, 05:18 PM|
USA, CA, Santa Clarita
Joined Jul 2005
Yes, it happens. I've gotten them on my fingertips usually from letting the peg/blade slide off my fingers instead of trying to properly time the release of the glider.
|Sep 08, 2011, 09:33 PM|
I've been getting them as I start to throw harder too. I've started using athletic tape on my throwing fingers and that has been a huge improvement. Not only are my fingers not sore, but I am actually getting more height because the peg releases cleaner with the tape. Plus the tape's not as hot as a glove would be. Cheaper too!
|Sep 30, 2011, 08:00 PM|
I will pay some $50AU to do this for me, any takers ?
|Oct 10, 2011, 08:14 AM|
Joined Dec 2007
I am thinking to purchase spectrum DX8, (I used DX 6i)
Does anybody know about Spectrum DX8 for F3K. Is it possible to make flaps on throtle stick to run from front to back. On DX6i it is possible to make only from neutral to back.
And how about launch button? Is any possibilities and how?
|Oct 10, 2011, 09:13 AM|
United Kingdom, England, Melton Mowbray
Joined Jan 2008
Launch pre set is programmed to the trainer button and works fine with spoilerons raised and up elevator.
Also have variable camber on the rotary knob, thermal and speed flight modes with elevator compensation and rudder to aileron mix.
I am new to DLG but for my needs the DX8 is a fine radio for DLG.
|Oct 29, 2011, 09:13 PM|
Joined Apr 2009
I put this info in another thread, for how one could take a DLG and get it pretty quickly flying decently at the field. But it will get lost in the original thread so I figured to move it here. The subject is close enough to the original of this sticky that it may have interest for the same audience.
*** WARNING *** - I've been typing again! (I should probably put this in a separate thread)
If one doesn't take the time to set up DLGs well, then one doesn't know how a well set up DLG should fly! One also doesn't have the practice at doing it, so it becomes a hassle and takes a lot of time. And the results are uncertain. That is because plane setup is a skill just like any other. It becomes faster and more automatic with experience. You won't get that experience without doing the work!
In the vast majority of the cases where someone puts their transmitter into my hands, the plane is set up sufficiently poorly to hurt the pilot's performance.
The throws you want may not be the throws wanted by someone else. Take a plane setup by IMAC pilot Jim Cokonis (ShadowFalcon). Is his plane fairly well set up? Yes... If you only want to move the sticks about an eighth of an inch for normal maneuvers. He has the skill on the sticks to do that with precision. Do you? If not, then his well set up plane would be poorly set up for you. The less precision you have with the sticks, the more toned back you need the control response to be, so that you can maintain adequate precision in flight.
Let's look at rudder throws for example. It turns out that the efficient range for rudder throws is about 13mm or about half an inch. Beyond that, efficiency goes to garbage. Amazingly enough, that is pretty true regardless of the percentage chord of the rudder. That was a surprising result from one of my analysis threads. So one could set up such that rudder throw is only a half an inch. Or, one could set up an inch of throw, but except for real emergencies, only use the inner half of that throw range. Both options could be considered well set up; it depends somewhat on how the pilot will use it. If you like to play close tag with trees, then you likely need that inch available. Otherwise, you'd likely be better off without it. When it comes to using rudder, it is better to use a little too little than a little too much. Having reduced travel available helps prevent over-ruddering.
CG is another one of those things... Some pilots make a study of how their planes fly. They can keep the plane flying efficiently regardless of conditions and regardless of CG setting. Other pilots have no clue. They need the plane to be fairly pitch stable to make up for this. Also, "optimal" CG position is a function of turbulence level, as are optimal airspeeds (more turbulence -> fly very slightly faster for same camber setting). That's just a minor fact of life in the Reynolds numbers range in which we play. The neutral point is not a static point for us. The behavior of our wings is not a constant. So there isn't a single perfect CG setting either. Even the range of desirable CG positions may change a little as conditions change.
Some manufacturers provide good guidelines for things like throws and CG. Others provide essentially no guidance. But in any event it is a good idea for pilots to have enough confidence/skill at the sticks to be able to safely fly the plane regardless of settings. It is also a good idea for the pilot to have the skills in plane setup to then be able to fix it so it flies well.
Heck, one should be able to take a mystery plane and get it set up reasonably well fairly quickly. That would still be set up better than the vast majority of planes out there. Then, fine tuning takes more time and familiarity with the plane.
For instance, take mystery plane. Let's say the pilot is pretty good at the sticks, smooth, and doesn't over-control the plane. So, let's set fairly conventional starting throws of +/- 3/8" aileron, +/- 3/4" rudder, (assuming top mounted stab) as much down throw as one can get without hitting the boom, and some reasonable degree of up throw - lets start at half an inch to make up a number. Put the starting CG about 3" behind the leading edge of the wing. Set the elevator trim to be parallel with the boom. Now the plane should be flyable regardless of the model. Perhaps not easily, or hands-off, but flyable.
Set the camber in cruise. Lacking info to the contrary, that is where the upper surface of the wing near the root is fairly flat across the hingeline.
Give it a toss and trim elevator so that it will try to fly hands-off.
Now launch it and get a little altitude. Put the plane in a vertical dive and let it build up some speed. If it pulls up, then give it some down trim. If it tries to go inverted, then give it some up trim. Now we have a trim position that would be somewhere in the ballpark for pitch neutral provided the CG was set approximately at the neutral point. Yes, there is some handwaving and some caveats here but it should be close.
Now, add a few clicks of up trim (perhaps 3 but how much will depend on the servo you are using and on whether or not you set up the transmitter such that each trim click moves the servo - which you should have done). Then leave trim alone... Adjust CG in minute increments until the plane is flying at a desirable speed for cruise trim.
This method somewhat decouples the elevator trim question and the CG location question which is why I presented it as an alternative to the classic methods. It should get you in the ballpark pretty quickly which is the point of the exercise.
Now lets look at response rates in roll and pitch. If the plane is super responsive in pitch but dead in roll, then increase aileron travel and/or reduce elevator travel. Get the plane to where the pitch and roll response seem to be at the same rate as one moves the sticks. One can generally set this in the dual rates setup, even if dual rates are not turned on by a switch. That is, one can use the same rate for all flight modes/conditions. I advocate that - less to mess with and mess up as one flies. Our DLGs don't really have a wide enough speed range to need multiple rates. If you have to mess with the travel adjustments you might have to re-visit the elevator trim as the servo can end up moving a little depending on your luck.
Next, lets set up pitch-neutral roll. In level flight, roll back and forth quickly over shallow bank angles. Make sure you are using only aileron to do this, no elevator! If the spring tension is not high on the sticks, chances are you can't do this well enough. Now, if the plane gradually pitches down, increase the differential slightly - make the down aileron go down a bit more and the up aileron go up a bit less. If the plane pitches up some, then do the reverse. Note the plane will likely slow down some during this maneuver but that is NOT the same thing as a pitch response. Making the plane move costs energy and that is paid for by either altitude (potential energy) or speed (kinetic energy) or both. What you want to watch is the angle of the tailboom (or whole fuselage) relative to horizontal. You don't want that angle changing.
Is this where you really want your differential? If you are a beginner/intermediate pilot, then I'd say yes. If you are advanced/expert, well then it is your choice. You should have the skillz to deal with the pitch change induced by aileron input.
Now realize I'm not an advocate of aileron->rudder mix. It is wrong more than it is right IMHO, in terms of percentage of flight time. But let's assume you want it. So this is when you'd set it up.
Go back to the small quick rolls. Watch how the fuselage changes pointing direction, left and right. When the plane is rolling in the clockwise direction, then the fuselage will yaw to the left. And vice-versa. So add a little aileron->rudder mix and check the results. Dial that mix until the fuselage maintains a constant pointing direction during the shallow roll maneuvers.
BTW, will this give you an axial roll? NO! It will just start out close to axial so it is not bad for initiating rolls from level flight. The required rudder correction direction is reversed when the plane is flying inverted (reversed at the sticks that is)... As I said, automatic corrections are wrong more than they are right. You can't beat skill at the sticks. But, you're the pilot. You pick your poison and take your chances.
Now, add in a mix for elevator->camber that adds perhaps 2mm down flaperons for half stick up elevator. It's just a starting point anyway. What you should find is that now the plane is suddenly a lot livelier in thermal turns and climbs more easily.
Now go do the loop test and dial in the up elevator throw and the elevator->camber mix. http://www.rcgroups.com/forums/showthread.php?t=1234569
At this point, the plane should be flying pretty well in cruise mode/condition and should thermal fairly well. It should be smoothly responsive on the sticks.
Now go ahead and duplicate this setup to create speed+launch and float flight modes/conditions.
For speed, adjust the camber to be 2mm up from where it was for cruise. That's a good starting guess if one doesn't have the info for that wing.
For float, adjust the camber to be 2mm down from where it was for cruise. Again, just a good guess lacking data for the wing. If Edge, go 1.5mm for starting.
Fly the plane in each of these modes, and trim the elevator to adjust the speeds. Don't bother trying to trim float if the air is not smooth while you are doing this setup. It is too difficult.
Now set up a launch preset. This would just be a couple mm up elevator added to the speed mode. Adjust for a nice pitch response on the throw.
Perhaps one can invent a quick and dirty test for how much elevator to use. Put the plane in a near vertical dive in speed mode from perhaps a quarter above launch height. Hit the preset button as one has speed approaching the ground. Make adjustments to get a good compromise between speed retention and altitude loss from when the preset is hit. Or, even better, use an altimiter.
For float mode, which is a thermal mode (cruise being the other thermal mode) reduce the elevator->flap mix for up elevator and down flaps. Since the flaps start farther down, there is less margin for them to go lower. For a starting guess, cut the motion in half.
For speed mode, probably just go ahead and cut the elevator->flap mix in half, both directions.
Ok, now just go and fly the plane for a while in a variety of conditions. Fine tune as you see fit.
PS - Forgot to mention about dialing in landing flaps, but I covered that anyway in this sticky thread. This post duplicates a lot of info from earlier anyway, but perhaps with a bit more of an at-the-field perspective and doing things slightly differently in a few cases. There isn't one single approach that works. But doing things in an appropriate order really makes the job a lot easier!
|Jan 05, 2012, 09:31 PM|
Australia, VIC, Melbourne
Joined Jan 2010
Thanks for this excellent setup info.
In post #2 you mention a launch preset mode. I assume you mean the launch rotation mode on a momentary switch, and that speed mode should be used for the remainder of the launch. Is this right?
This is what I've been doing but there is one issue, and pretty sure I've read other people mention it too. If I trim the elevator so the plane tracks vertically upwards after the launch rotation, I can't really use it as a speed mode for normal flight because the plane just wants to dive. If I trim for a hands off speed flying mode, then I can't use it for launch since the plane wants to loop.
Am I doing something wrong? Maybe wing camber in speed mode? I have the flaperon flush with the tabs.
|Jan 05, 2012, 11:00 PM|
Joined Apr 2009
Flaperons flush with the tabs may or may not be speed camber. It depends on the particular plane.
But in any event, it sounds like you have a combination of CG too far forwards, and correspondingly too much up trim. Then, as the plane flies faster at launch speeds, the horizontal stabilizer force increases in the downwards direction. The force due to CG does not change. So the plane pulls into a loop.
|Feb 28, 2012, 05:48 PM|
Joined Mar 2011
I am a little perplexed by my JR 12x. I am abuilder and flyer but not much of a radio programer. I have all of the surfaces going on my Stobel and my camber changing done, but cannot figure out how to get a flap function on the flap stick. I can get it on a fixed rate switch but not the stick. It's set-up in sailplane mode but some of the radio logic is still not revealed itself to me.
Ps I am kind of new to DLG as I have mostly been flying large scale sailplanes the last 8 years. Have a 10sx but did not do much of the programing--- sorry to say now
|Apr 07, 2012, 11:06 AM|
I gotta question for you. In one of your set up threads you say that to keep the nose from dropping when entering an turn you should reduce the flaperon on the descending wing, ie: the wing that has the rising flaperon.
Well, I tried this and I've noticed two things:
First, it works. Up to a point. But...having the nose drop when entering a turn seems normal to me and I don't see how it can be avoided. Minimizing the amount that the flaperon rises on the descending wing does make the turn a lot smoother and the dropping nose less pronounced.
Second, in order to minimize the nose drop in a turn I have very little up flaperon in a turn and quite a bit of down flaperon on the opposite wing. In fact, what I have amounts to a lot of reverse aileron differential which then requires a lot of rudder to counteract the adverse yaw. Seems like that would really add drag when entering a turn.
Should I match the amount of down aileron to the small amount of up aileron or is the down aileron supposed to have more deflection than the up aileron? BTW: I am using a rudder.
So. Am I setting up my glider correctly, or am I completely screwed up?
Thanks for the help,
Last edited by eteet; Apr 07, 2012 at 04:42 PM.
|Apr 07, 2012, 06:18 PM|
Joined Apr 2009
There may be some misconceptions here.
Pitch of the nose entering or exiting a turn is a function of the elevator primarily. It is a pilot input. Being late on the elevator makes the nose drop. Being early makes the nose rise.
Being out of sync with rudder input may also cause an apparent pitch change due to inappropriate yaw angle.
When in a turn, the plane needs to fly faster OR have more camber in the wing. The wing is being required to generate more lift than in straight line flight.
Flying faster can be accomplished by allowing the nose to drop a little on turn entry. As in level flight, with the nose down the plane should accelerate. Note though that this response is late. Dropping the nose starts the acceleration process. The plane is not instantly flying at the desired faster speed.
Increasing camber on the wing, via elevator->camber mixing, is essentially instant. It is also quite logical. As up elevator is pulled, the wing is being asked to generate more lift. Camber matches the elevator request... So this syncs up nicely.
What you may be confusing is the adjustment so that aileron input, by itself, does not cause a pitch change. That is tested by a quick shallow rocking of the wing, using ailerons only. If the plane pitches down / accelerates, then more down and/or less up aileron is needed. If it pitches up, then less down and/or more up aileron is needed. This then establishes the aileron position where aileron input is decoupled from pitch.
Note this adjustment can be flight mode dependent, but usually by little enough to not be really in need of tuning for each flight mode. Tune for cruise, and the rest should be close enough.
Then, if one really wants differential for some reason, tune from this position. Adding differential will result in a pitch response to roll. Suppose one is flying along looking for lift, floating or cruising. One is flying a straight line. Now the plane banks slightly to the left. Obviously we want to go at least slightly to the right. We use aileron to correct the bank. If differential is not neutral, then the plane undergoes a pitch response.
That pitch response can give a false impression of the quality of the air encountered, leading one to believe it is slightly good or slightly bad.
This of course can be overcome with pilot experience with the plane. But why go out of our way to make reading air more difficult? That is why I suggest using neutral differential for anyone other than real expert pilots. IF an expert wants differential then that is their problem to deal with.
As for adverse yaw, the vast majority of that is due to a roll rate. Differential setting on our DLG wings has very little effect on this. The reason is our wings are low camber, and even lower towards the tips. The response to aileron input is nearly symmetric. This is in contrast to full size sailplane and other airplane wings which have high camber. Their response is much less symmetric therefore differential has a greater influence on the yaw response to roll input.
I wish people would get this straight. It would prevent a lot of confusion and repeated mis-information.
One may choose to use differential to adjust the pitch response of the plane upon entering and exiting turns (when aileron input is present) but IMO it is not as good as doing it directly with the elevator. Regardless of setting, a pilot should have the skill to perform figure-8 turns without pitch response. If the pilot cannot do that, then using differential to make a correction is a bandaid attempt to cover a weakness in the pilot's skills. It is better to fix the skills first.
Rudderless adds a little complexity to this. Thought experiment time...
When one initiates a turn and doesn't have a rudder available, then the plane is going to be attempting to yaw away from the turn direction established by the roll. As bank is increasing, this shows up as a little up pitch of the nose, if one used exactly the same elevator input one would use if a rudder were present and a fully coordinated turn were being done. So one could argue in this case that having a little differential to lower the nose a hair while ailerons are being applied keeps the required elevator input the same as for ruddered planes. But the cost is the pitch response when one is simply attempting to correct a slight roll angle.
Note that in steady-state turn, when ailerons are being held relatively constant, differential does not matter. The position of the flaperons can be defined as a (camber+aileron+differential, camber-aileron-differential). Since there are two outputs (positions of left and right flaperons) but three inputs (aileron input, camber input, differential setting) I can match any position someone specifies using differential, without using differential.
The elevator->camber mix mentioned earlier is a bit trickier in some ways. The floatier the setting, the less extra camber the wing can efficiently support. How much camber the wing can support is a function of conditions. In really dead air, one can trim a more accurate airspeed and more camber can be used to reduce sink rate. But if there is air activity, then the extra camber would require flying speed to be maintained to a higher level of precision than is practical. So for best dead air float, one has to tune for the conditions, slightly. Sometimes more than slightly.
The response of the wing is also going to be dependent on turbulence level. More turbulence, and the optimal flying speeds are going to be slightly faster, without adding ballast. Add ballast, and of course the optimal speed is faster still.
Turbulence has other effects on the overall drag response of the plane.
These differences are a good part of the reason one should practice flying in a variety of conditions. One really needs to know the response pattern of the plane, to fly it effectively. One can get close, quick, with experience. But mastery requires stick time.
CG is another one of those things. In turbulence, people often move their CG slightly forward. Why? It improves the static margin. This helps the plane naturally maintain trimmed airspeed to a greater precision. This in turn keeps the wing flying a little more efficiently. More efficiently -> more air time. It is that simple.
But go too far, and the plane will phugoid. That requires pilot input to correct, thereby costing efficiency.
CG is a tuning parameter. It is plane dependent. A very slippery plane will phugoid at a little lower static margin than a draggy plane. Modern low drag DLGs are a little more sensitive to CG than some of the old bagged designs of yesteryear.
Most of this is OT for this thread, but hopefully it helps explain some of the reasons why I make the starting suggestions I made here in this thread.
Last edited by G_T; Apr 08, 2012 at 02:32 PM. Reason: Improved some poor phrasing. I should have proof-read.
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