Multiplex Easy Glider

[kennyc]

For my case, I moved my CG abt 5mm behind then the recommended. For throttling...... think mixing w a little down elevator helps.... at least this is wat I know Doug is doing. Mine dun really face this issue.

Perform the dive test to check the CG


Mike

Hi Mike, care to explain the dive test alittle? thanks!

[kennyc]

how do u trim this fellow? power off or power on?

power on it goes nose high
power off it feels head heavy

70mm CG
any comments?

For gliders, we want it to stay up when you cut your throttle, so your plane should be a neutral as possible when you cut your throttle.
since you say you power off it is head heavy, that mean you are nose heavy, move your battery pack backwards to the tail of the plane or add some weight.


when you throttle more then half, your glider should start pointing upwards. that is what you want. the plane to go up! you need to add a little down trim on the higher throttle. go ahead and mix the down trim if you are using a computer radio.

cheers!
ken

[kennyc]

I may be wrong, but check again on the direction of downthrust.
I have the impression that the more downthrust there is, the more the plane balloons.

I have a recent case where by too much downthrust was the culprit of a constant power on ballooning, and it was not a glider.

As Mike advised, some down elevator coupled in with throttle up will minimise the ballooning somewhat. I trimmed mine for power off, as this is the envelope which the EG spends most of the time within.

hope this helps.

Yes you are right on the down thrust . this is due to angle of the wing incidence, we cannot change this on this bird.
avoid adding anymore down thrust. again mix in some down elevator on higher throttle settings.

[X34]

Would overpowering cause it to balloon as well?

[fuse]

how abt mixing throttle to flaps?

[Cycross]

Actually it's all about pitch change.

mixing throttle to flaps will mean turning flaps into spoilers (i.e. upturned flaps) to lower the nose. you will lose lift to trade for speed and less pitch up.

mixing throttle to elevator only trims out the pitching moment. your basic wing lift is preserved.

hope my aerodynamics holds water

Update: I got to add I meant reflex and not spoilers, though the deflection is the same direction in general, just different magnitude.

[fuse]

sounds great.

one more thing i need to ask
deploying spoilers at 60 degrees during landing
the glider tends to roll left and i got to hold right to maintain flight path.

[joe yap]

Hmm... it sounds funny the way it was explained.

In fact, the downthrust is supposed to neutralise this phenomenon, not to make it worst.

A glider is always trimmed with the power off, to the best glide ratio. At that speed, the wing produces the lifting force just enough to give the flattest glide. When the power is turned on, the increase in airspeed will cause the wing to produce more lift and without compensation to correct the angle of attack, it will create a pitch up moment. The easiest way to compensate this is to incorporate down thrust, which will produce some pitch down moment when the power is increased. This is exactly why powered free flight planes have plenty of down thrust.

Ideally, an airframe should have just enough down thrust to fully cancel the pitch up effect, but for R/C birds, we can correct the last bit of this tendency by inputing some down elevator manually. Modern computer radio allows to to mix the elevator with throttle, but mind you the pitching moment is the function of airspeed, not throttle stick displacement. So, you can't cancel out this tendency totally by computer radio mixing.

Now for the pratical part. To trim out your powered glider, first climb your glider under full power to height, manually compensate for any pitching tendency. When reaching the desired height, which gives you enough time to trim and not too high that you cannot observe properly, cut the motor after leveling out the plane. At this point, make sure that the motor is being braked and the propellor folded and trim the elevator till it gives you the flattest glide without any hint of stalling or porpoising. After this, do not touch the elevator trim. Fly the plane without power until it's about 3 storey high and increase the throttle to full. Observe for any pitching tendencies. If it's pronounce, land the glider and add shims to increase downthrust. Adjust the downthrust to the point when the tendency is manageable or best still, totally neutralised.

[joe yap]

Having said all these, there's one very important point you guys need to observe. I've noticed some Easy Gliders have their motor mounts loose. If that's the case, you have very inconsistent results. The foam surface does not hold up the hot motor firm enough. I'll like to suggest that the motor to be mounted in a motor tube, which is permanently epoxied to the foam cavity meant for the motor. A motor tube can be easily fabricated by rolling 1/64" plywood on the motor itself and glued down with CA. A layer of plastic film laid on the motor before rolling the plywood over will prevent it from accidentally glued down on the motor. Once the CA has cured, simply slide the motor out of the tube. The motor can be later tacked into tube with 2 drops of CA for mounting.

[Cycross]

I think Joe is rite, I stand corrected
Kudos Joe!

[joe yap]

By the way, don't be surprised some planes have about 4 degrees of down thrust.

[fuse]

very interesting indeed!!!!
i shall add more down thrust then.

[joe yap]

For your reference, my Maestoso's downthrust is pretty pronounce. In fact, I could even add another degree or 2 to cancel the last bit of pitch up tendency. But I decided to fly it manually instead.

[fuse]

wow very nice !!!!
must be fast!!!


may i ask how do you use spoilers? and when do you put the throttle on a switch instead of the throttle stick?

[joe yap]

In the contrary, this is not designed to fly fast at all. It's a very lightweight HLG with a powerful setup to achieve very powerful climb, rather than to fly fast. The prop velocity is quite low but the static thrust is impressive enough to achieve close to vertical climb. For LMR competitions, you are allowed about 50 secs of power to climb and the rest fo the flight is done without power. This design is based on that.

I don't use spoilers for power gliders so far. I only use it on my scale gliders so far to dump lift when landing on the slope. For that, I use the throttle stick to control the spoilers. For powered gliders, you can only use a switch. For some computer radios, it has the landing function which you can setup for elevator,spoilers,flaps and ailerons by a flip of the switch. It takes some experiment to find the sweet spot for every individual gliders.