I'm new to RC and bought an AXN

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Re: I'm new to RC and bought an AXN

Postby GRM » Wed Mar 13, 2013 1:14 am

Hi,

I maidened my AXN this weekend and encountered a few problems.

PROBLEM 1

I used the recommended 2200maH 25C Zippy (180g) battery but with this pushed all the way to the front of the fusilage the CG is not on the wing spar line.

The plane was very twitchy in the air and even after trimming did not handle that well - admittedly there was a bit of wind but the lack of aileron authority was pretty disappointing - even though I have the connector rods on the innermost hole of the horn as per the build instructions.

I've now checked and if a use a 1750mah Rhino (130g) pushed all the way forward in the fuse the CG is pretty much on the spa line. (I'm using a Hobbywing 40A ESC 30g)

Has something changed in the production of the AXN since the build instructions were written - or should I just slide the 2200mah further back towards the tail to get the GC on the spar line ? The problem I see with this is that the power wires from the battery (which I have facing the tail as per the build video) are then inclined to interfere with the ELE and RUD servo arms.

PROBLEM 2

I didn't give this much thought to this during the build but the wing servos (HXT900's) do not sit flat in their positions in the wings - the trailing edge of each servo sits 1mm above the wing surface. This means that the amount of travel of the ailerons is not the same on each wing - to get them to be the same I've set the upper limit to be 75% of max in ER 9x and the max travel of each aileron is then +/- 12mm from the wing. Is 12mm sufficient to get decent aileron authority ?

Any help appreciated.

GRM
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Re: I'm new to RC and bought an AXN

Postby cynr100 » Wed Mar 13, 2013 2:29 am

Hi GRM,

Firstly the CG is important and how you achieve it is up to you, trial & testing repositioning of battery,ESC and cabling etc etc.
I have used both Zippy 2200 and Turnigy 2200, both give different positions for the correct CG. Nothing is stopping you from running any cabling in different directions or even adding small lead weights to the tail or nose to achieve CG.
There is no hard and fast rule for positioning of equipment except to achieving the correct CG.

Second, change the position of your control rods so that both ends are fixed at the mid point of the servo arms and control horn. Check that you have 100% end points on your Tx, now change the rod position on the control horn until you have achieved the control surface movement that you require. Make sure to check Tx settings on both directions of stick movement. Now that you have achieved greater control surface movement you can tone down the rate of movement by adding exponential (again check both directions of stick movement). I find 80% is adequate.

Third, get your mechanical trim right first before adding trim to the Tx you may need this later when trimming in flight. Remove all trims from the Tx and power up the AXN to establish servo centres. Power off and adjust all servo horns to a centre position (90deg to the servo body), adjust the rod lengths as required to achieve neutral control surface positions. If you are not happy with the aileron servos positions they can be removed and make alterations to achieve the desired placement.

Remember, if it doesn't look right it probably isn't.
Cheers
Dennis
Not enough time in the day for all my crazy ideas, I'm not slow, I'm just pacing myself
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Re: I'm new to RC and bought an AXN

Postby BillGriffiths100 » Wed Mar 13, 2013 8:50 am

For the heavier battery trim up a bit of white packing foam to fill the nose and then the battery can rest against it to get the right C of G.
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Re: I'm new to RC and bought an AXN

Postby GRM » Thu Mar 14, 2013 1:35 am

Thanks Gents.

Have made the necessary mods. Will report back.
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Re: I'm new to RC and bought an AXN

Postby GRM » Wed Mar 27, 2013 5:37 am

Hi,

With the COG set correctly on the wing spar my AXN now flies beautifully. I've now set up spoilerons on one AXN as an experiment and will also try a Thermal Scout.

Thanks again,

GRM
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Re: I'm new to RC and bought an AXN

Postby cynr100 » Wed Mar 27, 2013 9:29 am

:D :D

Spoilerons... :?: or flaperons... :?:
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Re: I'm new to RC and bought an AXN

Postby GRM » Wed Mar 27, 2013 10:11 am

Hi,

On a 4 channel planes if you have a programmable tx (like Turnigy 9x running er9x) you can program a switch so that flicking the switch will raise both ailerons or lower both ailerons.

Raising both ailerons simultaneously kills lift and is known spoilerons. Lowering both ailerons simultaneously increases lift and drag and slows the plane down,

So instead of sliding for some distance along the grass it should be possible to land on a spot almost.

There is a good discussion here http://www.rcgroups.com/forums/showthread.php?t=118971#post990930 on the merits of the two. I intend buying a faster glider at some point so I wanted to try out spoilerons on the AXN first. Spoilerons are recommended over flaperons on a number of sites.

How to set up er9x is here http://www.youtube.com/watch?v=BGg8EOB3xI4. The key thing is that you need a separate channel for each aileron servo - so in the build you don't use a y cable for the ailerons - each aileron servo cable is connected separately into your receiver (which must be 5 ch min - I'm using the HK TR6A receiver). I've done it a little differently than in the video from Greame Robinson as I've used er9x's offset functionality - which I thought was easier. In any case it's not hard to do and should make landings more presise.

GRM
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Re: I'm new to RC and bought an AXN

Postby Bio Hazzard » Wed Mar 27, 2013 11:53 am

Always being interested in using ailerons as flaps also, will try it on dx6i on the weekend and see if I can get it too work! Almost every landing ends with a bounce causing the plane to just slide past me (or sometimes into me) :lol:
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Re: I'm new to RC and bought an AXN

Postby cynr100 » Wed Mar 27, 2013 12:14 pm

I have my setup for flaperons but have never used them in anger, usually too busy getting the lineup and angle right. Changing them to spoilers might just save me from the occaisional goal post impact when I get my final wrong and have to decide on whether to go under or over the cross bar. :arrow: :mrgreen: :lol: :lol:
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Re: I'm new to RC and bought an AXN

Postby Bio Hazzard » Wed Mar 27, 2013 12:23 pm

cynr100 wrote:save me from the occaisional goal post impact

When I was flying last the guys at the park had some goal posts temporally set up, when the finished training they left them there....

There was nothing for me to do but fly my AXN through the goal posts!! :lol: I barley made it through....video soon to come :D
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