Yaw Drift on CX2

[jlr]

Hey guys,

A friend of mine bought a CX2 and he has read the manual and tried adjusting the gain and mixer, but his heli still has a slight yaw in a hover. He estimates that the yaw rate is 90 deg every 8-10 sec, and even if he does get it adjusted to hold steady it doesn't "hold" that adjustment and eventually begins drifting. He is thinking about getting a G90 for it and is asking my advice, but I don't know anything about these so I'm asking you guys.

Will the G90 help? I'm wondering if he is just expecting too much from this class of heli. Will a CX2 hold the tail absolutely locked as long as you don't give any input?

--Jeff

[BryMeister]

Wow! It's been a while since I have posted here! I hope that there are a few around who remember me. :lol: I've been hanging out on the TREX 450 forum, as I am ALMOST done with my 450 V2 build. Woohoo!

Yaw problems - This is a problem that affects each and every CX2 (and Lama) out there. There are several things that you can do about it, but nothing is going to make it go away completely. After flying it for a while, your friend will get used to compensating for the yaw drift with rudder input.

There are two main issues with yaw drift: battery voltage and heat. As you fly the Heli, heat from the motors and electrical components builds up inside the canopy. The heat causes the electrical properties of the components to change. Thus, a Heli that is dialed-in perfectly at the beginning of the pack will experience yaw drift as the heat builds up. Solution? Heat management. I have the heat sink installed on my X180 motors. So right there you have two upgrades that will help with the heat. The other thing you can do is to cut an opening on the top and bottom of the canopy to allow air from the rotor wash to enter the top of the canopy and blow all of the hot air out of the bottom. Some people will also drill holes in the plastic casing for their 4-in-1 or 3-in-1 units. I don't advocate that, though others may disagree.

The second factor is the decrease in battery voltage under load and as the pack is discharged. This will also lead to yaw drift. There is little you can do about this, though running your CX2 with a higher rated (15C - 20C) LiPo will minimize these effects.

Now, my question to you is why are you asking these questions and not your friend who has the Heli? If he's asking about G90 gyros and you don't know much about Helis, it sounds as if you should either (a) tell your friend to register his own account here on HeliFreak or (b) get yourself a CX2 and teach your friend how its done! :lol:

Now the question about the G90: The "new" versions of the CX2 are sold with a 3-in-1 control unit and a separate Spektrum AR6100 receiver. WITH THIS SETUP, you can, supposedly, add a separate "heading hold" gyro that is 'supposed' to address the yaw drift issues. However, Horizon (E-Flite) has not yet released the details of this setup (including which gyro will be used) to the general public, so it's a bit premature to start barking up that tree.

I don't think that you need a gyro with the CX2, though. Eventually, your friend will get used to how she flies. I manually compensate for yaw drift with rudder input. I don't even realize I'm doing it during flight. Your thumbs will learn! ;)

[jlr]

Thanks for the response Bry! Lot's of good information there.


Now, my question to you is why are you asking these questions and not your friend who has the Heli? If he's asking about G90 gyros and you don't know much about Helis, it sounds as if you should either (a) tell your friend to register his own account here on HeliFreak or (b) get yourself a CX2 and teach your friend how its done!


I guess he's just bashful - he had never been here, so he'll probably lurk the forums for a while and then I suspect he'll register and jump into the foray. ;)

The TREX is awesome - you're going to love flying it - no tail drift on that baby with a decent gyro! Thanks again.

--Jeff

[carlo_the_wonder_frog]

Best thing you can do to minimize drift is get a high quality battery, the stock e-flite battery is not even capable of providing all the power the CX2 needs, its always a bit short because of its low "C" rating of 8C, it can only put out 6.4 amps continuous. the CX can use up to 8 amps and the E-Flite battery doesn't do bursts. FlightPower and ThunderPower both have high quality LiPo's and FP has one that fits in the stock location.Its still going to do it, but just a whole lot less, 75% of the flight will require almost no adjustment.

Like Bry said, you eventually get used to it and auto compensate without thinking about it, just like the pros are with CP helis. Basically, reaction without thought. Now if only I did every move automatically inverted backwards, that would really be something.

[LockMD]

Hey Carlo,

Don't suppose you have a part # or something on the flight power battery that fits? I'm having a heck of a time trying to find.

[concretejjoe1]

I would like to know what the model # and the place to buy a good battery for the cx2 Thanks in advance!!!!!!!!!!!!

[carlo_the_wonder_frog]

Check this out, the battery should fit in the stock location.
http://www3.towerhobbies.com/cgi-bin/wti0001p?Q=1&I=LXRVP5&P=3

[LockMD]

What do you think of these? 850mah with 15C for only 14 bucks?

http://www.cx2parts.com/Batteries.html

[dogfart]

These look too heavy. I bought a TP 1,320 Ma battery to replace the 800 Ma stock battery. It was a little too wide to fit in the battery tray, so I attached it undernieth with velcro.

[LockMD]

Carlo, those are pretty long how is your CG with them?

did you have to modify the battery support at all?

[BryMeister]

I agree with Carlo, the stock batteries only provide good flight for about 4 minutes. The rest of the pack is hovering only. I have two sets of higher-rated packs:

DN 7.4V 850 mAH, 15C (2)
Xtreme 7.4V 850 mAH 20C (2)

The difference between stock packs and these are NIGHT and DAY. With the high-cap packs, I can fly my CX2 aggressively outside for a full 10 minutes with NO LOSS IN POWER through the entire flight.

The DN's are a stock replacement for the CX2 pack and can be obtained from Jamie at boomtownhobbies.com

The Xtreme packs are nice, but are shaped differently and will not fit into a stock CX2 battery holder. This isn't a problem for me, though, as I have long since cut off teh battery tray retaining clips from my CX2's. I got the Xtreme packs from Michael at USHOBBYSUPPLY.com.

Both Jamie and Michael run TOP NOTCH shops and offer customer service second to none!

I have also heard that commonsenserc.com has some CX2 packs, though I have no experience with these packs.

[LockMD]

I actually have a DN 850 15C I got from my lhs - I mainly fly low in the backyard - I think they must drain faster at lower levels cause I took it to work today and flew about 25-30 feet and I did notice a BIG difference on flight time. And they were a couple bucks cheaper then stock.

Now I have a pro acknowledging these DN packs, maybe I will just by more of them they do fit nicely. Unless Carlo responds with how to handle a possible CG problem with those EVO batteries.

Thanks for the reply Bry