Thursday, July 2, 2020

Ultrix CG: some random RCG

As they come a 600 lipo gets the COG just fine, its not that fussy but take the weight off the rear end.. its responsive enough even when nose heavy...

Do the bind inverted using the polystyrene brace from the box on a level surface

For flight switch the TX on, then the model.. then place the model down on some flat ground and wait for it to sort itself out..

Trimming is done in as3x mode, not safe... I adjust the push rod bends to raise both elevons by a tiny amount, I set mine with them raised by the thickness of the wing at the trailing edge..

With it set like that mine flies fine.. battery just stuffed anywhere in the nose.

I think its angle at bind affects its level flight so its worth rebinding, inverted, with the rear end raised a touch, so when its the correct way up the nose has effectively been raised and trying again..
Mine was going down at launch, not flat, this was initially sorted with TX trim.. and later rebinding.

As you can see from the video it was still going down slightly when the power/throttle was set lower, on the first launch.. but when the power was set higher it remained flat.. this was a nose heavy flight.. note the first launch was downwind, and this also makes a big


Both mine are balanced 1/16" ahead of those holes and fly perfect upright, inverted and everywhere inbetween, even in howling wind. If it's too nose heavy inverted requires too much down elevator.

Finger tips are not very accurate on tiny models. I use two short lengths of bamboo skewer that are rounder off and held in a vice.

I use 500 and 650 batteries with the mounting location marked inside the fuse. The 500 mounted as shown in the instructions and the 650 towards the rear with the use of velcro.

A few CG silly millimeters make a HUGE difference in this tiny wonder.

Also, made sure the elevon TE match the wing using the wire pushrod 'U' as the reflex seems to be built into the airfoil.


CG check ..................

May not work in safe mode.


The real CG test is trying both upright and inverted flight. If correct, the transition from one to the other will be smooth and predictable, both will fly straight and lev

I didn't quite know what to think of my Ultrix after the maiden the other day. It was amazingly twitchy, and quite unstable in normal flight but a delight to 3D. I only had the one battery, so couldn't experiment too much. I fully expect to burn through several batteries finding the correct CG and mechanically trimming when setting up a new model.

I read through most of this thread, but still haven't finished yet, but I see people saying battery position doesn't matter, cg doesn't really matter, some mechanically trim a bit of up elevon and others trim them neutral. In my experience, even at this small scale CG can make a big difference.

I spent last night messing with my 500 & 600 batteries to get the CG at the recommended location. The 500 was mid way back, and the 600 was fully back against the receiver. I had 3 batteries charged today and thought things would go better since I definitely knew where place the batteries to be close on CG. First two batteries I kept flying and then mechanically trimming, flying and mechanically trimming, repeat. It was still very unstable. Also, at 2/3 throttle in level flight it would dive when going to full throttle. It just acted tail heavy. I had one 600mah nanotech left and decided to just shove it as far forward as it would go and move back as needed. WOW! What a difference! It flew amazingly stable and predictable! I had to mechanically trim about a wing-width of up trim in. And absolutely NO nose over at full throttle!! Now that this thing is dialed in it feels absolutely locked-in! Love this plane! Still 3D's awesome as well! Three flights at a park and one in my backyard already! 


A forward location for the battery works best. That has been my experience. The 600mAh helps in this case too versus the stock 500 mAh.