300 XL (Tail issues)

[Livan75]

For the guys that have read the "SAB 255" thread, you know I did a stretch with SAB280 blades and f* them up on the third battery.

Basically the tail wont hold for shit... (sorry about the language)

I was pretty sure I figured it out but when I started to push it a bit, the heli made an unwanted 180 in a hurricane and slamed into the ground. Yes, stupid points on me for pushing it at zero misstakes altitude (its more fun) when dialing that thing in...

Anyway, I fixed the heli and used the plastic blades to get back to the dialing in phase again. Works super as long as I dont lean on the pitch, at full collective the heli have no problem doing a full 360 ccw. As long as not full collective is used or not at least slamed the heli flies pretty good...

If I'm not violent, the tail twitches a bit but holds, if I slam its becomes a slow piro upwards...

Some info:
Collective Pitch: 12.5* both ways
Head Speed: 3500 IU1, 3700IU2 (aprox)
TX Gain: +42 (should be 71 on a dx6 or similar)
Param D (BX): Blue solid (Very High HeadingLockGain)

Tail servo: Align DS425M, ball is 8,5mm off center on servo horn

Any higher gain and the tail bounces... I tried pre-comp but it only made it worse, same with lower head speed, lost all tail authority, even easier to do a full 360 only using collective... Only tail issue with current servo was when I had the ball at 10mm, that made the tail bounce even at super low gain...

Besides the piroing at full collective issue it flies great, did 5 packs and I love the extension, it feels alot lighter... manouvers like tic-tocs was the biggest difference, dont feel like a Heavy Little pig that wants to fall out of the sky all of the time...

"Get a new tail servo" is maybe a fix... but not the one I'm looking for at this moment...

[Uriah]

I had a similar experience a few weeks ago with my 4s 300X-L when pulling out of an ugly death spiral. The tail blew out exactly 180 degrees. I still have no idea what caused it. Below is the video. The belt is plenty tight. There's no binding anywhere...

300X Death Spiral Tail Blowout - 07/17/14 @ CRCF (0 min 13 sec)

[Nelsonisms]

When we increase the disk on these helis we increase the total torque in the system. Having a slightly longer tail boom helps to compensate for this somewhat, but we are still running the same length tail blades (mine has the Lynx 47mm plastic tail blades) at the same speed ratio. I've noticed this somewhat on both of my stretched Blade helis which both have higher powered motors as well.

The first thing is to make sure you're only putting in as much collective pitch as you actually need. Whereas I always felt like I needed at least 13 degrees on the stock 300X I've found I can easily get away with 12 on the stretch setup.

Make sure you've got all of the tail throw possible from your tail endpoints. And then you want to tune your tail gain so you are right on the bleeding edge. It's all the standard advice. Fly it fast through tight turns (try to over shoot the tail a little bit) and observe if you get the fast oscillations. If you do, don't panic and let it settle down or switch to a lower gain if you've set it up on a switch (recommended). Give it a some easy rudder inputs and that usually helps to get it to settle down faster. Keep turning up the gain until you do get the fast oscillations during these high speed turns and then back it off a couple of points at a time until it stops when you execute the same maneuver. It's important to note that you cannot tune the tail gain in a hover. Slow oscillations in a hover are not an indication that the gain is too high. That only means that your tail servo is probably a bit slow or weak, you may need to modify the mechanical gain or there is some kind of vibration that is affecting the gyro. The only way to really tune the tail gain to handle the kinds of loads we're talking about is in high speed turns.

I've found the best way to test for blow outs is to go up a few mistakes high and fly the heli fast forward into a stall with the nose pointed up. When it starts to slide back down tail first, pull out inverted backwards with full negative collective. If it's going to blow out, it will, but at least it's up high and not banked into a turn so it's easy to recover.

[Livan75]

Yep, but I kind of figured that the added length was enough since there was no other parts available when getting the extension (longer tail blades or different gears)...

I changed back to my X2 spec blades to check if something I've done when stretching but it holds like a champ!

Will do a few more tests, the most concerning is that it don't just kick 45 degrees and holds, that I can think I could solve, its that it keeps turning at full collective until I stop leaning on it (at least with a fresh pack)...

Might just try the stock tail servo...

[Uriah]

Originally Posted by Nelsonisms

When we increase the disk on these helis we increase the total torque in the system. Having a slightly longer tail boom helps to compensate for this somewhat, but we are still running the same length tail blades (mine has the Lynx 47mm plastic tail blades) at the same speed ratio. I've noticed this somewhat on both of my stretched Blade helis which both have higher powered motors as well.

Come to think of it, you may be onto something. Relative to the stock configuration, while the stretched boom length is proportionate to the length of the stretched main blades, the tail blades are not. So I think it's quite possible that there's no longer enough tail authority to handle really demanding maneuvers with the 47mm Lynx plastics (which is what I'm using alongside Lynx tail grips). Even though I more less botched the maneuver, a death spiral like the one in my video is extremely demanding on the tail upon exit of the maneuver. If this is indeed what the problem is, are there any longer tail blades out there that might work? A few extra millimeters in length is all that would be needed to make up for it.



P.S. I'm using a KST DS215MG servo on my 300X-L's tail.

[Livan75]

A short update, I put back the plastics and moved the ball from 8,5mm to 10mm and it was a significant improvement! Well, over a full 360 on full collective (probably more if I kept it pegged any longer), a 45 degree kick with a fresh pack is significant...

The violent oscillations was back (bouncing hard on the tail in a hover)... but 45 degree kick feels like I can fix over a continous spiral...

Would not die of chock if the stock tail servo works, will give it a go after work...

[Livan75]

Originally Posted by Nelsonisms

The first thing is to make sure you're only putting in as much collective pitch as you actually need. Whereas I always felt like I needed at least 13 degrees on the stock 300X I've found I can easily get away with 12 on the stretch setup.

11.5* and stock tail servo did the trick, sure hope Luca will make some bigger tail blades to use with the stretch, next step up that I have found is 59mm. The difference between 450 Pro and 450L tail blades is 1mm, so don't seem like it requires all that much... Maybe 49-50s?

It would be nice to at least know you have some room to fly a more aggressive setup...

[Scream]

Hey Levian,


Looks like you haven't been having the best heli-luck lately! If I had a pair of SAB 280s bite the dirt in less than a session, I'd be cursing so hard I'd have to start combining curse words to get the desired effect! You're doing better than me bro!


http://www.helidirect.com/curtis-you...-59-p-9089.hdx

Those seem like they'd be up to the task , although I can appreciate if you're not in any particular hurry to place an order there Fusuno makes a set of 60's that seem about right as far as color scheming goes and they are pretty common to find.

Thanks for the heads up on the larger tail blades gentlemen, makes perfect sense.

Any ideas what happens mechanically to make the exact 180 happen when it blows out? Just curious!

Cheers!
-=S=-

[Livan75]

Originally Posted by Scream

Hey Levian,


Looks like you haven't been having the best heli-luck lately! If I had a pair of SAB 280s bite the dirt in less than a session, I'd be cursing so hard I'd have to start combining curse words to get the desired effect! You're doing better than me bro!


http://www.helidirect.com/curtis-you...-59-p-9089.hdx

Those seem like they'd be up to the task , although I can appreciate if you're not in any particular hurry to place an order there Fusuno makes a set of 60's that seem about right as far as color scheming goes and they are pretty common to find.

Thanks for the heads up on the larger tail blades gentlemen, makes perfect sense.

Any ideas what happens mechanically to make the exact 180 happen when it blows out? Just curious!

Cheers!
-=S=-

Thanks, cant really blame anyone but myself for the blades, should have know not to push it on a new setup, or at least use the plastics that are indestructible... stupid costs money

I have 62mm blades for my dominator laying around so if 60ish blades works I can use the same on both. Quite sure that they are to long and will hit the main disc... would love to be wrong thou, anyone successfully using 60-ish tail blades?

[Nelsonisms]

Some 50ish mm tail blades might be cool to try, but those are going to be hard to come by. Probably our best best is to get some longer plastic ones and cut them down. I have some KBDD ones for my 450 that I never used so I might see if those will even fit in the grips and start chopping on them if they do.

Admittedly I don't fly my 300 very often. It's kind of the black sheep of my fleet. But I spent a fair amount of time dialing it in last weekend. I don't think I'm pushing it Uriah-hard but I got it to the point where it wouldn't blow out using the hard inverted pull-out method I described above which is usually a good indicator for me. I'm happy enough with it for what it is. The heli has TGY-306G-HV servos all around (cyclic & tail) @ 7V.