Longer tail blades, for better holding?

[RedOctobyr]

I'm looking for some feedback on tail blade options for better holding power. I explain the history of my situation at the bottom of the post, if you're interested.

I suspect I'm running out of tail thrust in pitch pumps at lower headspeeds (like 2100, or even 1900), and that the tail servo is responding properly, but the tail still swings. I can fly my stretched 450 at a governed 2000, and not get tail swings in (admittedly-slow) pitch pumps. So I'm looking for ways to add X5 tail authority.

One way is to do the mod of changing the TT-drive gear from 15T to the X4's 14T, to speed up the tail. Like running higher main HS, vs more pitch, I expect this will add aerodynamic drag, maybe impacting flight times a bit. I'd like to start with just tail blades.

I bought two Fusuno options that might be viable. See attached pic.

The left-hand Fusuno measure 85.6mm from the center of the hole to the tip of the blade. A bit longer, but also wider chord, so I'm guessing more thrust.

The middle blade, for comparison, is my old green 84.5mm KBDDs, the only blade type I've tried.

The right-hand Fusuno measure 95mm. I think the shorter Fusuno would fit fine. If they hold solidly, I'm done. But if not, would the 95mm be an option? The gap to the main blades seems pretty large, but I know that's significantly longer than stock. Ground clearance would start becoming an issue, but there are ways to help with that. KBDD makes some 92mm that might be a "compromise".

Any thoughts on using these? I'd prefer to stay with plastic blades, if possible, but I could go to CF if these didn't cut it.

Backstory, for those curious: my X5 is currently governed to 2100 and 2300, on a Castle Edge 100. These are fairy low headspeeds, I know, but I'm happy with the performance, and it's easier on the bearings, packs, etc. I was flying a DS655 on my tail, and getting signficant tail swings in pitch pumps. I lowered my governor gain to 5, and things got better, at 2100 & 2300; at 1900, the tail still blew out a lot, like 90°.

I have replaced all the tail grip bearings, made the tail grip links swing freely, checked things over repeatedly, etc. To the best of my knowledge, the tail is free and smooth, and mechanically OK.

I recently changed to an MKS DS760 on the tail. 760usec, I dropped the frequency from 560 Hz to 360 Hz, and now it comes down at ambient temperature, vs running quite warm at 560 Hz. Servo ball is at 14mm, like the DS655 was. I was able to raise my tail gains significantly, and the tail holds better.

I had a crash, and changed from cheap HK 520mm CF blades, to RJX FBL 520mm CF blades. I went from my green damaged KBDD 84.5mm tail blades, back to the original black KBDDs I was using. Wiped down the tail shaft and added some more TriFlow, these were the changes I think I could affect the tail.

Now the tail is holding better. I was able to raise my gov gain to 8, 2100 & 2300 are great for pitch pumps, and 1900 is OK now (it was bad before the crash, close to 90°, even at 5 gov gain). If I raise the gain any further, the tail swings hard, at 1900.

[bradg]

I switched from the stock lenth to 92mm for the same reason. I run 2200 headspeed. No more issues.

Brad G

[RedOctobyr]

Good info, thank you. What brand are those?

[bgymr]

I went to 95mm blades that my buddy gave me from his g570 kit. Locked the heli completely in. Prior I could blow the tail out when banging the sticks hard. I don't fly hard, i just bang the sticks lol.

But I am now lowering the head on the X5 and I think I will need to go back to teh stock lenght. But I am changing out to the X4 tail drive pulley to speed the tail up, in theory should give a similar holding power to the longer tail blades.

[RedOctobyr]

Thanks guys! I'm starting to think I should have tried wider/longer tail blades already. Oh well, live and learn. I wanted to be sure that longer blades weren't a stupid/dangerous idea, at least.

Any issues with the 95mm hitting the ground or anything? I take off from grass. I could add something to raise the tail height a little bit if needed. I'm going to start with the shorter Fusuno ones, but if they don't do what I want, I'll consider trying longer ones.

[bradg]

This probably doesn't help but the 92mm are Edge brand.

The tail seems low so I loosened the rear skid pipe set screws and squeezed the skid pipes together at the rear then tightened the set screws. That lifted the tail a little. Not the best solution.

Brad G

[czynot]

Size of tail blade depend on size of your main blade.
500mm+92mm = ok
523mm+85mm = ok
523mm+92mm = ?

[RedOctobyr]

Hmm, interesting point. I was assuming that the folks running 92 & 95mm were also running 520mm mains. But that's a risky assumption.

Are you guys running 520s?

I'll confess that I tried holding the 95mm lined up with the hole for the current tail blades, and it looked to me like they wouldn't be able to hit the 520mm mains, even if the mains flexed down. But I didn't look at it exhaustively. I was more interested in whether they clearly *would* hit, in which case they wouldn't even be an option.

[czynot]

anything over 85mm tail with 520 blades are risky. The main blades wont touch the tail if you fly slow. But it is different story when you do fast pyro flips and tic tocs. It also have to do with your gyro cyclic setting.

I do not think you can judge the main blade tip and tail blade tip distance from each other. Main blade can flex enough to hit the boom (boom strike) in some instances.

[bgymr]

I ran 523 Gaui blades with 95mm tails at 2500 rpm with piro flips and tic-tocs no problem. Never hit. But you are right, on landings they are damn near longer than the tail fin. But if you're in grass and don't mind a little green on your tail blades, there is no issue.

[RedOctobyr]

Agreed that you can't go just by how it looks when it's sitting there.

I tried flexing the main blade down, and trying to imagine where it would end up if it kept flexing further.

As I recall, it didn't look to me as though the arc of the main blade would intersect the circle of the longer tail blades, but I could have been wrong.

I will most definitely check more closely before installing significantly-longer blades, thank you. I don't want things to smash.

Sent using Tapatalk.

[dannylightning]

84.5 mm kbdd extreme edition tail blades. i have heard the non extreme editions are not as good.

have used beast x and v bar, and i have always used the kbdd tail blades, i cant get the tail to blow out unless i am going backwards at full speed and got in to a backwards loop and give it full collective. when i do that the tail blows out. but i have to try to make it blow out.

2300 rpm is the lowest i have ran and they were fine at that head speed

i am not sure i wold run 92mm tail blades with 520mm blades or larger. with 515mm blades you would probably be ok.

take a piece of string. and run it across the main blades to the end of the blade, move the end of the string that is at the tip of the blade down to the tail boom. see if the string will touch the tail blades. if not you should not have a boom strike. as you do this move the tail blades in a few different positions.

if the string touches the tail blades than you have a potential problem.

[dannylightning]

523 mains and 84.5 mm tail blades the string is taped to the head right in the center of the head block. and as you can see there is not much room for clearance if the blade were to flex down that far. due to the fact that the head flexes at the end of the blade grip closest to the head and not the center of the head button, you probably actually have slightly more clearance than this pic shows but probably not much so you should do the test your self, i just snapped a quick pic so you could see what i was taking about doing.

if you have the metal tail blade grips on your helicpter i am pretty sure those are slightly longer than the plastic ones i have, that would also come into play in the amount of clearance you have..

[Nelsonisms]

What's that saying..."A miss is as good as a mile"

[RedOctobyr]

Danny, that's a great test idea, thank you. I have the metal tail grips; sorry, I hadn't thought to mention that. I thought I'd read somewhere that the metal grips are actually shorter than the plastic?

I spun the blades until the main blade grips were pointed as close to directly-at the tail blades as possible, with the tail blade grip aimed towards the tip of the main blade (getting things close to each other). I tied my string around the main blade bolt head, and cut it off at the tip of the 520mm blade.

Then I swung the main blade off to the side, and pulled the string towards the tail blades. This is, I think, a bit more realistic than the way your quick example was done (coming from the center of the head), Danny, as the bulk of the flex would be in the blade, I expect, rather than in the head itself. As you said.

There is plenty of room to the KBDD Extreme 84.5mm blade.

There *is* clearance to the Fusuno 95mm blade. But it's very small

Now, the blade won't go in a straight line from the blade grip. It will curve. The length of the blade is fixed, so if it bends through an arc, it won't reach quite as close to the tail blades (no longer being able to take the straight-line path). I couldn't quite bring myself to just bend the (new) main blade so it got close to the tail blade, taking this arc into account. I do have a damaged blade which could be used for that test, I guess.

If I get to the point of trying the 95mm, I might consider sanding 1-2mm off the tips of the blades, just for a little peace of mind. But info from actual users flying 95mm blades is reassuring. I'm not going straight to the 95s, though, I'll try the shorter Fusuno first. 92mm blades might be a good compromise, more thrust, with a bit more clearance.

[dannylightning]

i would be a little scared with the amount of clearance you have there if you went with blades that were any longer than those ones but it looks like the 95mm tails would probably clear, scary but they might be ok. not sure i would risk it

with plastic blades you could get away with sanding them but i am not sure that would be the best idea, it could take ways some performance from the blade since you are altering the shape of the blade.

if you really need longer tail blades and dont feel safe with the amount of clearance with the 520mm blades you may want to get shorter man blades. 500mm and 515mm mains still fly quite well and would give you more room for longer tail blades.. you would probably get slightly better flight time with the shorter blades as well.

i am not 100% sure but i thought the metal tail blade grips were longer. i could be incorrect but i though that is what people were saying when those first came out. if they are shorter that would also be another option, i think you need a different hub if you get those though, i am sure some one knows for sure if they are longer or shorter

[dannylightning]

measuring from tail blade hole to tail blade hole i have 70mm with the plastic grips.

[RedOctobyr]

Thanks Danny.

I just measured mine, I have 2.68", measured from center-to-center of the bolts for my tail blades. Not sure how that compares to the plastic grips.

(Edit- funny, we must have been measuring at the same time; 70mm is 2.76", so it sounds like the plastic are a bit longer, if you were also measuring to the center of the holes)

Sanding down the tips of blades would probably reduce their holding ability a bit. But as I'm not looking to necessarily get a "full" 95mm of hold (that is, I'm not flying a 600 or something that would normally run them), I'd just be looking for more than 84.5mm, it might still be acceptable.

Hopefully it won't come to needing to go that long. I appreciate all the great info, and hopefully the blade/string pictures might be useful to someone else.

[Nelsonisms]

It seems to me that you really have to make a choice with this heli. If you want to run higher headspeeds then you should stick with the stock tail gear ratio and fly in the upper RPM range (around 2200 and above) exclusively. If you want run lower headspeeds (below 2200) you should change to the other tail drive gear to speed up the tail ratio and fly in the lower range exclusively. Apparently having one that can perform well in both scenarios has too many drawbacks.

I know I've been running the Edge 86mm blades on mine since the beginning and that's about as long as I'd feel comfortable with leaving me just enough ground clearance. It's just a bummer since they don't make them any more I'll have to change to something else if I ever bang up the two sets I have. The lowest headspeed I've ever run is 2200 and the tail has always seemed to hold on well for me there with everything I've thrown at it where I'd expect it to tax the tail. Mostly funnels, hurricanes, power loops and the like. I had a few blow outs at one time, but I figured out that it had more to do with my FBL configuration and tail endpoints than it did the blades.

[RedOctobyr]

You're right, that may be the way to go. My preference is lower HS. My flying, and what I want the heli to do, are perfectly happy so far with the 2300 I've tried, on the 15T motor pinion. I can't govern much higher than that anyhow without putting in my 16T. And I like the longer flight times, etc.

I'll probably start with tail blades, and see how that goes. I liked the fact that it wouldn't change the meshing of the 15T/14T tail-drive gear. But that gear is certainly another approach to the problem, without reducing ground clearance.

It's nice to have options, at least. I'm glad the tail-gear option was figured out, that would probably help significantly, at lower speeds.

For now, I'll see if I can get my settings dialed in a bit better, then maybe try the shorter Fusuno blades, the ones that are primarily a bit wider, and just about 1mm longer than stock. If I need more, I'll have to weigh my options.

Sadly, my flying isn't that tremendous. And so far, I'm not really comfortable trying to really-push the tail by doing hard, tail-down, backwards stuff. I've been learning BF this year, but I don't relish the idea of the tail suddenly whipping around in the middle of something hard, and using that as my tail-holding test. So, despite it being lame, pitch-pumps are the main way I check this stuff. It's repeatable, and safe (if it blows out, I'm still level, just sideways). I did just set up self-level on my iKon, so I guess I could use that to ensure the heli can quickly get level again, even if the tail was suddenly coming around and I was panicking a bit. Or just do that stuff higher, giving me more time to recover if it blows out.