HB fore/aft cyclic response issue? - RC Groups
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Jul 02, 2003, 07:09 PM
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Park_IT's Avatar

HB fore/aft cyclic response issue?

I've had my stock HB for roughly 1 month and I have had one heck of a time with one aspect of its control. Everything is stock, 7 cell birdseed battery, HS-50s, GWS PG-03 gyro, GWS receiver.

When flying my HB outside, in NO WIND, if it gets tilted back (tail dipping and nose pointing up), it's hard to get it level again. This can happen our of a hover or FF. When tilted forward, it comes back level no problem. Even when flying level, there is no tendency to tilt fore or aft - swash is level and there doesn't appear to be any CG issues. Servos are tightly secured and there's no flexing. Servo travel is good and EPAs are adjusted just before binding occurs.

Mixer is inside the 'receiver box', gyro is mounted on 'receiver box' cover, receiver is taped to the left of the tail boom (on the back of the 'receiver box'). Battery is in stock location.

I DO NOT have any type of head stiffener mod installed. Could this be the culprit? I've thought about installing a popsicle stick but I haven't purchased the longer screws.

Anyone else run into this, is it the cheap stock swash or is this just the symptom of a moron not installing the head stiffener mod?

I'll have to break down sometime and at least get the shaft collar mod...
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Jul 02, 2003, 08:39 PM
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Steve McBride's Avatar
I am by no means an aerodynamics or aircraft expert, but I wonder if your C.G. is not too far back? Considering your components are almost all toward the back makes me tend to believe this may be the case.

I would think it like an airplane - if your CG is too far forward, it takes a good deal of elevator to bring the nose up. And a heli flying backward probably behaves similarily as one flying forward, except if the C.G. is off for or aft, you may get different reactions to input depending on which way you are headed.

This is all just my theory - I am sure some of the experts will weigh in and help.

Good luck though!

Jul 02, 2003, 09:19 PM
"Simplify, then add lightness"
It could also be the horizontal fin. When going forward, with the nose tilted down, the fin will try to push the tail down, and level the heli. When going backward, with the tail tilted down, the fin will try to push the tail down further.

Jul 02, 2003, 10:10 PM
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AtomHeartMother's Avatar
You know, I did notice a difference when I removed my horizontal fin. I took that off and the boom supports. Mainly to help balance it after I went with a GWS DD tail motor. From crashing mine trying FF I would say there isn't enough throw in the world to recover from a tail slide with this bird. My guess is your only chance is to give it some throttle and full down elevator or swing the tail around if you have room. I think a head stiffener and swash mod are a good place to start. CF blades are my next investment. Then maybe I can zoom around in FF like in Steve's video.
Jul 02, 2003, 10:41 PM
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Steve McBride's Avatar
Actually, with the CF hornet blades, you can do a good 45 degree tail slide and recover with a healthy dose of forward cyclic and a jab at the throttle. The heli will respond to cyclic input quicker with higher head speed - thus the reason for the jab at the throttle.

I predict you will like the CF blades.....

Jul 03, 2003, 01:38 PM
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Park_IT's Avatar

JB Weld...?

After reading the replies, I just thought of something that could be to blame. I don't have a horizontal fin installed, but the vertical tail fin broke a few weeks ago at the base and the only way I could re-attach it was with a healthy dose of JB weld.

JB isn't the lightest epoxy on the planet and being that it's positioned way out at the end of the boom could explain why the HB seems to have suddenly developed apparent CG problems.

There isn't that much epoxy on there, but I suppose even a little weight that far out on the boom could cause problems.

I didn't even think of that - completely forgot about the repair (and the crash that caused it) - must have been a repressed memory....

Thanks all...I'm pretty sure that's the problem.
Jul 03, 2003, 01:54 PM
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Steve McBride's Avatar
Even a little rearward C.G. and the heli takes on a whole new personality. You can really see a rear C.G. when landing - the tail will almost drag before the skids come in contact with the ground.

Yes - a tiny bit of weight that far out can make a difference. Let us know f you have it fixed.

Jul 03, 2003, 02:21 PM
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Park_IT's Avatar
I moved the battery slightly forward and it seemed easier to pull the tail back up. I'll move it a little more when I figure out what I'm going to do with this heli.

My stock main motor finally burnt out after 30 or so flights. So, I'm trying to decide if I want to go BL, do the CP mod, get a hornet, etc, etc....

I might just end up getting another brushed motor - perhaps the 280BB so I don't have to get all new gear (just a new pinion).

Hmm - oh well, it will have to wait until after the holiday!