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HelicopterMain Discussion › Carbon tail blade balance.
07-10-2017 04:26 AM  4 months agoPost 21
PaulBowen

rrVeteran

Victoria, Australia.

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I always add tape to the lighter blade centre of gravity until both blades have the same mass and centre of gravity, the same as a main blade balance.

In the end I guess it comes down to whatever works. My tail blades rotate between 6000-8000rpm.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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07-10-2017 05:48 AM  4 months agoPost 22
EEngineer

rrProfessor

TX

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"In the end I guess it comes down to whatever works. "

True.....at those RPMS, I would want them balanced....by whatever method.....balanced is the main point.....

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07-13-2017 05:22 PM  4 months agoPost 23
AirWolfRC

rrProfessor

42½ N, 83½ W

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I always add tape to the lighter blade centre of gravity until both blades have the same mass and centre of gravity, the same as a main blade balance.
There goes that CG thing again

At a reasonably steady state rpm, moment of inertia is inconsequential - - - all that matters is the moment (see-saw balance).

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07-13-2017 05:27 PM  4 months agoPost 24
EEngineer

rrProfessor

TX

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Have you ever heard the sound emitted when the tape "pops" off?

WOW!

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07-13-2017 05:31 PM  4 months agoPost 25
AirWolfRC

rrProfessor

42½ N, 83½ W

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No - - because I don't use tape.
I sand off the tip of the heavy blade as necessary.
A lot less sanding than at the hub.

But if you have CG OCD you can sand a bit at both ends.

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07-13-2017 05:47 PM  4 months agoPost 26
EEngineer

rrProfessor

TX

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"No - - because I don't use tape. "

Not you...

I just meant in general....

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07-13-2017 06:47 PM  4 months agoPost 27
grimthenoble

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Sunnyvale,​California

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Better yet, buy 20 pairs of the same blade and find 2 that match perfectly! JK manufacturers should have all blades matched at factory, I mean it is the year 2017, we don't fly wood blades anymore.

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07-13-2017 08:07 PM  4 months agoPost 28
EEngineer

rrProfessor

TX

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What about the other 19 pairs?.....

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07-13-2017 08:56 PM  4 months agoPost 29
JuanRodriguez

rrProfessor

The Villages,​Florida

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Put them on Fleabay as "nearly balanced, less than 9 1/2 flights and of course 'never crashed' ! ".

Been there, done that and old enough to know better.....

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07-13-2017 09:39 PM  4 months agoPost 30
EEngineer

rrProfessor

TX

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And give them an "e-bayt"....

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07-15-2017 10:41 AM  4 months agoPost 31
PaulBowen

rrVeteran

Victoria, Australia.

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Ok now for a bit of confusion!

I had balanced my D3's Rail 106 tail blades and found them to be slightly different. So I thought out of interest I'd check the whole tail rotors balance as a unit and found it out of balance. The side with the tape was showing heavy so I removed my balancing tape strip and low and behold a perfect balance.

I'm not really sure why this is so but I will be checking my other helicopters.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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07-15-2017 05:08 PM  4 months agoPost 32
EEngineer

rrProfessor

TX

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I've had that happen, too...

Called it quits, then.....just stuck to ensuring the blades were of equal weight.

Not going to hack on the metal of the tail rotor assy....figured all that was closer to the axis of revolution and was less of a factor than having imbalanced blade weight "way out there".

Imperfect....but a touch better than nothing at all.

Decided I didn't want to go round and round in circles, pardon the pun.....

After all this, one can get into the "tennis racket effect"....which is great for another round of discussion....LOL

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07-15-2017 06:37 PM  4 months agoPost 33
ICUR1-2

rrElite Veteran

Ottawa, Ontario

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the final word on building


http://rayshelitech.com/

spending time, paying attention

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07-15-2017 07:31 PM  4 months agoPost 34
EEngineer

rrProfessor

TX

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Yes, of course....the "final word"...

Sorry, I'm not buying the dvd's....no offense to Ray

For me, it's what works best for me....in addition to helpful hints by Ray....or anyone else.

In short, there is no "final word"....because of the advance of technology....so, we all keep learning....or at least try to.

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07-16-2017 07:27 AM  4 months agoPost 35
Paul Woodcock

rrElite Veteran

Dubai - United Arab​Emirates

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Hi guys

When I first started with helicopters in 2001, I bought Rays book. It was absolutely awesome. Technology has changed but the basics of servo geometry, balance and shaft runout is still the same as on my Raptor 30 v1.

Getting back to tail blades. I have always just checked the weight. Most blades are about 7g. Modern carbon blades are usually within 0,1g. You would probably have more than that difference in the bearing grease.

Regards
Paul

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07-16-2017 07:50 AM  4 months agoPost 36
Richardmid1

rrProfessor

Leeds, England

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True but the bearing grease is much closer to the center of rotation so 0.1g there won't matter nearly as much as 0.1g at the blade tip.

60% of the time, it works every time!

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07-16-2017 04:09 PM  4 months agoPost 37
EEngineer

rrProfessor

TX

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"True but the bearing grease is much closer to the center of rotation so 0.1g there won't matter nearly as much as 0.1g at the blade tip."

Exactly....

But, rather than distort the airfoil of the blade....especially at the tip....I sand the edge of the hub of the heavier blade...which is concealed by the tail rotor blade holder.

And, using the integrated vibe analyzer of the VStabi MiniV....with the main blades removed....when spooled up to <1/2 throttle....one can see the harmonic peak of the main rotor head...and that of the tail rotor.

With the tail rotor harmonic peak, one can see the results of balancing(regardless of how one does it), with a minimization of this harmonic peak.

A quantitative method of measuring the results of such balancing.

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07-21-2017 12:55 PM  4 months agoPost 38
Paul Woodcock

rrElite Veteran

Dubai - United Arab​Emirates

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Hi guys

0,1g of grease vs 0,1g of tail blade hub material is basically the same.....

Theoretically, the mass should be added/removed at a position that makes both sides equal mass and having the same cg.

I still have my Koll rotor balancer. It was fantastic for wood blades and the early glass or carbon blades that were way out on mass, CG (for/aft) and CG (span wise).

For the newbies:

https://www.miniatureaircraftusa.co...or-pro-balancer

Mine has been in 'the box' for about 10 years. Modern blades are just so close to perfect.

Equal mass on each blade and the VBar vibration analyser work for me.

Regards
Paul

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07-21-2017 03:31 PM  4 months agoPost 39
AirWolfRC

rrProfessor

42½ N, 83½ W

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There's that CG thing again - - - -

I'm not sure any body else understands the difference between moment and moment of inertia.

As for the Koll balancer, I consider that a marketing gimmick.
- - - sure - - it does what it does but is what it does necessary ?

Clearly my answer is no.

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07-21-2017 03:43 PM  4 months agoPost 40
EEngineer

rrProfessor

TX

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My MiniV vibe analyzer works great....

They even have a Bluetooth mechanism to TX in-flight vibe data for later analysis.....

Logo 600SXs, 800XX, TDR IIs

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HelicopterMain Discussion › Carbon tail blade balance.
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