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HelicopterMain Discussion › Carbon tail blade balance.
07-02-2017 10:42 AM  79 days agoPost 1
PaulBowen

rrVeteran

East coast Australia.

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I put this post in the blade section a few days ago with little subsequent interest from the comrades.

https://rc.runryder.com/helicopter/t819589p1/

So

It's either a quiet weekend on RR and everyone is flying, or

It's a pretty boring topic, or

It's a topic that has been done to death!

Maybe I'll never know?

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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07-02-2017 03:01 PM  79 days agoPost 2
EEngineer

rrProfessor

TX

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I missed it...

I've had the same experience with all CF tail blades......

Mismatched by ~30-40 milligrams in weight...sometimes a touch more.

Rather than add sticky tape to the lighter blade, I sand off material on the heavier blade.

I sand the edge of the hub, not the blade, so as not to deform the airfoil.

Using a jeweler digital scale, I can match their weight to 0.001 milligrams....should be close enough....

Logo 600SXs, 700XX, 800XX

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07-02-2017 04:47 PM  78 days agoPost 3
flycatch

rrApprentice

Barstow, California

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Add a drop of thick CA to the lighter blade hub until the blades match in weight.

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07-02-2017 05:03 PM  78 days agoPost 4
EEngineer

rrProfessor

TX

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But, CA weighs less than the CF material that can be sanded off from the heavier blade....

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07-02-2017 06:00 PM  78 days agoPost 5
flycatch

rrApprentice

Barstow, California

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EEngineer-I learned this technique from a 3D fixed wing flyer. He told me that under no circumstance do you sand anything made from carbon fiber. The word "fiber" should explain why.

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07-02-2017 06:13 PM  78 days agoPost 6
EEngineer

rrProfessor

TX

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"3D fixed wing flyer."

Well, I disagree to a certain extent....

In my AMA pattern competition days, I learned never to add weight....

After you sand the CF hub of the heavier blade, you add thin CA to fill in the sanded CF area....

The main thing is to have an accurate scale...

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07-02-2017 10:10 PM  78 days agoPost 7
ICUR1-2

rrElite Veteran

Ottawa, Ontario

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Main gears

How many have balanced their main gears. while on the topic of balancing

I have noticed a difference on the larger sizes.

If I don't get lazy I'll weigh everything ( blade grips, tail grips, paddles) after assembly I'll balance the head and tail rotor on a HP balancer .

spending time, paying attention

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07-02-2017 11:40 PM  78 days agoPost 8
PaulBowen

rrVeteran

East coast Australia.

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I use the tape because it can be easyily replaced and re-balanced and has no impact on the blade structure. I also don't run the risk of breathing carbon fibres.

I also put the tape on the blade such that they have matching centre of gravity.

My Rail tail blades are usually the most closely matched as supplied, I'm not sure if this is just coincidence or quality control.

Futaba T18SZ, JR Propo XG14, Hirobo fanatic!

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07-02-2017 11:51 PM  78 days agoPost 9
EEngineer

rrProfessor

TX

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Each of us has their own methods to deal with it....some people don't even care....

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07-03-2017 12:01 AM  78 days agoPost 10
gologo

rrKey Veteran

Sedalia, Mo USA

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....some people don't even care....
Um.....that may be me I have bolted up tail blades for years w/o
even thinking about it really, and never been 'penalized' w. any
noticeable vibs. That has went for plastic and carbon.

Just has not been an issue......now you guys go and put it in my
head! Will have to check em out just to see....

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07-03-2017 12:13 AM  78 days agoPost 11
JuanRodriguez

rrProfessor

The Villages, Florida

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I have balanced tail rotor assemblies but not the blades individually...... works for me .....

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

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07-03-2017 12:23 AM  78 days agoPost 12
EEngineer

rrProfessor

TX

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"now you guys go and put it in my
head!"

LOL....sorry......

I used not to care, myself......then I got a MiniV and upgraded to Pro.

Then, the built-in internal vibe analyzer is available....and I checked it out.

I can seem the vibe peaks form the main rotor...and that of the tail....having a scale, I checked the tail blade balance and saw minute weight differences....

I figured, you balances the tires on your car....why not the blades?

Reduced the tail vibe peaks slightly...so there was a measurable improvement....no big deal to do it.

Plus, the tail rotor spins ~5 times that of the main rotor.

Also, on fixed wing aircraft, I would always balance the prop....and even the prop spinner....

Regardless, there is a measureable difference in a pair of tail blades....in general, about 30 - 40 milligrams, sometimes more.

I do it....and I have my method of doing it that works for me.

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07-07-2017 04:38 AM  74 days agoPost 13
EEngineer

rrProfessor

TX

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Oops....found that a pair of Rail CF 106mm off by 70 milligrams.....

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07-07-2017 12:47 PM  74 days agoPost 14
ICUR1-2

rrElite Veteran

Ottawa, Ontario

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just use a bolt that weighs 30 milligrams more on the light side tail grip

spending time, paying attention

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07-07-2017 03:35 PM  74 days agoPost 15
EEngineer

rrProfessor

TX

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A weight adder, eh?......

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07-07-2017 04:23 PM  74 days agoPost 16
RM3

rrElite Veteran

Killeen, Texas - USA

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How many have balanced their main gears
I have... and noticed one thing only,,, most are perfectly round ...BUT some (depending on quality) have the center off set. I guess they are molded in those cases... But making my own, I used the OWB housing that its bolted to as a mandrel and machined them as perfect As I could.

did it make a difference? a little, no more wobbling or gear mesh issues.

as for tail blades... clear masking tape... no sanding and refilling, it ruins the finish IMHO.

and yes it does make a difference especially when your spinning them at 10,000 rpms.

they key here is to balance the whole tail rotor.... not just the blades, remember the bolts/nuts holding them can vary too as can the grips themselves especially if they are injection molded.

showing a preference will only get you into trouble, 90% of everything is crap...

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07-07-2017 04:32 PM  73 days agoPost 17
EEngineer

rrProfessor

TX

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"it ruins the finish IMHO."

The hub edge....not the blade surface....

Who looks at the hub edge of a tail blade?......

Yes, you can balance the whole assy....even better, I suppose.

Then you get into the "is the bolt hole centered" thing, etc.

I just make the blades weight even....and go fly....

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07-09-2017 06:56 PM  71 days agoPost 18
Richardmid1

rrProfessor

Leeds, England

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You shouldn't add or remove weight from the root or the tip of the blades UNLESS you also need to adjust the c of g at the same time. You should first establish that the c of g is equal then add weight (tape) to the lighter blade at the c of g point.

60% of the time, it works every time!

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07-09-2017 07:10 PM  71 days agoPost 19
EEngineer

rrProfessor

TX

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I respectfully disagree....

I mentioned removing weight from the hub....only.

And nowhere else from the blade.

And at the hub, it doesn't matter at all....

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07-09-2017 07:32 PM  71 days agoPost 20
EEngineer

rrProfessor

TX

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Remember your Fourier analysis....the hub is a "boundary value condition"....it's fixed.

Logo 600SXs, 700XX, 800XX

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HelicopterMain Discussion › Carbon tail blade balance.
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