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01-13-2013 07:38 PM  7 years ago
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cmsilvoy

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Durham, NC

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Balancing CF main blades
Does anyone have a tried and true method for drilling and weighing CF blades to achieve balance or changing COG?

I need to add 1.2 grams to a blade to match a single to an existing set of 2 blades....I have an accurate gram scale and a KRP.

Wood blades were one thing, I want to be safe with these CF blades approaching 2300 RPM.

please, I have done a search so no smart alec answers.
If there is a thread out there, can some one point it out of post an answer so that all can benefit???

Thanks!

CHris
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01-14-2013 11:19 PM  7 years ago
heli-cuzz

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Pittston, Pa. USA

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I have taken a set of mismatched blades and balanced them by drilling a hole in the leading edge and into the lead weight inside.
Then epoxied a lead nail into the pre-drilled hole.
I first put the blades on a blade balance and played around with different weights to find the spot to be drilled. I do believe I drilled two holes to achieve a proper balanced set of mains.
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01-15-2013 01:13 AM  7 years ago
R.J.

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SF bay area, CA USA

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Don't know about tried and true, but here is what I have done. I think it depends on what kind of blade you are balancing. For the blades with safety wires (Rotortech, Radix, Edge, etc.), I have tried to stay away from drilling through the safety wire and the carbon tow "spar" in the leading edge. I x-ray the blades to determine the location of the lead, safety wire and carbon tow, then drill or slot just adjacent to the spar on the underside of the blade so that the balance weight is glued to the spar as well. Roughen the surface of the spar and glue in the lead weight with Hysol 9462. Lead position is determined by trial and error with Koll Rotor Pro to achieve correct chordwise and spanwise balance.
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01-15-2013 02:11 AM  7 years ago
cmsilvoy

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Durham, NC

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Thanks all.

Lead weight... check
Epoxy...check
Dremel...check
Xray...check...
Koll Rotor Pro (KRP)...check

Any more suggestions are very welcome

So, it all a go for the weekend. Will let you know how it goes and document all steps for a future post...
Chri
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01-15-2013 04:23 AM  7 years ago
Ace Dude

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USA

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Do you have the instructions that came with your Koll? That should have the process in there. Just read your original post. For 1.2g I'd just use a small piece of tape or a small piece of lead (fishing weight flatened) if the weight needed to be added at the root.  
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01-15-2013 04:31 AM  7 years ago
rcflyerheli

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Granbury, TX USA

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Not to be sarcastic, but I just gotta believe your average modeler isn't gonna have an xray machine in his shopLogo 700, Specter 700, Goblin 700, Trex 700DFC, Gaui X7, Logo 690SX, Logo 600SX; Trex 470 Trex 500
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01-15-2013 08:42 AM  7 years ago
R.J.

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SF bay area, CA USA

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Not to be sarcastic, but I just gotta believe your average modeler isn't gonna have an xray machine in his shop
I took the xray at the friendly orthodontist's office because I don't have an xray machine in my shop either.

But then again, not to be sarcastic, the average modeler doesn't have a Koll Rotor Pro balancer, nor does the average modeler know how to use one. I'm not even sure the average modeler these days has ever balanced a set of rotor blades.

The average modeler should probably do as Ace Dude says and use lead tape at the root instead of drilling into a blade.

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01-15-2013 11:47 AM  7 years ago
cmsilvoy

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Durham, NC

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Do you have the instructions that came with your Koll? That should have the process in there.
Yep, got it. But the KRP was from back in the day when blades were made of wood and you HAD to balance them...
For 1.2g I'd just use a small piece of tape
I'd rather not use tape....I'd rather drill and fill (see below)
Not to be sarcastic, but I just gotta believe your average modeler isn't gonna have an xray machine in his shop
I am not your average modeler

I appreciate all of the insight, and will embark upon balancing a set of 3 550mm blades to each other this weekend.

I'll take pics and describe logic so that all can see.

Best Regards,
Chris
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01-15-2013 01:48 PM  7 years ago
darkfa8

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Brick, NJ - USA

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Chris, I also use the KRP and balance blades using lead golf tape. I've never had a set of blades that didn't need balancing.- Dan Goldstein
Team Revolectrix
Lynx Heli Innovations
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01-15-2013 03:22 PM  7 years ago
Chief_USN

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Chesapeake, VA

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I've never had a set of blades that didn't need balancing
What kind of blades do you buy so I can stay away from them. Unless you are really, really, really picky about balance, every set of CF blades I have ever bought have been balanced out of the package.

Chad
Team HeliProz 12-14
US Navy Chiefs...Unity, Service, & Navigation to the Fleet since 1893
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01-15-2013 04:22 PM  7 years ago
darkfa8

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Brick, NJ - USA

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Chad,

I've been a product reviewer for 7 years in this hobby. I've had AHF, Align, Audacity, ARK, Chaos, Radix, SAB, Rotortech, Hirobo, Thunder Tiger, Gaui, Mavrikk G2, G3, G4 and G5 among a few others.

As far as my balancing tolerances, if the bubble isn't centered, it isn't balanced. I weight match to within +/- 0.1 gram.

I use a KRP, MyWeigh digital postal scale, lead golf tape and some CA to correct all the blades that come across my desk.

In recent memory, the Rotortechs and Gauis required the least amount of correction.
- Dan Goldstein
Team Revolectrix
Lynx Heli Innovations
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01-15-2013 04:46 PM  7 years ago
Chief_USN

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Chesapeake, VA

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I guess I will have to get a little more precise with my balancing then. I usually fly what I can get the cheapest or what is on sale and like I said, never had an issue. Don't get me wrong, I wasn't trying to insult your intelligence. I don't have the KRP you are all talking about. I do have a digital scale and I weigh the blades and then I check the CG by placing a bolt through the root and hang the blades together. If they hang the same, then I go with it. If they don't, I then place the blades on a straight edge to see where the CG is at and as long as they are within 1-2mm of each other, they're good. Never had an issue. I feel we kind of hi-jacked the thread with this.

Chad
Team HeliProz 12-14
US Navy Chiefs...Unity, Service, & Navigation to the Fleet since 1893
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01-15-2013 04:48 PM  7 years ago
R.J.

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SF bay area, CA USA

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Chris,

If you have an intraoral xray machine, that would be better as I had to do some correction for the magnification of the xray. I'd determine the location of the lead placement with the KRP, then xray that location with the xray sensor or film right next to the blade so that measurements will be accurate. I think we have the same profession except I am a wirebender.
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01-15-2013 06:15 PM  7 years ago
darkfa8

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Brick, NJ - USA

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Chad, no problem. The KRP is a good investment. Never any doubt.

Terry Moore was gonna make a video on how to balance blades using the drill/micro-balloons method.
- Dan Goldstein
Team Revolectrix
Lynx Heli Innovations
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01-15-2013 08:55 PM  7 years ago
darren heaver

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rochester, kent, england.

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I totally agree with darkfa8 I check every set of blades with a KRP and it is rare to find a set that balance on chord and span wise CG.

I am quite new to this but I am also a bit AxxL I will admit, when I mentioned it to fellow fliers they laughed and said you don't need to do that these days :-( but they are WRONG. I have purchased Rotortech 810 mm industrial blades costing a lot of money that are ( CG BALANCED FROM THE FACTORY ) to find they are not correct in chord and span CG and need balancing and once they are fly super smooth no vibes.

I learnt how to balance my blades after watching RAY's DVD series on heli set up. As he says on his DVD they are well balanced from the factory but not perfect. If you want to put the time in you can and will get them better.

I normally use lead tape and CA but have now purchased some lead powder so going to try that soon mixed with epoxy :-).

Good luck.
" one day I will learn to fly till then I will just hover"
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