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HelicopterMain Discussion › Here's How To Make a set of blades out of two single ones (crash survivals)
11-30-2007 04:15 PM  9 years agoPost 61
AirWolfRC

rrProfessor

42½ N, 83½ W

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but remember to balance the center of gravity,the blades have to be the same center of gravity
This is NOT necessary. It is actually a waste of time.

A simple see-saw balance is all that's needed.

This thread has more detail,
http://runryder.com/helicopter/t385...?top=1196439213

Reference material,
http://www.avionavtask.com/certific...or_Science2.pdf
On page 4 we find,
All rotor blades are designed with adjustable weight packages so that all blades can be shipped from the factory with the exact same span moment.
Notice that says moment, not weight or CG.

Junmping down to the "conclusions" we find,
The United States Army now employs dozens of Universal Static Balance Fixtures within all levels of maintenance, depot, intermediate and unit. The United States Army has saved millions of dollars in reduced rotor blade returns to the manufacturers and depot repair facilities. The United States Army has saved millions of dollars in reduced maintenance test flight expenses by cutting associated activity in half.
It looks like they like static balance also, when done right.

This article from the same source says it better,
http://www.avionavtask.com/certific..._Technology.pdf

If it's good enough for the full size, it's good enough for models.

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11-30-2007 08:33 PM  9 years agoPost 62
RappyTappy

rrProfessor

North Denver, Colorado

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Interesting and it makes sense that the CGs don't really need to match for a smooth hover. What about when introducing gyroscopic forces such as when using cyclic and tilting the disc, seems like it may not be the most desirable condition, but guessing wouldn't answer that question. Any testing done on that?

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11-30-2007 08:48 PM  9 years agoPost 63
Hamo

rrVeteran

Ireland

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RappyTappy, when I was doing my tests with blades balanced both ways I didn't just hover. I flew the helicopter for a few minutes, forward flight, turns piros, climbs and descends, the things I do normally. AirWolf's two step method appears to be all you need, so simple and so quick and what's more you don't need to buy a balancer. Just use a 4 mm screw, a few nuts and 2 drinking glasses.
Hamo

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11-30-2007 08:55 PM  9 years agoPost 64
eheliflyer

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NorCal

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I used Lead tape from a golf shop to balance and put a piece of reflective tape over it for extra security. I works perfectly.

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11-30-2007 08:59 PM  9 years agoPost 65
RappyTappy

rrProfessor

North Denver, Colorado

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Very cool Hamo, actual testing is much better than just theory sheets and website cut and paste for sure! Keeping it simple is what I like in this world where eveything is just getting more and more complex.

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12-01-2007 12:30 PM  9 years agoPost 66
Hamo

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Ireland

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To give more data of my tests, the two blades I balanced both weigh 120 grams on my kitchen scales. Before balancing, the CGs were out by half an inch, 12 mm. After balancing using the 2 step method the CGs are about 4 mm apart. I only added tape at the tip of one blade till they teetered. I flew today with these blades and there was no vibration, no visible problems, very smooth and blade tracking was good while hovering.
Hamo

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HelicopterMain Discussion › Here's How To Make a set of blades out of two single ones (crash survivals)
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