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Oct 23, 2003, 06:28 PM
Registered User
Rant

Balancing blades on a Corona - Not even close ???!!!


OK...I'm in the middle of my build where it calls to balance the blades on the Corona. Everything has been going great up to this point. When I check the balance as suggested, I have to add "tape" as suggested. Well, just to get an idea how much it might need, I start using 1/2 strapping tape I had laying around (no, I wouldn't fly it with that...I was just testing how much). After wrapping a good 5" at the very tip of the light blade, it still won't balance. For kicks, I also taped one of the 1" 4/40 bolts to the very tip. After that, I balances perfect. So, I've got 5 inches of heavy strapping tape and a 4/40 bolt at the tip of the blade....It's obviously not gonna balance with a little strip of tape. Anyone else have this problem or have any suggestions? Thanks in advance.

Also...this forum is great. I have learn a great deal from reading all of the post and am starting out brushless with a Mega motor. Can wait to fly.

Ken
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Oct 23, 2003, 06:59 PM
Registered User
Did you balance the head itself with out the blades and grips on it before you tried to balance the head with the blades on?

I only ended up using a piece of tape an 1/8 of an inch wide, and about 2 inches long to get my blades to balance. It worked out perfectly for checking blade tracking.

It sounds like you've got other problems besides the blades, or you've got two different size blades!
Oct 23, 2003, 07:47 PM
ab amicis auxilio parvulo
Aerospacer's Avatar
Balancing Corona blades:

I found a similar but possibly not as severe problem with my Corona. Then I noticed that without the MR blades on the head, it was noticeably out of balance in the MR feathering plate plane not the subrotor. I ended up getting it to balance by inserting a 6-32 phillips head screw into the hole that is in the end of the feathering plate for installing the feathering pin through the hub. This 6-32 screw's length can be trimmed to get head balance but cannot be so long as to extend into feathering plate vertical hole that attaches the blade grips. When the right weight is obtained, CA glue the screw so it does not come loose. The phillips head on the screw I used would clear the crotch in the blade grip without a problem.

After doing this, I only needed a small piece of tape on the MR blade. The only thing I could guess as to why this imbalance was there in the first place was that the linkage and arms on the cut-out side of the feathering plate were heavier than the solid side of the feathering plate where I needed to put the screw for counter-weight.
Oct 24, 2003, 04:05 AM
(aka Cliff Lawson)
Wright Flyer's Avatar
Ken,

To require the weight of a bolt to balance doesn't sound right. Try removing the blades all together and weighing them individually on a digital (kitchen) scale. They should weigh almost the same, if not then that could be the source of the problem. If they are about the same then the imbalance is somewhere else in the head.

Cliff
Oct 24, 2003, 09:56 AM
Gentleman, scholar and acrobat
Cush's Avatar
As Cliff suggests, it does sound like you have more of a problem than just an out of balance blade. But in any case, when you add weight to the blade you need to do it over the blade’s centre of gravity (CoG) - not at the tip, as this will cause additional vibration problems. The CoG on Corona blades is just outboard of the turbulator strip.

It's also easier IMHO to balance the blades dynamically – after tracking, just add small pieces of tape over the CoG of one or the other blades until things are as smooth as possible.