splais

My Feedback: (25)

I am going to be painting a 3 blade prop. Will need to sand first and then paint backside red and front side grey. After I do all this painting I'm sure it will need to be balanced again. Never tried to do a 3-blade. Am I correct, I can just keep spraying a little more clear on each light blade and it will eventually balance; basically same way I've done a 2-blade.

CK1

My Feedback: (60)

You are correct

abufletcher

You may need a different style of prop balancer with 3 blades, for example this one:

http://www.vogelsang-aeroscale.com/fema3dbalancer.html

FlyerInOKC

My Feedback: (6)

Nice! I may have to purchse one of those!

acerc

I have a hard time with the bubble type balancers. I use one from Dubro now and it works very well, very sensitive, and I have had as large as 34x14 2 blade and a 32x12 3 blade on it. Balances 3 blades as well as it does 2 blades.

http://www3.towerhobbies.com/cgi-bin...&I=LXD712&P=ML

acerc

Heres a couple shots of it with a 33x14 prop I just received, it is used. And it would appear the prop is one coat of clear from being balanced. This thing is sensitive enough I have to close the A/C vent in the ceiling in order to balance.

abufletcher

I actually also use that same Dubro Balancer on my larger props, e.g. the 24/10 for my Seidel 770. Since I don't use 3-bladed props I never thought about how those would work on a regular balancer. I guess I don't understand how that would work. Clearly the "heavy" blade wouldn't be heavy enough to outweigh the other two blades and sink to the bottom. Right?

splais

My Feedback: (25)

Because the prop, two or three blade, is a single unit, the heaviest spot will always fall.

abufletcher

That doesn't make sense to me. If there's one blade pointing down, that would mean there are two blades above the pivot point. It seems to me that a three bladed prop would always come to rest with two blades on the bottom and one sticking up.

acerc

As splais said it is a single unit same as a two blade. And the heaviest point will fall to the bottom. If all the baldes weigh the same the prop will not rotate whether it is 2-3-4 blade. Just work the three blade the same as you would a two blade. The only real difference is in the fact you may have three different weighted blades, that does add a little more work. But as for balancing it goes the same you just might have two blades to work on instead of one.

TFF

Balancing is the same, but what is different is that you can have one light blade and two heavy, two heavy and one light, three different weights. Many times you have to average between two blades the changes; its not necessarily going to be one blade that needs work, maybe all of them.

LesUyeda

". It seems to me that a three bladed prop would always come to rest with two blades on the bottom and one sticking up. "

Back to school, Abu. Physics particularly. If all things are equal, ANY properly balanced prop should stay in ANY position it is put into.

Les

wphilb

My Feedback: (10)

I had to balance a new three blade prop system from Troybuilt. Had I known of the Vogelsang unit I would have acquired it. 

N1EDM

My Feedback: (2)

There seems to be an assumption that two blades will weigh some identical weight while the 3rd one will be lighter or heavier. The trick is, what does one do when all three blades have different weights?

My first balancer, way back when, worked on the principle shown in Post #3 except that it cost about $1.99 I think. I wonder if it is still around. I'll have a look... I can't remember who the manufacturer was but I think it was one of the major suppliers.

Bob

wphilb

My Feedback: (10)

If you read through my post above I was trying to describe balancing when all three were different weights, that was what happened to me! Not saying I succeeded...

N1EDM

My Feedback: (2)

Hi Whit,
Sorry I was reading too fast. But I was really directing my comment to folks who were discussing having two blades down (equally).

I have come across articles in the past that discussed how to balance a 3-blade prop but unfortunately I cannot find one (as yet) on my PC. But I did come across a picture of that old prop balancer that I mentioned in Post 13, just to give you an idea of what it looked like. It's in the top and middle photos of the attachment.

I'll keep looking for that article.

Bob

wphilb

My Feedback: (10)

That's a helpful article! What I could read of it anyway. I intend to get a balancer from Vogelsang but will assiduously level the surface I will balance it on first!

CCFPILOT

It looks to me as if the Vogelsang has its own level indicator, and won't require precision leveling of the table.
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N1EDM

My Feedback: (2)

I have the the entire article. I can't recall if it has anything in it on 3-blade props or not. I was going to re-read it tonight.

I tried to upload it but the file is very large - about 8MB in pdf. I'm not sure if I could even email it out.

Bob

N1EDM

My Feedback: (2)

Whit, send me a PM with your home email address please. I presume you can take large files at your home email?

Bob

abufletcher

Les, I'm afraid I never had any physics to start with. [] All of my comments stem from the same simplistic mental image of a balance: What's on the left needs to balance what's on the right. Assuming we draw a vertical mental line through the center of the prop, I can see how a 2-blades prop should stay in any position with my "mental balance." But once I start trying to fit a 3-bladed prop all of my common sense goes out the window. The only two "balanced" positions are with one blade straight up and with one blade straight down. Or at least that's the way my mind wants to see it (and my mind also sees the "one blade up" as inherently more stable).

Guess this is why I'm an English teacher.

FlyerInOKC

My Feedback: (6)

Abufletcher, now that you have three blade balancing figured out how about tackling Schroeder's cat next?

wphilb

My Feedback: (10)

Done,

Many thanks!!

Whit

raptureboy

Here's how it's done and the Dubro balancer will do just fine and is very accurate. http://www.phprc.net/images/RC_Aero_..._Technique.pdf

LesUyeda

Abu. The problem is your mental image. A prop is not merely a 2 or 3 bladed "thing", it is a disk of a diameter equal to the total length of the prop. Think of it in action.

Les