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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › 3 blade heads why the new thing ?
07-03-2014 03:58 PM  6 years ago
wjvail

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Kroll was my typo . . . I have fixed that . . . and still see no need for it.
Ahh... Got it.

You don't see a use for one? Blades have to have many properties to perform well - two of which are, the same weight (mass), and that mass has to be correctly located (moment of inertia).

You could have two blades that have identical weights but if one blade balances at the root and the other balances at the tip, the system is going to be out of dynamic balance.

Further, lead/lag is largely effected by cord wise CG. If one blade has a CG on the leading edge and the other on the trailing edge, the dynamic performance of the blades will suffer badly.

If your comment was simply that today's blades come so well balanced that a Koll Rotor Pro has little purpose, I understand. If you believe it doesn't work well for balancing blades, we will have to disagree. I find it reasonably quick and extremely accurate.

If you are just opening the bag on modern carbon blades, you're right, there is no need for it.

You're not from a time when you had to make your own blades are you.?.?

Bill
"Well, nothing bad can happen now."
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07-03-2014 04:42 PM  6 years ago
RogerRabbit62

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Thuerigen germany

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3 Blades is also 50% more mass in the rotordisc.
You will feel this for sure.
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07-03-2014 06:43 PM  6 years ago
AirWolfRC

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42½ N, 83½ W

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The only thing that needs to balance is the Moment of Inertia . . . period.

That means see-saw style balance.

Rotor blades are essentially a flat plate of negligible thickness from a mass stand point. That eliminates the need to "dynamically" balance. That's something you do to car wheels where there is s substantial thickness along the axis of rotation and you need to be concerned with wobble.

The only other aspect of center of mass, CG, is the chord location of that point. It can, in the most extreme condition, have some effect on flutter of the blade. If the blades are the same make and model, even wood, that's not an issue.

So . . . the only thing left is Moment of Inertia about the blade bolt hole.

Blades CAN have different weights and different CG's
But . . . the weight x distance to the CG must be equal for all baldes on the same shaft . . . that means see-saw style balance.

. . . just say NO to Koll Kool-Aid
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07-03-2014 07:07 PM  6 years ago
don s

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Chesapeake, VA

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One blade will be the next fad.

Yes, you can fly on one blade (with a counterweight).
E820, Raptor G4N, X50F/E, E620, Forza 450, and some planks.
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07-03-2014 07:10 PM  6 years ago
AirWolfRC

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This photo is from Model Aviation magazine, Oct. 1987 pg. 102

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07-03-2014 07:20 PM  6 years ago
AWittleWabbit

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So that's why y'all buy single used blades!

Watch at YouTube

Here's one in action.
Heli-itis sufferer.
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07-04-2014 01:50 AM  6 years ago
Retired2011

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Lee's Summit, MO

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I wanted to see some tic-tocs!
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07-04-2014 02:31 AM  6 years ago
AWittleWabbit

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I wanted to see some tic-tocs!
1 bladed 3d

I see JR has a nice 3 blade head for their 450 hmmm.

I still want more tail

Has anyone on here tried a 3 bladed tail? Any thoughts?
Heli-itis sufferer.
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07-04-2014 02:59 AM  6 years ago
BobOD

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New York- USA

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I fly three blades on most of my machines. Been doing so for years.
Only hassle is that they don't match blades in sets of three so you have to balance. Benefit is stunning tail authority even with smaller blades.
Team POP Secret
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07-04-2014 03:06 AM  6 years ago
Retired2011

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I still want more tail
Sounds like Bob gets plenty of tail.

I have a 5 bladed head on a 450, in an MD500 Fuse.
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07-04-2014 03:34 AM  6 years ago
AWittleWabbit

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And stunning tail at that!

Maybe Align will make a 3 bladed tail for their 450 one of these days. I see the JR 450 has a larger dia tail. The Align 450 tail can't get much larger unless you land on a book.
Heli-itis sufferer.
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07-04-2014 05:18 AM  6 years ago
BobOD

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I am a tail man...I will admit.Team POP Secret
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07-05-2014 08:01 AM  6 years ago
Mojoe

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Brisbane, Australia

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Watch at YouTube

This one seems to work ok.
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07-05-2014 03:15 PM  6 years ago
Heli_Splatter

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Wrong...Think of having two sticks of aluminum in the blade grips with a 2g weight on each side of the main shaft. One weight is 6 in out the other 10 inches out. Dynamic balancing is important, static balancing is a starting point. Where you apply the balancing mass is as important as how much.
Rotor blades are essentially a flat plate of negligible thickness from a mass stand point. That eliminates the need to "dynamically" balance. That's something you do to car wheels where there is s substantial thickness along the axis of rotation and you need to be concerned with wobble.
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07-05-2014 03:49 PM  6 years ago
AirWolfRC

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Wrong...Think of having two sticks of aluminum in the blade grips with a 2g weight on each side of the main shaft. One weight is 6 in out the other 10 inches out. Dynamic balancing is important, static balancing is a starting point. Where you apply the balancing mass is as important as how much.
You need to go back to school.

Static balance is just what most people think , , , balance while static . . . not moving

Dynamic balance is balance while in motion . . . simple.

The main (if not only) reason for dynamic balance is (for example) in a car wheel where the left side has a different balance than the right side. If not corrected, the wheel will wobble at speed. To clear that up go here, http://en.wikipedia.org/wiki/Balanc...rotating_masses

A rotor balde does not have that kind of problem so static balance is more than adequate.
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07-05-2014 04:07 PM  6 years ago
BobOD

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Anyway, it's quite clear that 2 blades are better than one so only common sense that 3 blades are better still. Team POP Secret
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07-05-2014 05:34 PM  6 years ago
AirWolfRC

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The problem is that kind of sense is all too common
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07-05-2014 06:20 PM  6 years ago
BobOD

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Yes indeed. Team POP Secret
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07-05-2014 08:41 PM  6 years ago
Four Stroker

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Atlanta

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I have the Koll, HiPoint, and a K&S see-saw. I only use the K&S.

Hey, AirWolfRC is correct. Dynamically balancing a flat disc is crap. But you might check the static tracking and the chordwise CG.
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07-05-2014 09:04 PM  6 years ago
Heli_Splatter

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NOT... I know exactly what it means. When you put a tire on the dynamic balancer.. it is telling you how much weight to add and where.

In this much simpler heli blade example... first you add whatever weight is needed to get each blade to balance at the same point on each blade, then when you balance one blade against the other, you add the weight to the CG point of the lighter blade. Once the CGs are identical...by adding small weights at the CG point a dynamic balance has been achieved.

If both blades are made in a very controlled manner and exactly equal to one another, there is no need for a dynamic balance.

Hope you took notes.
You need to go back to school.

Static balance is just what most people think , , , balance while static . . . not moving

Dynamic balance is balance while in motion . . . simple.
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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › 3 blade heads why the new thing ?
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