Unbalanced sportcopter blades

eddie

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I bought my sportcopter blades about a 18 months ago,and had trouble balancing them in the beginning,I finally gave up and added

motorcycle shimmy dampners and just lived with it until several days ago I tried to balance them again,and could never get a good

balance,moving the adjustment one way and then the other it still stayed about the same.

Sportcopter advertised that they come balanced,tracked,and flown,I now have doubts about that statement.

It took 6"s of 3/32" diameter lead solder wire in one blade to balance it,my blades now run smoother than ever and I feel that

I can now finish balancing them. Let me say at this time I really like the quality,and the way they fly, they are really great and very

well built blades,its just that these blades were not balanced,if they were it was not very well done,The real problem was that I thought the blades were




in balance when I bought them and never questioned that the balance could possibly be the problem,I made a setup to balance the blades thinking

that I was wasting my time,the blades were way out and I really questioned my ability to properly balance them,I went through the procedure several

times to prove my results, they were the same everytime.

The old saying about don't believe everything you read or hear really came to bear this time,it cost be a lot of time and more than a 100 hours flying a

really set of crappy out of balance of blades,believing that Sportcopter could not be wrong.
 
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SportCopter

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Hi Eddie,
Every Sport Rotors rotorblade is tracked, balanced, test flown before they are shipped. We have documentation for every set of rotors that has been test flown and shipped. The problem in this matter may be you are using our Rotors on a Rotorhead that is not one of ours. We have found in certain situations some rotorheads may not be precisely manufactured out of spec and can cause vibration on any rotorblade. Because you changed the pitch block on the hub bar, the blades would have needed to possibly be re-balanced again. Which you had been informed when you called about this matter. We sell just the upper towers and bearing block to ensure the precision of a rotorhead. We also offer a whole conversion system (mast, rotorhead, air trim system) that attaches to any RAF or Sparrowhawk that eliminates this problem. Our quality control requires several people inspect the condition and sign off before any rotorblade set is shipped.
 

Mike G

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Eddie
I have to agree with SportCopter, if they tracked and balanced it on one set of teeter towers and pitch block and you installed it on another set of teeter towers and pitch block, then all bets are off.

Mike G
 

Kolibri

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Eddie, since I went with SC from the mast plates up, I'm not using the RAF rotorhead with my SC blades.
I've not experienced the balancing challenges you've reported.

Having visited the Sport Copter factory for a few days and toured the shop, I've no doubt that all rotor blades are balanced/tracked/flown personally by Jim Vanek.
He's a special gyro just for that purpose, and it has a lot of hours, lol.

The SC blades are balanced on their own head in the shop.
If they're installed on an RAF head after purchase, you're relying on the RAF head to have been made to SC's tolerances.
Also, your RAF rotorhead has some 600+ hours on it.

So, I really can't imagine that your SC blades were mutually out of balance on their own.
The issue has to be the RAF rotorhead itself.
I recommend replacing it with SC, not only for balance but for the superior parts and design.
I compared the two head side by side, and it was Yugo vs. a Mercedes Benz.

Regards, Kolibri
 

eddie

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I have a different RAF rotor head in use,I have rebalanced and tracked the SC blades,and today I finished up the cord wise adjustment and now have

a pretty good set of blades to fly with.

let me say once again that I have always liked the way the blades preformed.

Good to hear from you Kolibri,I was beginning to think that you had left the forum.
 

Mike G

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Eddie
Exactly how are you"tracking and balancing" your rotor?

The following is my opinion based on what I've seen in Europe, things may be different over there.

If you're buying a new rotor from an independent rotor manufacturer or the OEM (original equipment manufacturer) and you don't have access to a dynamic balancer then you should ask him to track and balance with your teeter block and towers and, if possible, your rotor bearing. That way any errors or tolerance stack up should be accounted for. This is basically what Sportcopter say they told you when you bought the rotor and if it's true, they are right
.
If you don't have access to a dynamic balancer then the kolibri solution is the safest way forward. More expensive but much less hassle.

Either way you should aways insist that they supply you with the balance report showing polar charts and corrections. You may not understand it but if in the future you have your rotor balanced by a Pro he should understand it (if he doesn't, then find another).


If you do have access to a dynamic balancer (and someone who really knows how to use it) don't bother paying the manufacturer for a track and balance.

This is a mistake I've seen a number of times and the final solution for the owner, who tried to do it cheaply, was to pay for me to travel to his gyro and track and balance and sometimes that gets expensive.

As a general comment to all manufacturers I would say that if your customer doesn't have access to a competent rotor balancer you should insist that they send you their rotor head for balancing. It would save you from this sort of public discussion that does nobody any good.

​​​​​​​MikeG
 

Kolibri

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Eddie, nope, haven't left the forum. Since I've gotten my RAF pretty well up to snuff over the past 225 hours, I've much less to comment or offer here. Have also been busy with FW travels. Since you've replaced RAF rotorheads and the second one is balancing better, the first one was the culprit.

MikeG, good info there, thanks for posting. I've not dynamically balanced my with a machine, but would be keen to. It flies pretty smooth, but could be improved.

Regards, Kolibri
 

eddie

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I think your right Kolibri,thanks again for the info. Mike G thanks for your info and concern I appreciated it.
 

spinkaan

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Hi


I would like to I


enquire about Rotortech rotor blades made in Poland as I believe someone in US has ordered a set. Would like to make contact t with this person??
 

eddie

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Those blades and rotor head are coming to a friend of mine,he has the turbo RAF that I installed the engine on,if the blades work as expected

I will have the SC blades for sell and will buy rotortech blades myself.

The polish company is called Gyro-tech,they make helio blades as well
 
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scott heger

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Eddie, with 15 years of flying on two different sets of SC blades (23' X 7" cord, and 25' X 8" cord) on a SC VORTEX, I literally never had to do anything to the blades once taken from the factory box , and they flew vibration free, and in-track. It did not matter how many times the blades were dismounted, hub bar taken off, blades removed from hub bar; the manufacturing tolerances and fit are so close they always flew the same. I ( on purpose) mismatched the #1 and #2 marked blade positions on the hub bar, and they still flew great. No manufacture would be that "lucky" to get so many smooth sets without spending some time flying them. Believe me, I have watched Jim Vanek fly new blades at the factory, and he does not "baby" them, more like crank and bank test pilot maneuvers. Of all the things that could break on a gyro, I felt most confident about the blade quality. For those that have seen me fly the vortex, they know it sometimes sounded more like a Huey than a gyro from making abrupt turns. I have flown the 30" SC blades, and with just me alone in the gyro flying, they really float substantially more than shorter blades at the expense of snappy response. IMHO ,the shortest blades were the best for fun flying, with the quicker spin up time, and instant input response. however the 25' blades flew in the 5,000 Foot density altitudes far easier and gave substantially more float on landing, as well as ultimately flying much better at 80-100 MPH speeds.
 

jm-urbani

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SportCopter;n1125438 said:
Hi Eddie,
Every Sport Rotors rotorblade is tracked, balanced, test flown before they are shipped. We have documentation for every set of rotors that has been test flown and shipped. The problem in this matter may be you are using our Rotors on a Rotorhead that is not one of ours. We have found in certain situations some rotorheads may not be precisely manufactured out of spec and can cause vibration on any rotorblade. Because you changed the pitch block on the hub bar, the blades would have needed to possibly be re-balanced again. Which you had been informed when you called about this matter. We sell just the upper towers and bearing block to ensure the precision of a rotorhead. We also offer a whole conversion system (mast, rotorhead, air trim system) that attaches to any RAF or Sparrowhawk that eliminates this problem. Our quality control requires several people inspect the condition and sign off before any rotorblade set is shipped.
My gyro is hosted in the averso rotor factory (the 2 partners are my mates) , and I saw it a couple of times, the rotor is built, balanced and test flown on a DTA jyro gyroplane and then mounted straigth away on the client gyro who finds vibs that often comes from the rotor head
 

Mike G

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Eddie
What do you and your friend expect to change by going to another rotor manufacturer?

jm
Why don't they simply balance the rotor on the clients gyro??

Mike G
 

SportCopter

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Hi Eddie,
We fly every set of rotors on our machine here and every set is working properly before leaving our facility. In most cases, we have seen that the towers are the culprit. We can offer you our dual bearing rotorhead towers at a discounted price, as it makes it far more precision. It also could be caused due to the pitch block being changed out. We are here to help and want you to be happy with your rotors. If you would like to ship them back to us we will inspect them, fly them and dial them in again (free of charge). Or if we find they need to be replaced we will replace them free of charge (less shipping). We had sent you an email yesterday mentioning this. Please contact us as we are here to help and many other people successfully flying our rotors on an RAF for many years.
 

Kolibri

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Eddie
What do you and your friend expect to change by going to another rotor manufacturer?
Yes, MikeG, I was wondering exactly the same thing.

____________
Eddie had his other turbo RAF friend are going to the Polish Gyro-Tech carbon rotors, and he is selling his SC hub bar and rotors. I believe this is unwise for several reasons.

While carbon rotors can be very good, and there's nothing inherently awful about them (except for lack of leading edge protection), too lightweight sacrifices some of the "flywheel energy" of the heavier aluminum blades. Is 30.8lbs per blade too light? Eddie won't know until he tries them, and I doubt there's a return policy from Poland.

The G-T blades come in max length of 3.85m, or 12.628 feet. Will that be sufficient length (even with a proper hub bar) to hang a heavy RAF with 230hp? What is the total rotor system diameter?

Also, there's the matter of the hub bar. What is its service life? Does it even approach SC's 3500 hours? I've compared photos of the two bars, and the Gyro-Tech bar hasn't SC's 7/8" big bolt, but instead uses two smaller bolts at the bar end. Also lacking is the SC's Heim joint to absorb much of the lead/lag forces. The G-T bar seems quite a bit thinner, too.

I would not pay € 2,500 to be the "test pilot" of months-old blades for a 5-year old foreign company. There are dozens of RAFs with SC rotors, thus ample flight experience. I'm unaware of any in-flight failure of SC rotors. I've 120+ hours on mine (and the SC rotorhead, upper mast, and air-trim) and continue to revel in their quality and feel.

For the € 2,500 (+ €200 for leading edge protective tape, + international shipping) that Eddie is spending on his Polish rotors, he could have bought SC's rotorhead and not suffered his vibration from using the crappy RAF head/pitch block on his SC blades.

Too cheap is . . . expensive.

Also, it'd have been better if Eddie had directly contacted Sport Copter about the vibration issue rather than erroneously impugn on this forum the quality of his SC rotors when all along it was his RAF rotorhead (as he'd been warned at time of purchase). When his Polish blades are similarly "unbalanced" . . . well, at least we'll all know why.

Regards, Kolibri
 
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Kolibri

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The total length of the two G-T blades is 25'4".
To enjoy a 30' diameter rotor disk suitable for the RAF, the G-T hub bar would have to be 4'9" long.
It seems unlikely that such a long hub bar is feasible, thus with a more usual 3' bar, the rotor disk diameter will be about 28'.
For a heavy RAF, this will require significantly more prerotation RPM for take-off.
 

Vance

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Kolibri;n1126347 said:
The total length of the two G-T blades is 25'4".
To enjoy a 30' diameter rotor disk suitable for the RAF, the G-T hub bar would have to be 4'9" long.
It seems unlikely that such a long hub bar is feasible, thus with a more usual 3' bar, the rotor disk diameter will be about 28'.
For a heavy RAF, this will require significantly more prerotation RPM for take-off.
Gyro-Tech's web page says maximum length of the blades is 4 meters. As I recall a meter is 39.37 inches and as I calculate it 4 meters is 157.4 inches or 315 inches for two. That appears to me to be 26 feet 3 inches needing a 45 inch hub bar if someone felt 30 feet was important.

What is wrong with a 45 inch hub bar?

Why will Eddie need more prerotation RPM if he goes with the shorter blades?
 

Kolibri

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Gyro-Tech's web page says maximum length of the blades is 4 meters.
The modified airfoil is 4.00m; the original is 3.85m.

Maximum blade length 3.85 m
http://gyrotech.eu/naca-8h12-original-airfoil-blades/

Maximum blade length 4.00 m
http://gyrotech.eu/naca-8h12-modified-airfoil-blades/

Even still, the slightly longer modified 26'3" rotors and a 45" hub bar is not a great package for the 1320lb. RAF.


What is wrong with a 45 inch hub bar?
Well, two things:

a) the hub bar is a non-lift producing hole in the rotor disk.
b) the longer the hub bar, the greater the mechanical leverage the rotors exert upon the bar.



Why will Eddie need more prerotation RPM if he goes with the shorter blades?
Because (assuming the same chord and airfoil) 28' blades have less lift than 30' rotor blades, and only increased RRPM can make up for that.

Regards, Kolibri
 

Vance

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Kolibri;n1126356 said:
The modified airfoil is 4.00m; the original is 3.85m.

Maximum blade length 3.85 m
http://gyrotech.eu/naca-8h12-original-airfoil-blades/

Maximum blade length 4.00 m
http://gyrotech.eu/naca-8h12-modified-airfoil-blades/

Even still, the slightly longer modified 26'3" rotors and a 45" hub bar is not a great package for the 1320lb. RAF.



Well, two things:

a) the hub bar is a non-lift producing hole in the rotor disk.
b) the longer the hub bar, the greater the mechanical leverage the rotors exert upon the bar.




Because (assuming the same chord and airfoil) 28' blades have less lift than 30' rotor blades, and only increased RRPM can make up for that.

Regards, Kolibri

I went to the Gyro-Tec website because the information in your original post seemed flawed; turns out it was. I don't know that rotor blades Eddie is purchasing so I feel your condemnation was premature.

I don't have enough information to have an opinion about the new blades. I look forward to learning more.

A. NACA did an interesting study on gyroplane rotors and found very little performance difference when they started the airfoil section of the rotor blade further out.
Spend a little time with the Rotorcraft Flying Handbook. http://www.faa.gov/regulations_polic...-h-8083-21.pdf
They have a nice illustration of how a gyroplane rotor works with its driving and driven regions.

They also have a nice explanation of coning.

B. In my opinion less weight from the lighter hub bar compared to the weight of the blades makes for less force trying to tear the hub bar apart (tension) and in my opinion a part of a hub bars function is a spring to manage coning so longer makes for less localized stress and less bend in the blades.
In other words I feel a longer hub bar is not necessarily a bad thing. I don’t know where the limits is.

I use my pre-rotator to keep the blades from hitting things and/or flapping. Most blades I have flown are stable around eighty rpm. It is my observation a higher rotor RPM in flight has nothing to do with the pre-rotation speed required for the blades to become stable.
 

eddie

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Thanks for your input vance,the polish machining,craftsmanship,engineering and quality products are second to none.

our blades and related hardware have been tailored to fit our RAF's,were excited about it.

on youtube there are tests of the blades ,hubbar,and rotor head,they are very impressive,

just look up (gyrotech rotor blades). and Kolibri a high price does not necessary mean a quality product,it could just be a high price.
 
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