View Full Version : Slinging Rotorblades
12-09-2003, 04:21 PM
Okay some basics on living with gyroplanes.
So we have blades up there and they have to be balanced and in alignment to fly reasonably smooth. When we take the blades off and put them back on, we have to do SOMETHING to get the blades in alignment with each other. Typically most gyro pilots do what is called Stringing the blades. This is one way to do it, BUT there is another, and I find SLINGING the blades to be a better way to do it and afterwards I get the smoothest stick with slinging not stringing.
So how do you Sling your blades? Here is what you do...
1. Lay out the blades and hub bar and using saw horses or something to work on, Assemble the blades and hub bar. Do NOT tighten the bolts down tight yet.
2. Make sure your putting side X on the hub bar with side X on the rotorblade, and side Y with blade Y. In other words make sure the blades are in the proper spot on the hub bar.
3. Now make sure the bolts are tight but yet loose enough to turn with very VERY little force on the wrench. If they are sloppy loose or too tight Slinging will not work. The goal is to get the bolts tight enough to hold it all in place but yet allow the blades to move slightly in the hub bar straps when spun.
4. Now after everything is checked and double checked, go ahead and put the blades on the machine. Install them as you would to fly them. you won't have to take them back off so make sure you tighten the teeterbolt and have everything put back together as you would to fly the gyro.
5. Now it is time to sling the blades. Go out to the runway or taxiway or where ever you have room to get the blades to near liftoff speed. Pre rotate, or pat up the blades by hand - however you normally get the blades going is what you want to do - and start a normal take off roll. IMPORTANT - remember the bolts aren't totally tight so do NOT leave the ground!
6. As the blades come up to speed, get them as fast as possible without leaving the ground. Then what you want to do is to get out of the way somewhere where you can let the blades come to a stop all by themselves. IF YOU USE THE ROTORBRAKE AT ALL, OR THE PRE ROTATOR after you got them up to flight speed you will have to start all over. the blades must come to a stop without anything touching them or any use of the rotorbrake.
7. Now that the blades are stopped, you can get on a ladder and reach up and tighten the bolts you left slightly loose and your all done. Be sure to double check all the bolts to make sure you got them all tight and give the gyro a good looking over before you fly it, But now that the blades are slung, the stick shake should be very little to none - as long as your blades are balanced and tracking properly.
12-10-2003, 12:29 AM
I was told by a few gyro pilots not to sling the rotorblades. They said after time the bolt holes on the blade straps or the hub bar will eventually elongate.
12-10-2003, 02:23 AM
I sling my blades. I find it works better and is easier than stringing. As for elongating the holes, I wouldn't think it would be an worse on the blades that banging them into alignment when you string them. Remember they don't jump to flight speeed immediately, they gradually increase in speed until they are at flight speed.
12-10-2003, 05:42 AM
The problem with Stringing the blades - at least for me - is I can spend half a hour getting everything perfectly lined up and tightened and If I just move the blades a inch the string is out again. Now if the bolts are all tight and so on the string shouldn't move but for me it always does.
I can get the blades reasonably smooth stringing them. but if I sling them I can get them almost baby butt smooth. It is a big difference between the two. Enough of one that you may never see me with fishing line and clamps in my pocket again!
And like Jamie said I see no reason the holes would elongate.
12-20-2003, 12:42 AM
I concur with Jamie and Ron. If done properly, I see no reason for the holes to become elongated, especially with DW's.
12-20-2003, 04:37 AM
Chuck, why would you say "especially with Dragon Wings"?
12-21-2003, 05:49 AM
Paul, I said especially with DW's simply because I have the most experience with those blades and the fact that there are six bolts all lined up in a row on each blade with very precise tolerances. However, your point is well taken in that it wouldn't matter what blades were being slung, if done properly. There should be no elongation of any of the holes. Thanks for pointing this out. Chuck ;)
03-06-2004, 02:17 AM
Jamie, Ron and Aussie Paul,
It seems to me that as much mass as we are spinning, that if we simply pre-rotated up to 180 or 200 rpm, the blades would be properly aligned.
Do you feel that it's really necessary to take the blades up to more than 200 rpm for proper alignment?
If not, it would be a lot easier to pre-rotate right in front of the hanger.
03-06-2004, 04:43 AM
I prefer to pre rotate and fast taxi to get the blades to accelerate on their own without being driven by the Pre rotator. I like to get them as close to flight speed as possible without leaving the ground.
You might experiment with just using the prerotator. It may work just as good.... Or it might not. I would guess not since your talking about pre rotating and then letting go to slow back down. It is too hard to describe in words, but I just think it wouldn't work as well. Try it and let us know what you found.
03-06-2004, 04:58 AM
Thanx for your input Ron,
I've had my machine in my barn since last weekend making some mods, adding the fuel flow system, etc.. I will probably take it back to the airport and put the blades back on it this afternoon.
I will spin it up to at least 180 or maybe even 200 r's, then tighten the bolts and try it. I'll post the results.
03-06-2004, 03:58 PM
When I put my blades together...I used a rotary laser with excellent results.
I simply made two marks exactly one inch from my leading age...(RAF blades)...then set up my rotary laser and projected a fine red line through these marks and adjusted till this red line was exactly over the center of the hub bar.
I torqued all the bolts watching the laser. It was simple...no clamps...the red plane of light doesnt care how much the blades are coned...it will find the center of the hub bar.
MY flight test surprised me how smooth the blades are.
03-06-2004, 04:04 PM
That is good Stan, But my thoughts are by stringing the blades to perfection - as your way of doing certainly sounds like it is - There may still be some rotorshake that could be gotten rid of by Slinging the blades.
By slinging the blades, the blades will find their own happy center - which is possible that the Center for that set may not be the same position as perfectly straight stringing would be. I may be wrong about this but then again I may not be either, All I can say is it works and I get the best results this way.
Stan for grins and giggles, why not try loosening the bolts on the blade straps a bit and pre rotate and fast taxi till the blades are almost up to flight speed and then without touching them or using the rotorbrake allow them to stop and then tighten the bolts and let us know if it got any smoother.
03-06-2004, 05:49 PM
Ron: I have no shake at all...either by sheer luck...or whatever. I am not touching them... ;D
MY way of using a laser isnt implied as better than using a string. but just another way of getting the job done. .The laser is just a tool I use all the time in my stair business and is so simple to use.
My intentions were to try this method first...then if I had some stick shake..to then sling them. But I would be stupid to mess with it now.
I fly Dragon Wings, and have used the slinging method for a couple of years now. I have noticed no elongation of the bolt holes, and still have a couple of bolts which need a little assistance getting them out.
It takes about 3 times as long to string vs. sling, and invariably, as I tighten the last few bolts, the alignment changes. When I made the decision to try slinging, I first used the string method, flew the blades, then used the slinging method. After three times of getting smoother blades with the slinging method after stringing, I no longer use my string.
I still carry the string in the bottom of my toolbox, but only if I end up having to load the blades somewhere where it's too busy for me to sling the blades.
What I try to do for slinging is to fast taxi down the runway a bit, turn around, and fast taxi to just short of liftoff, and end up near the hangar and my ladder. This may not be as easy at airports, with any kind of traffic, but I fly off a grass strip, and my two hangar mates hardly ever fly, so I have the place to myself 99% of the time.
11-20-2005, 04:48 PM
Bumping this thread up for Stuart..... I sure miss Chuck Irby :(
11-20-2005, 05:03 PM
sure miss Chuck Irby :(
Me too. :(
11-20-2005, 05:05 PM
Ron: I wish I had gotten a chance to talk to Chuck in person. We had sent many private messages back and forth. What a loss when he went.
11-21-2005, 10:19 AM
Glad to see this thread up again.
Sounds excellant. Centifugal force will self balance, which might be out of physical sling alienment.
Should I try this on my Skywheels (composite hub and blades)
I do have some shake. I havent removed the Rotor for the last 5 years.
Wanted to check the hub bearing and sling alienment.
Air Command Pakistan
11-21-2005, 10:28 AM
Me too Ron, he was a great guy.
11-21-2005, 11:08 AM
We used to sling the blades all the time on Hueys, Cobras and OH-58s when we were doing field recoverys. In field situation we usally didn't have the tools to track and rig the blades. We simply field balanced the blades on the head, sling them out at flight idle, torque 'em down and go home. Once we got the copter back to base we would re-rig. Every r/c helicopter owner I know does the same thing before the first flight of the day. Can't argue with a system that works.
11-21-2005, 04:12 PM
Rehan, after 5 years without having the blades off, I would certainly advise you to take them down to check the bearings, inspect everything and grease it all up. I see nothing wrong with slinging Skywheels.....
11-21-2005, 09:01 PM
I would sling my skywheels and they were very smooth.
11-22-2005, 10:46 AM
Thank you for the go ahead.
I have greased the bearing. Taking the blades off for may be a couple of hours at a time and then putting them on again.They are on the gyro the rest of the time.
I do rotate the tiedown blade in turns, the tiedown one (blade) does have more drooping or deconeing, wiz. Stick shake.
I hope this makes sense or am I just imagining things.
And also thank you to Tim Oconners.
Air ommand Pakistan.
06-12-2006, 03:54 AM
Bumping this thread up again for folks like David Holmes....
05-24-2008, 11:46 AM
Thanks alot for all the advice and help, you guys are a great source of info and helpful ideas. Russ
05-24-2008, 03:58 PM
I think that slinging is probably the best way to go though I never tried it. I did have a bad shake at one time after removing the blages and realigning on work horses with the string. Then someone in the know said that the friction at the end of the blades over the lever arm was significant and that it needed to be reduced or eliminated. BALLS were recommended! The blades were dropped onto the concrete floor with a smooth piece of wood under each blade tip and a ball (in this case inch and a half polyurethane kids toy balls) under each blade tip. The difference between stringing on the work horses and the floor with balls was amazing and the shake was completely rectified. None the less I think that logically flinging/slinging should be better than stringing! I'll try that next time.
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