Rotorblades for Twinstarrs

[barnstorm2]

Does anyone have or had any experience with a Twinstarr running DragonWings or any other blade then the RAF blades?

[Rick Whittridge]

Tim, are you planning on purchasing the Twinstarr in KY?

[Caribean_gyro]

DRAGON WINGS DONT MAKE THE SIZE YOU NEED. The old RAF are ok once you manage to fine tuned the vibration,joystick play and cracks. I will love to try the sport copter. but at 5k and almost 1 year lead time is out of my range for now.

[barnstorm2]

Tim, are you planning on purchasing the Twinstarr in KY?

I already did but I figgured with my luck I had better not post anything until I took delivery... ;)

I should have it in a few weeks. :)

I was getting ready to send you an email to hit you up for helping me learn about it and discuss modifications to the tail.

[barnstorm2]

DRAGON WINGS DONT MAKE THE SIZE YOU NEED. The old RAF are ok once you manage to fine tuned the vibration,joystick play and cracks. I will love to try the sport copter. but at 5k and almost 1 year lead time is out of my range for now.

29 DW won't cut it eh? I was afraid of that.:mad:

I don't have an extra 5k either.

I suppose I will just go ahead and get a new hub rather then shop for new blades.

The RAF Hub bar has pitch adjustments on it.:(

I have NEVER had to do any adjusting to any of the blade sets I have owned (DW and Mclutch) just sling'em and fly.:D

Am I going to have to adjust the new hub bar or can I just "Bolt and Fly"??:confused:

[Rick Whittridge]

Tim, You will have to tweek on them to get them smooth ! I would try the blades first before you invest in a new bar.I will be trying my 30FT RAF soon to see if they will work out. WOW that`s three Twinstarrs in Ohio that I know of. Congrats on your purchase of the machine.

[Caribean_gyro]

Tim Feel free to ask. AS I tol;d rick I have a wood replica bigger panel available. If interest.

price is cost I am not interest on making a business of this. Modifying the tails? there are 2 tail type a shorter and a longer tails. Reasoning is full enclosure capability. You need longer tails. I have the drawings for them.

If you guys can get honeeycomb and change the floor this will be 30% weight reduction. This is a must if you go crazy putting gizmo in front. AS me, retractable landing light, 28v converters, transponder radio gprs etc.

Harbor freight have what is call telescopic gauges. i FOUND OUT THAT AFTER ADJUSTING THE BLADES IN THE BENCH WHEN MOUNTED IN THE HUB THE CENTER WAS NOT IN THE CENter of the rotor head. SO you take the telescopic gauges measure between the rotor inside towers against the hub and you adjust the center bushing to be at equal distance . This did alot of improvement.

But this was after the I string the blades and balance them. next is track.

Also I suggest putting a grease cup in the 2 pushrod joint. I change the bushing to cge bearing. I will make some picture and send them, Too many input and yet you still have to get it in your hands.

chuckp

[MikeBoyette]

Tim,
Dad put DW's on one twin star years ago. I don't know if he will again give him a call.

[Brad_King]

What does the Twinstarr weigh all up? My Mad Max weighs about 850 empty and flies fine on 29' DW's.

Brad King
N6372K
Mad Mad II LTC

[EI-GYRO]

Recently flew in a Twinstarr with Averso blades. Very impressive.

[Chris Burgess]

The one I flew, 721 empty, 1300 max gross, on 30 foot RAF's. I would personally want the 30 footers for that max gross load.

[barnstorm2]

What does the Twinstarr weigh all up? My Mad Max weighs about 850 empty and flies fine on 29' DW's.

Brad King
N6372K
Mad Mad II LTC


I don't know, I don't have the paperwork yet.

Am I wrong in guessing that 29 DW would perform as well or better than 30 RAFs due to increased efficiency?

[barnstorm2]

Tim Feel free to ask. AS I tol;d rick I have a wood replica bigger panel available. If interest.

price is cost I am not interest on making a business of this. Modifying the tails? there are 2 tail type a shorter and a longer tails. Reasoning is full enclosure capability. You need longer tails. I have the drawings for them.

If you guys can get honeeycomb and change the floor this will be 30% weight reduction. This is a must if you go crazy putting gizmo in front. AS me, retractable landing light, 28v converters, transponder radio gprs etc.

Harbor freight have what is call telescopic gauges. i FOUND OUT THAT AFTER ADJUSTING THE BLADES IN THE BENCH WHEN MOUNTED IN THE HUB THE CENTER WAS NOT IN THE CENter of the rotor head. SO you take the telescopic gauges measure between the rotor inside towers against the hub and you adjust the center bushing to be at equal distance . This did alot of improvement.

But this was after the I string the blades and balance them. next is track.

Also I suggest putting a grease cup in the 2 pushrod joint. I change the bushing to cge bearing. I will make some picture and send them, Too many input and yet you still have to get it in your hands.

chuckp

Chuck,
Thank you.

Yes, I plan to add GPS and later extra toys. After I get the blade issue worked out front panel is next.

My direct email is gyro@oldmotorcycle.com

It sounds like alot of work to get a new hub bar on and set right. I have been turning wrenches for a long time now, I need to get some flying in. I am burnt on R&D!!!

I was told that stock twinstarr could use improvement in rudder authority in x-wind. That would be my motovation for enlarging tails. Also, (i will have to find the thread here) someone I thought posted something about putting a brace in between the tails to stop cracking problems...

[MikeBoyette]

Tim,
Be aware they lack good low speed rudder authority. This is due to the rudders being out of the slipstream of the prop.They used to also have a problem when going back on the tail wheel. If you let it fall back on the tail wheel like a reqular gyro it tries to tip ove backwards and will crunch the rudders.As for the 29' DW's I think that's what dad suggests for that weight. Come to think of it I think he may have put blades on two of them.

[barnstorm2]

Mike,

Do you recall if they kept the rotorhead or replaced it?

I will call your dad once I take posession of the machine.

[Rick Whittridge]

Tim, Did the owner say the blades were out of track? I was looking at your picture of the rotorhead. My machine does`nt have the side trim spring or the rear trim spring.

[Aussie_Paul]

DWs are not on the money for the "lead sled" machines. DWs do not have the chord to handle this application.

There seems to be only two manufacturers that have the "complete" package rotors for the "lead sled" machines, and they are Magni and Sportcopter.

WHY is it so!!!!!!!!!!!!!!!!!!

Aussie Paul.:)

[Caribean_gyro]

let see . the rotor head you have is the same as I have. xwind authority? I would say they have too much rudder. Remeber I have the bigger tails. What you dont want to do is foward slips in a strong x wind. ANd any way who want to do this , that is for planes. just power back and sink vertical.

Michael you mentioned falling back on his tail? The old designed had the wheel in a samll tube and it cracks. I have flare at 5 feet and drop with no event. Nothing I am proud off but did happen.

I have flown at 25 miles xwind landed in x wind done vertical decend in strong wind. I am still here. The machine is a good work horse. But as every machine as in every woman she have things she wil do but dont like.

AS for tail socket crack it happen alot on the machine with bigger tails. reinforce welding and I add a "flying wire" between the mast attachment bolt and the first rivet of the vert. stabilizer next to the rudder. This help hold the assembly when bouncing in the grass.

I will take some picks this weekend after I finish my acrobatic lesson in a YAk 52.

ps my twinstar has 300+ hours if any one like to know
ChuckP

[Caribean_gyro]

Also I saw the JC bolt with no cotter pin? This I would change out of the bat. a new one plus cotter pin

[Caribean_gyro]

pics on its way

[Brent Drake]

Tim, my Twinstar has the side spring. Makes good for hands off flying. I think I'd try a set of sport rotors blades. The same used on the Sparrowhawks.
Speaking of weight. Mine weighs 920lbs fueled and 1360lbs gross.
I'd stick with a set of 30' blades. Mine travels 306-08rpm one person and 316-20 with 2 people. I have not extended my tail. So far I have not found the
x-wind to be a problem. I'll always to-lnd on pavement so bracing the tail should not be an issue. On the x-wind thing, I have landed cross runway to avoid any x-wind issues. I done it a couple of weeks ago at Greencastle.
Brent

[barnstorm2]

Tim, Did the owner say the blades were out of track? I was looking at your picture of the rotorhead. My machine does`nt have the side trim spring or the rear trim spring.

Rick,

No the owner did not say the blades were out of track (though he did mention some stick shake).

But the hub bar is the original one (about 8 years old) and I am under the impression that these bars are prone to develop cracks and need to be replaced with a new one from RAF @ $500.00.

If that is so I will need some help getting the new hub bar on and properly adjusted.

[Rick Whittridge]

Tim, I contacted RAF about the hubbar on my machine & they said it was good for 500HRS but needs inspected .

[Rick Whittridge]

Tim, I will help you anyway I can with the blades.

[gyrowoody]

Hello all ;

I have read this thread and would like to make some comments on some issues raised ; tailsize, rotorblades , DW on Twinstarrs , and tailwheels digging in.

1> tailsize.
There are two sizes for the tails/rudders ; short version and longer chord version. The short version is OK and works well, has proven its track record for more than 11 years now without blemish. The longer tails were developed for the envisioned fully-enclosed model, of which there was only one prototype built. The fully-enclosed model needed the larger tails.
The larger tails are heavier and will need a reinforcing bracket welded into the V-socket that holds the horizontal spars.
As far as x-wind control is concerned ; it is not a problem. There is sufficient rudder authority available with the normal tails.
The tail construction of the Twinstarr is an interesting design since the rudder is not in the propeller slipstream, unlike most other gyroplanes. The "normal" in-the-propwash-construction is fine as long as the engine is running. When the engine stops (not in idle ; idle still produces quite a bit of residual thrust on most gyroplane engines) the rudders in the propwash loose a significant amount of authority, which you may deerly need in a real engine-off landing. This is where the Twinstarr (again) shines ; rudder authority remains constant : engine on or off.
There is in my opinion no need to change to larger rudders if you do not have the fully enclosed version. One can always approach more into the wind if you feel there is too strong a crosswind, like someone suggested earlier in this thread. Works fine.
I have at present a half-finished set of larger tails available for those that are interested, but I would not recommend these on an open Twinstarr.

2.Rotorblades.
The Twinstarr is one of the heavier types of gyroplanes (with the exception of the TwinstarrLITE version, which meets the Ultralight requirements over here in Europe and which is the strongest but also the lightest two-seat machine), by some referred to as "leadsleds". The max gross weight declared is 1200 Lbs,although the design allows for higher gross weights, as we tested succesfully at Farrington's years ago. That weight needs a rotor in the order of 30 feet to keep the rotor disc loading within reason. The RAF blades are available, although Mc Cutchens could do the job as well, and I have flown Twinstarrs down to 27 feet diameter on those. It is true that blade chord plays a role in this as well.
The RAF blades suffer from stick shake on the Twinstarr ( and on other non-RAF machines), because unlike the RAF, it does not have a flexible mast to absorb the longitudinal vibration. The rigidity of the mast of the Twinstarr makes for a very sturdy and solid machine with a good solid feel to it. However ; it would be good to dampen the rotorvibrations to eliminate potential hubbar problems (cracking etc) later.
The very best blades I have ever flown are the Averso blades (see my article in Popular Rotorcraft and Homebuilt rotorcraft), especially in conjunction with the Averso rotorhead. This gives a very smooth combination with plenty of performance. These blades are available in different diameters etc. That rotorsystem is so far my preferred choice, based on my experience with the Twinstarr since 1993. They may not be the cheapest, but they offer superb quality ; I have never had to adjust any of these blades; they fly straight out of the box. (DW do this as well, I understand).

3. There have been at least 2 Twinstarrs fitted with DW rotorheads and blades in Florida. They both flew as a pair all over the place (and also over Floridian water, I am told). Since I have not flown any of these machines in this configuration myself, I cannot comment on this. I know DW are blades with a very good design and reputation, but perhaps they are better suited for slightly lighter machines because of the smaller chord, as someone suggested. I leave it up to Chuck Beatty / Ernie Boyette to comment on that, since they are the authority and thus probably more knowlegeable on that design.
I know of a (3rd) Twinstarr owner who fitted DW blades, but decided in favour of the RAF blades after a while.

4. Tail not strong enough ?
This rumour comes form a particular incident with one of the mentioned Floridian Twinstarrs. The standard Twinstarr sits on its tailwheel when not laden with pilot or passenger, just like most other gyroplanes. (Not the TSLite, by the way).
One day, the owner of this particular machine parked it on a soft sandy spot that probably had some gopher or other holes/soft spots in it. Due to the softness of the sand, the tailwheel sank into a hole/soft spot and allowed the machine to tilt further back than normal and hence to come to rest on its tailsurfaces, with ensuing damage. Could have been prevented easily I think. I have not heard of any other Twinstarr to which this had happened,so I have to dismiss it as an isolated, preventable occurrence.



I have been continuously involved with the design from the beginning and own the manufacturing rights to the Twinstarr design (as well as to the Twinstarrlite), all molds, welding jigs, tooling, etc. I can supply parts to present Twinstarr owners if required. Please feel free to contact me via email on my private email address if you require anything. If anyone would feel inclined to the manufacturing of these models, we would be happy to talk to them.

Please take into account I will be away for about three weeks until mid-June, so please be patient for email answers.

Sincerely,

Woody DE SAAR
gyrowoody@yahoo.com

[C. Beaty]

Interesting. I checked the Averso web site:

http://www.averso.info/lerotoreng.html

and Averso seems to have relearned something discovered by Young and Kelly in 1943; that a smooth seesaw rotor requires the rotor to be as stiff as possible in-plane and the mast to be as limber as possible.

The struts for bracing the Bell rotor in-plane were called the Swedish Yoke, in honor of the test pilot who suggested it, Floyd Carlson.

Later on, the Bell rotor hub was beefed up enough that the external braces could be eliminated.

[Master Roda]

ATTENTION:

Lead time: 4-6 weeks (sometimes sooner)
Actual cost : $4500

Peace of mind: Priceless

www.sportcopter.com

[KenSandyEggo]

"I contacted RAF about the hubbar on my machine & they said it was good for 500HRS."

This is laughable. They're just hoping the bar lasts more than 500 hours before it cracks because of their poor design. A properly designed hub-bar should outlast all of our ages combined.

[barnstorm2]

Thanks guys!

I checked the Averso website. No price is listed and the largest size is 27'.

[Caribean_gyro]

woody. you stated you dont recomend longer tails in a open twinstar? and what about me? AS I said previously having bigger tails give me too much authority. I also had my timein the delta echo. So knowing I have more control is how I manage to fly my gyro.

What I tell very person that fly my gyro is easy on the rudder since you have more authority. But this from saying dont use it in open twinstar can lead to beleived there is a problem.

I am still looking to test the full enclosure, even if it looks like an oscar winner car.
chuckP

[MikeBoyette]

Tim,
He put one of his HD heads on one.

[Rick Whittridge]

Mike, The rotorhead on a Twinstarr is very HD to begin with , no need to change unless you are refering to a slider head! The blades are the problem with trying to get a smooth set. I`m not a Fan of composite blades because of the construction & hard to get dialed in then come back another time & they have changed again. They should be propped up when hangered to minimize this problem.

[C. Beaty]

DWs with a 7” chord are totally inappropriate for a 1300 lb. AUW machine.

With 29’ DWs, rotor rpm would be ~382 and tip speed would be 580 fps, consuming 25 hp just in overcoming profile drag. With any forward speed at all, compressibility would act like a drag brake.

What is needed is a 30’ rotor with blades of 14” chord. Then the rotor rpm would drop to a very acceptable 257 rpm with a tip speed of 403 fps.

With the triangulated rotor pylon of a TwinStarr, the ride would be jackhammerish even if you had a set of rotor blades blessed by the Pope.

The only solution to 2/rev is to use a slider rotorhead. That was the solution forced on Sparrow Hawk. RAF’s magic rubber bushing was patented, the slider head wasn’t.

[Aussie_Paul]

Thanks Chuck. I did not think that the Raf rubber bush in the mast was patented, only the "adjustable CofG".

You are right re the slider head, BUT, how do Magni accomplish such a smooth rotor?

Aussie Paul.:)

[C. Beaty]

Limber mast, Paul. A 2 x 2 steel tube is still softer than a 2 x 3 aluminum tube in the fore/aft direction. And it’s tall which makes it even more limber.

Additionally, the Magni hub design is stiffer in-plane than those scaled directly from Bensen which also helps.

I have no idea of Magni exact mast dimensions; it looks to be 2 x 2, could be less and most likely the wall thickness is less than that used with aluminum masts.

If 2/rev shake is to be tamed by mast compliance, steel tube is the way to go.

[EI-GYRO]

Chuck P, Woody is on a course in nl at the moment.
You may have to wait a few weeks for an answer.

Chuck B, the averso head is rubber-mounted, and the ride is very smooth.
For comparison, it is as good as the ELA, and way better than the RAF blades.
These are the only bases I have for comparison.

[C. Beaty]

Fergus, I’m not an apologist for RAF but in most cases, the blades can be satisfactorily free of rotor shake when properly set up on an RAF machine. To their credit, ¼ chord balance is pretty good and their airfoil has a zero pitching moment coefficient.

Any rotor will shake on a lead sled with an incompliant rotorhead mount. Especially a rotor with hub necked down at its center.

[MikeBoyette]

Tim,
Talked to dad today he is in total agreement with Chuck he will not sell blades for a Twin Star. The biggest he goes now is 28'. A slider head he will sell you though.

[Aussie_Paul]

Additionally, the Magni hub design is stiffer in-plane than those scaled directly from Bensen which also helps.

I am not sure how to interpret "stiffer inp[lane" Chuck.

Some pics of a Magni hub bar.

You will nitice in the last pic two mast set ups. This is to allow container shipping. There is a welded and bolted join in the Magnis that have to be container shipped. Would that reduce the mast flex?

I don't know what the 2" X 2" steel mast wall thickness is at this time.

Aussie Paul.:)

[C. Beaty]

Stiffer in a lead-lag direction, Paul. The side plates of the hub behave like the flanges of an “I” beam. I have to admit, the blade to hub connection of a Magni doesn’t look all that stiff.

With a Bensen type hub, most of the material near the center could be removed without reducing the lead-lag stiffness. Twice as wide would be 8 x as stiff.

The SkyWheels hub is probably the stiffest one of all.

Would you know the Magni mast dimensions, OD and wall thickness? I’d like to see how it compares with a typical aluminum mast for stiffness.

[Aussie_Paul]

I reckon that the Magni hub bar would allow a lot more lead lag "give" compared to a 2.5" wide X .75 or 1" thick alloy hub bar.

Would this allow the blades to operate the same as the Vanek elastermeric (sp) bush?

The Magni hub is very strong in the up and down plane but I would have thought that in the lead lag plane it would move relatively easily. I imagine that they tried a number of spacers to fine tune the amount of lead lag flexing of the hub bar.

Both Vanek and Magni IMHO achieve some of their smoothness by this method, but what would I know!!!

That is why I started this thread. I did not really want people’s personal preferences just some good solid facts.

The hub bar failures that we have had here in Oz seem to fit into two categories.

1) The manufacturer has the coning angle bend or machined coning angle wedges 8" either side of the teeter bolt, therefore making the blades bend the hub bar at the teeter block to try and cone from the teeter bolt. This develops cracks at the bolt holes that hold the teeter block to the hub bar. His answer has been to move the position to 4" either side of the teeter bolt. Still not satisfactory to me.

2) This manufacturer bends the coning angle at the teeter block BUT machines pitch blocks for the blade tangs to slide into very precisely, and these pitch blocks also slide very precisely along the hub bar. This gives no chance at all of any lead lag movement, and once again the hub bar develops cracks at the bolt holes that hold the teeter block to the hub bar.

IMHO these hub bars are subjected to the aerodynamic forces created on the blades forcing the hub bar to "give" and therefore fatigue at the teeter block to hub bar holes.

Just some rambling thoughts to try and learn some more.

Aussie Paul.:)

[barnstorm2]

Tim,
Talked to dad today he is in total agreement with Chuck he will not sell blades for a Twin Star. The biggest he goes now is 28'. A slider head he will sell you though.

Thank you Mike!

I will contact him after the holiday weekend!

I guess RAF blades and RFD slider head is as good as it gets.


Unless Averso comes up with a 30' and a good price....

I ordered the Mag flux kit and will look for cracks before flying it.

[C. Beaty]

It is more a question of resonance than of cushioning, Paul.

At resonance, a small input produces a large excursion. A child’s swing needs only a small, correctly timed periodic tap to keep it swinging.

I know it sounds counterintuitive to reduce shake by stiffening the hub but that is the exact case.

An ordinary set of rotors mounted on a mast too stiff is, unfortunately, resonant at or near the 2/rev aerodynamic input. Softening the hub inplane generally will bring the mast/rotor combination’s resonance even nearer to the 2/rev excitation and worsen shake.

Stiffening the hub in conjunction with a soft mast raises the resonant frequency of the combination above the aerodynamic excitation frequency.

If the mast had the stiffness of a rope, the only frequency we need be concerned about is the resonant frequency of the isolated rotor.

To help you visualize that, grasp a stick of welding rod between thumb and forefinger about ¼ of the way from one end. Give it a thump at either end or in the center and it vibrates for quite a while at its free mode of resonance. Your thumb and forefinger are located at a node, a point along the welding rod where there’s no translation.

Arthur Young and Bartram Kelly were not mistaken when they increased the in-plane stiffness of the Bell-47 rotor in order to reduce shake. Averso seems to have stumbled on to the same thing and added outboard drag links to his hub that straddle the rotorhead and stiffen the rotor in-plane.

Hub and blade cracks are always the result of the rotor system being at or near resonance to the 2/rev aerodynamic input. I don’t know why anyone would fly anything that’s shaking so bad the hub cracks.

********************************

The apparatus pictured below is what started me on the trail of rotor shake. The mast was fully triangulated and unyielding.

Try what I might in the way of undersling, hub stiffness and rotor rpm, it shook so bad that I refused to fly it any higher than I was prepared to fall.

I built a hub with an interleaved, doorhinge style coning hinge without undersling and with drag hinges 12” or so outboard. It shook even worse even though such a hub had worked well with the first set of Hughes blades I ever flew. The difference was that the Hughes blades were mounted on a fairly limber, round aluminum tube mast.

That’s when I came up with the slider and like magic, the shake problems vanished. Only later did I learn that Young and Kelly had tackled the shake problem in the same way.

The final evolution of the slider is pictured in the second photo. The horizontal coil spring is part of the slider mechanism. The hub was widened and stiffened so as to straddle the rotorhead. It is without apparent rotor shake.

The interesting thing is that travel of the slider mechanism is very slight, ~1/16” judging from the polished area of the lateral pivot. Simply tuning the thing off frequency has eliminated the need for extensive movement.

[EI-GYRO]

Sorry Chuck, I was only referring to the RAF blades on the Twinstarr.

Love the overhead tail.

[Aussie_Paul]

Chuck, do the coil springs work better than the leaf springs as a slider? Also I heard some time ago that you or Ernie had put a slider arrangement for the hub bar to slide between the towers.

Rumours or what? Thanks for your patience with me.

aussie paul.:)

[C. Beaty]

It’s six of one and a half dozen of the other, Paul.

The leaf spring of the slider really ought to be softer but then it is likely to bottom out from static load and lose its effectiveness. One way might be to make up a variable rate leaf spring by using a curved backing plate. That way it could be softer on center and stiffen up as the effective spring length was reduced by rolling up the backing plate.

Sliders probably could be made to work at the teeter bolt but then you would have a shoebox full of loose parts every time the rotor was removed.

[Caribean_gyro]

ho said vibartion is bad? First I started my quest for vibration dampenig with a Chuck B statement. that 2 bladed system will vibrate. Knowing this, I said if they will vibrate less get them to the less vibration.

First I am an advocated of proper designed joy stick. SO I change the bushing on my twinstarr for smaller holes. then I took my adjustable rimer. and open it to .250 then I change all bolts to close toleranze .249 , and fine tuned for a thight fit. just the grease and bolt to fill the gap. then I took the broze bushing and change it for seald needel bearings. The original concept will worn out at around 150 hours. I dont like loose stick, scares people.

Then I add 2 bearings in the joint block where the upper and lower push rod meet. with a grease fitting. The play in this joint was eliminated, plus the lubrication help alot.

Now the blade. I hang my blades always. I take them down every year. I dismanted the rotor head clean, inspect lubricate and assemble. Then I inspect the hub and blades , fix any crack or nick , balance them and back to the hub.

What I learn from the RAF , they have to be properly balance and properly center in the rotor head if not will vibrate a lot.

I use telescopic gages to measure the teeter block vs. the inside of my rotor towers.
Accomplishmnet ? vibration started at letting the stick go with movement of 12 inches left and right . to now a small 1 inch circle when you let it go.

Will the slider fix this , sure. But I am a freak and having a bolt moving with just the leaf of steel holding it. No way. the bolt with a spring sound more safety. but still like my bolts tight . Now why I manange to spend time and checkng my blades becasue the so call better blades are out of reach now. SO I have to deal with what I have.

Thanks
ChuckP

PS. Tim pics on its way did you got it?

[Caribean_gyro]

picture of how I support the tails

[Caribean_gyro]

mast point

[barnstorm2]

Softening the hub inplane generally will bring the mast/rotor combination’s resonance even nearer to the 2/rev excitation and worsen shake.
.

Chuck, Will Ernie's slider hub help my situation or act as a hub 'softner'?

[C. Beaty]

Yes, Ernie’s slider will definitely help but it won’t make up for deficiencies in balance, pattern or track. Those things you must do yourself.

[Victor Duarte]

I checked the Averso website. No price is listed and the largest size is 27'.

Hi Guys,
I know Xavier Averso personnally, he is my instructor and i am building his future website (not the actual :)) that will be online after our annual meeting in june.

Allow me to clarify some points for him .

first, you won't find any pricelist on his site. The reason is that Xavie Averso has a particular relation with each of his customers, he won't build and sell something that is not adapted to a particular machine.
Often, building a rotor ask for some modifications.

Second, he tests and flies every rotor before delivery, that means that he wont send a rotor to the other corner of the planet if he can't fly it on the machine.

Chuck P, he built several 29.5 footer but for local machines only.

Chuck B, yes he learnt the importance of the inplane stiffness from a friend trying to eliminate dramatic vibrations.. he mounted a retention strap on the trailing edge.. this immediately smoothed the vibrations..

For those interested, in will post more details after the meeting.
Xavier Averso should announce a new product line.

cheers

[barnstorm2]

Yes, Ernie’s slider will definitely help but it won’t make up for deficiencies in balance, pattern or track. Those things you must do yourself.

Chuck,

If I get Sportcopter blades with the dampening hub bar does that mean I will not need Ernie's slider head?

[C. Beaty]

Sparrow Hawk was forced to go with a slider when using Sortcopter blades. I doubt if there’s much difference in shake level between properly aligned RAF and Sportcopter blades.

On the other hand, I deduce from Chuck Patterson’s comments the rotor pylon of a TwinStarr is not as stiff as a 2 x 3 rigid mast as used on a Sparrow Hawk.

A triangulated structure is only stiff for a pure force applied at an apex. If the load –in this case the pitch pivot of the gimbal head- is applied above or below the projected point of intersection of the pyramid tubes, the pylon structure flexes from the resulting bending load applied to the tubes making up the pyramid.

My advice is to find out what you can do with the RAF blades you already have. If you’re not comfortable tuning them yourself, perhaps you could pay an experienced RAF tuner like Duane Hunn to do it for you. If the RAF blades can be smoothed up with your current setup, Duane’s your man.

[Master Roda]

If you keep your RAF blades, I encourage you to check for cracks frequently. Also constant adjustment will be required through the life of the blades (how many hours are on them anyway?). So learning how to track and balance would be valuable to you.

Sportcopter uses a slider, but in my opinion it does'nt help. My thought on that is that the actual oscillation is not on the same axis as the slider, rather it is offset.

Tracking may be the most important step, if they are not perfectly in track they will shake CONSIDERABLY more.

Hope that helps.
Jon

P.S. Sometimes a rotor will change its track at different RPM's, so check it at cruise.

[KenSandyEggo]

"Tracking may be the most important step, if they are not perfectly in track they will shake CONSIDERABLY more."

Not necessarily true, Jon. Some blades, because of inherrant differences between the 2 blades, especially glass ones, will fly much smoother when out of track by an inch or more. Blades are tracked properly when they are producing equal lift, and that may not be in the same plane.

I don't recall a slider on my Sportcopter blades.

"I doubt if there’s much difference in shake level between properly aligned RAF and Sportcopter blades."

From my experience, there's a world of difference, Chuck. Toss off the RAFs and install the Sportcopters, and you won't believe it's the same gyro, the ride will have become so smooth. A lot of RAF blades are impossible to "tune" or smooth out because of manufacturing discrepancies between the 2 blades.

[C. Beaty]

Blades that fly smoother out of track, Ken, are typically out of balance. The high blade will be the heavy blade because reducing shake by deliberately introducing out of track produces a force opposite to that caused by the heavy blade.

Out of track, out of balance and out of pattern rotors all feel about the same, stirring the stick and rotorhead in a 1/rev circle.

Out of track introduces a vertical lope in the airframe reminiscent of a galloping horse.

The only way to know with certainty that a rotor is out of balance is by use of a water level. Concrete floor slabs are rarely flat and level enough to use as a reference for blade balance.

The hooker is always 2/rev shake. That’s where sliders, limber masts, in-plane stiffness and magic rubber bushings come into play.

2/rev shake is reminiscent of a trotting horse.

The Sparrow Hawk uses a slider in lieu of a magic rubber bushing but the bottom line isn’t much different between the two.

No seesaw rotor can ever be smooth on a rigid mast or pylon.

[Caribean_gyro]

SO botto line if you can track ,balance and smooth out the blades then fly them. That is what I am going to do this weekend. Until $$$ is available and then I will buy metal ones.

also I track some flexc mounted in a mccutchen hub this pas weekend, it took me 5 flight but I snooth them out. They fly like the hugh blades, fast and had alot of inertia. you can throtle back and they float alot. only thing didnt like was slowing them with the brake. they dont stop.

ChuckP.

ps I will try to see if next time if some one in the back seat can video the pylon to see if it flexing.

[C. Beaty]

Seems to be you don’t like plastic rotorblades, Chuck P.

The AH-64 Apache has plastic rotorblades that can survive a direct hit from a 20 mm cannon shell and still fly home.

The BO-105 helicopter has been around for something like 30 years with plastic rotorblades.

I think nearly all modern US military helicopters have plastic rotorblades.

Plastic helicopter rotorblades are more expensive than metal blades but life cycle cost is lower because plastic lasts longer.

Admittedly, there’s a difference between AH-64 rotorblades and RAF rotorblades. The Apache blades come without the lumps and have a composite, multitube spar.

[Aussie_Paul]

.....I have flown 3 sets of the latest Raf blades and must say that after the hit and miss of the previous 20 or 30 generations, these 3 sets were great for smoothness straight out of the box.

I was flying an older set last week and could only get them acceptable certainly not to the standard I am used to these days with the Oz blades and the new Raf ones. I hope to experience Sport Copter blades in the not too dsistant future.

I undestand that the Raf blades are now made out of house by proffessional rotor blade manufactures. If this is the case then it shows in the end product.

Aussie Paul.:)

[Caribean_gyro]

Well beside the McCutchen. The problem with my RAF . If you let them hanging they crack on the trailing edge and if they were not correctly layup and any material move then when put to work they behaive diferent. As with the metal blade is either shine or paint plus letting it hang wont be that critical.

I have flown in mentone and in several machines that vibrate so I use this experience as a standard and try to bring mine to less. I am hoping a friend I have with a chadwick come by my place to do some measurements. I will like to know in numbers where my baldes are and what they are doing beside closing 1 eye and saying , " yep they look in track.

Once I get the video of them flying I will try to post a link for does that want to se them in action.

ChuckP

[KenSandyEggo]

As mentioned previously awhile back, Chuck, the older RAF blades could never be smoothed out because of the imbalance between the 2 blades, with heavy and light areas along their length. For the newcomers, a friend of mine whacked his RAF blades and then did an autopsy on them. There were thick sections, thin sections and sections that were hollow. Unless the opposing blade had the same exact flaws in the exact same locations, trying to smooth them out was futile, even with the best balancing gear available and an engineer/A&P/heli-pilot/heli-builder/heli-restorer doing the readings.

[C. Beaty]

I’m not trying to make excuses for RAF blades, Ken J. I am well aware of the crudeness of manufacture, at least in the ones I’ve seen.

I was sent sample sections several years ago from which I extracted ordinates in order to run a desktop wind tunnel simulation.

The surfaces are lumpy, nose shape was peculiar and the foam core was reminiscent of over baked meringue.

But to RAF’s credit, ¼ chord balance was pretty close and the pitching moment coefficient was nearly zero. Those are 2 critical items with any rotor airfoil that are too often ignored by other blade makers.

The violent shake that cracks hub bars is a different breed of cat from the nuisance shake that may result from lumpy surfaces.

Mount any seesaw rotor on a mast/pylon that is too rigid and you may generate hub cracking vibrations. This is a resonant phenomenon where the natural frequency of rotor/ mast combination falls at or near the periodic aerodynamic excitation. The same thing that a bow does to a fiddle string.

The correct course of action is stiff rotor and limber mast. Or RAF magic rubber bushing or slider. That places the resonant frequency of the rotor system above that of the aerodynamic input. Then it’s no longer a fiddle string.

******************
I remember reading in the PRA magazine a number of years ago where someone matched up blades from two different manufacturers, Rotordyne and Stanzee and got them to fly reasonably well after balance and track. At least that was the story.

[Caribean_gyro]

ok here is the latest . I magnaflux my hub bar . No crack was found . I ask th RAF people and got a call from Mark thorton. He mentioned that DOn farrington once send the hub for a check and it did have 1400 hours on it. I told him what I do that every year I magnaflux and check the hub bar and he told me that is ok what I am doing. The new bolt increase the strenght of it by 25%. That my current blade is designed to lift up to 1500 pounds.

That a year a go they were doing hub excehneg for 560.00 that now I should check the new price if I elect to change it. My take I will keep the current hub and keep flying it.
ChuckP