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Adventures in flutter

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jindoguy(at)gmail.com
Guest

Posted: Wed Apr 05, 2006 4:51 am Post subject: Adventures in flutter

As I mentioned in an earlier post, I encounered flutter in the left aileron

at about 75 mph on my fifth flight in my Mark III. Although I have tried to

maintain good airspeed control to stay out of the flutter regime, it

happened twice more, in both ailerons. After the last ime, I grounded the

aircraft until I could get the counter balances installed. I was doing a

general condition inspection pior to the installation and found that each

blade of the Warp Drive three blade prop had a divot in the forward surface

that aligned quite nicely with the left flap bell crank. The paint on the

aft most point of the bell crank was missing, too. That afternoon I ordered

plans from the factory and over the days I waited for them to arrive I began

to wonder if this was becoming a chicken and egg mystery. Did the prop hit

the flap bell crank and with that rythmic beat excite the aileron into

flutter, or did the flutter cause the bell crank to contact the prop? There

appears to be adequate clearance, about an inch, between the bell crank and

the prop when checking it statically, however, checking the plans shows that

the bell cranks have been installed improperly, and are rotated about 15

degrees past vertical toward the rear.

More checking of the plans revealed that the engine mount is built upside

down in a cross between the 582 and 618 design. Rather than a single motor

mount plate that bolts to the engine and the engine's vibration isolaters,

it is composed of two plates, front and rear, carrying the isolaters atop

which are two 2" square tube risers, running fore and aft. Studs going

through the risers attach the engine to the mount plates. There are no

inserts or spacers to keep the studs from squeezing the tubes (architectural

tubing that has no radius in the corners, I might add), but a square, 1/4"

thick spacer serves to spread the load of the engine to the vertical walls

of the tubes. Clear as mud, right?

So, with that back ground into the mechanics of the engine and ailerons and

how they may, or may not, be interacting to create the flutter in the

ailerons, here's my question to the group. I can replace the blades in the

Warp Drive prop and go back to a 66" prop, it's now 68", or I can replace it

entirely with an IVO or a GSC. The IVO has the option of adding the in

flight adjustable hub at a later date. If you are flying one of these props,

I'd like to hear your recommendation and insight.



--

Rick Girard

"Pining for a home on the Range"

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John Jung

Joined: 10 Jan 2006
Posts: 108
Location: Surprise, AZ, USA

Posted: Wed Apr 05, 2006 6:17 am Post subject: Re: Adventures in flutter

 	  jindoguy(at)gmail.com wrote: 	
		  So, with that back ground into the mechanics of the engine and ailerons and how they may, or may not, be interacting to create the flutter in the ailerons, here's my question to the group. I can replace the blades in the Warp Drive prop and go back to a 66" prop, it's now 68", or I can replace it entirely with an IVO or a GSC. The IVO has the option of adding the in flight adjustable hub at a later date. If you are flying one of these props, I'd like to hear your recommendation and insight.

Rick Girard 	




Rick,



Unless the Warp is contacting the bellcranks within an inch of the tips, or has too much damage, I would not change props. It appears to me that the prop is not the problem, and by changing the prop, you may make the problem worse or at least fail to fix it. I suggest that you fix the bellcranks, if you can, as well as the counterweights. I couldn't tell from your description if there is or isn't a problem with the motor mount. It sound like some that I have seen on Mark III's, and unless the bolts are not keeping some tension, there may be no problem. You might check that the non-standard motormount didn't move the engine farther forward.

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_________________
John Jung
Firestar II N6163J
Surprise, AZ

jindoguy(at)gmail.com
Guest

Posted: Wed Apr 05, 2006 7:49 am Post subject: Adventures in flutter

John, I guess I left it without saying that I fixed the problem with the

bell crank installation before I did anything else. As for the prop, it's

beyond my comfort zone to fly with a prop that has visible damage, so the

question to Mark III, 582 flyers remains, which do you prefer, the Warp

drive, Ivo, or the GSC prop?

On 4/5/06, John Jung <jrjungjr(at)yahoo.com> wrote:

 	  Quote: 	

 jindoguy(at)gmail.com wrote:

 > So, with that back ground into the mechanics of the engine and ailerons

 and how they may, or may not, be interacting to create the flutter in the

 ailerons, here's my question to the group. I can replace the blades in the

 Warp Drive prop and go back to a 66" prop, it's now 68", or I can replace it

 entirely with an IVO or a GSC. The IVO has the option of adding the in

 flight adjustable hub at a later date. If you are flying one of these props,

 I'd like to hear your recommendation and insight.

 > Rick Girard

 Rick,

 Unless the Warp is contacting the bellcranks within an inch of the tips,

 or has too much damage, I would not change props. It appears to me that the

 prop is not the problem, and by changing the prop, you may make the problem

 worse or at least fail to fix it. I suggest that you fix the bellcranks, if

 you can, as well as the counterweights. I couldn't tell from your

 description if there is or isn't a problem with the motor mount. It sound

 like some that I have seen on Mark III's, and unless the bolts are not

 keeping soom tension, there may be no problem.

 --------

 John Jung

 Firestar II N6163J

 Surprise, AZ

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=3D26583#26583

--

Rick Girard

"Pining for a home on the Range"

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Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Wed Apr 05, 2006 7:50 am Post subject: Adventures in flutter

I am at a loss to understand why you need the 2" risers - I am running a 

582 with a 68" Ivo & B box, and all I needed was a 1 3/8" spacer to get 

enough clearance.



Also, I have a 2.5 inch spacer between the Rotax prop flange and the 

prop, which gives me 5" of clearance between the flap bellcrank and the 

prop.



I am of the opinion that 1" of clearance between the prop blade and the 

bellcrank is not nearly enough, even considering the stiffness of the 

Warp Drive. A good dose of turbulence and a bit of gyroscopic precession 

of the prop, or one of my landings would be all it would take to get rid 

of all of that 1" of clearance, plus a bit more.



I have seen the 2" square tube risers that you describe, and they strike 

me as a poor design. I obtained a 6" length of 1.25 aluminum dowel and 

took it to a machine shop and had it cut on a lathe to 1&3/8" lengths, 

and then bored on the lathe so the bolts would go straight down the 

middle. That gives a solid block of aluminum between the Lord mounts and 

the engine motor mounts, and is probably sufficient for anything you 

could sit up there, much less a lowly 582.



There are some views of it on the bottom of this page here:

http://www.bcchapel.org/pages/0003/pg2.htm



It is possible that there is an interaction between the flaps, ailerons 

and the prop. With the prop passing so closely to the flap torque rod, 

which is attached to the aileron torque rod, it is not impossible that 

you could get a harmonic. Which is yet another reason to get an 

extension and move the prop back another 2.5 inches away from the wing.



Richard Pike

MKIII N420P (420ldPoops)



Richard Girard wrote:

 	  Quote: 	
		   



 As I mentioned in an earlier post, I encounered flutter in the left aileron

 at about 75 mph on my fifth flight in my Mark III. Although I have tried to

 maintain good airspeed control to stay out of the flutter regime, it

 happened twice more, in both ailerons. After the last ime, I grounded the

 aircraft until I could get the counter balances installed. I was doing a

 general condition inspection pior to the installation and found that each

 blade of the Warp Drive three blade prop had a divot in the forward surface

 that aligned quite nicely with the left flap bell crank. The paint on the

 aft most point of the bell crank was missing, too. That afternoon I ordered

 plans from the factory and over the days I waited for them to arrive I began

 to wonder if this was becoming a chicken and egg mystery. Did the prop hit

 the flap bell crank and with that rythmic beat excite the aileron into

 flutter, or did the flutter cause the bell crank to contact the prop? There

 appears to be adequate clearance, about an inch, between the bell crank and

 the prop when checking it statically, however, checking the plans shows that

 the bell cranks have been installed improperly, and are rotated about 15

 degrees past vertical toward the rear.

 More checking of the plans revealed that the engine mount is built upside

 down in a cross between the 582 and 618 design. Rather than a single motor

 mount plate that bolts to the engine and the engine's vibration isolaters,

 it is composed of two plates, front and rear, carrying the isolaters atop

 which are two 2" square tube risers, running fore and aft. Studs going

 through the risers attach the engine to the mount plates. There are no

 inserts or spacers to keep the studs from squeezing the tubes (architectural

 tubing that has no radius in the corners, I might add), but a square, 1/4"

 thick spacer serves to spread the load of the engine to the vertical walls

 of the tubes. Clear as mud, right?

 So, with that back ground into the mechanics of the engine and ailerons and

 how they may, or may not, be interacting to create the flutter in the

 ailerons, here's my question to the group. I can replace the blades in the

 Warp Drive prop and go back to a 66" prop, it's now 68", or I can replace it

 entirely with an IVO or a GSC. The IVO has the option of adding the in

 flight adjustable hub at a later date. If you are flying one of these props,

 I'd like to hear your recommendation and insight.



 --

 Rick Girard

 "Pining for a home on the Range"

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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

ElleryWeld(at)aol.com
Guest

Posted: Wed Apr 05, 2006 4:38 pm Post subject: Adventures in flutter

Rick 

if you install an  IVO prop you will get a 2 3/4 inch spacer that will help 

you with your problem with the prop running close to the linkeage I run an IVO 

and I like it very much 



Ellery in Maine



do not archive

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Earl Zimmerman

Joined: 13 Jan 2006
Posts: 35
Location: Elizabethtown, PA

Posted: Wed Apr 05, 2006 6:07 pm Post subject: Adventures in flutter

ElleryWeld(at)aol.com wrote:

 	  Quote: 	
		   

 

 Rick 

 if you install an  IVO prop you will get a 2 3/4 inch spacer that will help 

 you with your problem with the prop running close to the linkeage I run an IVO 

 and I like it very much 

 

 Ellery in Maine

 

 do not archive

 

  I agree with Ellery. I would go with a two blade 68" IVO.   ~ Earl

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by0ung(at)brigham.net
Guest

Posted: Thu Apr 06, 2006 9:11 am Post subject: Adventures in flutter

<<<<<<<<<<<<<<<<<<<<<

So, with that back ground into the mechanics of the engine and ailerons and

how they may, or may not, be interacting to create the flutter in the

ailerons, here's my question to the group. I can replace the blades in the

Warp Drive prop and go back to a 66" prop, it's now 68", or I can replace it

entirely with an IVO or a GSC. The IVO has the option of adding the in

flight adjustable hub at a later date. If you are flying one of these props,

I'd like to hear your recommendation and insight.



--

Rick Girard

"Pining for a home on the Range"

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>>>>>>>>>


	


In my opinion.



At this point I am not sure I would take apart the bellclranks,,,,  what I

think I would do is install a prop spacer,  3 inch or so.       the prop

spacer would eliminate the interference fit and also give you a boost in

performance. By putting the prop further from the disturbed air.  It will

also make it a bit quieter. I would then install the counter weights in the

ailerons.

I would not use the ivo prop as it is more flexable  and would cause the

prop strike problem to be worse.  Also the flight adjustable hub is best

served in an aircraft that flies much faster than the kolb will go.  As to

the 66 or 68 inch prop it would depend on the engine and gear ratio.   With

the speeds that the kolbs fly the 68 would be better if your engine and gear

ratio  will support it.



Boyd Young

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Denny Rowe

Joined: 10 Jan 2006
Posts: 89
Location: Leechburg, PA

Posted: Thu Apr 06, 2006 5:57 pm Post subject: Adventures in flutter

I agree on all points with Boyd.

Denny Rowe,

Mk-3, 68 inch Powerfin

---

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