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Wing strut vibration

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lcottrell

Joined: 29 May 2006
Posts: 1494
Location: Jordan Valley, Or

Posted: Wed Aug 01, 2007 2:41 pm Post subject: Wing strut vibration

I am getting a rhythmic vibration in my wing struts. I had  never noticed until I began trying to video out of the plane. I can stop it by  putting my hand on the strut. It is my understanding that TNK has stream lined  struts now. Will they stop this strumming? Any help would be  appreciated.

 Larry C

 do not archive

    [quote][b]

jbhart(at)onlyinternet.ne
Guest

Posted: Wed Aug 01, 2007 3:04 pm Post subject: Wing strut vibration

From: "Larry Cottrell" <lcottrell(at)fmtcblue.com>

..................

Will they stop this strumming? Any help would be appreciated.



Larry,



The answer is yes.  I streamlined the struts on the FireFly.



See:



http://www.thirdshift.com/jack/firefly/firefly91.html



Jack B. Hart FF004

Winchester, IN





do not archive

lcottrell

Joined: 29 May 2006
Posts: 1494
Location: Jordan Valley, Or

Posted: Wed Aug 01, 2007 3:23 pm Post subject: Wing strut vibration

I actually have plastic streamlined fairings for the original round struts. 

They perhaps are not aligned at the correct angle. Your finding was 6 

degrees. The wing is 9 degrees at flight stance. Would this be 6 degrees at 

flight stance?

Larry C

 	  Quote: 	
		   The answer is yes.  I streamlined the struts on the FireFly.



 See:



 http://www.thirdshift.com/jack/firefly/firefly91.html



 Jack B. Hart FF004

 Winchester, IN





 do not archive

jbhart(at)onlyinternet.ne
Guest

Posted: Wed Aug 01, 2007 5:30 pm Post subject: Wing strut vibration

I actually have plastic streamlined fairings for the original round struts. 

They perhaps are not aligned at the correct angle. Your finding was 6 

degrees. The wing is 9 degrees at flight stance. Would this be 6 degrees at 

flight stance?

Larry,



I built a meter (http://www.thirdshift.com/jack/firefly/firefly55.html) so I 

could determine the FireFly angle of attack at cruise.  It came out at six 

degrees, ans so that is what I used.  The basic configuration has not 

changed for some time and can be seen on the bottom of:



http://www.thirdshift.com/jack/firefly/firefly.html



The only angle in doubt is thrust angle.  I may have changed it and not up 

dated the drawing.



Jack B. Hart FF004

Winchester, IN



Do not archive.

jbhart(at)onlyinternet.ne
Guest

Posted: Wed Aug 01, 2007 5:39 pm Post subject: Wing strut vibration

I actually have plastic streamlined fairings for the original round struts. 

They perhaps are not aligned at the correct angle. Your finding was 6 

degrees. The wing is 9 degrees at flight stance. Would this be 6 degrees at 

flight stance?

Larry,



I have thought about this some more.  You are able to put much in much more 

power and speed into the strut than I can with my FireFly.  Do you notice if 

the strumming goes away when you slow down to say 60 mph?  If so there is a 

good chance the preformed/shaped aluminum struts may do the trick.  They 

should have higher stiffness.  



Jack B. Hart FF004

Winchester, IN



Do not archive.

gaman(at)att.net
Guest

Posted: Wed Aug 01, 2007 6:04 pm Post subject: Wing strut vibration

[quote][b]

John Williamson

Joined: 10 Jan 2006
Posts: 146
Location: Arlington, TX

Posted: Wed Aug 01, 2007 6:41 pm Post subject: Re: Wing strut vibration

Larry and All,



I had the same lift strut harmonic vibration on the Kolbra when I did the first few flights without the streamlined plastic fairings on. It would only occur at a very narrow airspeed band about 90 mph.  I installed the TNK fairings and have never had the vibration again.



As for the angle the fairings were set at, I just eyeballed them to an angle that looked okay.



John Williamson

Arlington, TX



Kolbra, 912ULS, 1,463 hours and counting

_________________
John Williamson
Arlington, TX

Kolbra, 912ULS, 1640 hours
http://home.tx.rr.com/kolbrapilot

lcottrell

Joined: 29 May 2006
Posts: 1494
Location: Jordan Valley, Or

Posted: Wed Aug 01, 2007 8:18 pm Post subject: Wing strut vibration

My vibration is in the 56 to 64 MPH range, or most likely all through all 

the speed that I can stay in the air. I notice it most in the 6000 rpm 

range. I also had it without the plastic cover so I am sure that it is just 

that the round struts do not have the rigidity that the streamlined metal 

ones do. Thanks for the help. Now for some creative financial planning.

Larry C

---

jindoguy(at)gmail.com
Guest

Posted: Thu Aug 02, 2007 8:00 am Post subject: Wing strut vibration

Larry, The Challenger II I have in the shop has the plastic fairings filled with insulating foam and attached with two small screws at each end. No harmonics anywhere in the speed range of 40 to 80.



Rick



 On 8/1/07, Larry Cottrell <lcottrell(at)fmtcblue.com (lcottrell(at)fmtcblue.com)> wrote:[quote] --> Kolb-List message posted by: "Larry Cottrell" <lcottrell(at)fmtcblue.com (lcottrell(at)fmtcblue.com)>



My vibration is in the 56 to 64 MPH range, or most likely all through all

 the speed that I can stay in the air. I notice it most in the 6000 rpm

range. I also had it without the plastic cover so I am sure that it is just

that the round struts do not have the rigidity that the streamlined metal 

ones do. Thanks for the help. Now for some creative financial planning.

Larry C

---

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Thu Aug 02, 2007 11:30 am Post subject: Re: Wing strut vibration

[quote="lcottrell"]I am getting a rhythmic vibration in my wing struts. I had  never noticed until I began trying to video out of the plane. I can stop it by  putting my hand on the strut. 

 Larry C



     	  Quote: 	
		  [b] 	




Be very careful with that vibration, that can fatigue the ends to the point of failure.  It would take many hours, but sooner or later something is going to let to, either the strut end, or the place on the wing that it attaches to.



My friend was flying a Flybaby, where a streamlined flying wire underneath the wing had a high frequency vibration.  It flew hundereds of hours like that until one day it finally fatigued enough to break in the pattern on downwind.  The wing came off, fortunately my friend had a parachute on, and was thrown out of the plane as soon as he released his belt.  Those high frequency vibrations that you can not feel can be very bad.



JettPilot

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

lcottrell

Joined: 29 May 2006
Posts: 1494
Location: Jordan Valley, Or

Posted: Thu Aug 02, 2007 7:48 pm Post subject: Wing strut vibration

That sounds like a good idea, but I am curious as to how you  got the foam all through the plastic fairing. Possibly easier than I think, but  I am used to things being harder than they sound.

 Thanks

 Larry C

 [quote]   ---

gaman(at)att.net
Guest

Posted: Fri Aug 03, 2007 9:32 am Post subject: Wing strut vibration

Larry, I had vibration in the struts also but they were engine or prop harmonics.Have you tried doing ground run-ups to check for this ?

Larry Cottrell <lcottrell(at)fmtcblue.com> wrote:[quote] --> Kolb-List message posted by: "Larry Cottrell" 



My vibration is in the 56 to 64 MPH range, or most likely all through all 

the speed that I can stay in the air. I notice it most in the 6000 rpm 

range. I also had it without the plastic cover so I am sure that it is just 

that the round struts do not have the rigidity that the streamlined metal 

ones do. Thanks for the help. Now for some creative financial planning.

Larry C

---

jindoguy(at)gmail.com
Guest

Posted: Fri Aug 03, 2007 10:08 am Post subject: Wing strut vibration

Larry, I didn't build the aircraft, so I can't say for sure, but the foam in a can stuff has always spread well for me in similar applications.



Rick



On 8/3/07,  gary aman <gaman(at)att.net (gaman(at)att.net)> wrote:[quote]Larry, I had vibration in the struts also but they were engine or prop  harmonics.Have you tried doing ground run-ups to check for this ?

Larry Cottrell < lcottrell(at)fmtcblue.com (lcottrell(at)fmtcblue.com)> wrote:[quote] --> Kolb-List message posted by: "Larry Cottrell"  



My vibration is in the 56 to 64 MPH range, or most likely all through all 

the speed that I can stay in the air. I notice it most in the 6000 rpm 

range. I also had it without the plastic cover so I am sure that it is just  

that the round struts do not have the rigidity that the streamlined metal 

ones do. Thanks for the help. Now for some creative financial planning.

Larry C

---

noelbou(at)vif.com
Guest

Posted: Fri Aug 03, 2007 10:14 am Post subject: Wing strut vibration

Hello Larry,



What about this picture ? (In attach. "shrinked to 13KB ")

But i think it's more of an optical illusion than realty ...

.. but to keep this on topic, on my Twinstar MK II

the "strut shaking" definitely is related to engine harmonics

and occurs at a rather low and quite narrow band RMP  ...

so it is less of a concern ...



Noel



gary aman wrote:



 	  Quote: 	
		   Larry, I had vibration in the struts also but they were engine or prop 

 harmonics.Have you tried doing ground run-ups to check for this ?

Struts.jpg

Description:

Filesize:

12.95 KB

Viewed:

384 Time(s)

Eugene Zimmerman

Joined: 10 Jan 2006
Posts: 392

Posted: Fri Aug 03, 2007 1:03 pm Post subject: Wing strut vibration

Hey,

You really ought to remove the black snake living inside that strut  

and fill it with foam.

Positively do not archive.

On Aug 3, 2007, at 2:14 PM, Noël Bouchard wrote:

 	  Quote: 	
		   Hello Larry,

 What about this picture ? (In attach. "shrinked to 13KB ")

 But i think it's more of an optical illusion than realty ...

 ... but to keep this on topic, on my Twinstar MK II

 the "strut shaking" definitely is related to engine harmonics

 and occurs at a rather low and quite narrow band RMP  ...

 so it is less of a concern ...

 Noel

 gary aman wrote:

> Larry, I had vibration in the struts also but they were engine or  

> prop harmonics.Have you tried doing ground run-ups to check for  

> this ?

> <Struts.jpg>

huronflyer

Joined: 03 Aug 2007
Posts: 18

Posted: Fri Aug 03, 2007 7:46 pm Post subject: Re: Wing strut vibration

Hi,

I fly another ultralight.

As of today I may consider Kolb, because of some performance differences.



Please I am not trying to be  a jerk; a very well know, popular ultralight had a bracket fail recently causing the stut and its other strut same side to fail.

Fortunately, they had a BRS.



I went to my planes forum and asked some heavy questions, the result was our 

planes attach point is designed better and includes an aluminum/nylon plug, to 

overcome unwanted over compression...an inspection of the ronnie bracket show

ed no visible fracture.



Anyhow, I am considering the purchase of a Kolb, but I know nothing about its

design integrity, i.e. struts, etc.



Would you be kind enough to give me some insight.



drh

jindoguy(at)gmail.com
Guest

Posted: Sat Aug 04, 2007 5:27 am Post subject: Wing strut vibration

WARNING: Strong Opinion following!!!!!!!

IMHO the Kolb, any Kolb, with it's welded cage, is the only ultralight based aircraft that's built like an aircraft and NOT like a lawn chair. There are things on my MK III that I'd like to change to get rid of some drag and make it a bit more efficient, but not enough that I'd ever consider getting rid of it. 



Rick



On 8/3/07, huronflyer <herrondr(at)yahoo.ca (herrondr(at)yahoo.ca)> wrote:[quote] --> Kolb-List message posted by: "huronflyer" <herrondr(at)yahoo.ca (herrondr(at)yahoo.ca)>



Hi,

I fly another ultralight.

As of today I may consider Kolb, because of some performance differences. 



Please I am not trying to be  a jerk; a very well know, popular ultralight had a bracket fail recently causing the stut and its other strut same side to fail.

Fortunately, they had a BRS.



I went to my planes forum and asked some heavy questions, the result was our 

planes attach point is designed better and includes an aluminum/nylon plug, to

overcome unwanted over compression...an inspection of the ronnie bracket show

ed no visible fracture.



Anyhow, I am considering the purchase of a Kolb, but I know nothing about its 

design integrity, i.e. struts, etc.



Would you be kind enough to give me some insight.



drh





Read this topic online here:



 

"Ya'll drop on in"

takes on a whole new meaning

when you live at the airport.  [quote][b]

WillUribe(at)aol.com
Guest

Posted: Sat Aug 04, 2007 4:55 pm Post subject: Wing strut vibration

What is a ronnie bracket?

  

  

 --> Kolb-List message posted by: "huronflyer" <herrondr(at)yahoo.ca (herrondr(at)yahoo.ca)>

  

 Hi,

I fly another ultralight.

As of today I may consider Kolb,  because of some performance differences.

  

 Please I am not trying to be  a jerk; a very well know, popular  ultralight had a bracket fail recently causing the stut and its other strut same  side to fail.

Fortunately, they had a BRS.

  

 I went to my planes forum and asked some heavy questions, the result was  our planes attach point is designed better and includes an aluminum/nylon plug,  to overcome unwanted over compression...an inspection of the ronnie bracket show  ed no visible fracture.

  

 Anyhow, I am considering the purchase of a Kolb, but I know nothing about  its design integrity, i.e. struts, etc.

  

 Would you be kind enough to give me some insight.

  

 drh



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