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Structural Failure

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DAquaNut(at)aol.com
Guest

Posted: Mon Feb 25, 2008 9:23 pm Post subject: Structural Failure

Fire Flyers,

  

     When pulling my engine through to get fuel to the  carb , I noticed a metallic rattle I had not heard before. It was inside  the wing. I  isolated it to the trailing edge and outboard edge of the  left wing as viewed from the seat.  Further examination indicated the  problem area was near the end of the wing spar.  I removed the wing and  brought it home. Reluctantly I cut through the fabric, To reveal the 5/16 " X.  035 alum tube running from the outboard trailing edge to the inside of  the outboard end of the main wing spar had severed completely . This tube  was possibly flattened too much by the factory as it broke where it was  flattened.  This was  a quick build kit.  This firefly has never  had the wings to hit the ground or anything else. It has never been slightly  wrecked.  Apparently taxiing on those little four inch wheels, over  stressed that 5/16" tube. Anyone heard of this happening to a Firefly?   

  

  

          Ed  FF #  62



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  [quote][b]

WhiskeyVictor36(at)aol.co
Guest

Posted: Mon Feb 25, 2008 10:12 pm Post subject: Structural Failure

In a message dated 2/26/2008 12:24:06 A.M. Eastern Standard Time,  DAquaNut(at)aol.com writes:

  	  Quote: 	
		     To reveal the 5/16 " X. 035 alum tube running from the outboard    trailing edge to the inside of the outboard end of the main wing spar had    severed completely . 

    

   Ed,

    

   This has happened to many Kolbs, including mine (both    wings).  Basically that tube just holds some tension on the trailing    edge spar and wing tip bow to help keep them in position, so as not    to have it bend back during rough handling or contact with the    ground.  It is not to serious and I continued flying for awhile, but kept    checking on it to be sure it wasn't bending back.  Finally,    I elected to repair mine by using a larger, 3/8" diameter    tube.  The worst part was making the decision to cut an access    hole in my nicely painted wing fabric 

    

   Bill    Varnes

Original Kolb FireStar

Audubon NJ

Do Not  Archive

	




Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

GeoR38

Joined: 25 Jan 2006
Posts: 60
Location: The Villages, fl

Posted: Tue Feb 26, 2008 4:12 am Post subject: Structural Failure

In a message dated 2/26/2008 12:24:06 A.M. Eastern Standard Time,  DAquaNut(at)aol.com writes:

  	  Quote: 	
		     Fire Flyers,

    

       When pulling my engine through to get fuel to the    carb , I noticed a metallic rattle I had not heard before. It was inside    the wing. I  isolated it to the trailing edge and outboard edge of    the left wing as viewed from the seat.  Further examination indicated the    problem area was near the end of the wing spar.  I removed the wing and    brought it home. Reluctantly I cut through the fabric, To reveal the 5/16 " X.    035 alum tube running from the outboard trailing edge to the inside    of the outboard end of the main wing spar had severed completely . This    tube was possibly flattened too much by the factory as it broke where it was    flattened.  This was  a quick build kit.  This firefly has    never had the wings to hit the ground or anything else. It has never been    slightly wrecked.  Apparently taxiing on those little four inch wheels,    over stressed that 5/16" tube. Anyone heard of this happening to a    Firefly?  

    

    

            Ed  FF #    62



	


 

 It happened to my firestar at the same location....no big deal, I just  replaced it with a slightly less crushed piece 

  

 George Randolph

 the Villages, Fl



Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

  [quote][b]

_________________
George Randolph
Firestar driver, The Villages, fl

WillUribe(at)aol.com
Guest

Posted: Tue Feb 26, 2008 7:53 am Post subject: Structural Failure

Hi Ed,

  

 I wouldn't call those tubes structural, per the builder's manual they are  installed to keep the wing bow from bending when shrinking the fabric.   Dave Rains old FireStar II had the same problem and flew it like that for a long  time until the lose tube started chaffing the fabric. It wasn't until  after he accidentally started the engine at full throttle inside the hanger  and ran the wing tip into the hanger wall was when we fixed  them.

  

 Regards,

 Will Uribe

 El Paso, TX

 FireStar II N4GU

 http://video.google.com/videoplay?docid=-1089406573728651489

 http://video.google.com/videoplay?docid=7821240344254343216

 http://video.google.com/videoplay?docid=1480724639524498797[/url]

  

  

From:  owner-kolb-list-server(at)matronics.com  [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of  DAquaNut(at)aol.com

Sent: Monday, February 25, 2008 10:21  PM

To: kolb-list(at)matronics.com

Subject: Re: Kolb-List:  Structural Failure 

  

Fire  Flyers, 

  

     When pulling my engine through to get fuel to the carb , I noticed a  metallic rattle I had not heard before. It was inside the wing. I  isolated  it to the trailing edge and outboard edge of the left wing as viewed from  the seat.  Further examination indicated the problem area was near the end  of the wing spar.  I removed the wing and brought it home. Reluctantly I  cut through the fabric, To reveal the 5/16 " X. 035 alum tube running from  the outboard trailing edge to the inside of the outboard end of the  main wing spar had severed completely . This tube was possibly flattened  too much by the factory as it broke where it was flattened.  This was   a quick build kit.  This firefly has never had the wings to hit the ground  or anything else. It has never been slightly wrecked.  Apparently taxiing  on those little four inch wheels, over stressed that 5/16" tube. Anyone heard of  this happening to a Firefly?   

  

  

          Ed  FF # 62



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tkrolfe(at)toast.net
Guest

Posted: Tue Feb 26, 2008 7:58 am Post subject: Structural Failure

WhiskeyVictor36(at)aol.com (WhiskeyVictor36(at)aol.com) wrote:  	  Quote: 	
		               

    

      In a message dated 2/26/2008 12:24:06 A.M. Eastern Standard Time, DAquaNut(at)aol.com (DAquaNut(at)aol.com) writes:

    	  Quote: 	
		       To reveal the 5/16 " X. 035 alum tube running from the outboard trailing edge to the inside of the outboard end of the main wing spar had severed completely . 

      

     Ed,

      

     This has happened to many Kolbs, including mine (both wings).  Basically that tube just holds some tension on the trailing edge spar and wing tip bow to help keep them in position, so as not to have it bend back during rough handling or contact with the ground.  It is not to serious and I continued flying for awhile, but kept checking on it to be sure it wasn't bending back.  Finally, I elected to repair mine by using a larger, 3/8" diameter tube.  The worst part was making the decision to cut an access hole in my nicely painted wing fabric 

      

     Bill Varnes

 Original Kolb FireStar

 Audubon NJ

 Do Not Archive

   	
   

   	
 Ed, Bill,

 

 How many hours did you have on it when this happened?  I haven't heard of this before and haven't had a problem so far ( keep my mouth shut or I will ).  Having to replace my aileron gap seals after nine years, not bad for book tape, and I have the wings off to do so.  Didn't notice any problem with this diagonal tube.  Have had some pretty rough landings over the years.  Will be keeping an eye out for this on my preflights.

 

 Terry -  FireFly #95

    [quote][b]

WhiskeyVictor36(at)aol.co
Guest

Posted: Tue Feb 26, 2008 8:38 am Post subject: Structural Failure

In a message dated 2/26/2008 10:58:47 A.M. Eastern Standard Time,  tkrolfe(at)toast.net writes:

   	  Quote: 	
		     How many hours did you have on it when this happened?

    

   Terry/Ed,

    

   Re the drag tube for the wingtip bow.

    

   I had 38 hours on the airframe when I heard the rattle in    the left wing, while the right wing went 115 hours.  By the way, I have    the early, original  model FireStar and the tube was only 1/4"    OD!  It broke at the bend where it attaches to the end of the main    spar.  I think the bend caused too much stress on the tube, like    maybe it was cracked a little during construction.  I built it, so maybe    my mistake.  The 3/8" tube I replaced it with hasn't broke    yet.  But of course it added a few more ounces.

    

   Bill Varnes

Original Kolb FireStar

Audubon    NJ



	




Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

  [quote][b]

travis(at)tnkolbaircraft.
Guest

Posted: Tue Feb 26, 2008 8:41 am Post subject: Structural Failure

Hello everyone Bryan of Custom Air has ask me to post on this list that  when he started building our Quickbuilds in 1999 he noticed this particular tube  being crimped from TOK quickbuilds. Bryan has always used a smooth radius on  this tube and has also corrected many crimped tubes from earlier  quickbuilds.This is not a structural issue but should be repaired if  noticed.

  

 Travis (at) Kolb

 [quote]   ---

Ralph B

Joined: 14 Apr 2007
Posts: 367
Location: Mound Minnesota

Posted: Tue Feb 26, 2008 9:10 am Post subject: Re: Structural Failure

This happened on my Original Firestar many years ago. It will affect the wing enough to cause a slight roll. When I repaired the tube, the roll tendency went away. This roll may be due to the 5-rib wing in these early Firestars. The 7-rib wings may not be affected. The Original Firestars used a 1/4" tube. I had to cut a large piece of fabric out of the bottom of the wing and then rivet in 5/16" tubing. Another thing was to make the bend where it attaches to the spar with a piece of 3/32" aluminum and rivet the tube to that. This way the tube wonâ€™t break again.

_________________
Ralph B

Kolb Kolbra 912uls
N20386
550 hours

DAquaNut(at)aol.com
Guest

Posted: Tue Feb 26, 2008 4:19 pm Post subject: Structural Failure

In a message dated 2/26/2008 6:13:24 A.M. Central Standard Time,  GeoR38(at)aol.com writes:

  	  Quote: 	
		         	  Quote: 	
		  

	


   

   It happened to my firestar at the same location....no big deal, I just    replaced it with a slightly less crushed piece 

    

   George Randolph

   the Villages, Fl



	


 

            George,

  

      Did you ever decide if it was caused by taxiing on  a rough  strip or what ?  I have removed the rivets using a flexible  shaft through a small hole about 6" from the main spar. I also had to put a hole  big enough to put my hand through right at the end of the main spar.  I  have a piece of 3/8" x .028  6061-T 6  ordered that I plan on bending  drilling and then sliding over the  original 5/16"   tubing  like a sleeve.  Plan on putting 3 rivets  in  it.  Hopefully that will secure it sufficiently.  Otherwise I will  have to do a lot more recovering and patching.

  

             Ed     FF # 62  



Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

  [quote][b]

DAquaNut(at)aol.com
Guest

Posted: Tue Feb 26, 2008 4:30 pm Post subject: Structural Failure

In a message dated 2/26/2008 9:58:47 A.M. Central Standard Time,  tkrolfe(at)toast.net writes:

  	  Quote: 	
		  

How    many hours did you have on it when this happened?  I haven't heard of    this before and haven't had a problem so far ( keep my mouth shut or I will    ).  Having to replace my aileron gap seals after nine years, not bad for    book tape, and I have the wings off to do so.  Didn't notice any problem    with this diagonal tube.  Have had some pretty rough landings over the    years.  Will be keeping an eye out for this on my    preflights.



Terry -  FireFly #95

 	  Quote: 	
		  

	
	


 

                Terry,

  

      I had 80 hrs on it when it was descovered. Hope to  have her fixed real soon.  If it isn.t one thing its another. Not sure what  caused it to break, but there is some comfort in knowing mine was not the first  and its not considered serious.

  

  

          Ed FF #  62 



Delicious ideas to please the pickiest eaters. Watch the video on AOL Living.

  [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Feb 26, 2008 4:36 pm Post subject: Structural Failure

Hi Ed:

  

 Usually, tubes break because of vibration.  Two strokes  are notorious for creating just the right frequency to stress crack and cause  breakage.  Of course, when an aluminum tube is bent, it has already started  the failure process.

  

 1/4" aluminum tubes are prone to break.

  

 Your fix sounds good to me.

  

 Primary function of the 1/4" diagonal tube is, as someone has  already pointed out, to act as a brace when shrinking the fabric on the bow  tip.

  

 The very important braces to check periodically, especially  the 5 rib FS and US wing, is the diagonal leading edge brace from main spar to  the leading edge.  This is what keeps the noses of the main ribs in  column.  The two braces on the nose of the inboard rib are not as  important.  Their function is to hold the IB rib nose when the fabric is  shrunk.

  

 john h - breaker of little aluminum tube braces in US and FS  wings.

 mkIII

 [quote]    

        Did you ever decide if it was caused by taxiing    on a rough  strip or what ?   

                 Ed     FF # 62   

 [b]

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

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