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flying VG's
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lcottrell

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

Posted: Fri Oct 26, 2007 10:43 am Post subject: flying VG's

John Hauck just left here heading South and on to points East.  We of course had a good visit and the weather for the most part was good.  

  

 After some modifications (see attached pic) to stiffen the  elevator, tightening a few wing U joint bolts, readjusting the cables to the  Elevator, he was able to evaluate the performance of the VG's on my firestar. I  will leave the report to him to make. I was very pleased with the three things  that we did to tighten up the surfaces of the plane. It flew well before, but  much better now. I cannot explain why these small fixes were not so obvious that  I would have already fixed them, but I did not know any better I guess. It never  occurred to me to check the flex in the elevators and to 

 realize just how prone to breaking that area could be. We just  put them on the top for now. I will put some on the bottom when I get the  chance. 

 Larry C

  

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jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Fri Oct 26, 2007 12:21 pm Post subject: Re: flying VG's

Hmmm...



Seems like that is not the best solution as it serves to further weaken the area of leverage by putting holes for the rivets in the part of the tubing that needs to be strongest.



Explaining further about my rational for above statement;



Tubing is utilized for its strength in compression and tension....not bending.



The elevator tube (not the hinge line tube) needs its strength on the top and bottom surface for the control fitting to act upon since the forces imparted by the control surface are carried mostly by those two planes of the tube at that location.



Unfortunately you put holes in that surface and reduced the effective section of the top to 60% or less so the loads must now be carried on the 2 lateral sides and bottom of the tube. 



I think a better solution would have been welding or some kind of support that drilled into the sides of the tubing.



To make matters worse the weakened area is covered and you will not be able to inspect it for the cracks that I predict will develop in that tube.



Be very vigilent when inspecting this area as it could pose a problem eventually.



Just adding my opinion where I believe safety is compromised.



I'll think about it for a while and try to figure out how to remedy what has already been done....but please don't make a matching support for the underside as it will only place you at even greater risk.

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Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
Schreder HP-11 Glider
Grob 109 Motorglider

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jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Fri Oct 26, 2007 12:47 pm Post subject: Re: flying VG's

Make a similar but bigger piece that wraps around the top AND bottom as a single piece and use the existing top rivet holes(after drilling out the other stuff) 



It would not hurt to go to a thicker gauge of aluminum either to help make up for the existing holes.



Put only a few ( 3 - 4) rivets in the SIDE of the elevator tube.

(I'd hate to suggest any more holes in that tube than already are there...making swiss cheese out of that part but it is better than adding a matching bottom part)



Any other suggestions would be welcome if some one out there has a better idea.

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Ray

Kolb UltraStar (Cuyuna UL-202)
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lcottrell

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

Posted: Fri Oct 26, 2007 1:52 pm Post subject: Re: flying VG's

Seems like that is not the best solution as it serves to further weaken the area of leverage by putting holes for the rivets in the part of the tubing that needs to be strongest. 

----------------------------------------------------------------------------------

Ray,

   With all due respect, "Mule Muffins".  The stress is now spread over a much wider area and the elevator now does not flex enough that the fabric wrinkles. It did before. ( go check yours. Hold one side of the elevator still and lift the other side) There is a steel sleeve inside the main elevator tube that goes the length of the gusset. The small tubing that forms the outline of the deflecting surface previously only attached to the main tube by one rivet. Now there are four rivets holding it still. I might remind you that breakage mainly comes from a part being flexed back and forth over a long period of time. I am quite confident that a gusset on this area will not weaken, but strengthen the elevator. 

    As for inspecting the plane, you bet I will. The better that I do, the longer I will live.

Larry C

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John Hauck

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

Posted: Fri Oct 26, 2007 4:17 pm Post subject: Re: flying VG's

Mule muffins!  I like that.



Hi Larry:



Don't think Ray has any idea what the problem is with the elevators.  That fix has worked for me for many hours.  With more than 2,700 hours on the mkIII, I am willing to believe that the fix works just fine.



The little things we did to your FSII made it feel like a new bird.



I enjoyed flying it.



VG's don't seem to add any improvement to the flight characteristics except in landing.  Larry's FS is a very docile lander.  I liked that.  As far as any other magic, I could not find any difference in it and any other Kolb off the shelf.



john h

hauck's holler remote, Winnemucca, Nevada

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

R. Hankins

Joined: 18 Jan 2006
Posts: 185
Location: Grants Pass, Oregon

Posted: Fri Oct 26, 2007 6:18 pm Post subject: Re: flying VG's

Larry,

Just trying to get this straight in my head.  Was there something broken on your elevator, or did you put in the gusset to spread the elevator control torque load further down the edge rib?  If this is the case, using 4 more rivets on each side of the gusset to help the two original rivets is not a bad idea, because there are rivets through the hinge into the crome-moly insert on the bottom side to balance the load.  Doesn't make me nervous at all.  Did you do both right and left elevators?

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Roger in Oregon
1992 KXP 503 - N1782C

lcottrell

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

Posted: Fri Oct 26, 2007 8:11 pm Post subject: flying VG's

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John Hauck

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

Posted: Sat Oct 27, 2007 8:11 am Post subject: Re: flying VG's

Roger H:



Missed you at the Alvord and the Rock House!!!



Your assumption was correct.  The top and bottom 1/8 by 1/2" rivet loosens up from the load of the longest arm of the elevator.  With enough time, the rivet will work its self right through the fabric.  The gusset mearly adds a tremendous amount of strength to this area and prevents slop in the attachment.  On 912's it is usually the left elevator that gets beat up first, and on two strokes the right elevator.



ADDING GUSSETS TOP AND BOTTOM DO NOT WEAKEN THE RIB AND THE CONNECTION as someone may have mentioned earlier.



john h

Still having fun in Winnemucca, Nevada.

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

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sat Oct 27, 2007 1:20 pm Post subject: Re: flying VG's

I did not know you were doing cross country this late in the year, Where are you flying to John ?     Is the colder weather giving you any problems ?



Mike

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Kolb MK-III Xtra, 912-S

John Hauck

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

Posted: Sat Oct 27, 2007 2:47 pm Post subject: Re: flying VG's

Mike B:



I am ground bound.  Not flying, except loaners.



john h

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

jbhart(at)onlyinternet.ne
Guest

Posted: Sat Oct 27, 2007 2:50 pm Post subject: flying VG's

John,



How many hours did it take for this to be noticeable?



Jack B. Hart FF004

Winchester, IN



At 09:11 AM 10/27/07 -0700, you wrote:

 	  Quote: 	
		  



Roger H:



Missed you at the Alvord and the Rock House!!!



Your assumption was correct.  The top and bottom 1/8 by 1/2" rivet loosens up from the load of the longest arm of the elevator.  With enough time, the rivet will work its self right through the fabric.  The gusset mearly adds a tremendous amount of strength to this area and prevents slop in the attachment.  On 912's it is usually the left elevator that gets beat up first, and on two strokes the right elevator.



ADDING GUSSETS TOP AND BOTTOM DO NOT WEAKEN THE RIB AND THE CONNECTION as someone may have mentioned earlier.



john h

Still having fun in Winnemucca, Nevada.



--------

John Hauck

MKIII/912ULS

hauck's holler, alabama





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=142166#142166

John Hauck

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

Posted: Sat Oct 27, 2007 8:06 pm Post subject: flying VG's

> How many hours did it take for this to be noticeable?

 	  Quote: 	
		   

 Jack B. Hart FF004

 
	




Jack H:



I can not remember how many hours when the 1/8 X 1/2" rivets started loosening up.  Probably 2, 3, or 4oo hours.  Not sure.   Would have to dig it out of my log book which back in Alabama.



I drilled out and replaced the rivets a couple times before I finally came up with the idean to gusset them top and bottom.  I also did the same on the rudder.



Had the same problem with my original FS.  Did not fly the US long enough to notice a problem.



The MKIII may be more prone to stress on the elevator due to the heavier weight and higher speeds.



john h

mkIII

Winnemucca, Nevada

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

jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Mon Oct 29, 2007 7:29 am Post subject: Re: flying VG's

I think reinforcing that area of the elevator is a good idea and I was not suggesting that you don't



My point was that it just seems better to avoid making swiss cheese out of the tubing your hoping to make more rigid by adding so many rivet holes (weak point) in the loading path of those parts.



I hope it works out for you....just suggesting a stronger fix based on the loading that part is subject to, and minimizing risk of a failure to the absolute minimum.



Its just hard to not speak up when I see something that could be better executed.



As you can see from my "Icon Picture" I have had to deal with much more delicate structures than a Kolb...perhaps I'm just being overly cautious.

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Ray

Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
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Grob 109 Motorglider

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lcottrell

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

Posted: Mon Oct 29, 2007 8:28 am Post subject: flying VG's

 	  Quote: 	
		  

 My point was that it just seems better to avoid making swiss cheese out of 

 the tubing your hoping to make more rigid by adding so many rivet holes 

 (weak point) in the loading path of those parts.

 "Mule Muffins" is just not much appreciation for trying to be helpful.



 The only consolation I have is that its not MY butt that hangs in the 

 balance.




	


Well Ray, I am sorry that I hurt your feelings, but I did it as gently as I 

could. There is no evidence that gussets have ever weakened any joint. 

Welding is not an option, and I am not aware of any glue that would do the 

job either. I guess it was your dramatic (Swiss cheese) representation that 

caused me to think that you thought that I was reckless as well as stupid.

Larry C

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1planeguy(at)kilocharlie.
Guest

Posted: Mon Oct 29, 2007 10:02 am Post subject: flying VG's

The only consolation I have is that its not MY butt that hangs in the

balance.



--------

Ray

Riverside County, CA



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<snip>



Ray,



I think what you might not have understood is that the tube is not the

weak link (i.e. twisting in torsion) the problem is the 1 rivet

connection between the top and bottom tubes that form the inboard "rib"

of the elevator.  That rivet will eventually work itself loose and once

things start moving they start moving worse and worse.  The aluminum

plate is to reinforce the "rib" to spar connection.  The spar tube

itself is plenty strong in torsion to handle things...a few holes for

more rivets isn't a problem.  Agreed a tab welded to the steel insert

might be great, but there are already holes drilled into the aluminum

spar there to rivet to the steel insert anyway...



Jeremy Casey

John Hauck

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

Posted: Mon Oct 29, 2007 11:59 am Post subject: Re: flying VG's

Hot damn!



Jeremy:  You took the words right out of my mouth.  I am sitting in the Rainbow Casino, Wendover, Utah, reading the mail.



Yes, the problem is the 1/8 X 1/2" long single rivet that secures the top and bottom inboard rib tube of the elevator.  The gusset is to reinforce the single rivet, top and bottom.



Again, if you all read what I write,  big smile, you might get the point.



Those two little gussets tighten up the connection and don't loosen up with hours.



Swiss cheese???  You could have been a little more tactful.  hehehe  However, you are basically telling me I don't know what I am doing, even though my fix fixed the problem and has continued to keep on working for several thousand hours with no problems.



Larry C  fixed those elevators at my suggestion using my idea for a fix.  There are a lot of other Kolbs out there flying that have the same problem if they are starting to pile up the hours.



Hopefully, you all won't think what I have been doing to keep my bird flying all these years and hours in not for naught.



Take care,



john h

Wendover, Utah



PS:  Anyone out there got more than a thousand hours on a single Kolb besides John Williamson's Kolbra?

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

mdnanwelch7(at)hotmail.co
Guest

Posted: Mon Oct 29, 2007 12:24 pm Post subject: flying VG's

 	  Quote: 	
		   PS: Anyone out there got more than a thousand hours on a single Kolb besides John Williamson's Kolbra?



 --------

 John Hauck

 MKIII/912ULS

 hauck's holler, alabama


	


  Yes, I believe I do.  Probably have two thousand hours, and another thousand to go!!     Oh, you meant in the air!      In that case, none........because I have these thousand or so hours left to go........hehe



  BTW, Nice gusset idea.  Do you feel that only topside is warranted, or both top and bottom side?  Seeing as how I haven't put fabric on my plane yet, should gussets be inside or outside of fabric?



                                                                           Mike Welch        0 hours in MkIII, 2000 hours ON MkIII

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jb92563

Joined: 23 Mar 2007
Posts: 314
Location: Southern California

Posted: Mon Oct 29, 2007 12:27 pm Post subject: Re: flying VG's

Maybe I'm not clear on the connection to the 2 tubes that form the inboard rib, but it sounds the same as on my Ultrastar. 



I agree that a gusset is a great idea, but aren't the tubes forming the rib only 3/8" diameter .....so if you put a 1/8" hole in it for a rivet, thats making it really weak right?



I'll drop the discussion after this post, because I'm sure you've been maintaining your Kolb for a long time and know what works.



I'll do some bending tests on my Ultrastar tonight and see if mine might  exhibit the same issue. I'd like to pro-actively correct it since I'm working on it now anyway.

..

PS: I edited my previous post because it sounded more dramatic than intended, but you got to it before I finished....drat.....its just a technical discussion...no big deal.

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Kolb UltraStar (Cuyuna UL-202)
Moni MotorGlider
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John Hauck

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

Posted: Mon Oct 29, 2007 12:51 pm Post subject: flying VG's

Mike W:



I would have put them under the fabric if I had know about the problem before I covered.



Yes, I have them mounted top and bottom.  



Also mounted left and right side bottom of rudder.  Rudder is same construction as elevators.



john h

mkIII



PS:  John Williamson - I just did the buffet at the Rainbow.  You know, prime rib, boiled shrimp (peeled and deveined), choclate eclairs, cream horns, and a very large slice of cherry topped new york cheese cake.  Food is as good as it was for the past several visits here with you and Gary Haley.  Heading east across Bonneville Salt Flats, Great Salt Lake, and south to Moab.

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

rowedenny(at)windstream.n
Guest

Posted: Mon Oct 29, 2007 12:58 pm Post subject: flying VG's

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