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601 xl wing-spar-skin -rivet strength

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psm(at)att.net
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Posted: Wed Apr 16, 2008 4:36 pm Post subject: 601 xl wing-spar-skin -rivet strength

Hi Jerry,



 I think your idea is OK except for the fact that the accidents seem to happen when the fuel is low rather than full.



 We really need to get definitive information on the failures.  I am hopeful that the lack of fire in the latest accident will help the investigators figure out what actually took place.



 Paul

 XL fuselage

 do not archive



 At 04:29 PM 4/16/2008, you wrote:

 [quote] 

 Our thought is that with 75-90 # of fuel bouncing on the skins as well as the flying forces, about 20 rivets may not be enough in the fuel tank area to carry the load.Twice as many should help.[b]

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cndmovn(at)gmail.com
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Posted: Wed Apr 16, 2008 4:37 pm Post subject: 601 xl wing-spar-skin -rivet strength

Jerry:



This might be a dumb question, but why?  I do not know of anyone who has a the front D-cell fall off.  By taking out the extra metal in the spar (the one area where you really need to be careful about weakening ) you might just compromise the strength of the spar.  The rivet does not replace the strength you removed.

 

Just my 2 cents.



Paul



On Wed, Apr 16, 2008 at 7:29 PM, Jerry Shepard <jshep00(at)centurytel.net (jshep00(at)centurytel.net)> wrote:

[quote]        We have 2  601XL projects in process in our  EAA chapter.

 Both have their wings done.

  

 We have the thought of adding a rivet between each  one along the spar, through both top and bottom and nose skins  which would  make them pitch 20, rather than pitch 40 as designed and built.

  

 Our thought is that with 75-90 # of fuel bouncing  on the skins as well as the flying forces, about 20 rivets may not be enough in  the fuel tank area to carry the load.Twice as many should help.

  

 In other places where there are severe load needs,  (longerons) the spacing is pitch 20.

  

 Probably only about a pound extra,  about 360  rivets.

  

  

  

  

    	  Quote: 	
		  

	


[b]

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planecrazydld(at)yahoo.co
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Posted: Wed Apr 16, 2008 5:35 pm Post subject: 601 xl wing-spar-skin -rivet strength

That is the single change that no one can argue strongly will have a likely negative effect. Closing the pitch will increase stability in the design (and just about any design unless they end up closer than 4D spacing). It will change the failure mode and the skins may just start to fail in bearing with that many fasteners - rather than what has been reported in the official reports for (I believe) 2 of the history of incidents, where the fasteners all sheared off or the heads all popped off at some point in the sequence of events.



Jerry Shepard <jshep00(at)centurytel.net> wrote:[quote]       We have 2  601XL projects in process in our  EAA chapter.

  Both have their wings done.

  

 We have the thought of adding a rivet between each  one along the spar, through both top and bottom and nose skins  which would  make them pitch 20, rather than pitch 40 as designed and built.

  

 Our thought is that with 75-90 # of fuel bouncing  on the skins as well as the flying forces, about 20 rivets may not be enough in  the fuel tank area to carry the load.Twice as many should help.

  

 In other places where there are severe load needs,  (longerons) the spacing is pitch 20.

  

 Probably only about a pound extra,  about          Be a better friend, newshound, and  [quote][b]

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Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Wed Apr 16, 2008 5:43 pm Post subject: Re: 601 xl wing-spar-skin -rivet strength

Before making such a modification I would be looking for actual signs of a problem, not making changes based upon guesses as to what might have happened.  If the tanks were pulling the leading edge off I think you would see smoking rivets long before you reached the failure point.  In addition, remember that Zenith already uses more rivets in each location than are required to maintain structural integrity. I've never seen an XL that looked like it had a problem in that area.



Tim

Do not archive

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cndmovn(at)gmail.com
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Posted: Thu Apr 17, 2008 6:38 pm Post subject: 601 xl wing-spar-skin -rivet strength

I think you just solidified your credibility in this post.  I sure hope you let your passenger know you fly the plane over the design weight.



On Thu, Apr 17, 2008 at 7:55 PM, Jerry Shepard <jshep00(at)centurytel.net (jshep00(at)centurytel.net)> wrote:

 [quote]       Thanks to all of you for your ideas and posts  concerning the pitch 20 instead if pitch 40 rivet line on the spar.  To  those who are concerned that pitch 20 may weaken the .040 bent "L"spar cap, if  it does, then the rudder and stabilizer should fall off and the longeron splice  should separate.  (look at the prints).  To those who think that Nick  and Chris walk on water, Do a comparison with 701 and 601 landing gear along  with landing gear from Grove for both, (3/4" X 3-1/4" for a hard  landing  sky jeep (at)  1100# with tundra tires and 3/4" X 7-3/4"  for a1320#  601  with 5" wheels) Plug that into your engineering  computer, also take a look at the 701 demonstrator upper channel for the nose  gear and notice an extra angle on the demonstrator that is not on the prints of  the 701.  also look at the extra bracing in the fusalage area on the  demonstrator not on the print.  They don't share everything. 

  

 Why do we add things that make airplanes more  rigid???? go figure.  I've talked to CH and NH on several occasions as to  Modifications and always gotton that vague answer, "probably be alright, however  we're not reccomending it.  By the way did those of you see the VG's on the  elevator on the demonstrator 701??? What kind of a crackpot would put those  on??? Roger said the really made a difference. (I wonder if they are on the  print?) They were on the demonstrator in December the last time I was at the  factory.  BY THE WAY!!!!  I AM NOT AN ENGINEER.   Just an  old maintenance man in the manufacturing area that spent a lifetime fixing  engineers indiscretioins among other things and Knowing full well that if the  skins come off of the wings, you better pray quick or have a chute or  both.

  

   PS, I fly a 701 with a Cam125 engine  REGISTERED AT 1320#  It is way over weight , It also has  30' wing  span,  I asked CH about this and he said it would probably be  alright.  The 701 is highly modified.  I think it is an "  EXPERIMENTAL AIRCRAFT".   Maybe its something like the CH  750.

    	  Quote: 	
		  

	




[b]

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