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XL rear spar

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jaybannist(at)cs.com
Guest

Posted: Sat Oct 31, 2009 8:54 am Post subject: XL rear spar

Let's put this hole in the rear spar in perspective.  See attached pdf.   Comments??

 

 Jay Bannister

XL_RearSpar.pdf

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ter_turn(at)yahoo.com
Guest

Posted: Sat Oct 31, 2009 9:43 am Post subject: XL rear spar

Another approach might be to use .032 instead of .025.

Terry Turnquist

From: "jaybannist(at)cs.com" <jaybannist(at)cs.com>

To: zenith601-list(at)matronics.com

Sent: Sat, October 31, 2009 11:53:56 AM

Subject: XL rear spar

 Let's put this hole in the rear spar in perspective.  See attached pdf.   Comments??

 Jay Bannister

         [quote][b]

z601a(at)anemicaardvark.c
Guest

Posted: Sat Oct 31, 2009 9:49 am Post subject: XL rear spar

I realize that castellated beams and truss structures are common in 

architecture, but I would not personally use either one for a spar. Someone 

else might.



If I remember correctly, a truss uses cross members for bracing, and is trying 

to make the overall structure stronger. When a hole is cut in a solid piece 

of metal for an aircraft, I seem to recall that the loads must flow around 

the hole, and the hole must neither be too big, nor too close to the edge of 

the material for this to work as intended.



If the hole in your spar came out - to scale - no bigger than your sketch, I'm 

glad for you. It would still be too close to the edge for my comfort. I think 

my spar hole for aileron pushrod access, when cut to the size shown on the 

plans, is proportionally bigger.



I could probably go dig up the data on hole size vs material width, edge 

distance, etc, but I'd bet the hole in the Zenith spar (at least on my 

aircraft) wouldn't meet the criteria. Before my bird flies, I want to take a 

hard look at this. I'm not about to ground the bird, hoping for engineering 

changes that may or may not come, but I am going to fix anything I establisdh 

to my own satisfaction is wrong.



Obviously, everybody is entitled to their own view. This is mine. 



On Saturday 31 October 2009 11:53, jaybannist(at)cs.com wrote:

 	  Quote: 	
		   Let's put this hole in the rear spar in perspective.  See attached pdf.  

 Comments??



 Jay Bannister


	


-- 

=============================================

                Do not archive.

=============================================

                Jim B Belcher

    BS, MS Physics, Math, Computer Science

                  A&P/IA

     Retired aerospace technical manager



     Mathematics and alcohol do not mix.

         Do not drink and derive.

=============================================

jaybannist(at)cs.com
Guest

Posted: Sat Oct 31, 2009 10:42 am Post subject: XL rear spar

Jim,

 

 I do respect your opinion.  I didn't intend to start something, nor to agitate anyone. I am obviously defending the design, but I am not an aeronautical engineer. However, I want to point out that structures answer to the same laws of physics, whether in a bridge, a building or an airplane. The compressive and tensile loads in a beam are primarily carried by the flanges.  The web primarily locates the flanges and resists horizontal shear, which is minimal, as evidenced by the configuration of a bar joist. That is the load you say "must flow around the hole", and it must not be close to the flange to work right.  But look at how large the "holes" are and how close to the flange they are in a bar joist.  Additionally, the flanges must be stabilized to resist buckling, which in this case is done by the wing skins; and the way they are fastened, they also contribute to the compressive and tensile strength of the flanges.  That is why I am not at all concerned by this hole in the rear spar.

 

 And BTW, there are many, many examples of trusses used in aircraft construction; especially in fuselages, but also in wing spars. 

 

 My drawing of the rear spar is to scale - though not the same scale as the beam or the truss.

 

 Jay Bannister

 

   

 

   

 

 

          	  Quote: 	
		  --> Zenith601-List message posted by: Jim Belcher <z601a(at)anemicaardvark.com (z601a(at)anemicaardvark.com)>



I realize that castellated beams and truss structures are common in 

architecture, but I would not personally use either one for a spar. Someone 

else might.



If I remember correctly, a truss uses cross members for bracing, and is trying 

to make the overall structure stronger. When a hole is cut in a solid piece 

of metal for an aircraft, I seem to recall that the loads must flow around 

the hole, and the hole must neither be too big, nor too close to the edge of 

the material for this to work as intended.



If the hole in your spar came out - to scale - no bigger than your sketch, I'm 

glad for you. It would still be too close to the edge for my comfort. I think 

my spar hole for aileron pushrod access, when cut to the size shown on the 

plans, is proportionally bigger.



I could probably go dig up the data on hole size vs material width, edge 

distance, etc, but I'd bet the hole in the Zenith spar (at least on my 

aircraft) wouldn't meet the criteria. Before my bird flies, I want to take a 

hard look at this. I'm not about to ground the bird, hoping for engineering 

changes that may or may not come, but I am going to fix anything I establisdh 

to my own satisfaction is wrong.



Obviously, everybody is entitled to their own view. This is mine. 

	
 

      [quote][b]

z601a(at)anemicaardvark.c
Guest

Posted: Sat Oct 31, 2009 11:23 am Post subject: XL rear spar

On Saturday 31 October 2009 13:39, jaybannist(at)cs.com wrote:

 	  Quote: 	
		    Jim,



 I do respect your opinion.  I didn't intend to start something, nor to

 agitate anyone.


	


Jay, I'm neither offended nor agitated. You asked for comments; you got 'em. I 

feel the design is a compromise at this point, and needs some beef up. I'd 

love to have Chris Heintz take on this, and possibly his beef up.



But barring that information, I intend to do a bit of research, and see what 

is allowable in this case. I suspect this exceeds the allowable. I seem to 

remember having some tables somewhere that address this issue.



I deeply respect Chris' abilities. But he is human, and not beyond error. A 

problem I've sometimes seen in one-man designs is that there is no oversight, 

and no one verifying the design on a step by step basis. Whether that is true 

here or not, I cannot say. But I wonder.



=============================================

                Do not archive.

=============================================

                Jim B Belcher

    BS, MS Physics, Math, Computer Science

                  A&P/IA

     Retired aerospace technical manager



     Mathematics and alcohol do not mix.

         Do not drink and derive.

=============================================

z601a(at)anemicaardvark.c
Guest

Posted: Sun Nov 01, 2009 8:00 am Post subject: XL rear spar

On Saturday 31 October 2009 11:53, jaybannist(at)cs.com wrote:

 	  Quote: 	
		   Let's put this hole in the rear spar in perspective.  See attached pdf.  

 Comments??


	


Jay -



In re-reading yesterday's mail., I feel I failed, in my reply to you, to 

correctly address the issue. I may (I hope not) have given the impression I 

was just being diagreeable, and flipping off the question. I thought some on 

the truss vs hole in the spar issue, and why I felt as I did. Here's what I 

came up with:



A truss is usually made by adding triangular bracing to a pair of parallel 

supports. The advantage over just using a solid piece of wood, metal, or 

whatever, is that the brace is lighter. As I recall, it can never be as 

strong as a solid piece of the same material of the same general size, but it 

can be lighter and cheaper.



But a major difference between it and a solid piece of material is that one 

determines the strength needed, and either designs or has built an 

appropriate truss. That's a design to requirement process.



Conversely, when one has a solid piece of metal, like a spar, or perhaps a 

wood stud in a wall, there is sometimes a need to have a hole penetrate the 

material. Of course, round holes are generally used, so that the stress is 

more equally distributed. The question then becomes, â€œhow big a hole, and how 

close to the edge can the hole be, before impacting the strength of the 

material?â€



That, I believe, is the question in the case of the hole in the 601XL rear 

spar. I see the truss as being a question of how we make it strong enough, 

and the hole a question of how we not impact the strength. Similar issues, 

but not quite the same.



-- 

=============================================

                Do not archive.

=============================================

                Jim B Belcher

    BS, MS Physics, Math, Computer Science

                  A&P/IA

     Retired aerospace technical manager



     Mathematics and alcohol do not mix.

         Do not drink and derive.

=============================================

jaybannist(at)cs.com
Guest

Posted: Sun Nov 01, 2009 9:51 am Post subject: XL rear spar

Jim,

 

 As far as I am concerned, we are sharing points of view, not arguing.

 

 On reading your last post, I think you are overlooking the fact that the spar is not like a rectangular wood beam or a stud; it has top and bottom flanges.  What you say would be absolutely true if there were no flanges.  Edge distance would certainly be critical.  But there are flanges; double flanges when you count the skins.  That makes the vertical part of the spar a web, not a stand-alone beam.  It would be more like a metal stud than a wood stud.  Those guys are pretty light weight, full of holes in the web and they are very "floppy" until you stabilize and reinforce the flanges with gypsum wallboard. Then they are as strong, or stronger than a solid wood stud.  The same with that spar.  It is very "floppy" until the flanges are stabilized and reinforced by the skins. And again, that web, where the hole is, primarily serves to locate the flanges, not to carry bending loads. Once again, look at the size and location of the "holes" in a truss.  That hole in the spar can be practically flange to flange and not effect the strength of the structural system. I say "practically", because from a durability point, the hole should obviously not touch the radius between the web and the flange.

 

 Yes, a truss does save weight,  but it absolutely can be as strong as a solid beam.  All structural members contribute to dead load.   Given two structural members of the same strength, the lighter one always wins because it allows more live load; and carrying the live load is why we have the structure in the first place. 

 

 Jay

 

   

 

   

 

 -

 

          	  Quote: 	
		  --> Zenith601-List message posted by: Jim Belcher <z601a(at)anemicaardvark.com (z601a(at)anemicaardvark.com)>



Jay -



In re-reading yesterday's mail., I feel I failed, in my reply to you, to 

correctly address the issue. I may (I hope not) have given the impression I 

was just being diagreeable, and flipping off the question. I thought some on 

the truss vs hole in the spar issue, and why I felt as I did. Here's what I 

came up with:



A truss is usually made by adding triangular bracing to a pair of parallel 

supports. The advantage over just using a solid piece of wood, metal, or 

whatever, is that the brace is lighter. As I recall, it can never be as 

strong as a solid piece of the same material of the same general size, but it 

can be lighter and cheaper.



But a major difference between it and a solid piece of material is that one 

determines the strength needed, and either designs or has built an 

appropriate truss. That's a design to requirement process.



Conversely, when one has a solid piece of metal, like a spar, or perhaps a 

wood stud in a wall, there is sometimes a need to have a hole penetrate the 

material. Of course, round holes are generally used, so that the stress is 

more equally distributed. The question then becomes, â€œhow big a hole, and how 

close to the edge can the hole be, before impacting the strength of the 

material?â€



That, I believe, is the question in the case of the hole in the 601XL rear 

spar. I see the truss as being a question of how we make it strong enough, 

and the hole a question of how we not impact the strength. Similar issues, 

but not quite the same.

	
 

      [quote][b]

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Mon Nov 02, 2009 7:37 pm Post subject: Re: XL rear spar

I have attached a Microsoft Word document which shows a fix for this weak area.  It was created by an aerospace engineer.  You might wanna give it a look.

rearspar.doc

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_________________
Ron Lendon
WW Corvair with Roy's Garage 5th bearing
CH 601 XLB
N601LT - Flying
http://www.mykitlog.com/rlendon
Corvair Engine Prints:
https://sites.google.com/site/corvairenginedata/

Last edited by Ron Lendon on Mon Nov 02, 2009 8:37 pm; edited 1 time in total

BobTezyk

Joined: 10 Jan 2006
Posts: 38
Location: Midlothian, TX

Posted: Mon Nov 02, 2009 8:15 pm Post subject: Re: XL rear spar

Ron,



For some reason, the pictures are not displaying for me in your Word document.  Could you see if you can post a PDF doucment?

Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Mon Nov 02, 2009 8:38 pm Post subject: Re: XL rear spar

 	  BobTezyk wrote: 	
		  Ron,



For some reason, the pictures are not displaying for me in your Word document.  Could you see if you can post a PDF doucment? 	




Done, find it on the forum.

Iberplanes

Joined: 10 Dec 2007
Posts: 174
Location: Igualada - Barcelona - Spain

Posted: Mon Nov 02, 2009 11:09 pm Post subject: XL rear spar

Hi Ron. 



Pictures are missing. Post it as a PDF file. You can download a free PDF converter from www.cutepdf.com 



bye, 

2009/11/3 Ron Lendon <rlendon(at)comcast.net (rlendon(at)comcast.net)>

  	  Quote: 	
		  --> Zenith601-List message posted by: "Ron Lendon" <rlendon(at)comcast.net (rlendon(at)comcast.net)>

  

 I have attached a Microsoft Word document which shows a fix for this weak area.  It was created by an aerospace engineer.  You might wanna give it a look.

 

 --------

 Ron Lendon, Clinton Township, MI

 WW Corvair with Roy's Garage 5th bearing

 Zodiac XL, ScrapBuilder 

 http://www.mykitlog.com/rlendon

 Corvair Engine Prints:

 http://home.comcast.net/~rlendon/site/

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=270665#270665

 

 

 

 

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-- 

Alberto Martin

www.iberplanes.es

Igualada - Barcelona - Spain



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

 Zodiac 601 XL Builder

Serial: 6-7011



Tail Kit: Finished

Wings: Not Started

Fuselage: Started

Engine: Jabiru 3300

  [quote][b]

_________________
Alberto Martin
601 XL - Jabiru 3300
http://www.iberplanes.es
Igualada - Barcelona - Spain

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