Author Topic: Compression struts in XL wings  (Read 301 times)

Offline Mark Kramer

Compression struts in XL wings
« on: January 11, 2020, 02:59:24 PM »
Hi guys, looking for some opinions on the 1/4 by 3/4 compression struts. Leonard clearly states in his plans to only install them on one side of ribs 3,5,7 and 9. Scott, I see in your supplemental wing drawings that you show them on both sides of the aforementioned ribs. Is it that you feel the extra strength would outweigh the minimal added weight? If anyone would like to chime in on this I would greatly appreciate it.
Thanks
Mark... fellow XL builder

Offline Tom XL-7

Re: Compression struts in XL wings
« Reply #1 on: January 11, 2020, 04:21:48 PM »
yes it should be both sides.   from plan clarifications and corrections dated june of 2010. you may be able to find these in the files if brought over from the old yahoo site. My drawings are even older . I have no idea what changes may have occurred to the drawings since then.

Offline Mark Kramer

Re: Compression struts in XL wings
« Reply #2 on: January 11, 2020, 06:15:22 PM »
Cool thanks. I’ve not had any luck with that yahoo site. My plans are not that old,I-77. I also purchased iron design wing drawings. He seems to agree that it should be both sides.
Thanks again
Mark

Offline Kamcoman77

Re: Compression struts in XL wings
« Reply #3 on: January 11, 2020, 06:15:52 PM »
My XL plans Page 37A with a plans change date of 9-9-12 have a note added."One Side Only" Ribs #3, #5, #7, #9. This numbering does not count the second rib next to Rib #1 or the rib next to the Tip Rib (plan only counts 11 ribs per wing). If you count every built-up rib starting at the root, the compression struts go on the 4th, 6th, 8th, and 10th ribs. The wing drawings on page 36 & 37 show single compression struts on the root side. I'm sure the only penalty for double compression struts is the weight. I wonder how much 16 pieces of 1/4" x 3/4" x 29" weigh?

Offline Mark Kramer

Re: Compression struts in XL wings
« Reply #4 on: January 11, 2020, 06:34:03 PM »
You are absolutely correct about rib count and numbering. I counted the two root ribs as #1, next one #2, and so on. I don’t have a small accurate scale, but I think the weight will be worth it.
Thanks
Mark

Offline Dan_

Re: Compression struts in XL wings
« Reply #5 on: January 12, 2020, 12:04:19 PM »
. I wonder how much 16 pieces of 1/4" x 3/4" x 29" weigh?
The short answer is 1.41 lbs (1lb 6.6 oz)...  Each rib compression brace weighs 1.41 oz so 16 of them will go 1.41 lbs.

Stika spruce weighs 28 lbs per cubic foot @ 12% moisture content. 

.25 X .75 X 29 = 5.4375 cubic inches so one must convert cubic inches to cubic feet, ETC.

I was taught... "take care of your units and your units will take care of you".  In other words set your units up to cancel and they will tell you when (and what) to multiply and when to divide. 

Units cancel when they are divided by one another.

If you (or anyone) would like to see the calc, I will take a pic with my cell phone of the piece of paper I scribbled on. 
O:-)


“A superior pilot uses his superior judgment to avoid situations which require the use of his superior skills.”

– Frank Borman, Apollo 8 Commander

Offline Tom XL-7

Re: Compression struts in XL wings
« Reply #6 on: January 12, 2020, 01:42:50 PM »
so I looked deeper and found I had XL clarifications and changes dated  Sept 14 2012, These did refer to page 37A compression struts. It also included new drawings. My originals clearly show both sides but these new ones show root side only. Furthermore a narrative from Leonard where he opened the prototypes (LE and XL) and they were one side only. no need to change if built with both sides.
So it appears up to the builder. 1.41 pounds is not insignificant. Leonard says "add only lightness".

Offline kalazzerx

Re: Compression struts in XL wings
« Reply #7 on: January 12, 2020, 06:28:20 PM »
I went with both sides - seemed to make more sense structurally to me but the plans to advocate only one side.  I believe I mainly went with both sides because I saw pictures of others doing the same.  Did not even notice the one side note until this discussion :)

Offline Leonard

Re: Compression struts in XL wings
« Reply #8 on: January 13, 2020, 11:42:43 AM »
Ok guys the engineer says you are just adding weight to put them on both sides so there too Leonard

Offline scottiniowa

Re: Compression struts in XL wings
« Reply #9 on: January 13, 2020, 11:15:25 PM »
Hi guys, looking for some opinions on the 1/4 by 3/4 compression struts. Leonard clearly states in his plans to only install them on one side of ribs 3,5,7 and 9. Scott, I see in your supplemental wing drawings that you show them on both sides of the aforementioned ribs. Is it that you feel the extra strength would outweigh the minimal added weight? If anyone would like to chime in on this I would greatly appreciate it.
Thanks
Mark... fellow XL builder
Guys, as some of you know, I did the supplemental plans a long time ago, I would have to chase down the exact dates but before the mentioned plans change to be sure. I have never said these (the plans) were to change anything. But really was asked in the beginning to make them to provide almost all the answers on measurements  and then of course to show visually how a particular area was built. To that level, I have been told many times, they did/have done this well.

I have never said to change how something was designed, and will hold my ground here as well.  This  forum topic seems to cover that, as there are probably plenty built both ways.

While I do a lot of design work, I have never suggested "a better way" on any structural part for this aircraft That is not to be confused with "show it better"  My goal has always been to help folks keep going with their aircraft.  Cutting out 30-40 hours out of the build time to me is a big deal. I think this craft and many others will continue to improve in various ways and that is a great part of the home builders "forums" such as this. Keep those questions coming!

Best of success to all!
best email address:  irondesignairparts@gmail.com

 


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