Rivet Edge Distance by a radius in material

[Prjmustang]

I am building a kit plane from plans and currently working on the spar, it is composed of a .040-2024T3 AL web bent into a "C" configuration, then there are cap strips .125" thick 2024-T3 which are stacked up 3 on each side of the web both top and bottom that make up a laminate structure .79" at the root and are shorter as they extend toward the tip. The 2 cap strips that are placed on the inside of the "C" next to the web need to have a .25" radius cut on the edge that sits next to the radius on the web which also has an .25" radius, the radius is only cut on these 2 cap strips. My question is how is the edge distance affected by the radius on the cap strip?

 

[rb1957]

as i understand it, the inner straps follow the formed radius, yes?

if you have 2D edge distance along the surface of the strap that should be ok.

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[Prjmustang]

The strip is not bent just a radius cut into it, and if I use 2D+.05 standard the rivet will end up being in the radius area. Is there a way to insert a quick drawing?

 

[rb1957]

"Is there a way to insert a quick drawing?" ... sure, use the "attachment" button at the bottom of the screen.

"The strip is not bent just a radius cut into it" ... ohh, i see, like a radius block. i'd place the rivet so it's off the radius and see what sort of edge distance that gives me. there shouldn't be much transverse load (towards the close edge) in the spar cap ... transverse load would be carried by the skin (no?)

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[Prjmustang]

I attach a drawing of the spar and a picture from another builder that is reaming the attach bolt hole, the part I am building is on the right side of that picture. For the first 20" of the spar it requires 5/23 rivets, so with the .25" radius the center of the rivet would have to be around 3/8" from the edge to stay away from the radius, is there a max edge distance then? To your comment above about transverse load is no since the web and the caps act as an I-beam - look at the pictures!




Pictures:

http://files.engineering.com/getfil...-4d59-49e0-befc-c12bc9b79bbf&file=Mutspar.jpg

http://files.engineering.com/getfil...40d1-9059-b8cdde3c1927&file=Spar_end_view.ppt

 

[rb1957]

typical design has 2D edge distance (from the rivt CL) ... so 3/8" is plenty for 5/32" rivets.

pictures didn't show me much ... the ppt sketch was very confusing (it's been rotated 90deg, right?; the straps are on the upper (and lower?) caps of the spar)

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[Prjmustang]

I guess the word "cap" is what is confusing, even though that is what they use in the plans, the orientation is correct, the strips are perpendicular to the skin, so the "cap" of the spar is really just the bent edges of the .040 web where the skin if riveted to. I added some more to the drawing to see if this helps!

http://files.engineering.com/getfil...4989-9748-47066ad78640&file=Spar_end_view.ppt

 

[rb1957]

not a stunningly efficient way to add inertia to the spar ...

"cap" is a common enough term for part of a spar (not just the flanges), just i'd expected the straps to be on the flange (rather than the web).

in any case, you're good to go ?

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