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Rib blank layout and grain direction

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Saz

Member
Joined
Jun 21, 2014
Messages
6
Just checking what all of your thoughts are on rib blank layout with respect to the rolling direction of aluminum sheets. I understand the long axis of the rib should be perpendicular to the rolling direction of the sheet from the manual (ie. the grain and lettering runs top to bottom on the rib rather than tip to tail). I will be cutting out blanks soon and wanted to make sure. It seems like the scrap I would gain from being able to fit more ribs on less metal would be worth it as I will have more to practice riveting on. I am much more concerned about rivets failing than the ribs since I thought that the listed strength properties of a metal didn't take into account the grain direction. I've also seen pictures and videos of other aircraft builders with the lettering running parallel to the wing chord and I can't find a specific mention on grain in any of the Bingelis books. Thanks for the help. sorry if I'm splitting hairs here.
 
I just finished my form blocks about an hour ago. I'm ordering 2' × 4' pieces of aluminum from Aircraft Spruce. I just don't want to deal with a large sheet. The cost is the same, and the grain will run lengthwise. I asked this question just a few days ago and it sounds like it's irrelevant.

Mike
 
Did you lay out the airfoil for the form blocks using the paper template or using the coordinates? I used the coordinates and this morning I set the template on the paper drawing. Well, the coordinates don't match the drawing. It has me concerned. Just wondering if you used the coordinates and if you found the same result.
 
Trust the coordinates, not the drawing template. Because of the variations in the printing process and the fact that the paper will stretch/shrink with the ambient temperature and humidity, the paper template needs to be double checked against the coordinates.
 
Hi Fred, hope you're staying warm.

When I put the rib template that I made from coordinates on top of the paper print the entire profile is dead nuts on except for the front 4" from leading edge back. The paper template is a 1/4" fatter than the coordinates. It's really noticeable. It's as if the leading edge was intentionally fattened up on the plans.

What makes me nervous are the Flying reports that say a thin leading edge stalls poorly and a rounded leading edge stalls really nice. Am I over thinking this? My coordinates are exact, I checked it like 5 times now.

Mike
 
Mike:
Don't overthink this. My airplane (and probably hundreds of others, including the prototypes) was built to the coordinate drawing originally supplied with the plans, which was included in your plans. It flys great, and the stall is not a problem. The sharpness of the stall is more related to the radius of the leading edge. If you keep it at the radius on the coordinate drawing, you'llbe fine. Just don't make it sharper when you bent the wing skins. By the way, have you looked at AirParts Inc for aluminum. The cut it off a roll to any length you want, roll it up, box it and ship it UPS.
 
I used the coordinates for my blocks as well and they don't match the paper template either. they look skinnier at the leading edge too. I definitely trust the coordinates though since they are probably what the paper template was built off of. If you've checked the coordinates 5 times I wouldn't be concerned at all. I'm getting my aluminum from a local FBO at the airport so that saves on shipping.
 
Yeah, those pictures look pretty similar to what I was seeing with my blocks. Thanks for the photos. What material are you using for your block?
 
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