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Permalink Reply by Joseph Begany on February 11, 2011 at 12:03pm

Tim

I don't have the page handy but there is a group of 6 guys building together in Canada.  They have a video of flanging parts on one of their pages.  In this video you can see the part warp as the flanging die is pressed into the hole and once it bottoms out you can see the warping work its way out of the part.  The flat rim of both the top and bottom dies meet and press together around flanged hole on each side of the web and the press takes out most if not all the warping. They are using a hydraulic press but you can see what is happening to the part as the flange is pressed into the part.

 

I would say that much of the warping is related to how evenly the flange is formed around the hole and how crisp the flange is formed.

 

There is another video on YouTube of a guy that goes through the process of flattening out his ribs very systematically.  When the process is done each rib will lie flat on the bench.  The process involves adjusting the crimps around the edge of the part.  I don't recall but I believe he was actually flattening RV-12 ribs but it doesn't matter.  It should not be to hard to find.

Joe B

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Permalink Reply by Tim Smart on February 11, 2011 at 3:03pm

Hello Joe and thank you for the reply.  I believe I know the one site where a gent was painstakingly working around a flange hammering with a radiused aluminum block to relieve the tension, the other I will look for.  To clarify, I know what you are talking about, I am using the flanging dies in a press and I have a large surface area (flat) that does press the sheet flat when it bottoms but I did have cupping on these two ribs.  I am very happy with the location and quality of the flange but I will look closely at the "crispness".  I believe you to mean where the immediate bend begins, less like a gentle rolling into the radiused area but a break into the radiused area.  Again thanks for you input -- Tim

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Permalink Reply by Chris Aysen on February 11, 2011 at 12:04pm

Tim - Always nice to communicate with another plans builder.... If you're talking about the longitudinal axis bending, aka "banana affect". Touching up the flutes with fluting pliers should straighten it up. Usually flanging the lightening holes help improve the situation (depending on grain direction).... Remember, these aluminum sheets also have a grain direction that plays a part in the final result of the bend. I understand about the nose rib; you shouldn't see that with the rear ribs. However, you can and should expect to see some bending no matter how the grain runs. I had a few ribs turnout pretty good very LITTLE bending.

Chris

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Permalink Reply by Tim Smart on February 11, 2011 at 3:16pm

Hello Chris, thank you for responding too.  I am not having the problem on the longitudinal axis but vertical axis.  The grain on these two rear ribs is running lengthwise.  I will take a closer look a the beginning  of my flange break, the cripsness as Joe mentioned.  He may have something there, perhaps I don't have enough pressure at the radius?

 

By the way, a quick look at your page your plane 1st class, looks great - safe flying -- Tim

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Permalink Reply by Chris Aysen on February 15, 2011 at 12:02pm

When I see how many guys are starting to plans build I start to get a little "yancy". I really miss building. It just not financially fesible at this time.

Best of luck my friend!

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Permalink Reply by martin acton on February 12, 2011 at 6:43am

Hello Tim. Im also new at this, and my first rib with a lightening hole also was reluctant to lie flat. I found that I was overbending the metal over the formers. I now also hold the former in my hand after removing from the vise, and give it a few blows all around the edges with the mallet. I also found that it is much easier to chase the front edge ( the 3mm bit) of the ribs with a small hammer very lightly, than to use the mallet. A gluestick held in the relief notch, and then hit firmly with a mallet works very well for me too. The gluestick leaves no marks either. Soon you will be an old hand at it :)

martin

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Permalink Reply by Tim Smart on February 15, 2011 at 7:35am

To all,

 

I believe that I have solved my problem with the cupping through the vertical axis of my ribs after flanging the lightning holes.  Being like many others I could not afford the cost of having my flanging dies machined so I made them myself with a router and fly cutter.

 

Earlier, Joe B., replied to my discussion and mentioned something about the flange being crisp which got me to thinking.  I increased the size of the top plate on the male half of my die to press the face of the rib over a larger surface area and relieved the taper (VERY SLIGHTlY) to allow the die to penetrate deeper in the female half and allowing more pressure on the flange face to help press it flat.  All of this helped some but not enough.

 

This morning I took a flange roller (purchased from Aircraft Spruce, the aluminum stick with two nylon rollers) and gently rolled around the flanged lightning hole.  I was not flanging the hole but I believe I was sharpening the initial radius relieving the stress on the face of the rib.  After doing this I popped the flanging die back in the rib and repressed (re-straightening the flange).  My rib no longer has the cupping.  The whole process took about 15-20 minutes to do the four holes in each rib.  A little more work but  worth it to me.  I am now very satisfied with my ribs, especially after Martin’s guidance and input about using a glue stick to guide the flutes in my flanges eliminating all scuffing, scratching and making a much better flute and cleaner rib.

 

THANKS TO ALL,  for your help & I hope this will help someone else who finds themselves where I was.

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