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Nose rib fluting

HeliCooper

Well Known Member
I am running into this while trying to flute the nose ribs. The first two pictures show what the rib looks like after fluting without an pressure. You can see there is a pressure forming a twist in the rib.

4wNy3jxl.jpg


Ap5vb7Nl.jpg


If I hold pressure on the rib you can see that the flange itself is straight on both sides. Pressure is very light. Guessing just a pound or so.

PGy6Rpgl.jpg


Also of note in this picture you see the gap under my thumb between the flange and the table. This gap is present on all the ribs before fluting and as far as I can tell is not correctable.

Should I just leave them fluted like this or do I need to figure out how to get that load off the rib?
 
Fluting

On my 7a, I was able to work them until they lay flat on the web side but I was more concerned with getting the holes to line up with a straight edge. I remember it took a long time. The flange edge is not perfectly flat. I doubt you will be able to get it flat using that side.
 
I was recently reading about this very thing in section 5.13 Fluting, and remember this note.

"NOTE: Do not confuse the twist in a part with a curved flange. It is normal for light pressure to be required to hold a twisted part flat on a table. Fluting does not remove twist from a part."

Also, I found this page helpful in regards to fluting. Looks like the images are no longer available, but the explanation is still good.
http://www.vansairforce.com/community/showpost.php?p=207970&postcount=1
 
Lay the part on a flat surface with the flanges up.
Get on your knees, eyes level with the part
Hold the flange down to the table and see if it needs fluting, do not worry about the other side
Only do one section of a flange at a time if there is a notch in the flange
If there is a bend in the part then lightly flute between each rivet hole
Check for straight, if the section of flange lays flat, job done
If not, flute some more

I could have done three ribs in the time it took to type this, try not to over think it. If the part lies flat on the table the holes will be in line as well
 
Look close and you'll see the flanges get wider through the curved areas from the forming process. Disregard that and use the web side edge for referencing.
 
I used the factory edge of my MDF benchtop as a reference for fluting. Much more comfortable (and in my case, more accurate) than fluting while using the benchtop while on my knees.

FP20052012A0008M.jpg
 
Thanks for the help guys. I don't know where I got using the flange side. Using the web side worked great.
 
One other thing that I do when I flute parts is to put frog tape down on the rib right next to the flange (sometimes partial on the inside flange) prior to fluting. This helps in case your fluting tool slides down to the surface of the part as you squeeze. prevents marring the skin.
 
One other thing that I do when I flute parts is to put frog tape down on the rib right next to the flange (sometimes partial on the inside flange) prior to fluting. This helps in case your fluting tool slides down to the surface of the part as you squeeze. prevents marring the skin.

I wrap each jaw of the fluting pliers, including the nose, with a layer of duct tape for the same purpose.
 
From the pic, it appears you are over fluting. You can take your fluting pliers and gently reduce the amount of gather on the side that is compressing (flatten the flute a bit). Should straighten right out, or get relatively close.

Flute gently, and space them out. Come back and put in intermediary flutes if necessary or deepen the flute to gather more material. You may find some ribs need very little while others need more.
 
+1 for JonJay. The twisted rib in the OPs post is over fluted on the side facing the camera. Flatten them (the flutes) out a little, work on the rest of the rib and it will come in. Turn them over (as you have already learned earlier in this thread).

I had one or two ribs that were a little recalcitrant. Examination usually showed a flange that was not as square as it should be or my own ham handed over-fluting.
 
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