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Old 03-27-2017, 11:55 PM
sumitku sumitku is offline
Join Date: May 2013
Location: Victoria, BC
Posts: 38
Default Fluting HS Ribs question

Folks hoping for some guidance here. I've read section 5.13 of the construction manual a few times and also read a bunch of posts on fluting and watched some of the referenced youtube videos.

I just can't seem to visualize what needs to be achieved from fluting. If you look at the below pic, when I lay the HS rib web flat on the bench it sits significantly raised up on both sides. To me this looks like it's due to the center of the web being bent a bit which I could reverse by bending at mid web in the opposite direction.

Or is the goal just to get each section of flange fluted so the web underlying just that particular flange lays flat, and not necessarily the whole rib web laying flat all at once.

Really confused here so thanks so much for any help!

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Old 03-28-2017, 12:54 AM
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N804RV N804RV is offline
Join Date: May 2013
Location: Mount Vernon, Wa
Posts: 396

I would think that the newer kit parts with the relief-cuts in the flanges wouldn't need to be fluted. I'd cleco the parts together and as long as all the parts line up straight, no fluting required. --- Is that not correct?

On ribs that don't have the relief cuts in the flanges, you need to flute the flanges in order to get the ribs to lay flat so that pre-punched holes will line up in the center of the flanges.
Ken W.
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Old 03-28-2017, 05:52 AM
Kyle Boatright Kyle Boatright is offline
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 3,458

You want to flute until the web of the rib is basically flat along its entire length.

When I look at your picture, I see the bend you are talking about at midpoint, but also see lesser curvature in other segments of the rib. The goal is to eliminate all of it (the midpoint bend and the curvature in the segments).
Kyle Boatright
Atlanta, GA
2001 RV-6 N46KB
2019(?) RV-10
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Old 03-28-2017, 06:41 AM
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MarkW MarkW is online now
Join Date: Sep 2011
Location: Edgewater, FL. KSFB
Posts: 1,051

Your picture appears to show the spar attachment end of the rib. You do not want to flute that end, only the rounded parts of a rib.
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Old 03-28-2017, 07:03 AM
Tom Martin Tom Martin is offline
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,429

Here is what made this part bend: You start with a flat sheet of metal cut out the notches, corner pieces etc. Just visualize what that part would look like if it was flattened out.
You will notice a couple of small holes on the flat area, web of the part. These are tooling holes. You would place the part on your wooden forming blocks on these pins. This is done so that you can make a bunch off similar parts.
Another wooden block is clamped on top of the pins. The "flanges" are sticking out. These are bent down, or hammered down. This bending, either in an expensive press or with a hammer, stretches the flange. This now longer flange is what curves the part.
Now you can shorten that flange by putting a crimp, or flute, in it. This gathers the metal and shortens the flange.
Simply put the web of the part on a flat piece of material, get down at eye level and put your fluting pliers in the middle of the holes and crimp it until the part lays flat.
Sometimes a couple of small flutes are better then one large one. Make sure none of the flutes will interfere with subsequent dimpling. Too much fluting will shorten the flange and cause the part to curve the other way!
This is one of what I call satisfying jobs in the project. You get to make something "right" with a little squeeze and a look!
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Last edited by Tom Martin : 03-28-2017 at 07:06 AM.
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Old 03-28-2017, 08:22 AM
Wyzepilot Wyzepilot is offline
Join Date: Oct 2013
Location: Red Bank, NJ
Posts: 74

If it were me I'd cleco it together and see if the holes line up with the skin. If I remember correctly they lined up perfectly in my kit without the need to flute. From what I understand the older kits with the solid flanges required significantly more fluting than the newer kits.

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