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  #1  
Old 03-27-2017, 11:55 PM
sumitku sumitku is offline
 
Join Date: May 2013
Location: Victoria, BC
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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
 
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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.
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Old 03-28-2017, 05:52 AM
Kyle Boatright Kyle Boatright is offline
 
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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).
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Old 03-28-2017, 06:41 AM
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MarkW MarkW is offline
 
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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
 
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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 online now
 
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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.

Dave
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Old 03-28-2017, 11:44 AM
sumitku sumitku is offline
 
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First off, thanks to all of you for taking time out to provide insight. Very appreciated.

Ken, Dave, yes I've heard that a few times that the newer relief cut kits may not need any fluting whatsoever. What makes me wonder is that the manual still says flute if necessary the curved flanges of the HS-1004 ribs on page 8-7. Also, the web certainly doesn't lay flat even though it does look like the holes on the flanges are in a straight line, at least on each flange section between the relief cuts.

Mark, not sure if I follow, my pic is looking at the side of the HS-1004 rib which indeed is curved and is going to rivet directly to the skin over it.

Tom, thank you for explaining the forming process that leads to the curvature. I had seen videos of scratch building but never put it together until now how the flanges elongate through the process. I definitely will be satisfied when I figure this one out!

Kyle, agreed I can see that curvature, though less, is still there on the flange segments themselves and would certainly aim for those with fluting. It's the middle of the web bend that still throws me. I've tried flexing it a bit with my fingers and that doesn't seem to be effective enough, so it feels as though I'd have to get more aggressive to take that bend out by reverse bending the web in the middle. Neither the manual or any posts that I've been able to find talk about doing this, so I continue to wonder if I'm doing something wrong in trying to bend that out.

Think I should give Van's a shout or is it clear that I should reverse that mid web bend in addition to fluting the flanges?
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  #8  
Old 03-28-2017, 02:44 PM
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MarkW MarkW is offline
 
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Oops. Looking again I see that. Those are I guess the short nose ribs.
Where they cleco in or not they should be fluted to lay flat. If you were to put a straight edge down the row of rivets you will find that they don't line up well. It is a short rib so it may not be too bad but it only takes a second to flute a rib once you get the hang of it. You will be amazed at how flat you can get them to lay when fluted correctly.

[IMG][/IMG]

Flute a small amount at the red lines and all around the rib on the curved sides. Not the flat spar flange. The more curved the flange the more fluting it will need. Start very slowly and work all the way around to all the flanges before adding more or less fluting. Quit when it sits flat.
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Last edited by MarkW : 03-28-2017 at 03:04 PM.
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  #9  
Old 03-28-2017, 03:40 PM
sumitku sumitku is offline
 
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Mark,

Thanks for clarifying and for the diagram! This statement seems to be definitive to me "whether they cleco in or not they should be fluted to lay flat."

Not sure why I'm so stuck on that bend in the middle of the web as being the main culprit, it just looks like the main cause of each side of the rib sticking up from the bench. For instance, I can rock the rib back on forth with the lever point being right at the midpoint of the web there.

I think I'll give the fluting a go and see what happens?
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Last edited by sumitku : 03-28-2017 at 03:43 PM.
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  #10  
Old 03-29-2017, 11:39 AM
jswartz jswartz is offline
 
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There are a couple videos on the EAA website that show a real person fluting a real rib and showing how to figure where to flute. I'm not sure whether the videos are available to non-members but while logged into the EAA website, this URL shows a bunch of their videos.
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