The Art or Science of Fluting - Is there one???

gpiney · #1 05-19-2006, 09:37 PM

I spent 2 hours tonight getting 2 HS-404 ribs to lie absolutely flat. I fluted, straightened, fluted, straightened so many times I forgot what got me there.
I was Dazed and Confused.

There must be some Science to the Art.

I first get the flanges to 90 degrees. I use a piece of cheap aluminum angle I had around to verify the 90 deg.. From that point on it is a mystery. I start by laying the rib on the web. I will notice that one 'corner' or 'side' is high. Where should I flute to get that high corner or side to relax??? Van's instructions and the threads on this site seem to suggest a willie-nillie approach - just start fluting. If it gets worse - straighten out with seamers and start over.

It's like being a bank robber with six weeks to figure out the combination of the vault.

Someone must have come up with a basic methodology for fluting based on the configuration of the part.

If you have, please share it with me.

Thanks in Advance

RV8RIVETER · #2 05-19-2006, 10:12 PM

Greg

Unfortunately, there is a "feel" to doing it. But, there is a basic way to get there as well. I find it best to take a flat piece of particle board or table and lay the rib on that. You can look to see how it lays. To take the upward curve out you have to "shrink" the edge, making it shorter which pulls the curve down. Even though it may seem willy nilly by putting flutes along the entire edge, you start that way because you want to shrink the entire edge.

After that you check against a flat surface again. If you need to flute more, I found it best to put the deeper flutes at or just past where the tab starts to leave your flat reference surface. Flute and check, flute and check, until you get the rib to sit on the surface flat across its entire length. Keep in mind it does not have to be perfect. Only that the skin holes line up with the rib. I assume you have the new completely pre-punched parts, so as long as the holes line up you are flat enough. In my case I only needed for the skin holes to line up on the rib centerline., so I had a bit more room for variation.

Which reminds me, you could also use a ruler to line up the rib holes instead of a flat surface.

Hope that helps.

Stephen Lindberg · #3 05-19-2006, 11:25 PM

With a little experience you will be able to sight along the flange and see the deviations from straight. It is best to spread out the correction by fluting just a little bit between each hole. It is an iterative process. Just keep making small corrections over the entire rib (both sides) until you are satisfied. It won't (can't) be perfect. After you have done about half of the wing ribs you will be spending 2-3 minutes to flute a rib. Piece of cake. I have a tool that works very well for fluting. Light pressure is all that is required to use it. It is a jeweler's tool used for sizing rings, I think. I bought one from Wally Anderson at Synergy Air in Eugene, OR. Much better than the tools made from pliers and welding rod. I could happily flute all day and not develop sore hands. I'll try to post a picture of the tool.

szicree · #4 05-19-2006, 11:41 PM

All I can offer is how I did it and it worked pretty quick and easy. First thing I did was got a pair of not so expensive vise grips and made them into fluting plieres by welding on three pieces of steel rod. If you don't have a welder, I'd bet some JB Weld would do the trick. The reason I like the vise grips is that you can pre-adjust the gap between the jaws with the little knob on the handle. This way when you snap them shut it always flutes exactly the same amount. Set them to create a very shallow flute and do the whole rib. If it's too much, start over, if not enough, dial the jaws shut a bit more and go over each flute again. If you creep up on it this way, when you're done with the first rib you'll have the jaws the right gap to do all the others. My experience was that the sections of rib that are straightest (like the lower surface) require the least fluting.

Stephen Lindberg · #5 05-20-2006, 12:28 AM

Here is a picture of the fluting pliers refered to in my previous post. http://img204.imageshack.us/img204/4/img15207sj.jpg

Steve · #6 05-20-2006, 07:26 AM

Bend the flanges square to the web face, if required. Flute the flanges until the rivet holes all line up. Use a straightedge and the Mk20-20 eyeballs.

Here's how I did it. Place the rib web side down. Lightly press the rib down. Flute around the part to remove the web arch formed by the manufacturing process. Now do the final fluting lining up the rivet holes. If the web face lies flat without holding it against the tabletop, it is coincidental.

Steve

briand · #7 05-20-2006, 09:14 AM

I start by squaring the flanges and deburring. Then I lay the rib on an elevated flat/smooth surface (in my case an end table set on top of my work bench), I start at the large end of the rib (web down) sliding it on to the surface until I come to a spot that rises off my table, I flute in the fluting location just before that spot. Then I check the other side (top or bottom whichever I didn't flute yet) to see if that needs a flute between its same 2 holes

JoeG · #8 05-20-2006, 11:57 PM

I am by no means an expert here, but this approach has worked well for me so far...

Most of my ribs seem to be fairly symetrically curved about the center. I have had good luck by starting in the center, and working my way out towards the ends. Using the Avery vise grip fluting tool, I can set a shallow depth to begin with and then gradually increase the depth as necessary to get the edges straight.

The other thing to remember is that there is no "rule" that says every flange space has to have a flute. By fluting iteratively and minimally, I have been successful in getting straight parts while not having to use the seamer to un-flute anything.

osxuser · #9 05-21-2006, 10:03 AM

Quote:

Originally Posted by JoeG

I am by no means an expert here, but this approach has worked well for me so far...

Most of my ribs seem to be fairly symetrically curved about the center. I have had good luck by starting in the center, and working my way out towards the ends. Using the Avery vise grip fluting tool, I can set a shallow depth to begin with and then gradually increase the depth as necessary to get the edges straight.

The other thing to remember is that there is no "rule" that says every flange space has to have a flute. By fluting iteratively and minimally, I have been successful in getting straight parts while not having to use the seamer to un-flute anything.

I do the same thing, I kind of square the edges first, but don't worry about them that much yet. The next thing is to flute, from the center out. Then resquare the edges. Get them close, but DON'T worry about making them completely perfect all around, you'll just drive yourself nuts. I have a 'good enough' point which usually ends up being 15min or so of work on one.

gpiney · #10 05-26-2006, 09:16 AM

After carefully reading everyone's posts, I thought I would try a couple things. On my first two ribs, it was pretty hit-or-miss, but I finally got it. While working on the second rib I observed a pattern. So I tried something on the third and subsequent ribs and It Worked.

Besides fluting pliers and hand seamers, you will also need a flexible straightedge. I have a couple of thin, stainless steel rulers that fit that bill.

First, square the flanges to the web. Very important step and must be done first. You can then deburr the edges. If you want to wait until all the fluting is done to deburr the edges, that is OK too.

Next, instead of lying the web on a smooth flat surface, hold the rib flanges out (web towards you) and center your flexible straightedge to the two outermost holes ( the HS is prepunched). You will see one of three possibilities:

1. The holes line up perfectly (not likely, but I had one flange that was close)
2. The center holes are low (below, hidden) to the straightedge
3. The center holes are high (above) the straightedge (most likely case)

By center holes I mean the prepunched holes near the center of the rib.

If case 1: Flip the rib over (flanges out) and do the other side.

If case 2: Start fluting between the Outermost holes on each end of the flange. This will raise the center holes. Work your fluting outside - in. After each round of fluting, check with the straightedge. Flute a small amount each time. In this case I would start with 2 flutes on each outermost side.

If case 3: Start fluting between the Center holes of the flange. This will lower the center holes. Work your fluting inside - out. Again, after each round of fluting, check with the straightedge. In this case, I would start with 3 flutes in the center.

When you are done with a flange, flip it over (flanges out) and repeat, depending on which case applies.

After you have done both sides, CHECK BOTH SIDES AGAIN. I noticed that the 'good' side may change after fluting the other. Once both sides have perfectly aligned holes, lay the rib web-down on a smooth, flat surface. Voila!
It should lie perfectly flat.

Using this method, I found that the last 2 ribs I fluted took a total of 30 minutes. On my next round of fluting, I should be able to cut that down to around 10 minutes a rib.

I would really like someone else to double check this method. If you are about to start fluting ribs or bulkheads, please give this method a try. Let me know if it works for you or if there are any nuances or improvements to the method.