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Deburring RV-12 Wing Ribs

M

Mich48041

Well Known Member
Friend
I tried deburring the nose ribs using a hand grinder with a Scotchbrite wheel. But the wheel caught and bent the rib. Luckily I was able to straighten it out. Now I use a file and Scotchbrite pad. But it is taking me forever. A friend of mine just assembled his wing with the parts as they came right out of the box, no primer, no deburring. He said that he never used a Scotchbrite pad. He has his wings completed and I am way behind. Am I being a perfectionist or is my friend building an unsafe aircraft? Or is there a happy medium? Also, I am only deburring the lightening holes, not the flanges. Is that OK?
Another question: The plans say to trim the rear flange off from the majority of the nose ribs. But the picture does not show that rear flange as a hatched area to be removed. I am pretty sure that the rear flange needs to be removed but thought that I had better ask before I ruin all of the ribs and have to buy new ones.
Thanks for your advice.
Joe Gores
 
DEBURR EVERYTHING!

Burred edges will cause scratches which will eventually cause cracks. Not deburring will make for a short lived aircraft and one I wouldn't want to fly. If you cannot run your bare hand all over the rib without feeling burrs, you are not done.
Yes, it takes time. But that's part of building. If you start taking shortcuts here, you really shouldn't be building an airplane.
Sorry for the rant, but this IS important.
 
Deburring

Mel,
Thanks for your input. I am going to take your advice and make sure that the rib edges are smooth. I had been concentrating on the lightening holes. But I will make sure the flanges are smooth too so that they will not scratch the wing skin or spar. I called my friend. He said that he did not deburr the lightening holes, but that he did run a file over the flanges so that a sharp edge does not touch the wing skin. I will not only use a file but also the Scotchbrite pad. It is always better to do a good job the first time. Doing so will save time and trouble in the long run.
Joe
 
Listen to Mel

Run, do not walk to the nearest phone and order a scotchbrite wheel for a bench grinder. I think that Van's sells them about as cheap as anyone. They are about 50 bucks. Even if they are a few bucks high, give them the business.

Go immediately to Lowes, Home Depot, etc. and buy a bench grinder that will accept the scotchbrite wheel. I don't care if you mount it to the wall, your workbench, a stand, whatever, but set it up now with the scotchbrite wheel. If you have a harbour freight store nearby, even cheaper. A hand held wheel is tough to control. Cheap bench grinder may be 50 bucks.

The ribs take a whooping 1 minute each to debur. Sandpaper on the lightening holes and away you go. You will use the wheel for the entire plane. When finished with the plane, the wheel will be half size.

Tip for you - take the floor attachment for your shop vac and attach it to the bench grinder. When using, turn the vac on and dust in the shop almost doesn't exist. I don't want to breath aluminum dust either. I used duct tape on mine and replace it about every 6 months.

Mel is dead on. Run your finger across the edge. If it remotely has the chance to cut you, you are not ready to build. I repeat, if it it can cut you, it can cause a failure.

While I'm on it, take the time to debur the holes too. Little ridges on the hole may keep the rivet from setting. Failure to set is a set up for failure. Also, the time and money may be wasted because loose rivets lose paint.

It's your hind end up there. Keep it up there by not having a failure.
 
Last edited:
QC

Just to carry on from this discussion, this is all part of our on-going
program of quality control.

Tools for this include a magnifier (binocular magnifiers on a
head band are great as they leave your hands free. Some also come
with lights). If you can't see defects at, say, 4X magnification, you know you can give it the check of approval.

Also, it is very difficult to do good work without good
lighting, so equip your workshop with good overhead lights as well
as localized lighting, such as spot lighting.

Your finger nail is also a good testing probe. If you can feel ridges or serrations by sliding your nail down the edge, it's time to put in more effort in de-buring.

Inspection is also important with your riveting - have a regular interval of checking to a standard. Are the rivets set squarely and are the pieces bearing
on one another? (no spaces between pieces being riveted)

It is also a good idea to make it a habit of documenting results of your testing program in your builder's log.

Good building,

Sam
RV Workshop learning Centre
Temora, Australia
 
just my 2 cents worth ...

I had the same problem as you ... it took forever to debur the scalloped flanges & flat flanges on the RV-12 wing ribs. I skipped the scotch brite wheel on my bench grinder for the reason you quoted. I tried the little yellow handled swivel debur unit and the large scotch brite pads that came with the Avery tool kit. Still very slow and not really happy with the results.

Then I opened my new Dremel 300 kit to see if that would work. It came with a tiny tiny circular abrasive pad that I wore down to nothing in about a minute. So, I saved what was left of that Dremel pad (metal center) and went to the grocery store (Publix, here in FL) and bought couple of packages of Scotch Brite pads (soapless) about 6" x 3.8" X 1/4" (approx) for $5.00 per pack with 8 pads each.

I then cut the pads into little circles (approx. 1 ?" dia.)and used what was left of the worn Dremel pad (the little metal piece) and placed a tiny Dremel drill bit that came with the Dremel kit and with my fingers slowly turned the bit and made a tiny tiny hole in the cut Scotch Brite circles so the Dremel mandrel would go thru the Scoth Brite circles. And with that little Dremel metal piece from the worn down Dremel abrasive pad, I mounted my homemade circle to the Dremel and voila. I was much happier with the results.

You still have to be careful not to catch and bend the metal and not to "overly" buff scratch the flanges. But it was much, much easier and results were far more acceptable, I believe.

Here ... take a look.

Dremel idea ...


Important ... Important ... Important ... !!!

REMEMBER: I'm a newbie builder ... be sure to check with Van's Aircraft before you do anything I do or I suggest or copy a method I use. I'm the furthest thing from an expert builder there is. I've never attended a workshop ... so reader beware ... and refer to my builder's web site with caution ... !!


That said, good luck.
 
wing ribs

Be careful and follow the instructions exactly on which wing ribs to trim and which not to trim. It can get confusing. There are several categories of ribs. First, main and nose ribs. Then, within those categories, untrimmed, aft flange trimmed, nose tab trimmed, and a couple with the nut plates. The left and right ribs are trimmed differently and I do believe that one wing has all the aft flanges trimmed off the the other doesn't.
I had to make stacks of like kind ribs then put a sticky note on each stack to keep them counted correctly.
Should have the left wing riveting done today. Anyone else have a backache from bending over the wing with the rivet puller?
Bart
 
The cut and polish wheels will grab in certain cases both bench mounted and the small ones that mount on a die grinder.

You will figure out which angle and direction combo causes this and won't take you long to learn not to do it that way.
 
Tip for using bench mounted SB wheel...

I felt a little "slow" when I finally figured out that deburring on the wheel goes MUCH smoother when you hold the work PARALLEL to the wheel instead of at a right angle. A ScotchBrite wheel can ruin a rib in about .0001 seconds if you hold it just right...

For parts you fabricate from .125 stock, a bench top belt sander followed by a few passes at right angles on the wheel will take out all the kerf marks from the saw, then a few passes parallel to the wheel gives you a nice "satin" finish.

Roger
-9A slowwww QB
La Grande Oregon
 
And then there's stress risers

We all worry about future cracks in our aircraft structure caused by stress risers and we want to smooth down all sharp edges to eliminate them. I've been following the adivice of the EAA info site that recommends if you can't cut your finger when you run it down the edge of a piece of aluminium, don't worry about it. Maybe we are over deburring, in fact sometimes, I think we create more stress risers than we correct in an attempt to smooth the metal.
One more thing. An electro-pencil is supposed to be a very bad thing to apply to metal because it creates really bad stress risers. Now, go look at the main spars near the exteme inboard end and you will see the spar serial number etched with an electro-pencil.
Go figure.
Bart
 
Bartsey said:
One more thing. An electro-pencil is supposed to be a very bad thing to apply to metal because it creates really bad stress risers. Now, go look at the main spars near the exteme inboard end and you will see the spar serial number etched with an electro-pencil.
Go figure.
Bart
Click to expand...

The general guideline is that it is bad, but it still depends on where it is used.
The stress riser produced by an electro-pencil is primarily an issue if there is any relative motion in the material at that point to cause a crack to start. Thin sheet material like skins and ribs can have relative motion from vibration and load/unload cycles. It is not an issue with thick heavy structure such as on the wing spar. If it has any relative motion at that location, you have a much bigger worry than whether you will have a crack develop in the future.
 
Just finished deburring my ribs

Hi:

I just finished deburring my ribs last night (except for the nose ribs). I did all of this with the blue film still on.

I used a very small (about 1 inch diameter) on a hand-held Souix die grinder. I went at a 45 degree angle to the scalloped edges down the inside of the rib and then again down the outside of the rib. I took extra time on the sharp corners of the little "notches".

Van told me that I only have to debur the holes which I drill myself, but I still deburred the holes with a little deburring bit that you can stick into an electric screwdriver. About 1 rotation each and that is all it takes.

I then used the scotchbrite pads to do the insides of the lightening holes.

I have felt every edge with my fingers and they do not even come close to cutting my skin.

The little 90 degree corners on the notches are sharp but hey - they are 90 degree corners and they do not rub on anything. The file just makes a mess of those. So, I am going to leave those alone.

I would say that I have about 20 hours into the ribs so far but I feel better having done this.

When I finish deburring the rest of the little wing parts I will prime only where metal is going to rest against metal, (again, just to make me feel better) and then I will start clecoing things together step by step with the plans.
 
Alan - excellent presentation

Thank you for your effort.

The tool you have designed really fits the bill. It will make the job fairly easy for a lot of builders. :)

Mike
 
Deburring and blue film

George and I have been using an old Radio Shack soldering iron (see our stuff on blogspot.com, (rv12builders) ) to remove the blue film. I started deburring with the film on but my older and wiser partner said to strip the film off first. It makes a smoother job.
George and Meade
#16
 
deburring tight areas / corners

some weeks ago there was a link to a video in the forums - I could't find it though.

What was done is the following:
Take a used 1" scotchbrite cut & polishing wheel, cut it into smaller pieces (hacksaw works well), fit on piece at a time to a dremes screw-on mandrel and shape it against a 6" deburring wheel into a conical shape.

Maybe someone remembers the link to the video - It's a great time-saver.

Mario
 
Soldering Iron

For plastic removal, use a dedicated nib for your iron. If you round
and polish the tip you wil be less likely to scratch the surface of your
Alclad.

Sam
 
Scotch-Brite wheel for $8

I ordered a Scotchbrite wheel from Van's. In the meantime, I bought a 3M Scotch-Brite wheel part number 9413NA locally for $8. You can see what it looks like here: http://www.idealtruevalue.com/servlet/the-60934/Detail
Or do a Google search on 9413NA 3M. This is a 5 inch diameter wheel with a 2 inch long shaft designed to be inserted into an electric drill and is rated at 3500 RPM. I modified the wheel so that I could mount it onto my bench grinder. First I drilled 3 holes in the center hub 120 degrees apart and equal distance from the center. I put #6 machine screws through the hub to hold it together while I cut the center shaft off and drilled a half inch hole for mounting on the grinder. It works very well. The wheel wore down from 5 inches to 3 inches while deburring the ribs.
I took a few ribs to the local EAA chapter meeting for show and tell. Everyone that I talked with said that it is not necessary to deburr the lightening holes or the inside of the flanges that do not come in contact with the wing skin. One experienced builder said that he used to do a good job deburring until he inspected a type-certificated airplane and saw that it was not deburred. I came home and finished deburring the rest of the ribs and did a good job so that all edges are smooth. It took me a few days longer but I feel more comfortable with a job well done.
Joe Gores
 
Scotchbrite

I think Joe's find is worth a look, though the composition is different in
the two wheels (Vans and True Value). This is obviously reflected in the
pricing.

It is worth mentioning, again, that abrasives containing silicon carbide
are not considered chemically compatible with aircraft aluminum alloys.
While this is arguable, the major manufacturers do not specify this material
when ordering abrasives. If anyone would like more details, I'd be happy
to respond to an email.

Cheers,

Sam
 
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