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Pressed Wing ribs

STEEL

Registered User
Hi there.
I have taken over a scratch build project
Fuselage is about 80% done and slowly starting to plan and think about the next big sections, the wings.
I have the Aluminium wing spars and want to do Aluminium ribs.
Here is my question(first of many I suppose).
Has anybody tried to "press" their own ribs.
My thoughts are to build a male and female plug out of ply and then press a precut rib shape to the desired shape with cutouts etc, similar to those that can be purchased, but with the cost saving of doing it yourself.
Thanks,
Neal
South Africa
 
I did a Cub Crafters factory tour a few years back. IIRC the ribs were pressed using a 100T 'rubber' press. The 'rubber' presses the flat aluminum onto a very hard plug and it bends into all the voids. There were some elaborate steps in the heat treating, and I would imaging the plug is not exactly the same shape as the final product to allow for some 'spring back'? My apologies if this is not an entirely accurate description of the process.

Bottom line is I was left thinking this certainly justifies the $100 per rib that Univair charge.

Aerodon
 
On this website somewhere Bill Rusk met a person from Wisconsin somewhere that did that, I thought they looked very nice, maybe bill knows where to find it here? Bill? Maybe you guys could get together? Found it, go to page 20 of Bills build, steel form though.
 
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made the ribs for my last two airplanes from 2024-t3 .025. really nothing to it. formed them over a hard wood block. Flanging the holes is the biggest challenge...
 
Hi there.
I have taken over a scratch build project
Fuselage is about 80% done and slowly starting to plan and think about the next big sections, the wings.
I have the Aluminium wing spars and want to do Aluminium ribs.
Here is my question(first of many I suppose).
Has anybody tried to "press" their own ribs.
My thoughts are to build a male and female plug out of ply and then press a precut rib shape to the desired shape with cutouts etc, similar to those that can be purchased, but with the cost saving of doing it yourself.
Thanks,
Neal
South Africa

I have made Cub nose ribs by hammering them around a form block. See the picture.

A friend of mine scratch built a Sonex and showed me how he made all the ribs. Not only did he make the form blocks, he made patterns to cut out the blanks which he did with a router. I think he liked the bull-at-a-gate approach as it was with great delight he told me about zipping his overalls up to the top so the hot chips didn't go down the inside of his shirt!

He made some MDF blocks in a lathe to press out the lightening hole flanges. He told me they worked very well. You can also buy commercially made flanging dies. However I bought one recently and I'm not that happy with the way it works.

There is a heap of stuff about doing this sort of work on the internet and there will be videos on you tube too. Best to find some types of planes that people scratch build like that and search for those, rather than Cubs.

Good luck!

Andrew.
 

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Here's an EAA video on hydroforming small parts:

http://www.eaavideo.org/video.aspx?v=1277219627001
Excellent video. But note that he is making a SMALL part. Notice that the flange has been cut into small tabs. Note how much force that he is using to run the press. Notice how rugged the steel box is. A full sized rib is NOT a small part with tabs. The tabs will work for a riveted skin but not a particularly good idea for a fabric covered wing. Unless you have acess to a large hydro press and heat treating equipment you may be better off making your ribs from an angle bent around a form block for the caps with riveted angle or channels to criss cross holding the caps to shape. There are pictures of this type of rib on this site.

Take a look at the tooling below required to press a rib.
P1010657.jpg
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I fortunately have a CNC router at work, so I can cut the plugs as well as the aluminium accurately and I think with the tips from the video, I am going to give it a bash!
So the correct material to use for the ribs is the .025 2024 T3 aluminium sheeting?
Thanks,
Neal.
 
I had not seen the post above yet.
That is some mean steel plugs to press a full rib.
I will see what I can think of...
 
What about carbon fibre ribs,
I enjoy working with epoxies and CF and can vacuum bag it over a plug should form that quiet easily.
Any reason not to use carbon on something like this?
 
Pressed wing ribs

1179.jpg Working on a carbon rib this one is 7 OZ! Just build new molds to try it a little different. But yes they can be done!
 

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We ride on the ribs. After some experience with carbon fiber, I don't ride on carbon fiber parts. Have there place, but not structural for me anyway.
 
So the correct material to use for the ribs is the .025 2024 T3 aluminium sheeting?
Thanks,
Neal.
If you use -T3 there will be a fair amount of hand work involved to shrink the puckers which will be formed due to the compound shape changing. This is why -0 is used on production forming followed by heat treating to -T3. If you have access to a heat treat facility you will be better off using 2024-0.
 
I fortunately have a CNC router at work, so I can cut the plugs as well as the aluminium accurately and I think with the tips from the video, I am going to give it a bash!
So the correct material to use for the ribs is the .025 2024 T3 aluminium sheeting?
Thanks,
Neal.

Hi Neal,

Some study in order. Check out:
http://www.univair.com/content/univair-SL100.pdf
http://www.univair.com/content/piper_catalog.pdf go to page 122
http://www.de-aircraft.com
http://www.supercubproject.com
These should give you some ideas and you can see what others have done and chosen for materials.
If I recall correctly, Bugs (supercubproject) said on this site that D&E ribs are made from .025 2024-T3

The rib in the picture I posted was made from .025 6061-T6. I have made other ribs from 2024-T3, but it is hard work. 2024 is also more expensive than the softer alloys.

I hope this gets you on the right track. There are no drawings for working from when going down this path. You need to be able to justify what you do, at least to yourself, so some understanding on how the loads work in an aeroplane wing will go a long way.

Wait until you get into the debate on what the actual Cub airfoil is :lol:

Cheers,
Andrew.
 
I gave some serious thought to using solid polyurathane blocks instead of MDF or plywood since it it tough, resiliant, and provides lubricity to the process. If I had access to a CNC setup I probably would have tried it. I have used poly rods to bend curves and that worked well...maybe someone else has used it in this application.
 
hmmm.... you might be responsible for me getting a 100 ton press... I asked landlord if he had a bigger press for sale than my little 20 ton, he said no, but then remembered someone moving to lower 48 wanted him to sell their 100 ton homemade setup, will see if this pans out :) looks fun!

I guess I heard about it wrong, it's only 50 ton=100,000 lb press
 
Isn't somebody rolling out original Cub ribs? Aren't they lighter than the nearest competitor? They certainly seem strong enough, so long as all you do with them is fly.
 
We ride on the ribs. After some experience with carbon fiber, I don't ride on carbon fiber parts. Have there place, but not structural for me anyway.
I understand your feelings. You don't seem to mind riding on a large dacron handkerchief or in the case of the original Cub, cotton. Give some thought to the loads that the ribs actually carry. They are not primary wing structure in a Cub. All they do is to give the fabric some constant shape and keep it from flapping about. Take the gross weight of the plane times a load factor of a multiple divided by the square feet of the wing. What is that number? How is that load applied to each rib? How does a carbon rib compare to an original rather flimsy Piper rib? I don't know much about making stuff from carbon fiber except that it is strong and light weight. In my opinion it is worth a shot. Can a carbon rib be made lighter than Piper's?
 
Is there a reliable method for attaching fabric to carbon fiber ribs? Will the flange edge cut ribstitch cord like a pressed aluminum rib? Will the carbon fiber hold a screw or a fabric clip? Just glue? jrh
 
I understand your feelings. You don't seem to mind riding on a large dacron handkerchief or in the case of the original Cub, cotton. Give some thought to the loads that the ribs actually carry. They are not primary wing structure in a Cub. All they do is to give the fabric some constant shape and keep it from flapping about. Take the gross weight of the plane times a load factor of a multiple divided by the square feet of the wing. What is that number? How is that load applied to each rib? How does a carbon rib compare to an original rather flimsy Piper rib? I don't know much about making stuff from carbon fiber except that it is strong and light weight. In my opinion it is worth a shot. Can a carbon rib be made lighter than Piper's?

I'd tend to disagree in the case of a rib stitched, Piper rib. The lifting force acts on the upper fabric which is held in place by the rib stitches that transfer the forces to the lower capstrip of the rib. This is why using Martin clips or screws in original Piper ribs is a bad idea - the ribs weren't designed for the top capstrip to be pulled on in tension, but for the entire rib structure to bear the forces in compression. Univair's stamped rib are a different story.

John Scott
 
I sure agree with that. I hate seeing holes drilled in Piper ribs.

But I got a field approval for PK screws - it was either that or recover the wings, since they had been in there for decades without supporting paperwork.

It was on a Super Cub, and the thing flew fine, if a bit bumpy on the rib cap strips. Apparently, PK screws were approved for the PA-19. I have no idea what the difference is between a PA-19 and a Super Cub.
 
I'd tend to disagree in the case of a rib stitched, Piper rib. The lifting force acts on the upper fabric which is held in place by the rib stitches that transfer the forces to the lower capstrip of the rib. This is why using Martin clips or screws in original Piper ribs is a bad idea - the ribs weren't designed for the top capstrip to be pulled on in tension, but for the entire rib structure to bear the forces in compression. Univair's stamped rib are a different story.

John Scott
John,
I agree with everything which you have said except that I'm not sure what I said that you disagree with. Is it this "They are not primary wing structure in a Cub."? I separate "primary" and "secondary" structures as "which one can you fly home without?". You can fly home with a rib smashed to smithereens. Can you do that with the spar? The loads on an individual rib are very small. The ribs have nothing to do with holding the spars in position. There are other components which do this job. As mike mcs well knows, when you fly wrecks home on a wing and a prayer you quickly learn what is primary and what is secondary.
 
Pete,

In retrospect, I think it was a statement and a question you posed that spurred my reply. The rib does actually do more than just give the fabric shape in that it is the structure underlying the fabric that transferrs the lifting force to the airframe. As to how the the load is transferred to each rib, it is by the rib stitches and transferred in compression from the bottom up.

John Scott
 
since we seem to be getting off topic, I throw my take on a ribs "jobs"

to me, the most important thing they must do is keep the spars standing upright between compression members... if that fails you gonna come out of the sky... those spars are only strong enough when they are upright... in my head, i think pipers ribs are designed wrong as far as which direction the diagonals at the spars are....

but I think we are over thinking that they EVEN designed them, think it was just a GOOD ENOUGH thing... has room for improvement... everything in life has room for improvement..

what was the link to that youtube video from 1943?? of them making cubs that shows the guy making ribs??
 
since we seem to be getting off topic, I throw my take on a ribs "jobs"

to me, the most important thing they must do is keep the spars standing upright between compression members... if that fails you gonna come out of the sky... those spars are only strong enough when they are upright... in my head, i think pipers ribs are designed wrong as far as which direction the diagonals at the spars are....

but I think we are over thinking that they EVEN designed them, think it was just a GOOD ENOUGH thing... has room for improvement... everything in life has room for improvement..

Wish I'd have said that!
 
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