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Thread: Pressed Wing ribs

  1. #1

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    Pressed Wing ribs

    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

  2. #2

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    it will be hard to make a straight strong rib using plywood as a stamp.

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    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

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    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.
    Last edited by tempdoug; 05-17-2015 at 02:36 PM.

  5. #5

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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...

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    Quote Originally Posted by STEEL View Post
    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.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  7. #7
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    Here's an EAA video on hydroforming small parts:

    http://www.eaavideo.org/video.aspx?v=1277219627001

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    Quote Originally Posted by fancypants View Post
    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.
    N1PA

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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.

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    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...

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    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?

  12. #12
    8856Charlie's Avatar
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    Pressed wing ribs

    Click image for larger version. 

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ID:	20126 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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    There are a lot of ways to make ribs. I have hammered out a lot of ribs over plywood blocks , here are some youtubes I saw that might helpClick image for larger version. 

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ID:	20127 .
    https://www.youtube.com/channel/UCMQ...fe_NItA93DyYAQ

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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.

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    skywagon8a's Avatar
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    Quote Originally Posted by STEEL View Post
    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.
    N1PA

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    I have mostly used 6061 t6
    DW

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by fancypants View Post
    Here's an EAA video on hydroforming small parts:

    http://www.eaavideo.org/video.aspx?v=1277219627001
    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!

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    Quote Originally Posted by STEEL View Post
    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

    Cheers,
    Andrew.

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    Lowrider
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    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.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    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

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    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.

  22. #22
    skywagon8a's Avatar
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    Quote Originally Posted by don d View Post
    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?
    N1PA

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    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
    You can't get there from here. You have to go over yonder and start from there.

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    What about this outfit? http://www.de-aircraft.com/index.html


    Sent from my iPad using Tapatalk

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    Quote Originally Posted by skywagon8a View Post
    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

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    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.

  27. #27
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    Quote Originally Posted by Longwinglover View Post
    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.
    N1PA

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    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

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    www.SkupTech.com mike mcs repair's Avatar
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    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??

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    Quote Originally Posted by mike mcs repair View Post
    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!
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

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    www.SkupTech.com mike mcs repair's Avatar
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    I also remember a story told by/or in a good book?? Farewell Nanook: Mary Oldham - Amazon.com about polar bear hunting, where she describes hearing the rib stitches breaking in turbulence(back in cotton days).. and yet not coming out of the sky..

    She was the first? registered female big game hunting guide up here?.... she did not get a license the first year it was offered, because SHE HAD WRITTEN THE TEST .. my stepfather used to work/fly for them, he has guide license #12

  32. #32
    www.SkupTech.com mike mcs repair's Avatar
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    youtube-ing.. since I now have 598 lbs of a 100,000 lb press sitting on my floor waiting to be reassembled and put to work...

    https://www.youtube.com/watch?v=eZ062_wUWCE

  33. #33
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    Quote Originally Posted by mike mcs repair View Post
    youtube-ing.. since I now have 598 lbs of a 100,000 lb press sitting on my floor waiting to be reassembled and put to work...

    https://www.youtube.com/watch?v=eZ062_wUWCE

    That's a great video, amazed at the animation they had back in the 40s. Seems like you should have one of those in your shop!
    Thanks again.

  34. #34
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    Quote Originally Posted by mike mcs repair View Post
    ...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...
    Mike it is the compression members which hold the spars upright in a Cub. The ribs are just going along for a ride. Of course they do help some, but the compression members are primary.
    N1PA

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    Quote Originally Posted by Longwinglover View Post
    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
    Totally agree.

    Quote Originally Posted by N86250 View Post
    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 do not believe that properly installed rib stitch cord will be any more susceptible to "cutting" with a properly shaped carbon rib than an aluminum one. There should not be any relative motion between the cord and the rib which would be necessary to do some cutting. The reinforcing tape under the cord should hold the cord away from the rib edge. I think that it would be very interesting to try carbon ribs if there is enough weight advantage.
    N1PA

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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Mike it is the compression members which hold the spars upright in a Cub. The ribs are just going along for a ride. Of course they do help some, but the compression members are primary.
    but when the spars get bent, that always happens in between the ribs.... they may look flimsy, but.... so they help "enough"

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    Compression members help in keeping spars in vertical alignment but the ribs do the job in the 3' to 4' spaces between the members.

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    www.SkupTech.com mike mcs repair's Avatar
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    hmmm.... you might be responsible for me getting a 100 ton press I
    asked my 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!
    bump...

    Anyone got some good videos or links for press forming stuff, making dies, routing blanks and such????...

    I did get the 100,000 lb press put back together after 6 or 7 weeks laying in pieces on my shop floor... now need to learn what I can do with it(how to)...

    pictures of my first try doing a pressed cessna style nose rib with the rubber pad method.
    I was quite happy with the finish part, compared to the original I tried to copy, especially for a first try, with a total of 1 hour 15 minutes invested start to make wood form to a finish part...
    look in "press forming" album
    Picasa Web Albums - mike

    some videos of routing blanks, pressing & making ribs & such I found on YouTube
    https://www.youtube.com/watch?v=eZ062_wUWCE
    https://www.youtube.com/watch?v=RA_a0pD5-UU
    https://www.youtube.com/watch?v=RhG8gISbWMA
    https://www.youtube.com/watch?v=mUSljM05pzo
    https://www.youtube.com/watch?v=1Jx1I9MmPh4
    https://www.youtube.com/watch?v=SYnX5-2m4HQ

    https://www.youtube.com/watch?v=iY6Gbf_rOkY
    https://www.youtube.com/watch?v=EWGAIVDpDLc
    https://www.youtube.com/watch?v=jYHzPskP7fc


    Later in this video, for showing how to make dimples..
    https://www.youtube.com/watch?v=PUgXlYMLAkI

    good supplier for urethane rubber in liquid http://www.dascarplastics.com (which the site is really is now owned by http://www.specialtyresin.com but the prices are better..)

  39. #39
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by skywagon8a View Post
    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.
    have not tried this yet, but in my mind, I bet if you make it a 2 step process you can get away without puckers, but the key is you will NOT press a truly FLAT(finished) (rib/part) shape at first, but more of a curved piece(where the curved flanges would normally make excess/puckers) just to get the flanges standing upright, then a second operation to flatten the part & pull/stretch out the excess(normal puckering material)

    I might be full of it with this thought..., but will give it a whirl anyway...

  40. #40
    Lowrider
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    Very COOL!! Was the 100 ton press necessary to get good results?
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!

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