How many scratch builders out there ? you are all going to need them----

[fairchild1934]

how many of you out there have all ready done this ? And how many of you are there that will have to do it ????
Is anyone trying to figure this out ?

I can get a 3 sided box bent ok I think---- its bending those flanges cleanly that is the problem. Tried an oak insert - but as expected-- you cant get a clean bend because the material wont keep a clean, sharp corner to bend against.

I am beginning to think it might be easier to ben those flanges all the way to 90 degrees. Anyone see a problem with that ? (in stead of 30 or 45 degrees. )


I tried making a steel version of the Bob-stick. That worked but it was hard to support the other half and force it to bend at the intended bend line. More of a bow than a bend with a bend line. Kind of a lumpy mess----

Tim

[SpruceForest]

Delrin works fine, while anything harder than aluminum is going to have to be very well polished on the interior/contact surfaces. I used mine extensively for flattening ribs and even did a few lightening holes just to see how bad they turned out (not bad...), but the hydraulic press technique detailed elsewhere resulted in far less residual stress in the ribs even where the approach is used ONLY for lightening holes. Spare rib done with press, Bob stick for straightening, the Vans Air Force flange straightener, and the usual fluting pliers.

Even with snips, hammer, and Bob stick, you'll likely get something better than what I've seen out of Cessna when it comes to wing ribs. Also - don't discount what can be learned by doing a half-dozen throw-away ribs... I have a box of them in the shop, and it was cheap tuition on the way to acceptable aircraft parts. The first ones were mild big-box aluminum to test out the process, and moving to 2024 generated more scrap, but what I learned got used on all 160 patrol ribs, so a half dozen 'wasted' rib blanks was money well spent.

IMG_0732.jpg

[sjt]

If the question is how to make 90 degree flanges : I saw Vans aircraft versions of this tool


vans.jpg measure.jpg
c.jpg
t.jpg

p.s. make that lever very very long.

[sjt]

All ribs when first made start out as potato chips. The first rib takes one hour to straighten. After doing 15 ribs it takes about 2 minutes per rib.


I use an mdf form with the proper edge radius .
Then I might give a hint as to where I want the flange flute
t.jpg
The cheapest and way to bend flange is with a $7 hammer form harbor freight:
t.jpg



There are youtube videos on solving potato chip

https://www.youtube.com/watch?v=mI9yARLfmU0

This bearhawk builder is always helpful

https://www.youtube.com/watch?v=_F7jObc0ajA

I myself used this method:

https://www.google.com/search?q=rib+fluting+technique&oq=rib+fluting+technique&gs_lcrp=EgZjaHJvbWUyBggAEEUYOdIBCDYxNDRqMGo0qAIAsAIB&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:6ba71a02,vid:pIvFpVV6kIQ,st:0

[fairchild1934]

sorry----- im NOT talking about aluminum wing ribs------ I AM talking about the steel control surface ribs. ( I have that process figured out well- I can make those all most flawless now-)

I didnt seem to get any useful responses in the other post-- so I thought I would ask it again---- from a different point of view.

I made a steel version of the bob-stick to turn the flange. But it does not work well because its nearly impossible to support the work on the other side of the bend line.

I am starting to think what we need is a special pair of pliers -- with 3 handles. A pair of outward pushing jaws having the jaws to be able to swivel a little---
and another 3-rd lever that turns over the flange while the other jaws apply pressure from inside out as an opposing force against the flange bend line.
Have the jaws about 2 inches wide--- so you could work your way from one end of the rib to the other.

Tim

[fairchild1934]

PS----- could possibly have used piper control surface ribs--- as they are about the same cross section shape as Bob's--- but basically none of them are the correct length. ( they are only about 15$ each- not not too expensive)

[sjt]

t.jpg
I have not gotten to that point for steel. My plan was to use my press to to hold. The press will hold no matter how hard I hit.
I might have to upsize the hammer.

[sjt]

b-spot has a video

https://www.youtube.com/watch?v=ki8_gRa5mTk&t=17s

I used up my oak stock and will have to get more.

[fairchild1934]

I think I watched B-Spots videos on that but I think he only showed the profiled stab ribs. They dont have the inward flange on them that make the complication in forming. but I will watch again just to refresh-- as his videos are very, very good..... liquid gold !

[sjt]

I am not sure if my drawing is the same.
On the patrol drawing 24
"Ribs may have lighting holes cut out after forming"

The holes might be made on a drill press

material .032 1018 steel

I think you are referring to section A-A




for some reason I can not draw it with ascii characters
3/8
______
/ *******|
********|
********|
********| 7/8
********|
\____ _|


If you do not have a hydraulic press maybe using a finger brake with all but one finger removed.
Maybe use finger to clamp a short length of 5/8 x 3/8 piece of steel that will hold rib while bending the lip.

[fairchild1934]

I watched B-Spots video. Unfortunately -- he just skips that step and does not bend the flange on his.
Stan--- just holding the rib is not exactly the problem--- its supporting the part you dont want bent-- and getting a nice bend line in stead of a frumpy, curvy
mess (which is what I am getting--) It like using a metal brake without using the hold -down bar on the other side of the bend line.
If I use something to bend it a few inches at a time- even gradually--- you end up with stretch ripples in the edge- no matter how gradually you do it. (like with using 2 inch seaming pliers)

im getting frustrated that no one seems to know how to do this ...... is no one making the flange ? or have most people just bought the ribs from avi ? The lofted ribs wont be a problem because they dont have the bent flanges.

Tim

[Rob]

I am a little confused on what you are asking. Are you asking about the 45 on the rudder and elevator ribs? I bent everything in box brake. Really not an issue. Here is a sample piece I did awhile back for another project. Bend radius is a little off because didn’t take the time to adjust set back. But you get the idea. Bent sides up into a U channel. Put edges back in and bent the 45. No form blocks are needed for these ribs.

[geraldmorrissey]

Can you get down to 1/2" wide on the narrow end?

[sjt]

Rob,
On one of the drawings it lays out the option of using 025 4130 instead of 032 1018.

Which one did you use?
stan

[Rob]

*** 1018 .032 ***

[sjt]

I think Tim is building a patrol. The patrol rib was always different then the original 4 place.
If I am not mistaken, all bearhawks now have profiled tail feathers.
The original 4 place was a pure rectangle.

It might be a good idea to bend an 045 exactly as the above pictures - and then add the airfoil curve.

[sjt]

Also, it occurs to me that the section AA on Bob's drawing was an artifact of the original rectangular profile tail feather.


______
/




\____ _|


maybe Bob would allow the 45 lip to be omitted on the updated tail feather design that is an airfoil shape.



The 45 seems like something that would help resist a torsional twist in the long direction. That would not be my first guess as the loads it would experience.

There is a T5 4130 tube welded internal to the control surface that would prevent a twist along the long direction anyway.