Manufacturing Ribs

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Horizontal Tail
Manufacturing Ribs
Spars Construction
Outboard Wings
Center Wing
Rear Fuselage
Forward Fuselage
Landing Gear
Instruments Panel
Fuel System
Subaru Engine


Being a scratch builder, I have to manufacture my own parts... nothing ready to assemble here.  I started the project with the rear wing ribs.  This decision was made for a couple of reasons:
It is low cost
It allows me to buy some tools without buying many different materials (only two sheets of 0.025 6061-T6 aluminum are required--Gear box ribs are made of 0.032")
It allowed me to familiarize with metal working (including using snips)
I like to see real airplane parts hanging in my workshop
Getting the right form
I was very fortunate to get already made form blocs from my mentor.  It saved me quite a bit of time and allowed me to start quickly working on the real thing.   This said, I verified that the form bloc for the rear ribs was accurately made.  For this, I used the coordinate table presented in the plans and drafted the points on a sheet.  I then verified the contour of the rib with my plotted coordinates. 

Everything was perfect (on the dot) except for two coordinates that were within 1 mm (and it could be because my dot was not perfectly positioned!).  I am amazed by the quality of that forming bloc...

While the wife is away
One thing was clear when my wife accepted that I would build an airplane... I don't bring any material, work, part, etc in the family room.  Well, I still had to cut that 12 foot sheet and my workspace in the garage is not ready....

For this, I drawn a 25mm line around the forming bloc and made a rough cut.  This is a great way to learn how to use the snips (I never worked with metal before).  If I would do it again, I would use the same sequence (wing ribs and then, tail group).

Making a master blank
After making the final cut, I filed it down to the line to have a very precise blank.  t is worth investing time here since I will be making 20 copies of this blank (see next step).
And copying it
Using a router, I made identical copies of my master blank.  This arrangement is like a sandwich where I have a small plywood at the bottom, then my master, then a plywood, then rough cut blanks, then a plywood (does this bring appetite?).

In about 10 minutes, I can make 4 identical blanks with a level of precision that I would not attain with snips.  I made a mistake on my last set of blanks while not being cautious enough.  The router lifted up a bit and it made a 1mm by 3cm grove in the four copies.

For this work, you need a straight router bit with a bearing at the bottom.  It costs about 25$ Canadian.

Pile of blanks rapidly cut, slowly smoothened
Smoothening the blanks is quite a tedious task.  Maybe I overdo it (at least, this is what Art Mitchell told me). 

One thing that I can say is that I really like the small deburring tool... it makes the task much faster.  For the double edge deburring tool, I got mixed feeling.  It does too much... the edge becomes sharp instead of just deburred.

Getting it out of the mold
I am missing a picture which would show the forming process.  This is achieved by positioning the rib blank between the forming blocs (there is a left and a right one) and by bending the flange using a dead bolt hammer.  When we take the rib (it is not longer a blank) out of the forming blocs, it looks like this (shaped like a banana).

I straightened it using fluting pliers (idea that I got from Chris' Zodiac Pages)

Making it lighter
The next step is to cut the lightening holes in the ribs.  I use a circle cutter mounted on my drill press.  While the builder manual suggest cutting only half the thickness from one side and then finish from the other side, I got better and faster results cutting directly from one side.

The holes then need to be smoothened carefully.

Don't put your finger in there!
Wooden dies are used to flange the holes.  I simply put the rib with dies in the press and operate the 6-ton jack. See my tool page for more details on the press.

I know that people use other methods, but I found it difficult to get rid of the "popping effect" in the rib with other method.  Because the metal is harder to bend in one direction than another one, it is difficult to get a uniform flange with other methods.  The result is a curvature in the rib and a popping effect when we push the middle of the rib (similar to those juice bottle caps).

This is self explanatory...
Let's go for the nose ribs (August 1999)
The process for making the nose ribs is essentially the same (so I will not repeat all the pictures).  One small difference is that it is much easier to make nice ribs if we start to make the flutes before and during the forming process.

I made four additional ribs (when compared with the plans).  Two of them are required because I am going with leading edge fuel tanks (there is an additional rib at station 170 of the outboard wing). The other ones are for a possible landing light.  I did not drill the forward lightening hole on four ribs (the ones potentially surrounding the landing light).

It's taking shape
It did not take too long do move from the state in the previous picture to the state on this picture.  It may be noticed that instead of building the ribs one by one to a final state, I perform each operation on the whole batch of ribs.... this is a trick that was well exploited by Henry Ford.  At this stage, I still have to make the lightening holes.
With the other ones...
In reality, I have a few more ribs than that on the wall... after I took the picture, I realized that my gear box ribs were not of the right material (0.025" instead of 0.032").  I had to make four additional gear box ribs.


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