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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... |
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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). |
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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). |
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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. |
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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. |
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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). |
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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. |
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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). |
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This is self explanatory... |
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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). |
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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. |
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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. |
