Completion of Cowling Fabrication

The cowling is finally all fabricated.  Many hours went into this.  Fortunately, much of it was original and useable, some was fabricated back in the '60's and done fairly well.  The rest I had to make.

The side panels were the last I had to complete and a lot went into these.  Thought I would take you step-by-step through the fabrication...




Previous posts showed the original, although un-useable side panels, and the templates I made from cardboard.

The template was traced on to the piece of aluminum.  I used .040"  3003-H14.  This half-hard alloy is very formable and easy to work with.

A very common way to strengthen the edge of a piece of sheet metal is to hem or fold over the edge.  Lincoln-Page used this a lot on most of the metal panels.  This is easily done.  Here you can see the forming die I made from a piece of plywood.  It is used to hem the opening of the access door.

Clamp the metal over the die and bend the edges down 90 degrees with various hammers.  I use the tear-drop shaped hammer in the curved corners.

The metal panel can then be flipped upside down and the edge beat over so it has a nice 180 degree fold around the perimeter.  This increases the strength of the opening considerably and removes the sharp edges. The half-hard 3003 alloy goes around the corners nice without cracking.  The larger projections on each side are where the hinge and latch go.

Here you can see the finished opening from the outside.

Long, straight edges can be done on a brake, or like I did here with a couple pieces of angle iron or even the edge of a bench.  Again, just clamp the metal tightly, bend it over 90 degrees (I like to use a soft, rubber dead-blow hammer).  Remove the panel, flip it over and fold it over the rest of the 180 degrees, slowly and carefully beating it over with a hammer.  I'll use a crown-faced body hammer for this.

Next step was bead rolling.  I didn't show how to do it.  Of-course, you need to have some sort of bead roller.  The process is pretty easy.  Probably the more difficult part is keeping everything straight and the curves consistent.  Drawing lines on the metal where you want the beading to go helps a lot.

Then it was time for louvers.  I showed in the last post how to make these.  Clamping the metal securely is important.  Here you can also see the brass piano hinge riveted on in the top of the photo.

And here it is - mostly complete.

 I had to make doors also.  They have a hemmed edge as well and made the same way.  A small brass piano hinge holds them on.

This access panel is meant to be easily opened during engine starting to "tickle the float" of the carburetor.  This floods the carburetor to allow fuel to be drawn into the induction system as the prop is being turned over.

The latch that holds the cover closed is shown here.  This is pretty cool...the original is shown on the upper right.  A brand new latch and bezel shown below.  They look like they could have been made from the same tooling!  These types of latches are commonly used today as women's purse latches.

The only part left to finish were some inside reinforcements that were originally installed:  A couple of angles on each side of the louvers and a triangular shaped hat-channel near the exhaust opening.

Then it was time to install and check fit.  Trimming was required to make sure the panel lines all lined up correctly.  Also, the locations of the mounting studs had to be determined.

This is one of the rear studs.  These were all just temporarily installed to determine where the cross hole had to be drilled for the hair-pin clip.  Then, they were  removed for nickel plating.

All that was left were the latches for the upper doors.  It uses a spring-like arrangement as shown here.  This allows the doors to be easily opened for lubricating the rockers and valves prior to each flight.

The original latches were rather haphazardly installed.  Plus, I wanted them oriented a little different for a better hold-down.  This meant some holes had to be plugged.

Here is an easy way to plug holes in aluminum (or any metal for that matter) if you know how to TIG weld or gas weld aluminum.  This is nothing I invented, but learned this years ago...clamp a piece of copper to the back side.  The aluminum welding rod will not stick to the copper and it has a higher melting point than aluminum.  This helps to keep the hole from getting bigger as you weld it closed and makes for a neat, easy to grind weld.

 I like using 1100 aluminum welding rod for this.  This makes for a more ductile weld that can be ground, then planished or English wheeled for a smooth finish without worry of cracking.






Of course, this was only one side!  I then had to repeat all the above on the other side.  Making something the second time though always goes much quicker.  

So now, there is still a lot of work to do on these.  I have to make some minor repairs to the original panels then do all the "body work" i.e., smooth out all the dents and wrinkles.  I really don't like using body filler so it will all be smoothed out with the English wheel and hammer/dolly.  Then, into the paint booth for primer and paint. 

I have a week off for spring break soon, so I am going to get the last wing painted then work on getting all the metal panels completely finished.  Check back in a couple weeks!