Curtiss Jenny Restoration

Welcome! We hope you enjoy following the restoration process of a 1918 Curtiss JN4D Jenny. Once completed, the aeroplane will be flown and displayed at the Candler Field Museum in Williamson GA (30 miles south of Atlanta). You can contact me below by clicking on "VIEW MY PROFILE"

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Location: Peachtree City, Georgia, United States

Wednesday, November 16, 2011

Burnishing

I wanted to try a few things today. We are planning on burnishing the cowl like they did back in the 1920's. They used a wire wheel to burnish back then, but I used a 2 inch Riloc pad - basically a round scotch brite pad!

I practiced a few times with a drill press while I was visiting David Harwell at Barnstormers Workshop. This worked really well, but I got to thinking - How will I be able to burnish deep into the cowl? The throat of the drill press is only a few inches deep.

So, I tried burnishing by hand. That way I could make the neat little swirls anywhere I wanted. Much as I tried to hold the drill still, the pad wandered. The swirls looked awful. Oh, well. So much for that theory.

Paul Dougherty made a really pretty burnished cowl on the Golden Age Air Museum's Winstead. I always admired the cowl, so I called Paul and he told me how he did it.



Basically, you make a 2 inch hole in a thin piece of plywood. This keeps the pad from wandering.



Then, you just move the hole down the line and burnish with a portable drill. I clamped a wooden guide to keep everything straight (like Paul told me to do). This worked really well.

The Jenny cowl has lots of louvers and beads. Before you can do any of that, the flat cowl must be fully burnished. Using the practice piece, I experimented making the 3/16 in. radius bead using an Eastwood bead roller. It worked very well. The beads were 3/23 in high just like the Curtiss drawings specified.



On a more productive note, the first side cowl was trimmed today.



I couldn't resist hanging up the test piece!



Anyway, the perimeter of the side cowl was cut to match the lower longeron.



Here is what the cut out looks like at the lower wing attach point. More hand filing will be done later.



More soon

Brian

2 Comments:

Blogger ben said...

What is or was the purpose of burnishing?

3:25 PM  
Blogger Brian Karli said...

Hi Ben,

The purpose of the burnishing was to hide the machine marks in the sheet metal. Imagine a curved cowl - there would be many stretch marks from the shot bag and hammer used to form the bump. The swirls were a quick and easy way to hide those marks.

Cheers

brian

8:07 PM  

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