Like many builders, I really had no clue how I was going to make the formed control horns. Fortunately over the years I had gleaned enough information from other builders to be ready to give them a try.
My first attempt was to simply make two bends. In the following pictures you can see the bends making facets not a smooth curve.
Though it wasn't exactly like the plans I thought it turned out ok 
However, someone said they though I could do better. Well, who could turn down such a challenge.
My next attempts match the plans much better and wasn't that difficult. Like every thing on this plane it just takes time. Here is how I do it.
These are the tools I used 
they consist of two bending blocks, a 1/2-inch round bar, pen, bronze bar and
hammer (not pictured) to
form the metal. I use the bronze bar to form the metal because wood
splinters to easy and bronze is softer then steel so it doesn't leave a mark
when you pound on it.
After cutting out the horn I first drill the holes and make the cuts for the flanges that need to bend out. As you can see I didn't do so well at following my line on one corner. I fixed it by drilling the hole a little larger.
I then mark the location of the bends. I added a little bit of extra material in the leading edge to help get the curved shape. Maybe 1/16th of an inch.
I then bend the two flanges out.
Next I bend the leading edge. It needs to be bent around a large radius so I made a 1/4-inch radius on my bending block (ground on a grinder then smoothed with sandpaper).
Line up the bend line on the horn with the start of the radius on the block. In the picture you can see that I am above the line on the one end. I realized I had forgotten to to take this picture.
