Straightening VS Rib Flanges - Homemade bending tool

It appears that I neglected to include some pics of a homemade rib flange bending tool that I built for the purpose of straightening the rib flanges so that they are 90 degrees perpendicular to the web. this is important because the skins must lay on the rib and spar surfaces to create a smooth, laminar surface for the air to flow over. If the flanges are not aligned correctly, the part will contain rises and valleys in the skin. This will negatively affect the ability of the air to flow smoothly over the surface, increasing drag, and, in the worst cases, causing undesired flight control problems.

There are several posts on VAF that describe how to build this simple tool. I basically made mine with a large enough particle board base to accomodate the wing ribs that I will hopefully be working on about a month from now. The rib shown in the pic is the bottom main rib of the VS. A 2x4 and 2x2 are cut to size, and attached with a hinge. The most important part of the tool is the 11 degree angle that was cut in the 2x4, and the clearance angle at the bottom of the 2x2 handle to allow for the bulge of the rib web stiffener holes. Most builders have found that this "over" bent angle actually sets the angle of the rib flange to the correct 90 degree angle, due to the spring back affect of the metal. You need to raise the bending handle up just enough before attaching the hinge to allow for the thickness of the web on each rib to keep from deforming or scratching the aluminum when the bend is made.

To operate it, you basically place the rib in between the bend handle and the 2x4 as shown, apply a fair amount of forward pressure on the handle for a second or two, and then move the part another two inches to perform the bend of the next section of the flange. When done, you check the angle of the flange with a straight edge to ensure it is 90 degrees to the web, and make minor corrections by hand as necessary. It does not work for curved surfaces very well, so you have to be careful not to change those. That said, most of the rib flange can be straighted using this method. I applied some electrical tape to the bottom of the handle and to the surfaces of the 2x4 that actually touch the metal, to help prevent any scuffing or scarring of the alclad aluminum.

The tricky part about using this tool is that the amount of force required to complete the bend depends a lot on where you grip the handle, and the length of time that the force is applied. It is possible to "over" bend the flange by applying too much force. A little practice is all it takes to get the hang of it. The other option is to pound on the flanges with a rubber mallet. This is very hard on the hands, and it takes a long time to do each rib flange. The bending tool works so much easier and faster, so it is well worth the small amount of time it takes to make this tool.