Fittings. How fitting.

  Not much has happened on the Ace this year. The winter was long and spring has been very cold, so I spent a long time waiting for the garage to warm up. Now that there's a little heat down there I've been making some headway on the next step of my wing build: fittings. I copied the parts off the plans into CAD and then printed them onto cardstock to use as patterns when laying fittings out on the steel stock.

 

 First I tackled the brackets that will hold the pulleys for the aileron cables. I have a lot of extra material in case I had to remake these. The next step was to bend up my fittings. There is one fitting that mounts to the forward side of the strut which gets bent to a 90° angle. The fitting which mounts to the aft side of the spar gets bent at about an 85° angle. I forget the exact number, but don't feel like looking it up at the moment.

Next I cut out the aileron control horns. My Harbor Freight porta-band chucked into my vice works well for cutting these sorts of things. These get bent up at a 90° angle as well. They are a little weird, however because the flange which gets bent is slightly inset into the rest of the control horn. I managed to bend one of these up using a device called a "press brake." Mine is a small thing that slip onto the jaws of my vice. I managed to bend one control horn and get the other half-bent.

Unfortunately, the large vice I was using decided this was the time for an old repair to split and I had to take time off to braze the  thing back together. It looks almost as good as new, except for the chunk missing from the base on the right side.

With this repair done I was able to finish bending up the last control horn. Once again, unfortunately, the metal split along the corners of the bend. The cracks formed because 4130 steel has a grain to it. The piece of steel I had was only big enough to lay these fittings out in one orientation, but I didn't realize until later that this put the grain of the steel running along the bend when it should be running across the bend for better strength characteristics. These cracked corners are supposed to get welded after being bent, which might remove the cracks, but I would never trust the fitting. These will eventually be remade, but I'm going to finish the cracked ones anyway to practice for when I have to do the new ones. They will get the corners of the bend welded and a spacer welded onto both ends where cables will attach.

 

The next pieces of hardware I tackled were the drag-wire attach fittings and the jury strut brackets.

The drag wire brackets mount between the spars and are used to attach the drag wire fittings to the spars. The drag and anti-drag wires create a series of x-braces inside the wing to keep it from distorting under fore and aft loads. The fitting itself is pretty simple, a strip of steel with rounded ends, bent up at 30° with four holes drilled in it. The shape is rough cut on my bandsaw, shaped on the belt sander with an 80 grit belt, then finished with 220 grit sandpaper. 

The jury strut fittings are two pieces. One piece gets bent into a U-shape, the other is a tab which gets welded to the base of the U. The U will eventually get bolted to the spar and hold a jury strut. This smaller strut keeps the large struts from bending when under compression loads. Below is a picture of the finished fittings. Upper left are the aileron pulley brackets, upper right are jury strut fittings. One fully bent up, one partially bent, and the other two unbent until I can figure out a better way to try bending them. The first two were rather uncooperative. And, on the bottom right are the drag wire attach brackets.

 Last of all, I started in on the brackets which will hold the struts to the forward spar. Four 1/4" bolts clamp a pair of brackets to the spar. The strut will bolt in between the brackets at the remaining hole. Also in the final picture are my new Kant-twist clamps. They're very handy for holding together identical pieces for shaping and drilling.
More to come!