Sat Jan 10 2009

Fitting gear weldments

In preparation for doing the final trimming for the gear leg hole in the forward bottom skin, I needed to do a good job of fitting the main gear weldments. I decided to continue working on the left one before moving on to the right weldment. In order to fit everything in I needed to remove the three platenuts on the top flange of the forward F-704 bulkhead. It's frustrating that Van's instructions tell you to put these on, but later you find out that they need to be removed. Grrr.

The bottom bolt which is being used to space the forward and aft F-704 bulkheads apart needed trimming. I masked the area off with a couple shop towels and used an abrasive cutting disc to trim it off. Those discs go through the studs like a hot knife through butter.

It turns out I needed to trim the top stud a little more, too.

I also had to remove the lower longeron.

With the weldment fitted into place it was obvious that one of the flanges needed a divot trimmed out of it to clear the rivet head which is currently being overlapped.

I marked the location using the other rows of holes as a guide...

...and used a carbide burr in my die grinder to file the clearance.

That worked pretty well, but with the weldment back in position, I could see that all the holes needed to be elongated somewhat. They are just barely interfereing with the rivet heads. It seems odd to me that these wouldn't be in the correct position...after all, they're in the same piece of metal as the top main bolt holes and those bolts go in just fine. It seems like Van's CNC punch program must be somewhat in error.

So I marked out all the holes and elongated them by about 3/64 inch.

The clearance looks good around all these rivets now.

Once the weldment was in position, I could see that the flange which connects to the aux longeron is welded at the wrong angle. The bottom of this flange needs to be pulled in about 1/8 inch. It's actually pushing the F-7101 web outward somewhat. I'll have to call Van's to check on this.