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Installed Landng Gear Weldments – 4 hrs

November 17, 2011 Leave a comment

Thursday Nov 17, 2011

This post summarizes the results of several short work sessions over the last three days concluding with a two hour session tonight.

Well it’s time to install the landing gear weldments. I did quite a bit of work to fit these months ago before the forward bottom skin was riveted in place. I thought that would make the final installation quick and easy. Not so. The first thing I found was that the weldments would not even slip into place because the flanges interfered with the outboard nutplates on the top flange of the main spar. So I had to drill out the nutplate on each side.

Then I found that the left weldment would not slide up flush against the spar on the outboard edge. After searching a while I found the weldment was bumping up against a rivet in the F-7101 gear attach web plate. You can see the rivet up in the corner near where the weldment tube ends. This did not happen before because that rivet was not there when I initially fit the weldment to the spar. This photo was taken after I used my rotary tool to grind off about 1/8 inch of the weldment in that local spot.

Then when the weldment seemed to fit right I started putting in the bolts and nuts. That’s when I found that the bolts are not long enough. The ends of the bolts are barely flush with the ends of the nuts instead of one or two full threads protruding. You can see one of the nuts on the right side in this photo below. The nuts on the aft side with torque stripes are a good comparison.

So back to the posts on the builder forum I went and quickly found that this is a known problem. The drawing calls out AN4-12A bolts but you need AN4-13A to get adequate nut engagement. Fortunately I found a set of 12 AN4-13A bolts in the kit also so I used those. I don’t know if the longer bolts are needed elsewhere or if Vans put these in the kit knowing the 12A’s are too short. I can get another set to replace them later if necessary. Dear Vans – please correct the drawing! How tough would that be? Once I put the 13A’s in and tightened everything up, the engagement looked good.

Here is a view of the left (pilot’s side) weldment with all the bolts in and snug. I still need to go around and torque them all and add torque striping.

The right side weldment was basically the same story. The same gear attach web rivet interfered with the weldment and I ground a little bit off to make it fit. By the way, I put a bit of touch-up primer on the bare steel before I did the final installation of the weldments. Here is a view of the right weldment installed. I’m glad this is done.

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Categories: Cabin Area, Fuselage