Sun Mar 14 2010

Fitting landing gear weldments

After picking Kody up, we worked on getting the landing gear weldments installed. I thought this was going to be a piece-o-cake since I had this weldment fitted previous to riveting the fuselage together. Well, it didn't take long to expose the first problem. The aft end of the outboard floor stiffeners prevented this flange from sliding into position. Hrm...this is gonna suck. Had I realized this before installing the stiffener it would have been a five minute job to file some clearance, but now that their installed, the access really sucks.

After using a die grinder to cut a slot, breaking out the tab with needle nose pliers, and filing a radius on the bottom with a hacked-off piece of a chainsaw file, the flange fits. I'm not really happy with the job...maybe I'll do some more work on it later.

Last item before dropping Kody off was to drill this 5/8 inch hole on each side of the fuselage to allow passage for the brake line bulkhead fitting.

After returning home, I did some more work on the trimmed areas of both stiffeners. It took about an hour and a half of filing in cramped quarters while leaning over the edges of the fuselage, but the clearance notch now looks much better.

Thinking that I should be problem free at this point, I positioned the weldment and went to install the first bolt, the AN4-23A. Wouldn't ya know it...the bolt goes through one half of the bulkhead, but not the other half. It appears to have been drilled for an AN3 rather than an AN4.

Sure enough here's the note I missed to drill 1/4 for spacer bolt. Gah! Out comes the drill and...

...a few minutes later the holes are drilled and spacers and bolts inserted.

After inserting a bunch of AN4-12A bolts through the weldment and the forward half of the F-704 bulkhead, I noticed that the exposed thread portion seems rather short. Sure enough, holding the required nut and washer up next to it shows there won't be the required 1 thread (minimum) sticking past the nut.

Sooooo...out come all the AN4-12A's and in go a bunch of AN4-13A's. I wonder what part of the plane I'm stealing the -13A's from? Oh well I guess I'll find out. I'm starting to sense a pattern of incorrect hardware length callouts. Of course, maybe this has been fixed on the full size plans. I generally use the preview plans because of the more convenient size.

I thought getting the washer and nut on the bottom two bolts was going to be tricky, but a little tape on the end of my steel scale made installation a snap.

Same thing for getting the nut started.

Here's an area I was concerned about. It's where the weldment matches up to the F-7111 gusset plate. At the aft end there's about 1/32 inch gap. I decided to just try tightening the bolts down to see of it pulls in.

Yup. Looks good. These bolts are all torqued, but I haven't marked them with torque seal yet. I had to torque most of them from the outside (turning the bolt) due to limited access around the weldment.

Last item for the night was to install and torque these two screws which attach the forward arm of the weldment to the lower longeron. I really like they way this skin fits with dimples. You may recall that the plans normally call for these holes to be machine countersunk, but with careful planning, I was able to drill then dimple the skins before assembly. The interlocking nature of a dimple fitting into a machine countersink should be stronger than the machine countersink the plans called for.