CHAPTER 35 - Building the Forward Structure
With the firewall and F604 bulkheads clamped in place relative to each other, I began by clamping the F6101s in place, using a piece of angle stock to make sure the lower longeron would be flush with the bottom of F604. (Ok, time out! The fuselage is built upside down. Lower = up in the photos. And left is right. Clear? Good, because it kept me visualizing the fuselage inverted - right side up - through the whole process to keep from screwing things up.) Then I measured the firewall to spar distance before trimming the longeron stock to fit. Then I measured it again while I clamped it in place. (As George said in his video, do one side then the other - but I cut and fitted both longerons at the same time.) After measuring - oh, I don't know, maybe a dozen - more times, I finally took a deep breath and drilled the longerons to the weldments and the F6101s and the F6101s to F604. I also drilled the F604Fs to the main longerons. Now that I was through working in that close area, I fabricated the clamps to hold the longerons to the jig and clamped everything in place. I had already shimmed and centered the F604 but had been relying on it's weight and lots of measuring to keep it from shifting.
Next I began the job of fitting all the other parts. The second photo shows the nearly completed left side. I have only to drill the main longerons to the firewall weldment and the F684 gusset to the firewall.I fabricated the stringers before tackling the F602 bulkheads. During this process, I found that the small clamps I had used to put the firewall in the jig were just getting in my way, so I purchased some deep clamps, which you can see in the third photo. When I had been cutting lightening holes in my flap spars and braces, I saved the cutouts. You can see them employed here to keep the clamps from marring the weldment coating.
The F602 should have been pretty easy, but I measured the flange cutaway using the whole width of the longeron angle, leaving 1/4" gaps at top and bottom instead of the 1/8" I had intended. Fortunately, I only did this on one side, so I worked on the other while I waited for Van's to send me a replacement. I also attempted to cut the slots using a rotary rasp in a die grinder. This did not produce the results I had hoped for, so I also did a bit of work with small files cleaning up the notches. Speaking of notches, I was not happy with the way the F684s fit behind the weldments. I didn't find anything in the plans about this, but the part would not fit so that it's forward edge would be near enough to the firewall for comfortable edge distance. My solution was to notch the upper end, as you can see in the 4th and 5th photos.
With the arrival of the replacement F602, it was an easy matter to cut it to fit and attach it in place. The last photo shows the completed installation. The arrow points to a piece of masking tape that was used to hold the spacer that goes between the F602 and F6101 so that the F602 flange will be flush with the longerons. The only thing that remained was to use the landing gear weldments to mark the cutouts on the lower longerons for the main gear. Once marked, they were cut using the die grinder, and finished on a bench grinder and scotchbrite wheel.
During this time, the F605 parts came back from the painter and I lost no time in assembling it and riveting it together. Big Mistake! Fortunately, I had the foresight not to rivet the F605F and F605G to the assembly, but I did put rivets where the outboard seat ribs would have to go as well as the F626 (I was thinking that the seat and baggage ribs would all match up, for some reason). Another error was to reveal itself, but I'll tell you about that in the next chapter.