Longerons Match-Drilled

There's no turning back now. In the afternoon, after finishing Section 28 in the morning, I went back to the dreaded longeron bending. I had finished the left one before and now it was time to do the right one - this time with the help of the bending dies I had received a few days before. A first trial fit session where I used a piece of scrap cut off the longeron showed that the back die (the one without the cut out for the flange) was too tight. I filed it a bit wider and polished it with a SB pad to allow for easier removal of the angle after bending. I also added a marker on both dies that indicate the center line where the bend is being added for easier positioning with the markers on the flange of the longeron.


Here you see the dies in action. I was first worried that I wouldn't have that much control over the bend as with the mallet (well, 'control' is not a good word here) as I couldn't immediately verify the shape with the template while the longeron is in the vise. The dies make a direct positioning impossible and I had to remove the longeron after each bend to check if it turned out ok. I did this by clamping it into my second, smaller vise attached to the second work bench. Although this sounds awkward and slow, it turned out to be way superior over the mallet "method". And that is because I never had to go back to a previously bent spot. There's no vertical bend when using the dies. I checked it multiple times and there just wasn't anything to remove! I also developed a good feel for how much pressure was needed to accomplish a certain bend angle and so I hardly had to rebend a particular spot.
After the procedure the longeron looks pretty good. Not like it was salvaged from a shot down plane like the other one did. And it matched the template better than the mallet-treated one, too.


This was taken when doing the final template check. It took me 1.75 hours to bend the center area and the aft 4 degree angle, including the weight reduction cut. Boy, I so wish I had had those dies when doing the left longeron!
After a short break and a little victory dance I went back to the work bench to do the match-drilling - despite the fact that it was getting late. I just wanted to close this chapter for good (I hope I did and won't curse myself when installing those longerons!).
Before I drilled the first hole I triple checked the correct alignment of the canopy deck (formerly known as 'template') and making sure that the clamps would provide enough clamping power to hold the deck in place while drilling the first hole.


Using a drop of Boelube on every hole helped a lot to get this drilled in almost no time. Oh, and my beloved Sioux drill also contributed a lot to this. The parts where deburred and moved to the work bench that holds all the parts that will have to go surface prep and then get primed. It was quite late then but I am happy to have closed page 23-02.


Ignore the lumber in this picture. It just happens to be stored there as well and it has no connection to THIS plane whatsoever.