Cut the slots in the longerons. I used the aft deck as a template, marked the slots, drilled a hole at the end of the slot, and then cut the slot slightly undersized with a die grinder and cut-off wheel. This is the first time I’ve actually used the cut off wheel, and it worked pretty well. From there I filed the slot until it was the correct width and location.
I almost forgot that I also trimmed the aft end of the longerons and made the little cut out on each. I drilled a 1/4″ hole at the corner of the cut out and then trimmed the rest with a hack saw. A little clean up with a Vixen file, and it looks great. I normally cut everything on the band saw and clean up with the belt sander or Scotch-brite wheel, but the longerons are just too much hassle to maneuver around the garage. It’s much easier to just use hand tools for this little task.
Of course putting in the downward bend and twist on the second longeron took all of 20 minutes. I bet the guy that does the longeron bending for the quickbuilds can crank out a complete set in under an hour.
I also did a little tweaking of the twist in the area of the curve. It seems that doing the curve added a twist, so I took that back out with a Crescent wrench.
I consider the longerons ready for assembly.
Drilled the aft canopy deck to the other longeron and then started the sharp downward bend. The bend isn’t too difficult, but definitely takes some serious downward pressure and hammering. I kept watching the other dimension to make sure it wasn’t bending side to side. I got out the side skin as suggested in the instructions and checked the bend against that. I ended up needing slightly more than 2-3/4″ downward deflection, at least the way I was measuring it. After getting the bend to match the side skin, I started the twist with a Crescent wrench. Again, this was not difficult, but took significant force and several iterations. Using the Smart Level, I verified that I had a 17 degree angle at the end compared to the straight section. After twisting, I ended up with a slight inward bend. I just reefed it back outward by hand, checked the other dimensions again, and decided it was a done deal.
The most time consuming part was finding enough room to lay out the side skin and position the longeron over it. I sure wish I had a 3-car garage… and no cars.
I took another look at the first longeron, and it looks good. On to the other one. I flipped the template over and traced the outline through to the back side with a pen. The second one took about 1/2 hour to get the curve looking good. I spent about 4 hours on the first one, so it’s true what they say. The second one goes much easier. I did a little more tweaking to get the curve nicely lined up with the aft canopy deck.
Adele was nice enough to take some picture (albiet blurry ones) of the process. Here I am holding the angle down and whacking it. You can see that I have the template laid out below the vise, so I can easily take it out and check my progress.
Here I am comparing it against the template.
After the curve was just right, I clamped some 0.032″ to the outside of the longeron and then clamped on the deck, getting everything lined up just perfectly. It really turned out great, within 1/32″.
I then drilled the deck to the longeron.
It feels really good to make progress on these longerons that I was so worried about.
The whimpy vise I’ve owned for almost 15 years is just not cutting it anymore. I went by Sears today and picked up a real he-man vise. I tossed aside the old vise and installed the new one in it’s place. Man was that a good move. It made the longeron bending much easier and more predictable. The new vise is 3 times bigger, and doesn’t turn when you whack on it. Despite what this picture shows, I ended up removing those cool yellow plastic cushions. They were absorbing too much of the hammer blow. I ended up just putting a rag in there to protect the soft aluminum angle from the vise teeth.
Another change I decided to make was to use the template on the plans. I cut it out and taped it to a relatively straight board. I did several iterations of tweaking on the right longeron to the point where it follows the template well within 1/16″ and lays flat in the horizontal direction. It’s looking great. There is a slight twist between the 38″ and 69″ stations, so I might work on that a little bit more.
I also discovered why I thought the aft canopy deck wasn’t matching the template. The front end of the deck should be at the 28″ mark, not the 38″ mark. I’m really glad I discovered that error before I messed anything up. Once I figured that out, everything started making more sense.
After tonight’s success on the first longeron, I’m feeling more confident about the process and actually looking forward to working on the other one.
Pulled out the longerons again. When the fuselage gets riveted together (no progress on that this weekend), that will be the next thing I need. I carefully measured and cut off both longerons and laid out the marks for the bends. Following the instructions I labeled front/aft, top/side on each end so I wouldn’t get confused while bending.
I made my first attempt at doing the shallow curve on the right longeron. On the first pass I wasn’t wacking it hard enough, so not much happened. On the second pass, I compared my progress more often with the aft canopy deck. That helped gauge better whether I was hitting it hard enough or not. I think it was Matthew that suggested just using the aft canopy decks as a template. The template on the plans isn’t quite the right shape (actually it is–see my 12/6/2004 entry). It definitely takes some patience working on the bends, which I was starting to run short on–mostly because my piece-of-junk vise was acting up. A good place to stop. I got the curve fairly close, but it needs a little more work. And I got the vise problem figured out.
Between a million other activities today, I didn’t have much time for the plane. I started thinking about how to bend the longerons and decided the vise mounted on my workbench wasn’t going to work. My bench is hemmed in on one side by a wall and the other side by the freezer. I moved the vise to my portable tool cart. The cart is very sturdy despite that it’s on wheels. This will give me flexibility to do the longeron work anywhere–even in the driveway.
I wasn’t too productive. I mainly read over the longeron bending instructions and made some measurements. I need to get the hard top for Julie’s car out of the garage before I can do any work with the longerons. Plus, I’m not sure what the point is of bending the longerons now. They’ll just take up more space, and I don’t think I need them for at least a few more weeks.
I did some measuring and trimming on the aft canopy deck parts. Different trimming is required for a tip-up vs. a sliding canopy. I noticed from the plans, that it’s better to do some of the trimming later, after back-drilling to the longeron.
With all of the bulkhead stuff done or waiting for priming, it was time to move onto the longerons. I pulled them down from storage and started reading through the instructions.