Scott & Tanya Card RV9A build log (N4822C)

It took me half of another day to finish up the second longeron. More of the same. Yes, the second one went a little faster, no surprise. None the less, I was able to hang them both up, out of the way and completed, after another three or four hours of work.

The F-721 aft canopy decks that are match drilled to the longerons require some very specific trimming (modification) depending on which canopy type you are building. The sections to be removed are clearly described on the plans so I marked those up and cut them out mostly on the band saw.

When I cut the longerons to length, I also cut the four j-stringers that go in the aft fuselage. Now it was time to prep the ends so they fit to the bulkheads. The instructions only explicitly tell you to trim one end of one set of stringers. You find out later, after clecoing much of the rear fuselage together that most ends of most stringers need to be trimmed. So here is where we see something that actually looks like an airplane fuselage come together. This was a very exciting (and easy) step putting something big together.

 

  

  

  

  

 

I did what seems like a pretty normal two hour battle with the very aft tail cone section just to get the last two bulkheads clecoed into place. This took lots of prying, adjusting, and patience. After that pain in the butt, I figured I was properly warmed up to attack the task of bending the longerons! This is a much talked about step that many of us are apprehensive about. I’m one to jump in and figure it out, if only for the “character building” experience. The trick with the longerons are that they have to be right the first time, take lots of patience and time to get right, and will have to be replaced at great (shipping) cost if something goes terribly wrong in the care department… Oh, but wait, don’t most of those things apply to every step of this project? So what is the big deal, lets bend some longerons…

I started by moving my bench vice to a table more in the center of the garage. The longerons are made out of 1/8″ aluminum angle that is almost 15 feet long. I made the length measurement and final length cut with my new cutoff saw and cleaned up the ends. On my other bench, I clamped up some blocks and a long 1×2 to act as a very wide support for the long end away from the vice. This was super useful. It made it very easy to deal with the length of the angle. The first shallow bend is what forms the left and right sides of the main cabin. The bend progress is compared to a full size template on one of the plan sheets. I just taped that sheet to the bench top right by the vice for quick comparison of the longeron along the way. The instructions say “Aluminum angle can do maddening things when you try to bend it.” They aren’t kidding, but you eventually get it figured out. The deal is that when you whack it with a hammer in one axis, it also wants to bend a bit in the other axis.

Alright, so you clamp the angle in the vice, apply some preload force, and whack it with a dead blow hammer, move the angle about 1″ and repeat a gazillion times. Make sure you wear some thick gloves for this. My hands hurt and are swollen after a day and a half of this. Eventually, you get the angle to match the outline on the plans. Then a part is match drilled to the longeron. After that, a sharp single downward bend is applied to each longeron where it descends forward of the cabin toward the firewall. I used a length of very straight (select) 1×2 as a gauge for longeron straightness and bend offset. This worked well, way better than a 4′ rule.

After the sharp downward bend is in place, we’re on the home stretch applying a twist in the forward section. This is kind of funky as you clamp the longeron in the vice at station ?? and grab it with a large adjustable wrench and twist until you have imparted a 17 degree twist in that section. After much tweaking, tuning, banging, testing, aching, cursing, whacking, and twisting, they are done. Tanya’s comment was “Those things sure look wonga!”. Yep, aren’t they pretty. Just another right of passage.

 

  

  

  

  

  

  

  

  

  

  

  

 

I spent a few evenings during the week constructing some very sturdy saw horses. I got this idea from looking at the saw horses that Walter used. I have sufficient experience with the standard 2×4 saw horse to know that I didn’t want to be building on them for the better part of a year. The ones that Walter used are made by a small company on the west coast that only distributes them out there. I couldn’t find them anywhere in Texas. So, I accepted the welcomed distraction to produce my own clone of their design. Here is a PDF of what I produced.

The cross members are made from 2×6 boards, the legs are from 1×8 boards (something other than white pine would be much better if you can find it), and the end gussets are from 1/8″ luan ply. I made jigs for most of the cuts and drilling of screws. They turned out super strong and steady. All parts were glued for rigidity. These were very simple to build, and lots of fun! I made three different widths all 24″ tall. I even made enough extra parts so I can put together another one if I find the need later.

 

  

  

  

  

  

  

 

This is a BIG batch of parts that I have ready for primer. I spend most of the evening on Saturday washing parts in prep for primer on Sunday. It started getting late and I kept finding more piles of parts that were ready to be washed and primed. I ended up washing parts until after 11pm (way past my bedtime). Oh, yeah, Tanya helped too for a while (she went to bed). I think she may have felt sorry for me. So with all the parts washed and dried overnight, it began raining Sunday morning. This isn’t exactly ideal for priming, but oh well. Knowing that it was going to take a good while to prime all these parts, Tanya and I rolled out pretty early and got to it. With both of us doing our part, I shot primer and Tanya arranged parts on the trays and moved them in and out of the booth, I was in the monkey suit for about three hours. Not too bad, but I was definitely ready to be done. I have included a picture of how I store all of the hose and masks for the forced air breathing system.

Later in the day, with everything cleaned up and the parts dry enough to work with, I started assembly. This is the fun part. It basically amounted to sitting down with the rivet squeezer and the pile of parts and riveting everything together. I had completed all of the sub-assemblies by the end of the day. After a couple of weeks of work, it all goes together in half of a day.

You may notice that I have adjusted the priming process for the fuselage. We are no longer acid etching and Alodining all parts. All parts get a quick wipe with MEK to remove all stamp and layout ink, then they get scuffed with a scotchbrite pad, washed with soapy water, and primed.

 

  

  

  

  

  

  

  

  

  

  

  

 

Ok, where are we… Oh, yeah, bulkheads, bulkheads, bulkheads. I fabricated all of the parts and pieces that are made of various stock. I’ll admit that there was a fair amount of head scratching trying to figure out some of the assembly details, but no rocket science involved. I got a cheap little 6″ cutoff saw to cut the longer lengths of angle. It is a pretty aggressive little tool that seems to melt the metal just as much as it cuts it.

With all of the bulkhead parts roughly stuck together, I got out the bottom skin for some more pre-assembly and adjustments. There were two things that I wanted to get accomplished by putting things together with the bottom skin. First, it seems that every -7 and -9 kit that I have heard of has fit issues between the forward most bulkhead, the bottom bellcrank rib, and the bottom skin. The problem is that with all these parts put together, the holes in the bottom skin don’t match up with the bellcrank rib at all. This seems to be a clear kit issue that everybody encounters. My solution was to do some creative minor part reshaping. A little here, a little there, and the holes come into alignment. First I made a little jog in the lower (forward facing) bulkhead that essentially pushed it forward about 1/16″-3/32″. I used some wood blocks, clamps, and a mallet to accomplish this. I jigged it up very carefully so as to only effect the section above the flange and not get the whole thing all bent out of shape. I gave the doubler plate a little bend at the bottom to accommodate the new shape. I also made a small adjustment in the forward flange of the bellcrank rib. I pounded it down and over kind of in the direction of the arrow in the picture. I only moved it about 3/64″. Now all of the holes all line up! This adjustment sequence took about an hour an a half.

The second thing I wanted to accomplish with all the bulkheads arranged on the bottom skin was to try to roughly work on the flange alignments on each bulkhead. Usually most parts require the flanges to be adjusted to exactly 90 degrees. The bulkheads are different in that the skins are not perpendicular to the bulkheads, so the flanges have to be bent at an angle. I used a piece of aluminum angle as a long straight edge along all of the bulkheads to gauge the angle to bend the flanges to. I did this around each bulkhead. Also included in this process is a little fluting here and there. It took me about two hours of this to get the flanges roughly in shape. I know that they will have to be tweaked when it comes time to really aligning things with the skins, but at least it will be close.

While we have things setup, I thought I might as well prepare the bracket for the TruTrack autopilot pitch servo. Just a heads up for the next guy, the TruTrack drawing is incorrect (pictured) in the way that it depicts the flange on the bottom of the bellcrank rib. I just improvised and put a few more rivets in the bracket web.

Then it all gets taken apart for hole and edge deburring and scuffing for primer.