June 6, 2010

The Vertical Stabilizer - and the Rudder - 7.5 Hrs.

After all the work on the HS, I have really been looking forward to getting the vertical stabilizer and the rudder mounted to complete the empennage fitting.

The plans have you start by cutting 5/8" off the front spar of the VS. Now why on earth Vans didn't just make this part the correct length, or at least have you do it before riveting it all together, is beyond me. There's no way to slide this through the band saw. Cutting disks work, but it's a hassle working with that tool. I ended up just using my good ol' hack saw, slowly but surely cutting through.

Once deburred and cleaned up, it's ready to go.

You put the VS in place and clamp it to the aft end. Wow. Looks cool!

The plans also have you clamp this bracket plate in place on the front spar of the HS. It's not on too tight for now, because you have to measure and fit everything. At this point, I started measuring. I spent a lot of time on this. You measure from the top of the VS to the end of the HS on both sides to triangulate and make sure it's the same, to insure that the VS is perpendicular to the HS. I must have clamped and unclamped it dozens of times. Then, depending on how things work out, the bracket plate can go either on the forward side or aft side of the VS front spar, and you may even use a shim plate if necessary. Turned out, I didn't need one. Then you drill the aft spar of the VS to the end of the fuselage first. Enlarge the holes. Then, before you bolt it temporarily in place, you superglue a washer on the left side. This is supposed to offset the VS by 1/4" at the leading edge. I wanted something more accurate to make sure I had it right.

I put a piece of masking tape on the aft end of the top skin, marked with the centerline and the 1/4" offset. Another piece of tape on the leading edge of the VS marked in the center made it easy to see. I could insert my thin ruler in here to make sure the lines on both sides of the ruler were lined up on the 1/4" mark. This way I was able to nail it.

The height of the front of the VS is measured on the back end with a straightedge, to make sure all the hinge brackets line up in a straight line. It's amazing how sensitive it is to small movements. They change everything. So it just takes a lot of time to get everything in place, all the measurements correct, the offset just right, and the back end hinge brackets straight. Once everything is accurately clamped in place, I double-checked the 1/4" offset and the vertical alignment of the hinge brackets for the rudder. Also checked the triangulation on both sides to make sure it's still perpendicular to the HS, one more time. Then you can finally start drilling things together.

It's time to drill the bracket plate. I laid down some paper to keep shavings from falling into the fuselage. The top row of holes can't be reached at this angle. Later, when the VS was removed for deburring and riveting, I clecoed the plate onto the back side of the spar and drilled them from the rear.

Now, finally, it was time to drill the 4 holes at the bottom of the rear spar. I scratched my head for quite a while on this, trying to figure out just where to drill the holes. The drawings just show them in place, but no dimensions are given. Every other hole I've seen on the plans has dimensions so you can measure to a point where a hole gets drilled. Not here. Well, I finally figured it out. Boy, am I glad I took my time and didn't just drill something somewhere. Here's where time spent studying drawings pays off. Way back when I put the F-712 aftmost bulkhead together, seen here, I fabricated and riveted the tie-down block in place that holds the aft tie-down ring in place. It's on the forward side of this bulkhead where you really can't see it. You can barely see the lower end of it through the hole at the bottom of the bulkhead here. Well, four rivet holes were left empty, which are the pilot holes through this block. Yay! No measuring needed. Now if I can just figure out how I'm going to back-drill them from inside this tiny compartment.

UPDATE: June 4, 2011 Well, it's hard to believe it's been a year since I put this page together. A sharp-eyed friend of mine, Ed Lynn, noticed something wrong in the picture above. QUICK... before reading any further... can you look at the picture above and tell me what's wrong? Well... as it turns out, there are two rivets missing from the lower white bracket that holds the rudder bearing. I can't believe I missed this! All I can think is, it's been 4 years since I riveted the empennage parts together, and I was such a newbie at that time. The drawings are clear if you read them carefully. These holes aren't pre-drilled because for a taildragger RV-7 there are a couple of bolts that go through this bracket instead of two more rivets. Anyway, here's a picture taken tonight after carefully drilling those holes, countersinking and deburring, and squeezing the rivets in. Lessons learned: 1. Study the plans more thoroughly! 2. You can't have too many eyes looking over your project. 3. Don't get offended or embarrassed when someone calls you on something like this. You can't have too many really good friends, and this is what friends are for! I told Ed I'm gonna have to get him over here to look over the rest of my project and see what else is missing. Thanks, Ed!

And with that said... the story continues...

Once again, my right-angle drill comes to the rescue. A #30 bit is used and it's a tight fit, but once I got the drill down in there, it was easy. There's no other way to drill these holes. Once these pilot holes were drilled through from in here, enlarging the holes to full size can be done from the back end. I gradually enlarged them and used my #12 reamer to enlarge the holes to final size.

Next, I unclamped and pulled the VS off for deburring and cleanup of all the drilling mess. Every hole was deburred. Now it was time to rivet the attach bracket plate to the front spar of the VS. All the rivets were easily reached with the squeezer. Then you can put it all back together and bolt it in place!

Seen above, the rivets on the attach bracket plate. Four bolts through the front spar of the HS hold it in solidly in place so the rudder can finally be put on.

Wow!!! How cool is this! It's amazing how the rudder doubles the size of the tail. It's so tight in here in my shop that I have to move the rudder to slip around it to get to the other side. The rudder swings perfectly smoothly. I took a few minutes and bolted on the elevator pushrod. It's exciting to go to the front, grab the control stick, and move the elevators up and down. Neato!

The only downer to this whole day was this part. Way back when I built the empennage, I went to work on the fiberglass parts while I was waiting on the wing kit. I thought it would pay off later to have all this work done. I was naive enough to assume that the parts, as they come from Vans, were sized just right. Was I ever wrong. As you can see above, the bottom of the rudder sticks down below the bottom of the fuselage by more than an inch. This is completely unacceptable and it will all have to be re-done. So that was totally wasted time. I guess I can just chalk it up to a learning experience. Fortunately, I believe I can salvage the part and trim it to fit right and not have to buy a new one. Boy, am I glad I didn't rivet this piece onto the bottom of the rudder. I'll get to this later.

Here's a final shot from another angle. I had to sit back and just stare at it all for a little while. These empenage parts have been waiting for 3 years to join up with the fuselage, and sometimes you just have to take a breath and savor the moment. It sure looks like an airplane, doesn't it?

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