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Joe Graham's Online RV-7 Builder's Log

The Empennage Begins

February 20-24, 2006

OK. The shop wasn't exactly organized yet, and the weather had decided to behave like it was actually winter. But I REALLY wanted to break out the tools and get to work. So, I donned a couple sweatshirts and headed out to brave the elements of the shop. My thermometer was barely breaking 50 degrees, but that was acceptable.

The first step in the RV-7 construction process is the assembly of the Horizontal Stabilizer Rear Spar Assembly. This begins by "breaking" the edges of the HS609PP Spar Doublers. So I go to my nice big box of parts... and I couldn't find the doublers... Just my luck. I didn't do the complete inventory of the box when I received it - I figured Vans has this stuff down by now - so now I have to go order the missing parts... But wait... What's this!!! The "bottom" of the box was really an extra piece of cardboard inside the box, and under that... the missing 609s! WHEW!


Photo by Joe Graham

The HS609s come from Van's pre-drilled (actually the holes are pre-punched; though under-sized so they can be final match-drilled to the proper rivet diameter) and properly shaped longitudinally. The plans call for the ends of the 609s to be rounded off. As you can see in this picture they are squared off to begin with.

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Photo by Joe Graham

OK, OK, so I have to find the files and the ScotchBrite cloth. But first, I wanted to see how they would actually fit before working on them. The HS603 Spar is formed by two identical channel halves which butt against each other in the middle. The 609 doublers overlap the channel butt joint and give the whole spar the necessary strength and rigidity. So I clecoed the doublers onto the channels. Look at how well the pre-drilled pilot holes line up in the pictures below. The doubler and channel holes line up so well, it looks like one hole... Gotta love that modern CNC technology.


Photo by Joe Graham


Photo by Joe Graham

I wanted the rounded ends to look good, so I used the end of my steel rule to draw a cut line. It turned out to be the exactly correct size to make a template. Here is a picture of one end after rough grinding.


Photo by Joe Graham

... Which reminds me. Here is a picture of the most invaluable tool for this step. The drill press with a ScotchBrite 7M finishing wheel. When I started tonight, I hadn't yet set it up. After working on the first HS609 with a file for about 20 minutes, I decided to stop and get the drill press setup. The time saved was well worth the momentary setup detour.


Photo by Joe Graham

And here is a picture of an important feature. All edge rivet holes have to be within 2 to 4 times the diameter of the hole in distance from the edge of the part to the center of the hole. That sentence is accurate but takes a bit to interpret. The picture makes it simpler. In this case, the rivet hole is 1/8" in diameter, so the edge of the doubler must be between 1/4" and 1/2" distance from the center of the hole. In this case it is 1/4 inch. I barely touched the very tip of the doubler with the grinding wheel, so the part comes pretty much cut to the minimum length from the factory.


Photo by Joe Graham

I originally took this picture to show how well the doubler surfaces mate to the spar channel. This is after I had rounded them and cleaned them up. I think its also a cool "perspective" photo. Note the nice round ends on the doublers. That took some time. I'm pretty pleased how well they turned out.


Photo by Joe Graham

After the doublers were finished, the next step was to locate and drill the elevator hinge brackets. These photos show the HS411 assembly as I was drilling it out and afterwards. I clecoed it from the back side as I went along. You can see that it is actually three pieces, the left and right HS411 brackets and the VA146 bearing assembly. Eventually this assembly will be riveted together and then the whole thing will be riveted to the Spar Doublers. You can also see the spar channel butt joint (Look at the channel flanges) in this photo.


Photo by Joe Graham


Photo by Joe Graham

I now have to prime the VA146 and rivet the parts together to form the HS411. I'll put that picture here when it's completed.

And... Here it is. My first completed assembly with rivets! You can see that I primed the VA-146, which was "optional" according to the plans. There's a never-ending debate among RV builders about whether or not primer is necessary on aluminum parts. Vans says that you should prime if you think it is needed and that you shouldn't prime if you don't think it's necessary! Now there's some definitive direction!

I have, for the moment, decided to prime mated surfaces as a minimum. Depending on how I feel at the time, I may prime a bit more in certain areas. For now, I am using a rattle-can Self-Etching Primer made by Duplicolor. It's their professional series Primer; part number DAP1690. The nice thing about the cans is that there is no mixing and no spray-gun clean-up. I picked up a couple of cans the other day at O'Reilly Auto Parts for $4.99 a can. Not a bad price, but I'll have to see if I can find it for less in case quantities somewhere.


Photo by Joe Graham

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