January 23, 2010

Roll Bar Assembly - continued - 8.5 hrs.

Man, this thing is turning into a PROJECT! This is a lot of time and work, but it's fun. I have more appreciation than ever for the older RV-6 and 6A kit builders, where nothing is pre-punched and this kind of layout and planning is common. The cabin frame definitely appears to be unchanged from the RV-6 kit. Today I continued working on it. The forward and aft pairs of channels are held together with long aluminum straps inside the channels that are riveted in place. It's now time to install and drill these straps to the channels. The first order of business today was to put a radius, or chamfer, all along the edges of these straps so they nest in the rounded corners of the channels and fit properly in place. So I spent a long time filing away at them until I got a good smooth radius on both sides of both straps. I didn't get a picture. Sorry. Boring stuff. But it needed to be done first.

I'm using the "masking tape" method for layout of the rivet holes, like my friend Mike Bullock describes here. The only difference is, I don't have one of those fancy rivet fan spacers. Since the kit I bought is a modern pre-punched kit, I didn't see much use for one. I've never had a need for one until now. I don't want to buy one now because by the time it ships here, I could be done with this whole thing. Besides, I don't think there will be another opportunity to use it. I thought about checking around my chapter to borrow one, but then I realized that by the time I drive somewhere to borrow it, then return it later when I'm finished, I could have easily just measured it out by hand. No big deal. So let me explain.

In the picture below, you can see the blue masking tape on the inside arc of the bow. First, I just taped this piece of tape in place. Then I measured up from the bottom the distance to the first rivet, as shown on the drawing, and marked the spot. I made another mark at the top of the bow 1/4" from the end of the channel joint. Repeat this for the other side. Then, carefully unpeel the tape and tape it down on a hard surface or one of the long straps. Now, it's laid out to measure and mark for rivet spacing. First, I made a horizontal line the length of the tape 1/4" from the top of the tape, for the edge distance indicator all along the tape. Next, measure the distance from the first rivet on the bottom to the last rivet on the top. In my case, it measured 25-5/8". There are 19 rivets that go in, so that means there are 18 spaces between rivets. So you divide the distance, 25-5/8", by 18 to get the spacing between rivets. Make sense? I wanted to get to within 1/32" tolerance, so the spacing worked out to be 1-13/32" between rivets. The plans say no more than 1-1/2", so I'm easily within specs. So I carefully marked the tape for each rivet, then taped the tape back on the bow as seen below.

Now it was easy to clamp the strap in place and drill. Push the strap firmly down, clamp it in place, drill and cleco, do it again all around the bow. I decided to drill to #40 first, then to #30.

In the close-up pictures above and below, you can look closely and see the marks on the tape. I think this is much easier than trying to accurately measure and mark directly on the channels.

Next, do the same taping procedure for the outside of the bow. This time, there are 21 rivets, making 20 spaces to divide the distance up by. The measurement came out to be 1-15/32" between rivets, still under the 1-1/2" maximum. Perfect. Measure, mark the tape, put the tape back on, drill to #40 and cleco.

Above, the outside of the bow is now drilled and clecoed to #40 about halfway around the bow. Below, the inside of the bow is drilled to #30.

That's as far as I got tonight. This method is working real well for me. I'll continue with more drilling next time.

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Contact me: swayze "at" europa.com (replace "at" with the @ sign... no spaces... you know the deal)