Over the past few days I realized that I am missing the main wing spar doubler extension pieces that are necessary for the Sport Wing modifications. Because of this little oversight, I’m now at a full stop in the main wing spar progress and have decided to proceed with the rear wing spars.
When starting construction on the rear wing spars it is important to note that the rear wings spars are NOT symmetrical. The top and bottom flanges are at different angles to the web, as shown in the image of the plans below.
Because there is an Upper and Lower flange, this also mean that there is a left and right rear wing spar or conversely that there is an inboard and outboard end of each spar!
As per the Van’s building instructions be sure to write notes on the spar, “TOP”, “BOTTOM” etc. Write big and write on both sides. It’s really embarrassing to build two left spars!
So the first thing I did, was identify which angle was which.
As shown in the image below, I identified left/right, up and tip/root ends of the spars.
Additionally, same as with the main wing spars, the rear spars also get trimmed to a shorter final length. In the image below, this spar has already been trimmed for lenght and an additional 1-inch was left to be able to attach the rear spar to the wing jig.
I then proceeded to prepare the W-407B and W-407C flange strips. Note that the W-407B flange is longer when mounted in the spar channel, as it projects past the inboard end of the spar web.
When preparing the flange strips, I started by marking the outboard rivet location, and then identified the required edge distance on the inboard end; both in from the spar edge (1/4-inch) and also 3/4-inch horizontally.
With the edge distance marked, I was able to then use a straight edge and connect the lines horizontally from the root edge distance marks out to the rivet location previously marked.
The last step for today was to mark out the rivet spacing along the flanges. I used a rivet spacing fan as seen in the picture below. As I was doing the layout as per the HRII plans, I quickly found that the dimensions given were not accurate. More details to follow in the next post.
That was all I had time for today, but as always please comment. I love to hear from my readers. Thanks again for coming along for this ride, you make my work worthwhile.
Leave a Reply