Luis & Fab's RV-7A Construction Log

The front spar is the other main component in the horizontal stabilizer. The main differences between the front and rear spar is that the rear spar is angled ‘back’ at 6 degrees, and it uses short aluminum reinforcement angles instead of the long reinforcement bars.

The aluminum angles came from the factory as shown on the first picture below; they were pre-cut and pre-drilled. So, I just clecoed them to the spar and match drilled all of the holes in the center section, except for the four called out in the plans. I marked these with ‘NO’ just so I wouldn’t drill them out by accident.

Once the angles are match-drilled, they ends have to be tapered. I marked them up using the dimensions given in the drawing as shown below. I still don’t have a bandsaw or other cutting tool, so I first tried using a coarse wheel on the grinder. It turned out OK, but it was hard to get a straight tapered edge.

I ended up using a vixen file. I thought I’d be there all night filing away, but this file is an aggressive bugger! It only took me about 5 minutes per side, and I was able to get a nice smooth edge to about 1mm from my drawn line. I then used the Scotch-Brite wheel to grind it down to final size.

Once the two reinforcement angles have been tapered, the tapered ends have to be bent back 6 degrees. The bend is made along the line shown in the picture above. The manual says to secure the angle and whack it with a hammer. I figured the best way to do this would be to sandwich the tapered end between two blocks of wood and just push until I reached the desired angle. The only caveat is to make sure the angle is perpendicular to the wood, so the bend occurs along my line. To check the bend, I made a cardboard template using a protractor to draw the 6 degree angle.