Stephan's Sonex #1627 Builder's Log

I worked on polishing of the rear spar for the horizontal stabilizer and deburring of the spar channels. The rear spar had a lot of relatively deep cuts and stratches, presumably made while the spar was being fabricated. I used red Scotchbrite pads to smooth the surface and then used grey Scotchbrite pads to further polish it. I then cleaned with Paint Thinner and then sprayed with self-etching primer. I cleco-ed everything back together and riveted the whole rear spar assembly.

I worked on up-drilling the entire horizontal stabilizer and elevator assembly. 

I worked on installing the left hinge on the horizontal stabilizer today. I again used the elevator as a guide and added the end-stop to ensure everything is flush with the edge of the stabilizer.

I did not have a piece of hinge left that spanned the entire required length so I made it out of two pieces instead. I had previously confirmed with Kerry at Sonex that this was acceptable, and he indicated that as long as the hinge pin spanned the entire length, it wasn't a problem.

I positioned the elevator with the hinge pieces in place and drilled and cleco-ed everything together. 

I worked on installing the right hinge on the horizontal stabilizer assembly today. I wanted to use the elevators as a guide to determine the correct position of the hinge, but the elevators were still all cleco-ed and these clecos interfered with the installation, so I removed them and used #4 stainless steel screws to temporarily fasten the hinge half on the elevator. I did this for both the left and right elevators. I marked up the other hinge half using a ruler and installed the hinge onto the elevator using the hinge pin. I then added an end-stop using a piece of channel stock to allow me to ensure that the elevator is installed flush with the edge of the horizontal stabilizer. I then positioned the elevtor in place and lined up the hinge to the correct position and drilled and cleco-ed everything in place. 

There is about 1-2mm of play laterally with every hinge, and when I installed the right elevator, I had it pushed all the way to left. This means that the elevator can actually move 1-2mm to the right and scrape the end-stop, so I moved the hinge down 1-2mm to avoid this. I wanted to make sure that when the fiberglass tip is in place, the required minimum gap is maintained even if the elevator slides latterally a little.

I noticed this problem after drilling the first hole, causing it to be off a little. However, once up-drilled, the issue is no longer there. Hence the 1/8" (copper) cleco in the corner of the first picture below.

I cleco-ed the entire horizontal stabilizer assembly together and marked the centre line on each of the ribs as well as the the forward spar. Throughout the process, I used a heavy piece of metal from my bending brake to hold down the ribs and assembly while drilling and cleco-ing everything in place. I routinely checked to make sure that the ribs were perpendicular with the table surface using a straight edge. I proceeded to lay the skins over the stablizer assembly and lined up the pre-drilled holes in the skins with the centre line on the ribs and forward spar assembly. With the exception of the the longest rib, all the holes lined up reasonably well with the skin. 

The longest rib did not line up correctly. It turns out that the attachment bracket position was a few millimeters off and this caused the angle of the rib to not match up. I left this issue for now and proceeded to drill and cleco the skins in place. I did this for the left and right side before turning the whole assembly over and drilling and cleco-ing the other side. 

I up-drilled everything with the exception of the tips and the edge where the hinge will be positioned. 

I contacted Kerry at Sonex concerning the tight bend angles for my main spar and forward spar channels. He indicated that they were indeed tight but that there will be very little load at the tips and therefore these were not a concern. He suggested I use the hand seamer next time for these bends. I proceeded to fabricating the ribs and brackets for the horizontal stablizer.

I didn't get a chance to clean up my 8ft bench and remove the drill press and grinder that I had mounted to it, so I decided to work on the horizontal stablizer instead of the elevators. 

The first hour or so was spent making the main spar channel and forward spar channel parts from channel stock. Each end of the channel stock had a flange that needed to be bent either 90° or 22°. I used a wooden block that I cut to size that fit the channel and then tapered the block so that I could easily make the bend to 90° (which requires you to over bend it by about 5-10° - hence the tapering).

I rounded out the tip of the slanted end of the block so that I would have the proper bend radius. It turns out that wood may have compressed at the tip when I made the bend and I actually ended up with a bend angle that is much less than the 1.6mm bend radius that the plans call for. The parts with the 22° bend don't show any significant material compression near the bend, but the 90° parts hint of material compression at the bend.

I proceeded lining up the channels on the main spar and confirmed the overall length before drilling and cleco-ing everything in place.