Building An Airplane From Plans
Dan primed the horizintal stabilizer parts and skins. We had gotten a gallon of 3M Mar Hyde Self Etch Primer. Dan used his compressed air paint spray gun. He has a lot more control over the spray width and delivery than with the spray cans we’ve used so far. He put a really nice light and consistant coat on, great job. Safety notes: Dan used a respirator with cartriges and had the workspace venting with a fan pulling air out a window.
Dan dimpled the hoizintal stab frame and skins and I finished preparing the frame parts for priming.
We found a used DRDT-2 dimpler for sale on the Vans Air Force website last fall and used it with a 120 degree pop rivet dimple die from Avery (We also evaluated the Cleveland die and the results are the same.) The DRDT-2 made the dimpling go really fast, but there are a few places that cannot fit (notice just below the die on the bottom beam in the picture).
Dan had modified a pair of large vice lock pliers. A freind welded on some smal channel to the jaws. The top channel has a hole for the male die half. The lower channel has a 120 degree counter sink hole with a through hole for the male die pin, essentially Dan replicated the female side of the dimple die in the lower channel. We’ll post a picture. It works really well, fits in all the tight corners on flanges.
I prepped the frame parts for priming by roughing them up with 240 grit sandpaper to take the shine off and get some swirls. I would finish up with maroon Scotchbite pad. Lots of surfaces to cover.
June 12, 2011 Dan and I have been struggling with the bottom nose rib on the vertical stabilizer. Dan fabricated a form block that matched the plans exactly. When we installed this rib the skin would not sit right, it had a flat or shallow dish. When I went to rivet it the stems of the pull rivet would break off meaning the ball had pulled up too much. We are using flush rivets so the rivet holes were dimpled. We had to Dremel tool the stainless stem off and drill out the poorly set rivet, a real pain. I think part of the problem is that the natural curvature of the skin does into sit right on the rib, the rib pulls the skin in. Here is a picture of the rib from the plans sitting in the frame with the skin:
Notice the gap between the rib and the skin towards the top.
Dan made some CAD layouts on Autocad increasing the radius at the front of the rib. Dan made a new form block and made the rib. Here is a side by side layout. The primed one on the right is the original design from the plans. The left one is the new rib
Here is the new rib sitting in the frame with the skin. Notice the closer fit.
Fast Forward to Oshkosh 2011. I walked the flight line looking at all the completed Sonex planes and noticed that almost all of them had the awkward skin layout at the top of the bottom rib.