by Scott Todd » Sun Sep 26, 2021 11:40 am
I'll throw in my two cents as an Instructor, builder of three flying airplanes, test pilot of 13 new airplanes, and retired Aerospace Engineer.
At 60 mph, those rivets sticking up may cause enough drag for a knot or two. There are basically two parts to drag. Parasitic and Induced. Parasitic is the antennas, rivets, handles, etc. Induced drag is that caused mostly from the generation of lift. The induced drag is WAY higher than those rivets that mostly live in a boundary layer. Sonex uses flush pulled rivets on the wing leading edge to appease some critics that think this part of the boundary layer may contribute to more drag.
As the speed goes up, the rivet heads will contribute more drag. How much is pretty hard to say without a ton of math or computer simulation. But since the Xenos is a motor glider designed to operate around 60, it doesn't matter.
Cessna's and Pipers are NOT primed on the inside. Go to the airport and look inside some of them that have been on the ramp for more than 50 years. Some get corrosion, some don't. Are they taken care of? Do they collect standing water inside? Are they taken care of? I know I said that already. A well loved airplane with regular cleaning, good annuals, and covers, can last a lifetime outside. Your Xenos, most likely hangared, will most likely last longer than you.
Weight is everything. Save it every place you can.