Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/271000
22 Vol.3 No.3 / March 2014 A PEREIRA GP-4 the same time. Plus, the spar is 24 feet long and it's one piece. This is defi nitely not an airplane you're going to build in a back bedroom. My business has 22,000 square feet of shop space, so I isolated an 80 by 50–foot area in the middle and set it up to build airplanes. "A woodworker friend of mine told me how to build a good worktable, 24 feet long and 4 feet wide, and that worktable was a godsend. It was made of 4-inch by 3/8-inch angle iron and topped with three layers of 3/4-inch plywood and chipboard. We routed one edge so it was perfectly straight to use as refer- ence. This thing was so stout, you could have put a Buick engine on it and driven it to Sun 'n Fun. It gave me an absolutely true, stable surface to build on, and that was critical." Besides being 24 feet long, the main spar was a project that used a lot of Mike's boating experience. It was a box spar, meaning it had front and back faces joined by intercostals, with the top cap being seven laminations thick and the bottom hav- ing fi ve laminations. Each lamination was a half-inch thick! Not only was the spar tapered in both the front and top views, but the dihedral was built into it. Building the jigging to hold every- thing in correct position entailed as much work to do right as building a complete wing on many other aircraft. Mike added, "The wings are skinned with 3/32-inch plywood that I brushed with very thin resin before closing the wings. I then covered them with super-thin fi berglass. I epoxy-primered that, block-sanded it, and fi lled the low spots with micro balloons. At the most, the buildup is ten to fi fteen thousandths of an inch thick in some areas. "The fuselage is much easier to build than the wings. It's a basic box fuselage, and you can build the sides laying fl at on the table and stand them up. That, however, makes the fuselage look too fl at and square. So I took long pieces of 0.2-inch-thick, 18-pound foam and milled it into a very slight curve on a CNC machine. I glued that to the sides of the fuselage which, when covered, makes the fuselage look much better. At least to my eye it does." The cockpit canopy is framed in tubing and slides on rails that are actually just chrome-plated square tubing with a slot cut in it. Mike said that the canopy tries to "fl y," so to keep it in place, a crosspiece behind the seats engages with locks in the fuselage, which reduces the gap seals and keeps the canopy fi rmly down. In keeping with his goal of building the airplane inexpen- sively, when it came time to hang the most expensive part of any airplane from the fi rewall, Mike again decided to trade elbow grease for savings. Mike said, "The engine is a Lycoming IO-360-A1A, but it wasn't the prettiest engine you've ever seen when I bought it. "I could build almost anything with all the tools I had in my business, but I didn't want to drop a huge amount of money right up front for a kit." Mike Mahar and his GP-4. Mike is a hard-core builder who delights in scratch building because, "You have to love solving problems by yourself." E A A E X P _ M a r 1 4 . i n d d 2 2 EAAEXP_Mar14.indd 22 3 / 3 / 1 4 1 0 : 3 1 A M 3/3/14 10:31 AM