OCT 2014

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: https://experimenter.epubxp.com/i/401344

Contents of this Issue


Page 12 of 46

EAA Experimenter 13 "The J-3 clone project took a dif erent direction and became much more complex when I attended a Cub restoration semi- nar by Clyde Smith Jr. at Ponca City, Oklahoma, in the fall of 2008. I took along a photo album of my project and discussed it with Clyde and Merle Helt, an old friend from Ponca City, who had built a Wag-Aero Sport Trainer as a PA-11 replica. Merle and Clyde pumped me up about how easy it'd be to convert this project to a PA-11 and how much better a PA-11 was compared to a J-3. I swallowed their bait—hook, line, and sinker—and started down that path. "Some people think the Cub Special is just a J-3 with a C-90 on it, but there are lots of subtle changes that aren't obvious. I had an O-200A that I'd picked up a few years ago and planned to use it instead of the A-65 that came with the project. I over- hauled the O-200 and installed a C-90 camshaft to improve the rpm/torque curve. Most of the noticeable dif erences between a J-3 and a PA-11 are ahead of the fi rewall. "The outline of a PA-11's nose is dif erent than the J-3, which meant everything up front had to be changed. Before the cowling and engine work could be done, I had to change the fuselage to duplicate the PA-11 structure. I removed the two diagonals the J-3 has in the forward bay under the nose tank and replaced them with a cross-member. The PA-11 had one 11.5-gallon wing tank and no header tank. However, I put a tank in both wings and a header tank. "I bought the 11.5-gallon wing tanks from Wag-Aero and had to move the fi rst ribs outboard from the root rib about an inch outboard to make the tanks fi t. Wag-Aero tanks have the fuel pickups at the aft of the tank, so if one is low on fuel and in a nose low attitude, they could un-port the pickups. Wag- Aero also makes a 2-gallon header tank to avoid that problem. I plumbed both wing tanks to 'T' into a common line behind the baggage compartment with fl ow via a single line to the header tank. The only fuel shutof valve is at the bottom of the header tank. I have 25 gallons on board. "The engine on the PA-11 is about 4 inches lower than the J-3, which is why the nose slants down, which gives much better visibility. The windshield is more streamlined, attaching farther forward at the bottom. I made the attaching strip at the bottom in fi berglass. "The J-3 mount had come from Univair, which was very cooperative in swapping it for a PA-11 mount because I had the original paperwork for it. The fi berglass nose bowl came from Wag-Aero and the fi rewall from Clyde Smith. I hung the engine and positioned the nose bowl on the crankshaft and started on the cowling. The PA-11 has a pressure cowl rather than a cylinders-in-the-wind J-3 type, so it fl ows back to the boot cowl in an unbroken line. I mocked up the cowling and the boot cowl using lots of taped-together poster board and started cutting metal. "I had no plans showing those details, so I depended upon photos of old PA-11s and did what I thought looked about right to fabricate and fi t those parts. I really like how the hinge pin installations secure the cowl cheeks. I can have the The GA-11 has an actual back seat, not a canvas sling as the J-3 did. Claude Jochmans started to build a Wag Aero J-3 look-alike, but, when Gary bought the project, he went all-out PA-11 and then some with it.

Articles in this issue

Archives of this issue

view archives of Experimenter - OCT 2014