We started laying down some tack welds on the Wing Box. A few more tubes need to be fitted and tacked and then the assembly will be removed from the tooling and welded completely.
Now that parts inventory and preparation have been completed the fuselage boom assembly can commence. We started by locating all of the parts necessary for assembly. The bulk heads were fastened to the boom sides as outlined in the instructions. This was followed by attaching the top and bottom skins to the boom. We ran out of cleco fasteners in short order and had to wait a couple of days for more to arrive. The additional cleco’s allowed us to fasten all of the parts that comprise the fuselage boom although we still did not have enough to fill every hole that would need to be riveted. The next step will be to fasten all remaining 1/8″ holes and then double check the fitment prior to starting the riveting process. We don’t want to have to drill-out any incorrectly placed rivets.
Time lapse of Fuselage Boom assembly.
Our first shipment of parts has finally arrived from Rainbow Aviation in Corning, CA. The parts were delayed due to a slip-up on the part of UPS–not sure how you ‘lose’ an 8 ft. long wooden crate. This initial shipment includes all of the parts necessary to build the Fuselage Boom, Vertical and Horizontal Stabilizers, Elevator, and Rudder.
The first step in the process was to check for any damage and then inventory all of the parts. It took us almost 3 hours to go through all the part numbers.
The next step involved preparing all of the parts for assembly. This basically required that all edges and holes of the aluminum skins be deburred (removing all sharp edges left over from the machining process). This took 3 to 4 students about 3 meeting periods to complete.
The Forward Spar requires that 2 holes be drilled near each end. After using the tube template to locate and center punch were the holes are to be drilled, we need to make sure that the holes are parallel to one another and that we are drilling normal to the tube at that location. To ensure that the two 1/4″ holes were aligned with one another we designed and printed two clamps that the tube would tightly slide into. Then we mounted the clamps to a scrap piece of 3/4″ plywood. The drilling jig would now rest on the drill press table and guarantee square and aligned holes.
The Wing Box fabrication starts with the assembly of the welding fixture. Using deck screws we built-up the tooling to accept the 4130 steel tubing.
The boom mounts are the first parts that need to be bolted on to the fixture. Unfortunately at the time of wing box mock-up our shop was not quite set-up for welding. That meant we could not weld the boom mount washers to the 1.125″ tube. In the mean time we designed and 3D printed temporary inserts to act as the washer. This would allow us to align and bolt the boom mounts to the fixture. At that point we could proceed with the coping and fitment.
Brian Carpenter @ Rainbow Aviation has refined the coping process using templates generated using his CAD files. He has produced a good video that describes the process. Brilliant!
Using the OMAX Waterjet Machine we can easily cut the boom mount washers from 1/8″ 4130 steel. The waterjet doesn’t even break a sweat as it accurately pierces through the material. We will be using this machine to cut all of the required flat stock parts. We also use this machine to fabricate some of our competitive robots and a myriad of other projects.
While waiting for the 4130 steel to arrive*, we started by cutting the tooling fixtures with our ShopBot CNC router. Using the dxf files from the builders database and 3/4″ plywood, we cut the 4 full sheets of ply which will provide all the tooling required to weld-up the fuselage frame.
Time lapse video of the CNC operation.
Our project officially launched with a visit to Rainbow Aviation in Corning, CA where Brian, Carol, and Jasen gave a tour of their facility and provided details of the EMG-6 motor glider. Following the visit we decided that the EMG-6 would be the perfect platform for our project. It’s a solid design that is configurable and the fact that all of the design files are open-source will make it convenient for us to configure the propulsion system as desired.