Building a Giant Scale Electric EINDECKER Part 2 John Bernard N1KUB AMA 58903 IMAA 28971 In Part-1 of this series, we explored the 100 Eindecker kit from SR Batteries and started building the fuselage. In Part-2 of this three part series, we ll finish off the fuselage, build the tail sections and wings, start covering the aircraft with aluminum sheeting, and install the electric power system. The fuselage assembly was continued by next installing the tail plate gussets and the support block inside the tail plate for the landing skid support. I then installed the pull-pull wires to the bell-cranks. Do this now, because it would be very difficult completing these steps after you finish the top and bottom cross bracing. Once the top and bottom bracing and cross braces were completed, the fuselage not only started looking almost done, but the structure became very rigid. Take your time to line up the top bracing with the vertical side bracing. You will be able to see the structure somewhat through the final covering, and any miss-alignment will be very visible. You can see here that the rear of the fuse has been completed; rudder and elevator pull-pull wires installed, and to keep the wires in place, tape them to the bottom tail plate. This keeps them from snagging on everything as you move the fuse around. We finish off the main fuse structure by installing the front cross brace behind the firewall, the small remaining chin sheeting, and the fuel tank support plate. Even though this will be an electric plane, this support plate is necessary and part of the structure, so don t leave it out. It also helps strengthen the landing gear area. We can put the fuse aside for a while and build the top hatch. The top hatch is removable which allows great access to everything. The top also acts as support for the landing wires, so it is built quite strong. The pictures show the pieces and the final structure. Constructing the assembly is very straight forward, and all the pieces were laser cut. Only minor final sanding was required. There are two hardwood blocks that must be placed inside the assembly to support the landing wire braces. These are glued in place after the assembly is completed. Trial fit the hatch to the fuse. It should be a snug but not overly tight fit.
Building the Tail Sections The horizontal stab is unique in that the leading edge is a fiberglass tube. Trim this to length and save the remaining piece for the rudder. The use of a fiberglass shaft makes an almost ding-proof edge, and a perfectly straight stab. The rest of the stab is built up of interlocking laminations and ribs that make for a very strong but light structure. The hollow fiberglass shaft fit s over tabs on the edge pieces. Build this over the plans, and you re done in about 20 minutes. The two elevator halves are built in the same manner as the horizontal stab, with their trailing edge composed of the same shaft material as the leading edge. When completed, bevel the elevators hinge joint to the angle shown on the plans to allow proper elevator travel up and down. The tail sections go together very quickly, as all the pieces are laser cut. The horizontal stab slid easily into the fuse for a trial fit. The rudder has a lot of pieces, but if you dry fit everything first and lay it out in sequence, it goes together quickly. I used thick CA to laminate everything. This dries slower, and gives you a bit of time to position each piece accurately. This is a full flying rudder, so we only have one piece to make. The black piece shown in the picture is the fiber tube that is the pivot for the rudder. This is the piece cut from the leading edge of the horizontal stab. Glue this in place, making sure it is perfectly centered in the rudder. I used balsa-lite filler to cover the tube as can be seen in the final picture. This is not called out in the instructions, but seemed to look a bit better. The black piece seen below the rudder is the support rod that the rudder pivots on as well as the support for the tail skid. This is just a trial fit, plus I wanted to see how it all looked! Next The WING Do yourself a favor gather the pieces for both wings, a wing at a time, and lay out the pieces in order. You will be sliding the ribs onto three fiberglass spars. If the ribs are put on out of order, they have to come off. Also locate the three building jigs. Assemble as necessary. These jigs make building and rib alignment very easy just follow the manual. The jigs help accurately space the ribs as well as hold the ribs perfectly vertical to the plans. Don t overlook the ¼ block spacer used to build in washout in each wing panel.
Once the ribs are roughly in place, the jigs are used to accurately position and glue the ribs in place. The trailing edge is built up and the wing tip pieces are laminated and glued in place. The aileron is built up as per plan, and again, all the pieces are laser cut. Install the servo plate (double check the orientation to make sure it s installed correctly). Shaping and minor sanding finish the job. The servo is mounted on a nice plate that provides a clean installation. All the pieces are Ply and laser cut. Even the servo pilot holes are laser cut. This goes together quickly, and is a great design to use in other models as well. The last pieces on the wing to put together are the 8 flying wire attachment points. These come in three pieces that are laminated together, and fit in matching slots provided in the two plywood ribs. The plans call for hex head wood screws in these, but I inserted 4-40 blind nuts, and will be using 4-40 stainless cap screws. I got in the habit of using stainless for everything to eliminate any rusting problems, plus the stainless hardware seems to last forever. If you buy it in bulk from MicroFasteners, it s only a few cents per fastener. Finish sand the wing, coat it with your favorite prep (Balsarite for fabric works great) and go build the other wing (preferably a right and left wing). I use Robart Hinge Points to hinge large models, and will use Hinge Point Pockets to make the surfaces easily removable. This makes covering a lot easier in my opinion. Drill out or slot the wing and ailerons and wings for the hinges of your choice and final fit the ailerons. Install blind nuts for the control horns as required. You may as well do the same for the horizontal stab and elevators while you re at it. These use a special double control horn for each elevator. The final thing we need to do before getting ready to assemble all the pieces, is to build the two cheek cowls. These fit around the wing, so need to provide enough clearance to allow sliding the wing in place. When I first looked at these and read the instructions, I figured these would be a pain to build. They went together fairly easily. Just take care when you are sanding everything to shape, and follow the manual carefully. These will be coated with thin CA to harden the surface and then sanded smooth. They are then covered with aluminum tape.
Covering with Aluminum We pretty much have most of the major assemblies completed at this point, with some minor assembly that has to be done after the aluminum covering is applied. The easiest place to start is with the firewall. Make sure the firewall is sanded smooth and all dust removed. Cut a piece of aluminum tape a bit larger than the firewall, and carefully remove the backing tape without creasing the aluminum. Carefully align and smooth it in place. Cut the tape away from the mounting holes in the firewall. Once this has been done, go over the edges and trim the tape to cover the edge all around the firewall. It should look like a bare aluminum plate at this point. Now file all the sharp edges smooth on the cowl, lightly sand the entire cowl to remove any deep scratches or marks from shipping, and mark the mounting holes according to the dimensions and instructions given in the manual. Drill a pilot hole in the edge of the firewall at the top center and mount the cowl. Using the holes you drilled in the cowl, drill the remaining holes in the edge of the firewall to mount the cowl. Seven holes in all makes for a very secure mount. Remove the cowl and let s put a nice finish on the aluminum. I started with the firewall, figuring that if I made a mistake, it wouldn t show. Wrap steel wool around a small Dremel brush. This is used to make the swirls shown in the photos. Set the Dremel on the lowest speed. You should be able to get a firewall out of one steel wool pad. Change the steel wool out for a new piece before you do the cowl. It looks like it s tedious and takes a long time, but it actually goes quite quickly, once you get the hang of it. Remount the cowl and admire your work. We ll be gluing a shelf for the batteries in the slot at the bottom of the firewall, so this is left uncovered for now. Remember the cheek cowls? Cover and finish them too.
This is the top hatch and one cheek cowl covered and swirl-finished. You need to cover the hatch before installing the landing wire support. The swirl finish really makes the aluminum come alive. Both the hatch and cheek cowls were coated with thin CA to harden the surface, and then sanded perfectly smooth. Any imperfections will show through the aluminum tape, so make sure the sanding job is as good as you can get it. Again, make sure all dust is removed just as you would do for any covering prep. Here is a picture with all the above work done. We only have a few more steps to complete to get the model ready for covering and final set-up. In this picture the hatch, cheek cowls and firewall are covered in aluminum, and the engine cowl mounted. The wings are trial fit, and the rudder and horizontal stab are temporarily in place. I mounted the axle to the landing gear assembly previously built, and installed the Williams Bros. wheels. By the way, Williams Bros. looks like they re going out of business due to health issues, and these products are getting scarce! The motor is dry fit (I had to see what it would look like with the prop installed). I mounted the landing gear wire support as per the plans. The top plate was silver soldered to the main support nad the support was epoxied to the base plate. The forward support wires were final fit and wrapped with copper wire, then silver soldered as well. You can see the two landing wire tabs mounted on the plate. These supportt the 4 landing wires on each wing, and along with the flying wires, keeps the wing on and supported. Four nuts are all that are used to assemble the plane at the field two on top shown here, and two on the landing gear.. We ll go over this in detail later
The Power System I purchased the complete Eindecker E1 Deluxe Electric Power System from SR Batteries. The electric power system is made up of an AXI 4130/20 motor, a Jeti 77 OP Speed Control, a radial mount for the motor, and two SR 2400 MAX NiCad packs. This setup spins a Zinger 18 x 8 wood prop. The connectors shown at the bottom right of the photo are the connectors for the charge jack and the motor arming fuse. It s amazing the thrust this small motor has. This setup will fly this 16-18 lb model. For comparison, a G-26 is the recommended gas engine for this aircraft. A mounting slot will cut in the aluminum cowl to mount the connectors for easy access. The batteries are held to the firewall with Velcro pads, a Velcro strap, and the batteries also sit on a 3/8 hardwood shelf. The blue component directly behind the motor is the speed control. The servo lead from the speed control is the only wire going into the fuselage. The batteries can be quickly removed for another set, or charged in place. The motor is interesting as the outer case rotates. This is called an outrunner motor. The motor has three ball bearings, and seems quite sturdy. When I test ran it, the motor was spinning the wrong way. Reversing two of the three motor leads solved this very quickly. Static subjective tests (grab the tail and see how hard the motor/prop pulls) seems to indicate about the same thrust as a G-23 Zenoah.