The landing gear is complete so now we are able to attach the fuselage frame to the tail boom. This milestone provides for a good photo-op.
The E-Hawk airframe employs a conventional landing gear configuration (tailwheel-type) which consists of two main wheels forward of the center of gravity and a small wheel to support the tail. In this edition of the blog the E-Hawk team fabricates the main gear structure and suspension struts. We also install the wheels, rotors, and brake calipers. The tail wheel assembly will be fabricated and installed at a later date as will the brake lever and hydraulic lines.
In this installment of the blog we work on fabricating and assembling all of the parts required for a working rudder. We start with machining the rudder pedal bushings and finish with connecting the rudder cable. See the pictures below for all of the steps in between.
In this installment of the blog we continue to work on the flight controls. A number of tubes on standoffs are strategically located and fitted with nylon bushings to act as pivot points for the torque tubes. We also weld up the control stick and add pulleys for the rudder cables to run on.
The fuselage frame is at the stage where a coat of primer will help protect it from oxidation. Although our shop is climate controlled during the day, the high humidity in the Hawaiian air will find a way to infiltrate. So it’s off to the paint hanger to apply a coat of primer. We will still have to do some welding (e.g. motor mount) in which case we will simply strip away the paint in the affected area.
In this blog we are able to finish most of the welding associated with the structural part of the fuselage frame. We also fully attach both the upper and lower keel tube to the frame. Coming up next will be flight controls.
With both upper and lower keel tubes now part of the fuselage frame the full length of the fuselage is known. Bolting it to the tail boom and empennage gives the full length of the aircraft which now allows us to determine if the assembly can be removed from the building. The partially assembled aircraft also allowed for a photo op.
Here we attempt to get the fuselage out of the building. Although we were unsuccessful here we may still have a shot if we have more people available help with the lifting and negotiating.
Now that we have bent the lower keel tube and installed it we can proceed with fitting the rest of the forward fuselage tubes. The keel pockets are located on the keel tube and clamped in place so that we can properly fit the Rudder Bar, Nose Skid Tube, Instrument Panel to Rudder Pedal Down Tube, and the Lower Instrument Panel to Rudder Pedal Down Tube prior to welding.
As we wait for the bulk of the wing parts (mostly aluminum tubing) to arrive, in-house fabrication has begun. We can easily cut most of the 2.5D parts out of flat stock, be it aluminum or 4130 steel, on the waterjet. We also produce our own CAD for the parts that are missing drawings within the EMG-6 builders database.
After a long summer break, the E-Hawk Team is back at it again. Today we manufactured the lower keel tube from a length of 6061 T6 aluminum tubing (1.0″ OD x .058″ WT). This part requires two bends with a 9″ radius. We do have a hydraulic pipe bender however we don’t have a die that will make the 9″ radius bend. Instead we decided to design specific tooling that would allow us to make the correct radius bends. For that we used Onshape to create a bending die comprised of two halves of 3/4″ plywood cut on the CNC router (Shopbot). The two halves were then glued and screwed together and mounted to a larger piece of plywood. The assembled jig was then clamped to a sturdy table. The straight length of tube was measured and marked with the bending parameters and then filled with sand (actually waterjet abrasive) to prevent it from collapsing during the bending process. It was then placed in the jig and clamped down on one end of the fixture with an aluminum strap. The team then proceeded to manually bend the tube around the die up to the correct angle. Following the first successful bend the tube was readjusted within the fixture and the process repeated for the second bend.