EAA Chapter 25

A Community of Aviation Enthusiasts in the Twin Cities

Legal Eagle Taking Shape

Filed under: Member Projects — admin at 7:13 pm on Tuesday, January 11, 2005

by Pete Gavin

from On Final January 2005


 

We last reported on Frank’s LEU project in September. At that point, he had framed up the tail feathers and completed the ribs and spars. For this update, I visited Frank’s project again and included material from his building log. As you can see, he has made a lot of progress over the past few months. Note: Frank has enlisted the help of Howard Longpre throughout this project.

Constructing the Wings
The most visible accomplishment since September’s report has been construction fabriand rigging of the wings. He has assembled the ribs onto the spars and constructed the remaining wing parts – the diagonals, D-sections, and leading and trailing edges. Frank says, “Getting all of these pieces cut to correct size and properly aligned and glued in place was like putting together a puzzle.”

They fabricated 18 false (foam) ribs for the leading Dsection. For these, they called on Marv Getten’s experience and used Marv’s special electric foam cutter. This is a homemade saw that uses a long wire to cut through multiple foam blocks at the same time. This ensures that they are of uniform size and shape. The leading edge consists of .8 mm plywood. Howard’s recommendation was that they make female forms to hold the plywood in place with straps while gluing to the leading edge ribs.

The aileron structures are built as part of the wing then cut loose for final assembly. They employed this same form and strapping method to apply their D-sections. The aileron pockets were strengthened with more plywood and closed out with poster foam-board material.

Frank commented that “Howard is a real treat to work with, and so capable…his machinists background is conveniently put to good use on the project.” Brass bushings were inserted in the outer aileron hinge blocks, and added into the design at various places. Both wings and ailerons were then finish sanded and varnished. Everything is now ready for the covering phase.

Rigging the Wings
The way the wings were originally designed, the leading edges of the wings were offset by about 1/8″ front to rear. This made it simpler to make up the wing attachments, but then the sections covering the gap between the wings would be slightly skewed. Frank corrected this by rearranging the attach brackets so that the leading edges came out lined up. This allows the sheet metal covering the gap to be square with the wings.

The initial wing alignment test was performed out on the lawn. Frank & Howard then moved the fuselage and wings into the living room for the rigging process. The initial trial assembly did not go smoothly. Both parasol attachment posts on the fuselage were slightly miss-aligned. It was impossible to get the bolts in both fore & aft brackets and through the posts at the same time. In the past, Frank had made several email and newsgroup submissions to the builder’s support group. This was the first time he actually grabbed the phone. After talking about the situation with John Bolding, there was only one option. Howard built a jig to help align and re-locate the parasol posts. Frank borrowed an acetylene torch to apply heat and bend the posts into position. They came out perfectly aligned.

They then built wing scaffolding and utilized a self-leveling dual laser to level the wings. The procedure was to level the wings, them move each wing tip up 3 inches for dihedral. They then affixed the forward strut attachment hardware. Instead of using the round struts per plan most builders are going with streamlined. Frank ordered streamlined struts from Carlson Aircraft. This project has all the basic attributes; translated this means there are gotcha’s. Howard had fabriancated the strut attachment hardware per the drawings. He found a place that did aluminum welding. They did a great job…problem was they only needed to have a seven degree angle, not fifteen. The wings and struts are now rigged.

The original design with the round struts required jury struts to keep the main struts from vibrating. These are not required with the streamlined struts, but Frank still intends to install them for extra strength.

Flight Controls
The control system mounts via nylon plate standoffs holding a one-inch aluminum tube that is positioned horizontally between stations 2 and 3. Brackets and guard shields fabricated out of AL sheet secure the 2″ pulleys called for in this control system. There is a riveted control stick shroud that mounts on the horizontal tube, and a control stick installed with bolt, washers, etc.

The elevator cable that goes through the horizontal tube is designed to pass by the bolts that go through the tube. Frank’s plane will use sailboat rudder and tiller blocks for the elevator and rudder cable fixtures through which the cables must pass to the tail. He is using a small brake lever from a local bike shop to activate the brakes. The lever was designed for 7/8″ diameter handlebars, which was ground out to 1″ for the control stick. A single hand lever will close both brake bands simultaneously; thus the brakes provide no directional control.

Once again, Howard has applied his creativity to Frank’s ultralight. He has fabricated most of the aileron bell cranks, rod, pulley guards, and spacers used throughout. He made some neat nylon/plastic stand off fasteners for routing the cable via brass fairleads fore and aft of the rear strut. These were machined such that each half will contour to the shape and screw together over the streamlined struts.

Frank borrowed the Nicropress tool (belonging to EAA Chapter 25), a cable cutter, and No-Go gauge from Chris Bobka. Wasting no time, they quickly fabricated aileron and elevator control cables to final length with turnbuckles for fine adjustment. Getting the cables cut to exact length can be a real challenge, and took more than one attempt in a couple of cases. These are now installed and ready to go. The day I visited they were starting on the rudder cables.

The fuselage still needs a few tabs welded to the fuselage for rudder pedals, standoffs and fairleads. Bert Sisler has agreed to help out with the welding once Frank decides on their final placement.

Fuel Tank
The tank is constructed of fiberglass and 1/4″ PVC foam. Frank’s was crafted by making a mock tank out of 1/4″ plywood from which the top laminate could be easily formed. The mold was lined with poly and tested for volume. The box was then disassembled and the pieces used for patterns in cutting the foam. The seven separate pieces of foam were laminated with the fiberglass on both sides. The box (minus the top) was glued together with epoxy. All inside corners were given radiuses of flox and more fiberglass which actually is both the structural and sealing surface, the epoxy is covered as most fuels will attack it.

After the box was constructed Frank installed the finger fuel strainer in the outlet. The filler tube is actually a household sink drain PVC tube. It is goes in the tank’s top before installing the top. From Frank’s experience working on his father- in-law’s Express project…he sealed the inside joints of all mating surfaces along the top with flox. The next challenge was finding a way to apply the same flox seal to the inside joints where the sides meet the top. He prepared curved strips of fiberglass and bonded them along the inside of the tank where the sides meet the top. He then filled the gap between the curved strips and the sides with flox, wetting every surface down with resin before pressing the top into place. The cover was weighted down with whatever ballast Frank could apply. It’s all done, and nice and light. It will be holding roughly 36 lbs. of fuel.

Engine
The engine was ordered from Hummel Engines while at Oshkosh. Delivered mid-October. It is a 1/2 VW full case upgraded to 1200cc. It has Nicosil aluminum cylinder walls keeping temperature down which translates into more horsepower. It comes with an Aerocarb carburetor, tuned manifold, exhaust, and a rotor-less distributor. It’s rated at 45 HP, and will probably be turning a 60 x 20 propeller. The engine has been run in a stand prior to shipment.

Fuselage Main Gear
The fuselage is standing on the main gear, and the wheels, tires etc. fit well. The design calls for compression springs over one of the cross support tubes, as one tube slides inside the other. Frank chose to use the stronger 1000 lbs. per inch die spring option. Some LEU builders have used valve springs from a diesel truck. From the advise of previous LEU builders, these springs are pre-loaded 1/4″ (or about 250 lbs.) Frank described the brake and axle work that remains.

Future Plans
Frank appears very eager to tackle the fabric and covering task, but will probably wait until the weather warms up. This generates a lot of fumes and one needs to be able to move a lot of fresh air through the workshop. Most of our m e m b e r s kn o w Frank…he loves to say “I am 90% finished, with 90% yet to go!”

One challenge that he is open to hearing about your experience with, is what to do about a tail wheel spring? Frank’s drawn up a sketch of what he thinks is needed, and is trying to find a shop that can fabricate it out of SAE 1050 – 1095 mild steel.

Stay tuned–more to come!

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