Time for Fabric

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 With the Fuse painted, it was now ready to fabric cover. However before I tackled the largest fabric covered component I decided to first test my skills on some smaller parts. The Turtle Deck was my first experiment in learning the fabric cover process.  I researched various covering methods and products and decided on The Poly Fiber System.  I liked the Instruction Manual and I also attended a two day class which helped me gain some confidence. But the most important aspect was the product itself.  The Poly Fiber System is durable, easy to install and easy to repair.

In the photo above the fabric has been glued to one side of the Turtle Deck and is in the process of being heat shrunk.  The next ironing at the highest temp setting will smooth the wrinkles away. 

Floorboards and Re-Welded Seats

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While my main effort was to complete all the welding on the fuselage I had to re-focus my attention to the wood floorboards and seating attachment issues.  That’s because metal tabs and seat mounts had to be welded on the fuse to hold them down.  I chose 5/16″ exterior grade plywood and carefully cut it out to fit around tube joints and around the control sticks.  This was not to be the final finished floorboard.  In fact I ended up fabricating three different floorboard patterns until I ended up with a suitable design that evolved with other changes I made along the way.

During this early phase of construction I was reminded of the labor intensive method used for annual inspections for my Cessna Skyhawk.  My A&P (Airframe & Powerplant) Mechanic at the time had the complete cockpit interior removed including the seats and carpeting and all the floorboard inspection panels were also off.  This close up inspection is to check for airframe corrosion, control cable integrity, pass through wiring integrity, fuel line integrity, etc. But my mechanic also found a large mouse nest which certainly did not belong there!

This led me to think how easy or difficult it would be to inspect my homebuilt when it was finished. The plans specified that all interior sidewall sheet metal panels have a lip or 90 degree edge to be used to attach to the wood floorboards.  This would require me to completely remove all the metal sidewalls just to get to the floorboard removal and that would be incredibly difficult and time consuming.  The plans also specified a fabric belly and Yes, I could have added several removable inspection rings but they are very small and difficult to get into. Thus I decided in the months ahead to design a system of easily removable full width belly panels and omit the fabric belly altogether.

During this phase of building was the time I also purchased and modified a pair of Cessna 172 seats and removed the upholstery and removed 3 inches of metal frame width and re-welded them back together.

2 + 2 Seating

2 + 2 Seating

The Wag Aero “2 + 2” model designation refers to the airplanes seating arrangement which means there are two seats in front and two seats in back. However the seats in back are really only suited for children of 12 years old or less or one adult passenger. The fuselage measures only 5 inches wider compared to a Piper Super Cub which makes one wonder why the Sportsman designer thought the extra five inches would allow side by side seating versus the tandem seating arrangement for the Super Cub,

I soon realized this cozy seating arrangement when I jury rigged a couple of front seats using cement blocks and 2 X 6 board seat backs and also placed a fabric sling in position for the back seat. I also made a cardboard template of the instrument panel and for the first time I could sit in the cockpit and feel for myself the interior layout of the aircraft.

I was struck with just how narrow the cockpit was. I immediately rechecked the plans to see if there was any error, but it checked out right. I then measured the interior width of my Cessna 172’s cockpit and was quite surprised to find it was only one inch wider than the Sportman. These measurements were taken at the width of the instrument panel. The major width difference between these two airframes is because the Cessna’s cockpit width remains mostly constant all the way down to the floorboard where as the Sportsmans cockpit width tapers down from 38 inches to 30 inches nominally, thus affecting the seat width. It was now no surprise why Wag Aero specified to remove 3 inches of seat/back width from a Cessna 172 seat and reweld them back together. Using standard Skyhawk seats would never have fit.

My concern for this ergonomic issue was not over and many months later I would develop a solution for this narrow width problem by designing special plexiglas bubble doors that would add 8 inches of interior elbow room to the cockpit without modifying the airframe. In later posts I will describe the tooling and fabrication methods used.

Flight Test Video of Elevator & Horizontal Stabilizers

Let’s look a few years ahead at a three minute flight video showing the Aircraft Tail behavior during Cruise, Landing and Side slip maneuvers. A noticeable misalignment of the Elevator and Horizontal Stabilizer occurs in these various flight control movements. An adjustment to the Forward Spar will be needed to realign these surfaces.

Welding the Elevators, Trim Tab, Stabilizers, and Rudder

Welding Tail partsMaking the tail parts require accurate welding fixtures.  Plywood panels were purchased and painted flat white.  Then a 2″ pencil grid was drawn on the entire face of the panels.  I then transposed the full size shape of the stabilizer, elevator and rudder on the plywood panels and located  each rib location, hinge knuckle, cross brace etc. per the plan. The tubing was bent using a spring and soft rubber hammer and plenty of hand persuasion.  Gradually I got the metal to agree with my curvy drawing.  The horizontal stabilizer had a tricky leading edge taper that required spliting the last outboard length a few inches from the end and then removing sufficient material and then squeezing the ends together and re-welding the seam back together.  The seam was then ground smooth.

The metal tubes and ribs were cut to size and fitted tightly together on top of the plywood pattern. Wood blocks were used to keep everything in their place during welding.  Only tack welds were used to temporarily hold parts together.  The assembly was then removed and finish welded on a welding table.

Welding the thick hinge knuckles and bushings was the most difficult due to the differental thickness of the knuckle and the parent tube.  It was important to keep the heat directed to the heavier wall tubing and avoid burning through the adjoining thinner parent tube.  Also keeping the hinge knuckles aligned  was done with sacrificial bolts that sometimes became unknowingly welded to the finished assembly.

The plans also called for small 1/8″ rods in certain end locations.  This was used as a anti bending brace to avoid end deformation during the later fabric cover and shrinking process.

Designing a Lift & Latch Mechanism

Fabricating the Turtledeck 2 of 3The plans do not show how to lower and lock the turtledeck down or how to lift it and keep it  up.  As an Interior Designer (my regular occupation) I have designed a lot of specialty store fixtures, concierge desks, etc., so I decided to use a lift mechanism typically used to raise and lower custom tables made by Suspa in Grand Rapids. It is a manually operated self contained (non-electric) single acting cylinder system and hydraulic pump.  I located the pump under the sheet metal deck of the turtledeck compartment with a detachable crank handle facing out on the pilot side.  You crank it clockwise to raise the turtledeck or counterclockwise to lower it and it will stay put wherever you stop cranking.  I bought a complete second system just in case it ever failed but to my surprize it has been remarkably dependable after being raised and lowered hundreds of times during several hot and cold seasons.

Another concern was keeping the turtledeck locked down for flight. You obviously don’t want something 8 feet long flopping around back there.  An architectural panel latch available from Southco was used to latch and lock the front and rear ends of the turtledeck. This mechanism uses two detachable hex wrench operated  thru-bolts that when rotated hook to brackets and pull and lock down both ends of the deck.

At this point in time I had my first visit from my EAA Tech Advisor, Bud Potts who offered a lot of technical know how and made many other visits throughout the building process.  All aircraft builders should take advantage of this useful EAA resource.

Learning to Weld

Welding ProjectsWith the fuselage securely attached to the rotisserie it was time to learn to weld the 4130 steel tubing.  Using a oxygen/acetylene gas rig and jewelers torch I test welded several scrap pieces together but it was’nt until I got expert instruction from Chuck & Craig Garret from my local EAA Chapter 145 that I finally gained some confidence.

I started welding on the fuselage lift handles and then the wing spar brackets, elevator bell crank assembly, floorboard mounts, rudder pedal mounts, engine mounts and landing gear and wing strut brackets.  They say the best way to test a weld is to try to tear or break it apart.  Unfortunately that destroys your weld.  Sadly, a few years later I put some of my welding to a real world test during a bad landing/ground loop event.  The good news is, the welds survived – the bad news is, the landing gear did not.

I will post more about that event in a future post including photos of the damage and the repairs made to the aircraft.

Preparing the Fuse

Fuselage on RotisserieThe newly purchased fuselage was attached to a homemade rotisserie fixture on wheels.  The fixture supported the fuse and allowed it to be turned and held in place for welding parts on, attaching floorboards, installing components, and for fabric covering and painting.

The fuselage stayed on the rotisserie for 4 years until it was removed for sand blasting and painting.  It was then re-attached and the rotisserie was motorized for easier turning. It stayed attached for another two years for fabric covering and painting until it was finally removed and let to stand on its own wheels.

N728DC Super Sportsman Welcome

N728DC Super Sportsman

Welcome to the Cleared to Land FLIGHT bLOG.  This is the first post of hopefully many posts that will describe with text, photos and videos the building and flight testing process of Experimental Aircraft N728DC. Your comments are always welcome.