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.

Mating, Squaring, Leveling, and Aligning the Tail

Mating and Alignment of the TailAfter the tail parts were finish welded per the drawings it was time for a trial fit on the fuselage.  The rear spars of the horizontal stabilizers were joined together to a rotating sleeve while the front spars were joined together into a moveable and adjustable forward stabilizer mount.  This arrangement is different than the traditional jack screw found on the Super Cub.  That is because the Sportsman utilizes a cockpit adjustable trim tab on the left elevator very similair to the Cessna 172.  The adjustable range on the front spar provides a way to adjust the aircrafts pitch to keep the elevators centered during normal cruise flight and then use the cockpit adjustable trim tab for reducing control pressures.  During test flights the pitch angle of the stabilizer was changed several times until an optimal setting was found.  Future video posts will show the before and after effects of making these pitch adjustments.

The next trial fit was to attach the elevators to the rear spar hinge points and to my shock and displeasure there was a huge 1″ gap between the left and right elevator horns.  These two horns should have had only 1/8″ between them to receive the upper and lower cable attach lugs.  What went wrong?  Did I make a mistake or were the plans incorrect?  It didn’t matter – it had to be corrected and this became my first welding repair.  The tubes were cut near the end by the horns.  An insert tube was rosette welded between the two and a larger tube doubler was joined over the joint and finger welded over the existing tube.

Flying wires or tail brace wires were attached and a level was used to check tail alignment across the hinge lines of the left and right elevators.