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.

Deciding on a Hinged Turtledeck

Fabricating the Turtledeck 1 of 3The Sportsman 2+2 plans provide the builder 2 Turtledeck options – A fixed in place Turtledeck or a hinged Turtledeck.  I chose the hinged option and I have never regretted it.  The hinged turtledeck has its origin from the U.S. Navy Piper HE-1 designed to carry a patient litter.  From a practical weight and balance stand point there is only so much you can load behind the passenger compartment, but also from a practical stand point having a hinged deck allows for very easy preflight inspection of all things below and makes sense for easy fabric repair, for access to replace aging rubber fuel lines and for checking elevator cable tension all without ever needing to remove or cut fabric.

Fabricating the thin wall steel channel puts your welding skills to a real test.  Most all of the light weight structure is made from .035″ X 3/8″ x 3/8″ Piper mild steel channel, including the stringers and frame channels.  Too much heat and you burn right through it!

My styling side got the best of me when I could not resist to change the shape of the window from trapezoids to nautical portholes similar to ones found on one of my favorite STOL aircraft, namely the Helio  295 Super Courier!  Granted my Super Sportsman is no Super Courier but why can’t it look like one!   I welded  small steel rings to the channel structure so the fabric would have something to attach to and used clear plastic lenses from wall clocks for the round bubble windows.  Luckily they still make the clock so I have a replacement source for the windows. My next post shows these porthole windows installed.