Seaplane Preparation / Part 5 of 5


The wings, tail surfaces, turtledeck, and fuselage were fabric covered at different times and each horizontal lower fabric covered  surface required the installation of drainage grommets. They are intended to drain away any water collected by condensation or otherwise from the lowest point in the airframe.  As an example, each pair of ribs in the wings has it’s own grommet on the bottom lowest portion of each rib bay.  An ordinary drainage grommet is the size of a quarter with a hole in it and is glued to the fabric.  Then you glue a larger diameter fabric dollie  over the grommet and then  take a soldering iron and burn a hole through both fabrics and through the hole of the grommet. If your going to put your aircraft on floats the Poly-Fiber Fabric Instructions advise you to use “Seaplane Grommets” which have a molded shroud that is open on one side.  These are mounted so the open hole or drain port points backwards thus avoiding the collection of water during take-offs and landings.

Another item unique for seaplane operations are flying dock ropes. These ropes are usually two to three feet long and hang below the leading edge of the wing tips. They help manipulate the seaplane while docking by providing a rope to grab and pull the seaplane to the dock. I reinforced the metal wing understructure and mounted 1/4 inch eyelets for the later attachment of the flying dock ropes.

The last and perhaps most costly item needed for seaplane preparation is a “Seaplane Prop”.  My 80 X 44 wood Sensenich will not survive the severe duty of water operations.  Water spray is like gravel and will quickly harm the soft wood surface. My hope is to use a Catto Composite 86 X 38 climb prop that is light weight with reinforced nickel edges .

Re-Fitting, Sandblasting, Priming and Storing the Tail Parts

Preparing Tail Parts for Covering
With the tail parts re-attached to the fuse it was time to re-check control movement of the elevators, trim tab and rudder.  When this checked out, the elevators and horizontal stabilizers were removed for sandblasting and priming.  A strobe light bracket from Univair was welded on the top of the rudder and later wired with a quick link harness prior to fabric cover.

The vertical stabilizer remained attached to the fuse and all the remaining tail parts were then hung from the rafters until the rest of the fuse was ready to cover.

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.