Finishing the Turtledeck

Fabricating the Turledeck 3 of 3After the metal fabrication and system testing of the lift and lock mechanism was complete it was time to finish and protect the metal.  A backyard sandblasting set up was used to clean and prepare the metal for paint.  This set up was used for all smaller parts like tail pieces, rudder, landing gear legs, etc.  I found out that sandblasting is very messy and its impossible to recover used blasting material when you do it outside. All future sandblasting was done by Southwest Sandblasting in Grand Rapids who do an outstanding job.

After the turtledeck was sandblasted it was cleaned with MEK and hand brushed with a 2 part epoxy primer from Randolph Coatings quickly followed by a 2 part epoxy J-3 yellow finish color.  The 2 part epoxy paint protects the metal from corrosion and is impervious to MEK and all other Poly Fiber chemicals used for fabric attachment and finishing.

Because the inside fabric of the turtledeck can be seen when it is raised I used untinted Poly Brush to avoid having pink brush marks visible.

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.