I am building gullwing doors for an un-pressurized 200+ mph airplane. If you were to lay out the doors flat, they would roughly approximate a parallelogram (tops and bottoms parallel and horizontal, fronts and backs roughly parallel and about 20 degrees from vertical, raked back at the top). The hinges will be at the top surface near the corners, and two catches are planned for the bottom near the corners. The forward catches are around the glare shield, and the aft catches are just aft of the shoulders of the tallest passengers, so I am looking to make them as low profile as I can. I have previously worked out what stiffnesses and load capacities are needed (FEA, Vne speed, generous safety margins, etc), but now I am trying to fit in some minimum thickness latch mechanisms. The forward catch will have a live load of as much as 500 pounds, so it has to be designed to hold 750 in the metal parts and to carry 1000 in the composite parts.
I have referred to Bingelis' books, plans for all kinds of ships, every photo I have ever taken of homebuilts, and I am still trying to figure out the details for a low profile set of simple latches. It seems like everywhere I can find plans they are either awfully ugly or bulky or both. Since building a simple cover is part of my plan, I am mostly looking for ideas on a low profile design – one no thicker than 1" would be ideal, and if it is ugly, well, so what?
I am currently leaning towards having a receptacle in the bottom edge of the door, and the moving parts and handle in the fuselage wall, with a molded cover. The thought I have right now is making the receptacle out of one piece 3/8" plate, one piece ½" plate, and couple pieces of 0.050" sheet. The ½" plate would have an L shaped track, the 3/8" plate would have access for the arm, and the 0.050" piece would cover the outsides. This assembly would be riveted together, be about 3" x 3" x 1" thick, and buried in the door frame, with threaded fasteners (for adjustability). Then the fuselage mounted parts would include a roller on a ¼" thick aluminum (steel?) arm pivoted from its middle with a linkage going between forward and aft latches and the handle. Some clamping force could be provided by having both a roller and some ramp on the track. Detent could be provided by having the track slope back slightly after achieving its tightest point. A secondary detent could be achieved at the handle. Further adjustability could be provided by attaching the arms to the fuselage wall with threaded fasteners.
Does this sound like anything that is done? Are there any problems that you folks can foresee with this scheme? Do you guys have any other ideas about building low profile catches?
Billski
I have referred to Bingelis' books, plans for all kinds of ships, every photo I have ever taken of homebuilts, and I am still trying to figure out the details for a low profile set of simple latches. It seems like everywhere I can find plans they are either awfully ugly or bulky or both. Since building a simple cover is part of my plan, I am mostly looking for ideas on a low profile design – one no thicker than 1" would be ideal, and if it is ugly, well, so what?
I am currently leaning towards having a receptacle in the bottom edge of the door, and the moving parts and handle in the fuselage wall, with a molded cover. The thought I have right now is making the receptacle out of one piece 3/8" plate, one piece ½" plate, and couple pieces of 0.050" sheet. The ½" plate would have an L shaped track, the 3/8" plate would have access for the arm, and the 0.050" piece would cover the outsides. This assembly would be riveted together, be about 3" x 3" x 1" thick, and buried in the door frame, with threaded fasteners (for adjustability). Then the fuselage mounted parts would include a roller on a ¼" thick aluminum (steel?) arm pivoted from its middle with a linkage going between forward and aft latches and the handle. Some clamping force could be provided by having both a roller and some ramp on the track. Detent could be provided by having the track slope back slightly after achieving its tightest point. A secondary detent could be achieved at the handle. Further adjustability could be provided by attaching the arms to the fuselage wall with threaded fasteners.
Does this sound like anything that is done? Are there any problems that you folks can foresee with this scheme? Do you guys have any other ideas about building low profile catches?
Billski
