Sun Sep 20 2020

Sun Sep 20 2020
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Forward fuselage and canopy structure

	I made a decision today to re-do the forward fuselage structure. Why? Several reasons: With the inclusion of wide UHMW blocks, the pivot bolts need to be substantially longer than as originally specified by Van's. These ribs started out as Van's factory ribs, with their associated lightening holes. Unfortunately, those holes are located in non-ideal locations with respect to the modifications I'm making. Because the canopy structure is a formed and welded structure, I have far less ability to make that conform to the required shape. However, I can easily (?) fabricate new ribs and bulkheads. Essentially, I think remaking these ribs and bulkheads is going to be the path of least resistance to achieve a sufficiently good fit. The existing forward fuselage ribs extend far enough aft to support the panel. However, the location of these ribs is designed for a six-pack layout. If I install a glass panel (which I plan to), these arms will be in exactly the wrong position. So, I would have to cut these off anyway and find a different position for support of the panel.
	Because this is a kit-built airplane rather than a plans-built airplane, there aren't a lot of dimensions available to determine the "right" position for various parts. I checked the plans and they state that the roll bar which is part of the canopy structure should have it's flanges 1/4" away from the face of the roll bar. So, I placed the canopy side rail in position, spaced appropriately from the roll bar, and marked the forward edge...27 1/2" from the forward edge of the side skin.
	That side rail is supposed to be 1/8" off the top of the longeron. But since the side rail extends forward about an inch and a half beyond the point where the longerons take a downturn, the spacing of the WD-716 canopy forward structure / weldment actually needs to be spaced up about .272" above the longeron.
	I made up some .272 thick spacers from a piece of oak on which to rest the canopy structure.
	Then, in order to sort out the warped shape of the forward canopy weldment, I ran over to Home Depot to pick up a piece of very flat 1/2" thick plywood. I cut a piece of it and drilled and clecoed to the longeron gussets.
	Slots are needed to allow the canopy pivot arms to pass through.
	Slots added. After this photo, I cut and glued a doubler (3/4" particle board) to this plywood. BTW, the reason for using 1/2" plywood is that it replicated the space required between the aft face of the forward fuselage structure and the forward face of the canopy structure.