First off I know this sounds disingenuous, but this info is mostly based off photos (which I sadly cannot provide) which clearly show this model from it's very first moments and onward... that Beasley pic is a snap from the design in the process. What I *do* know, from most of these pictures, show moments Fall 1975.
Jim Mallasch, a McCune hire who worked in wood making patterns for Detroit Auto, working on the Y-Wing armatures and what look like vacformed shells from the naked wooden pattern. That vacformed shell, which I think *may* be what amounted to a mock up body, is what Beasley is shown with. It has smaller engine domes. Unsure if any had that brass T in the end.
There is also a photo from a *different* ILMer showing a stack of these Y-Wing vacform bodies all assembled in a corner, later in '76. I have posited that this was perhaps the first idea (to use vacformed shells with plant on parts), before they switched to a faster build iteration using castings with parts already in situ.
Then there are pics of Jones and Mallasch with the armatures but now the body is a resin shell with all parts cast and present. Based on the sequence, and details/access points, this is Gold Leader.
There are also pics of Huston working with the wooden patterns, and a pic of him trimming (?) the Y head (pattern?).
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So, we know Mallasch was let go right at the end of '75, for being too "slow" for production speeds.
We know Huston took over Y-Wing duties, as we asked him for back story on the pics a couple of years ago and that's what he said.
To add color to this little oral history, Lorne said he didn't touch the Y builds because they didn't appeal to him . Love it.
We know Beasley and McCune worked on the patterns as there's printed public pics of them doing so.
Who did the actual parts plant-ons? Possibly Mallasch? (Mallasch passed in the 90s I think I recall). Huston remembers doing some. Haven't asked Beasley, Jones def worked on it. McCune did too.
From the study of the parts I restored, and holding production castings from ILMer's closet keepsakes, this is how the Y-Wings were built:
Pattern was styrene donors and shapes, glued to a wooden buck made from many pieces of laminated and faceted wood, which was primed a very dark grey/black. Then once parts were glued down, it was primed a medium grey.
Hero Y-Wings had machined acrylic and metal armatures with mounts in the front underside of the head/neck, engines, top, bottom. Some were plumbed for lights. All had the engine exhausts integrated in place - styrene, machined acrylic.
Artoos used in Y-Wings were shorter than the X-Wing plugs, most likely from the same pattern.
Engines were styrene donor shells, plant ons were in house injection plastic.
Resin castings for the body were top and bottom body, top and bottom neck, butt plate, the back bulkhead of the head, head casting included a hand carved recess for the canopy to key to, and the cockpit was part of the top head casting. The head castings tended to run thin, apparently. There were cast detail plates all over the thing too, some acted as electrical port covers. Some stuff was from larger pattern plates also on other builds.
We have been told that the canopies were in-house injection plastic too? We *do* have examples of the engine plant ons, the guns (also used on the Death Star Turrets and even the Galactica Viper), and the egg "clamps" also used on the Falcon. So can't confirm the canopy was and I tend to think they were cast resin...
So I'd say Huston being on the first Y is accurate yes, I think he was lead.