fighter_ace06 wrote:
Just another update for all who are interested. Sorry we have slowed down on the updates a little but we appreciate everyone who is following our progress.
I have a question or two but first I wanted to go back and completely re-read this thread from the start to see if it had already been discussed. If it was, I didn't see it...
On page 5 you described the stripping process and there was some discussion of the Anodized sheet metal and the unusual sizes - .064 thick sheet metal used on the firewall (for example) then compared to .063 thick aluminum sheet which is common now. We ran into that alot with our Goose; .072 vs. .071, .064 vs. .063, etc. The biggest issue was Grumman's original use of so much .028 - which hasn't been available in a very long time. Fortunately, they may have seen that writing on the wall and the drawings for the fuselage structure and skins includes a note that .032 was authorized as a substitute for .028. It's kinda like the whole 2x4 board issue - which for a long time has been only 1.5 x 3.5 inches.
Anyway, there was further mention of Grumman's use of Anodize for corrosion protection later on page 8. At some point, there was also a comment to the effect that "most of the fuselage was Anodized" but you didn't specifically comment on whether or not the wing structure and parts were Anodized as well.
Now, in this particular photo it shows that you're going back and reskinning the wing(s) with .032 AMS-QQA-250/5, i.e.
Alclad instead of Anodized Bare aluminum sheet (which would be spec. no. AMS-QQA-250/4)
We ran into the same kind of thing working on our old Grumman G-21 Goose, which is the same vintage, but because the Goose is intended to still operate in the water, even potentially salt water, we figured that it was very important to go back with the Anodized Bare aluminum sheet, even though the Type 1 chromic acid Anodize that Grumman used way back then is generally no longer available because of its environmental considerations. (Type 2 sulfuric acid Anodize is supposed to be able to meet the same Mil-spec for corrosion protection, but we'll just have to see about that....)
Since you're in Texas and the Wildcat is not a seaplane, that obviously is not as much of a concern for you. I do know for a fact that
Alodined Alclad does not last very long in salt water at all. We have a second Goose, built in Feb. 39 and originally owned by Texaco, that at one point while operating in the New Orleans area sank in salt water. All of the original Anodized parts and skins are in relatively fantastic shape, but some of the non-Anodized and Alclad parts have since turned literally to dust.
More significant that just the corrosion issue though, Alclad sheet is something like 5% weaker than Bare sheet because of the non-structural properties of the 1100 grade pure aluminum coating which make up 5% of its overall thickness (.063 and thinner, half that for thicker sizes.)
Here's my questions (in case you were starting to wonder) - are you sure that Alclad is per spec for the wings (or anything else in the Wildcat for that matter - Alclad wasn't spec'd by Grumman for a Goose at all, not in fact until McKinnon came along in the 1960's and used it in some of his mods) and if not, did you take the differences in tensile strengths into account? (All of the Grumman drawings for the Goose include the tensile strength specifications, so I am assuming that so do those for the Wildcat.)
Finally, one additional question; what did you work out about the trim cables on p. 8? We will have the same problem with the Goose and we have been assuming that we'll have to find a new supplier or someone else to fabricate new ones. If you've already come up with a solution, I'd bet it would work for us too - if you don't mind sharing that info.
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