I have an old Cushcraft long-boom, 18-element 2-meter yagi, model 4218XL. There's a copy of the original assembly instructions at
http://www.popular-hifi.com/shack/ant_cc18/cushcraft_2m18.pdf
Several years ago, while the antenna was on the ground, some kids twisted and broke most of the elements. I held on to it, thinking that someday I'd rebuild it, and 'someday' is now.
I'm wondering what aluminum alloy to use for the replacement elements. As far as I can see, the original alloy is not specified in the manual.
Cushcraft currently sells a 17-element yagi, model A17B2. I haven't yet compared the boom lengths, element lengths, or element spacings between the two (the A17B2 manual can be downloaded from the Cushcraft download page at
http://www.cushcraftamateur.com/support.php?productid=A17B2), but upon looking at the parts list at
http://www.cushcraftamateur.com/Product.php?productid=A17B2 it appears that the antenna may be using aluminum alloy 2011 for the elements, well, for the directors anyway.
I'm not sure which treatment, but 3/16" diameter (0.1875) 2011-T3 round rod is available from onlinemetals.com -
https://www.onlinemetals.com/merchant.cfm?pid=21565&step=4&showunits=inches&id=288&top_cat=0). I've never worked with it, but apparently 2011 alloy is considered to be the 'easiest-machining' alloy of aluminum, but it is not as strong as some other commonly-used alloys.
The longest director is about 40", and so maybe mechanical strength is not the most important parameter.
Anyone have experience using 2011 alloy for yagi elements?
BTW, there are lots of references to an article about improving the 4218XL by ditching the strange reflector assembly and replacing it with something more usual (written by K1FO, unfortunately now a SK), but I haven't yet located the actual article - I'm a sometimes member of a Northeast VHF group, and so I can probably find it through some of those members, but in case anyone else has experience with that mod I'd be interested in hearing about it.