Sorry for bumping. But I was just starting to calculate my own spoke-length and came to wonder if the numbers above also fits my 110mm rear hub, or if it's specific for, say, 120mm. I too have a double-sided rear hub.
According to this calculator:
http://www.bikeschool.com/spokes/index.cgi

I'd need 285.4mm spokes if I'd do a 3 cross (36H) with a Alex TD17 rim. Yes, I know it's a crap rim, so don't bother.

Am I onto something here or is it totally out of the blue?
Yeah, this'd be my first build thus all the newbie questions

/J