This is a post by Tony Camera on another forum. It is a good place to start for aluminum arrows:
"Here's the deal: There are only seven arrow spines you need to work from #25 to about #100. (Note this is an approximation and you see why in a second).
IN GENERAL for 28" ARROWS +/- 1: ( 27 - 29") and 100 - 125gr heads:
#25 - #33 1716
#34 - #42 1816
#43 - #52 1916
#53 - #60 2016
#61 - #70 2117
#71 - #80 2216
#81 - #100 2219+ (Might want to play with 23xx and 24xx, gets a little dicey at those weights)
If you go to a 30" arrow, jump up one spine, 32", then go two spine numbers. Ditto for going shorter, 26" one spine down, for 24" two spines down.
This WILL NOT give you the perfect aluminum arrow for a given bow. It will give you a tunable arrow, and that's all you need for starters. Once the arrow is tuned, you'll know if you're compensating for a stiff or soft arrow by the tuning requirements. Then you can go in to finer arrow choices.
For example, if you have a #41 @ 28" bow and are using a 29" arrow, you'd pick an 1816, right? And that would work. If you find that you have to move the rest/strike plate out a little more than you like, then you NEXT set of arrow might be 1914s. It’s the same weight as the 1816s, but a little stiffer."
Tony has many more years of experience with recurves and longbows than I and I've learned to believe his posts.
Hope this helps,
Allen