I'm looking to get some woodies made for my Treadway, and I'm not sure of the spine or diameter, I'll need.  The bow is 50#@28" and I draw 27" so 47# at my length, and shoot a 28" arrow.  I want Cedar or Sitka Spruce (tapered).  The bow is cut 1/8" to center, and has a FF string, and I will shoot 125gr heads.  

Thanks,
Mike

I would start with 50-54.  Spine is not always and exact science, but these will be close if not right on.  Bob Burton's Whispering Wind site has a very good spine chart for woods.  His hex pines are good shafts, too.

I would also start with 11/32 diameter arrows spined 50-54.

If your drawing less than 28" you will need a weaker spined shaft.

Kellys chart is a great place to start:

http://www.arrowsbykelly.com/Spine_Charts.html

It will also depend on how center-shot your bow is.
Gary

Well you have to start somewhere. I'd go with the 50 to 54 like suggested but leave them long so in effect they will have less effective spine. That way you can have lots of adjustment like using lighter or heavier points and shorting as needed.

I shoot a shrew at simular stats as you but it is more center cut, I'm dialed in to 57 pound spine @ 29 inch arrows BOP using 160 to 175 grain points.

I'm sure you should be able to get where you want with the 50 to 54 range.
Ron

Mike:
Using a 125 gr point I would suggest 45/49 spine cut to 28" BOP. The bow will also shoot 50/54 with no problems.
Bob

I owned a Treadway and they need a pretty stiff spine to shoot well, I would say at least 50-54  cut 28" and maybe even a tad stiffer. They are a pretty hard R/D. I was always told for a high performance longbow to add 10# to a 28" arrow if ya draw 27" that would be about 57#s. Shawn

  If you look at this group the dark colored arrows are 50/54#  Tapered cedars. I shot them out of my Horne's Traditionalist 28"s with a 145 grain field tip. The bow is around 50#s for me at my 27" draw.They also fly well out of my 46# Mohawk Longbow. They are both D Style Longbows though.I would buy a cedar arrow test    kit from 3 Rivers and see what works best for you.

I agree with what has been said about it is trial and error.  That being said if it were me I would start out with a 55-59 shaft.  Shooting a 28" arrow out of a reflex/deflex longbow shooting fast flight in my experiance will take a stiffer spine shaft.  But that is just my 2 cents.