How to do bare shaft tuning
First get as close as possible to the correct spine for your bow:
For wood: Start with the draw weight of your bow. (E.g. Longbow 50lb @ 28”) So you will start with a 50 spine arrow. For every inch of your draw above 28” add 5 to the arrow. For every inch of your draw below 28” subtract 5 from the arrow spine. (I have a 27” draw so for the bow mentioned above I will be at 45 now). For fast flight string add 5 to the arrow spine (now at 50 again). For center cut shelve add 5 to arrow (my longbow is not center cut so still 50). For recurve add another 5 to the arrow. For every 25gr above 100gr of point add another 5 to the arrow spine. So my starting point will be a 50-55 spine arrow.
For carbon and aluminum: Use the specific manufacturer’s chart. For my Boreal longbow, if you draw above 28” use the recurve chart.
With the arrow at FULL LENGTH and the desired weight of FIELD POINT on (no fletching), shoot at an appropriate target at 10 paces. For this hold your bow up vertically. The arrow should start out showing a weak spine. For a right handed shooter the nock will be to the left of the impact point on the target. For a left hand shooter the opposite applies. Do not worry if you do not hit the center, you just want to establish the correct spine for your shooting method.
Now shorten the arrow ¼ “and repeat step one. Your arrow should start comming in straighter. Keep shortening your arrow until your arrow hits the target with the nock in line (almost is also good) with the impact point.
Now the arrow will either hit with the tail high or low. If it hits with the nock high, move the nockset on the string up a wee bit and the opposite goes for nock hitting low.
If you are happy with the flight of your arrow it is time to fletch you arrow and enjoy the flight of a perfect arrow in flight.
NOTE: You might use a couple of different arrows and in the case if wood arrows even break a few when you first start out with bare shaft tuning. For wood arrows I use a bag target rather than a foam or strawbale target.That is a small price to pay for setting up your equipment. You will now have arrows that fly as they should and enhance your archery experience. Never do bare shaft testing with a broadhead as the arrow might have unpredictable flight. Rather use a field point of the same weight as the blade that you intent to hunt with.