For a lot of recurve archers who use modern adjustable risers the alignment is usually deemed to be correct as soon as getting the string to run centrally down the middle of both top and bottom limbs is achieved as seen below:-
Now this is just a start and is not proof your alignment is correct or your riser or limbs aren’t twisted.
To test for a twist in your riser the best way is to use a CMM but for those who aren’t fortunate to have access to such an instrument the use of a couple of straight parallel shaft arrows will be ideal, all you need do is rest the strung bow between two chairs and place each arrow across each limb just above the limb pocket and at right angles to the string as shown below:-
by lowering your angle of view you will eventually be able to align the arrows
Now as can be seen in the following image when both arrows are at eye level that each arrow is in the same plane, if you find your arrows don’t line up in this way and the arrows are askew your riser will most likely be twisted
If you do have signs of a twist in your riser you can easily shim the edge of one of your limb pockets by attaching a section of metal taken from a feeler gauge of the required thickness to get your riser back into “true”
Now moving on, to further ensure that your riser is set correctly, you need to view each limb looking down from the tip and by sighting along the bowstring and lining up the end loop serving and the centre serving you can see where the tip lies in relation to the centre of the lower part of the limb, ideally they will be central as seen in the following image
If either of the limb tips are showing to be more to the left or right of the centre of the lower part of the limb then further adjustments need to be made. You’ll be pleased to hear that your nearly done, however one final test is to draw the bow back 15-25″ to get the bowstring from out of the limb grooves, the best way to do this is to put a towel or riser bag over the grip of your bow and stand astride your bow and step on each side of the bag (and don’t what ever you do let the riser bag slip from under your feet )
Now when you draw the bow ideally you would want the string to remain central down each of the limbs and line up with the limb markers (Bieters/tape or limb bolts) as shown below (string drawn to about 25″) :-
If when you do this and there is a disproportionate part of the limb on one side of the string while the string is still lined up with the limb markers this would give indication of a twist within the limb or imprecise limb adjustment (this can also lead to the string “snapping” back into the groove when the bow is let down), sometimes and with a brave heart regarding limb twist this can be addressed by making adjustments to the string nocks heights at the limb tips by careful filing or sanding, a process best done by someone with the knowledge and experience.
Also longrod alignment is usually deemed a critical part of bow alignment set up, it shouldn’t be, if you follow the above procedure and the long rod is off to one side it is showing that the longrod is not straight or the longrod bushing is not square to the limb pockets. So in short, setting alignment using the longrod is just crazy!
Now with everything lined up accurate arrow centering can be achieved, and with correct arrow selection, a general good bow tune even the sight will be in-line and central for all distances.
and if you are fortunate to have a well made riser the longrod will be central too.