Most all recurve target archers know about limb alignment systems, what they do and why. Most everyone has figured out how to use their limb alignment system to make sure their limbs are lined up with one another. And that's great.
But I've discovered after working on countless bows for friends and students that a very small percentage of these archers understand the second step in the process of getting your bow "lined up" properly. That is - getting the string path ON PLANE with the riser.
More often than not, I see bows that have the limbs lined up with one another, but the string path is not on plane with the riser, so that the arrow is being shot off plane. This makes a bow difficult to tune, and unforgiving to shoot. I believe this is the cause of many so-called "untunable" setups, and it most certainly has contributed to the problems that led people to come see me to "fix" and tune their equipment.
When I show folks how to check to see if a bowstring is on plane with the riser, I see light bulbs go off over their heads again and again. Not sure where the disconnect is, but there is one. Maybe the instruction manuals just aren't covering this. I'm not sure.
Anyway, there are a few ways to check this, but here's what I do:
Find a part of the riser that is perfectly and equally flat on both sides of the riser. With a strung bow, lay a bowsquare on edge against this surface and run it back to the bowstring. Measure the bowstring position on the square from both sides of the riser to see if the distance is equal. If not, make a note of which direction the string needs to be moved to get "on plane" with the centerline of the riser. I note the direction as either "toward" the sight window, or "away" from the sight window. This eliminates confusion with right or left when the riser is flipped to access the alignment screws.
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Then adjust the alignment screws or washers equally on both limbs in the direction the system needs to go to get on plane, and recheck with the bowsquare until the distances are equal on both sides of the riser.
Some folks have used the stabilizer to "line up" the plane of the string when they check limb alingment. This is not a good idea, unless you first know if your stabilizer is straight. How do you check this? Simple. Just lay a straight arrow flat along the surface of the sight window and look down on that arrow to compare it to the line of the stabilizer. If the stabilier is straight, the arrow and the stabilizer will be perfectly parallel. Very few stabilizers and/or stabilizer bushings or tapped holes are perfectly straight. So if yours isn't, just make a mental note of which side it points to, and how much. That way, when you line up a set of limbs on that handle in the future, you can then use the stabilier to give you an idea of whether the string is on plane or not.
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Even though the string is not lined up with the stabilizer on this particular bow, the string is still on plane with the centerline of the riser and in proper position to set plunger centershot and begin tuning.
A bow with properly aligned limbs that are on plane with the centerline of the handle is a real pleasure to shoot and will be a more accurate and forgiving bow. Don't underestimate the value of this adjustment. In the past few months, I've made this adjustment to several very accomplished archer's bows, and they immediately noticed the difference in the feel and tune, and left with a new sense of confidence in their equipment. And that's always nice on competition day!