Weight stacking refers to the effect of added weight on the hook translating to added pressure required to move the trigger. Imagine setting the trigger tension on your release while you are just holding it in your hand. There is no pressure on your release aid at that time and you probably get it to exactly where you want it. Now imagine coming to full draw where the full holding weight of the bow is applied to the hook; it will take far more effort to move the trigger because the added weight increases the friction between the two sear edges.
Most double sear mechanisms employ a technique called isolation to eliminate weight stacking. They accomplish this by using two entirely separate searing mechanisms, packaged together in one handle,that close and lock independently of one another.
While they are typically closed and locked independently, they always fire in sequence, but only the primary sear is acted on by the user. The hammer component of the primary sear then acts on the secondary sear to release the bowstring.
Weight stacking occurs in the secondary sear; the heavier the bow, the harder that sear is to activate. The primary sear, however, is physically isolated from the secondary sear, often with a visible gap. Theprimary sear includes a powerful spring that the user loads when they cock the release aid mechanism.That spring is selected by the designer to move the hammer with at least enough force to activate the secondary mechanism even at extreme holding weights.
Moving the trigger ALWAYS requires the same amount of force and it is defined by the power of the spring acting on the hammer, not the holding weight of the bow. Every time you cock it, the same amount of pressure is required to do so and every time you activate it the same amount of pressure is required on the trigger.
Advanced searing mechanisms make it possible to adjust the power of the spring so you can set the trigger pressure just the way you want it, but it remains isolated from the secondary sear and will always produce a consistent trigger feel.
The dictionary defines a “sear” as the catch that holds the hammer of a gun’s lock at cock or half cock. While Webster’s hasn’t caught up with archery technology yet, the same basic definition can be applied in archery release aids. In the simplest of forms, an example of a sear in an archery release is where the hook and the trigger overlap to prevent the hook from swinging open until the trigger has been pulled. The sear is specifically where they overlap. There can be multiple sear edges in a release aid so the most applicable definition of a sear is, “When two edges of separate parts overlap preventing one piece from moving until the other is intentionally moved.” You might also hear people refer to it as a “sear edge”.
Two or more components assembled into a release aid body that collectively form at least one sear.They may come in and anything from single sear configurations, which have two parts, to double sear configurations, which have 4 parts. Some have flat edges, others have a flat edge and a roller sear.Theoretically there could be more sears involved, but there is no technical benefit for more.
The vast majority of hunting releases are designed using a single searing mechanism. Their primary strength is that they are very simple and can be packaged in a very compact and reliable unit. In this kind of release, the hook that holds the bowstring is prevented from opening because one of its edges directly overlaps an edge on the trigger. When you move the trigger, the edges move away from each other and once they have clearance the hook opens and the bow fires. This is the essence of a sear, when two edges of separate parts overlap preventing one piece from moving until the other is intentionally moved.
Single sear release aids are not very adjustable and they are very prone to variation. Weight stacking is a significant source of variation and it can occur from a number of factors. In hunting situations, it comes more from having to take awkward shots where your form is not exactly the same as it is when you are practicing. Bending at the hips, aiming off your knee, trying to lean one way or the other to make a shot, or just plain excitement all introduce variation into your form and that will affect how hard you are pulling into the backwall of your cam.
A double sear mechanism has two independent sear sets, packaged together in one body. Each set is secured independently of one another, but they fire sequentially to release a bow string when activated. The purpose of a double sear is to isolate the effects of the bow’s holding weight from the pressure required to move the trigger.
The primary sear is between the trigger and the hammer. The hammer is preloaded with a powerful spring, which is why you have to cock a double sear release aid. The trigger overlaps the hammer and prevents it from moving until the trigger is intentionally moved. The secondary sear is between the hook and what is called the stay; the stay is what prevents the hook from rotating. This is completely isolated from the first sear and when the release aid is cocked it will not open on its own when you draw a bow back.
When the trigger is moved, the hammer is released and the stored energy in the spring behind it causes the hammer to advance aggressively until it hits the stay. The stay then swings out of the way clearing the way for the hook to open.
Weight stacking is not a factor because the spring powering the hammer is selected so that it can always overcome the maximum friction between the secondary sear components at full draw. If you need more power, you design in a stronger spring. The heavier the spring, the harder it is to cock.
Double sear mechanisms are complicated and don’t lend themselves to compact packaging. For that reason, they are typically found in handheld style release aids because they typically have more room inside. Geometries are particularly important and balancing them with the needs of an ergonomically designed handle offering wide ranges of adjustability is not easy.
When one of the components in a searing mechanism has a rolling member to facilitate the motion across the sear edges. It reduces frictional load, but typically induces additional trigger decay. Theseare typically found in single sear mechanisms.
This refers to the amount of time it takes the trigger to fully release the hook after the trigger has passed the point at which the release will fire without any further external pressure on the trigger. The higher the trigger decay, the slower the hook releases the bowstring. If it takes a lot of time in between when the trigger initially moves and the hook actually opens it leaves a lot of opportunity for the hook to interfere with the smooth release of the bowstring. The lower the trigger decay, the more forgiving a release is to movement while the bow string is advancing.
The distance at which you can successfully and ethically attempt a kill shot. It increases with accuracy.