Recurve Limb Stack

[Neil Turner]

I have just plotted the force draw curve for my bow (68" 34# limbs draw weight 40.5) and find that the curve crosses the stack line at about 26". My draw length to the pressure button is 29" so the limbs are stacking for the last 3". How will this effect the performance of the bow and should I be worried.

[marty]

Nothing to be worried about. Nothing bad will happen to the bow.

However, a bow that stacks isn't going to be as efficient as a bow that doesn't stack (area under the force draw curve is less so the stored energy will be less). It will also feel heavier, especially if you shoot with a clicker.

Hope you didn't pay a lot of money for the limbs.

[noel mac]

neil, which hoyt limb did you have?
i have the vector carbon limb and did this same exercise to give me confidence in my equipment. early on i was using #46 then dropped to #42 then dropped agian to #39 and when i went back up to #42 it felt so heavy it wasn't funny so i plotted the force draw curve as well and ended up with a straight line on the graph, so i started to lift weights :lol: and now its or should i say i'm o.k. and MY limbs don't stack not the bows!

[James Park]

I am surprised that you say the curve crosses the stack line at about 26". For the Avalon I had, this happened at about 30". Hence, I wonder how you have defined the stack line.

[Neil Turner]

Thanks Marty, good to know that the bow will not do anything weird.

Noel, I always thought your limbs moved smoothly. I have syntactic Carbon Plus limbs. The bow does not feel heavy, I have had it up to #43 and feel no difference. I read about stacking (Archery Anatomy by Ray Axford – Order online through dva.asn.au) and thought I would test my bow with the above post the result. Also using mid point bow weight efficiency of bow is 58%.

Jim, stack line was draw from brace height at #0 to draw length at #operating (40.5). Curve runs parallel once it has crossed line. This was my first go so I will repeat it to confirm the result. I used it as more of an exercise to see how my bow works, get to know your gear sort of thing.

[James Park]

The way to find the stack point is to draw a line starting from the brace height and zero pounds, tangent to the force-draw curve. Then, find the draw length for which the force-draw curve starts to deviate above the straight line. That is the stack length. For my 68" Avalon is was 30".