One thing I am learning: You can build a bow that stores gobs of energy and has a nice FAT FD curve. But making that bow shoot that energy into the arrow can be even more difficult. A high energy storage bow does not equal an efficient bow. AKA static efficiency isnt equal to dynamic. The trick is finding the balance.
What makes a high energy storage bow? To start with, a proper tiller. That will change depending on the bow design. Then you want the correct amount of bending surface area. Think "PSI" pounds per square inch. Each inch of wood can have X amount of stress before failing. So make sure you have enough inches to absorb all that stress evenly across the working limb and not begin to fail. Though experimentation I have come up with a formula that expresses that based on the woods density. Im actively building a program to help with that and will post it on the new PA page when its done. The next thing is you want the energy storage to start off high and slowly taper off to low amount as you draw. You want the bow to stack in reverse, aka high early draw weight gains per inch of draw that drop every inch you pull it. The only way I know to make that happen is the bow has to get effectively longer as you pull it. That requires a lot of string contact at brace that lifts off at full draw. Feel free to add more if you think of them.
What makes a dynamically efficient bow? One that has no set. Thankfully that happens when you have the correct tiller shape and you are PSI balanced per the woods density as mentioned above. So thats two birds one stone there. Then you need a short bending section. The shorter the area you have flexing the higher the frequency the limb will vibrate at when released. That also frees up the rest of the limb to act as a lever. Now the trick here is to put the correct number of square inches into as short a bending section as possible, which can make a bow comically wide. Dont laugh too hard though, those wide short limbs will make a bow VERY powerful. The issue you run into next is the wider and shorter you make them the thinner they get to allow the needed bend radius to make your full draw. The thinner limbs like to loose some stability so you have to find a good balance. Lastly there is the question of whether you are shooting heavy or light arrows. The lighter the arrow is, the less leverage the bow needs on it to accelerate it. So lighter arrows can be shot from a short bow. Heavier arrows need longer levers to get all that mass up to speed, so longer bows are favored by heavier arrows. You will see evidence of that already between the old English long bows and the shorter bows of the asiatics. Thats a crash course in what what knowledge I have gained via years of making bows chasing speed.
What are your fastest bows and what makes you think made them fast?
