Bow design affects speed. A short bow, for example, will generally fire arrows faster than a longer bow. Before even getting into the type of arrow to fire or how draw weight affects anything, an archer must consider this difference first if he wants to start off with a design that will accommodate faster firing.
When choosing arrows for speed, there is a fairly simple concept for archers to remember in their selections. A light arrow will always fly much faster than a heavy arrow and shorter arrows will generally be lighter than longer arrows. This means short arrows will go faster. Longer arrows also have greater drag that slows them down in flight.
When determining arrow weight against speed, archers need to remember a basic rule. The rule is that a six grain change in the arrow's weight will always equal a one-foot-per-second increase in the arrow's flying speed. So when an archer chooses an arrow, he needs to make a big change if he wants it to go faster.
When considering draw weight against speed, archers have to follow a different rule. The rule is that each single pound of draw weight will always equal an increase of two feet per second in the arrow's flight speed. The difference with draw weight is that the archer must actively exert more pressure when firing.