SA,

In your second example..If both bows store the exact same amount of energy regardless of how it is done, they will only produce the same speed and KE if the percentage of efficiency (as BF posted about) is the same between the two.

Also a note regarding arrow weight adn efficency as BF posted.

Yes in general, the lighter the arrow the less efficient the system becomes (and KE is lower). However that is not always the case: the BKII cams in particular are an exception: At the various arrow weights I have tested it, they produce the same or HIGHER KE as arrow weight is dropped. The cams are optimized for lighter arrows. Once a certain threshhold is reached when lowering arrow weight, the bow gains roughly 1 FPS for every 2 grains of arrow weight dropped..as the arrow approaches 5 grains per LB it is producing slightly more KE initially than it does with heavier arrows.

JeffB <img src=icon_smile_big.gif border=0 align=middle>