A Crazy Fool said:enlglish longbows are a lot bigger than normal "longbows" in D&D terms i would call the greatbows not longbows. I might venture 1 inch as a maximum as opposed to 3/4s of an inch, but it depends on the bow and the archer
Actually, the D&D longbow is based on the English longbow. The 3/4 inch figure comes from testing English longbows.
BTW, the longest, heaviest handdrawn bow is the Kenyan longbow. 7 foot stave with a draw of up to 150 pounds. But, the bow stave is not made of particularly springy wood, and so it has a shorter range and lower initial velocity than smaller bows.
You see, draw weight really isn't what determines how fast the arrow goes. What matters is how much of the energy imparted to the bow by the act of drawing it back is transferred to the arrow. The faster the bow springs back after release, the more energy given to the arrow. An arrow from a very springy 40 pound bow will be much faster than one from a not that springy 60 pounder.