It would seem that recovering arrows after an encounter isn't as easy as I though and for reasons I wasn't aware of and that buying arrows in a town you just passed may not be so fitting. I'm no bow expert, not even by a long shot (no pun intended), but doing some research for the bow and crossbow mechanics I've stumbled onto some interesting things I'd like to share which can be turned into some interesting plot twisting ideas. Getting the party to make an unexpected journey to some town, or curb their path a little by means of these.
It has just come to my knowledge that bows are more effective at making arrows fly the heavier the arrow is. So a light arrow will have less energy transferred into it and the bow will vibrate a lot more than when a heavier arrow is used. Take for example the following graph:
The blue line is the kinetic energy and the red line is the momentum. It is interesting to notice how the kinetic energy increases as the arrow weight increases. Under first impression this should not be so. After all the bow is like a spring and the energy it has depends on the pull being done. For the same pull distance the same amount of energy is stored in it. It can't create more energy simply because it has a heavier (yet same length) arrow notched in it. So the conclusion is the bow is more efficient in transferring its stored energy to the arrow when using a heavier arrow. Obviously the arrow weight has to be within the ranges for the bow. This bow is 60 lbs, a 70 lbs bow's graph uses higher weight values, going up to 1400 grains (see image reference below).
So how does this come into play? I really dislike having to waste too much time keeping track of things. It can lead to too much paperwork that doesn't add to the adventure. But when I stumble upon stuff like this I like to take note of it and keep it in mind for future use.
Under the assumption that the party member have bows, the arrows would have been built to better fit their particular bow (this is the general abstraction). When they stocked up in town before leaving for the adventure they got just the right arrows for their bows. No real worries there, they had the time and money to get just the right stuff.
Move forward a few days if not weeks and the party is now beginning to feel the strain of ammunition. They've recovered arrows as players usually do and kept on. But say you want to slow them down, need them to take a turn in the adventure or you're just seeing them go the wrong way. Here are a few ideas based on a simple rule that improper arrows will have some sort of penalty when used:
- The arrows you just took from the orcs are ok, but they're not the right weight for your bows. You'll be shooting at -1 to hit (or damage) as long as you don't restock. Modifiers may vary. You may hint that the party do something to get better arrows.
- You've come to a small town, but the local smith doesn't have just the right arrows for your bow. He can build them for you, but it will take him a few days. This way you can stall the party for a few days and maybe create an event in town that contributes to the adventure, a raid, some merchant passing through, a "natural" event (of divine source), etc.
- You've come to a small town, but the smith suggests that you travel to another nearby one to get the arrows of the type you need. He doesn't have the material for such type of arrows or would take too long to get. This can help you lead the party in another direction.
- The fighter's and the rogue's bows are quite different given their size and strength. One's arrows does not fit the other's. They can't share ammo so the rogue needs to get more somehow. This can be used to promote other activities for a player who is always shooting from the rear.
- You want a particular character to use the magical arrows the party just found. Make the arrow's weight fit that character's bow. All other characters have a penalty when using them.
Overall the scarcity of arrows should not be a game stopper nor a reason to stall the game with undue paperwork. But in certain situations the weight difference and effectiveness of an arrow can be used by the GM to lead the adventure without having to pull the party by the nose.