Saturday, February 02, 2013

Building my character's bow - Part 1 - The Range

In this article I'll go over the set of new rules I'm creating for using bows. Bow use will encompass attributes like STR, DEX and CON and will have a different spin on range and arrows. I'll allow for light arrows which give less punch, but better aim and heavy arrows which allow for more punch at the expense of less aim.

First change is doing away with the long, composite, and short bow paradigm of D&D. These types of bows will still exist, but they represent the actual manufacture of the device and not so much the range or damage. A composite bow will be smaller and more expensive than a normal bow (self bows) for the same draw weight. So a composite bow will be smaller and lighter than a bigger bow of the same pull, but will fit better in a dungeon.

Your character's STR value defines the maximum draw weight that can be pulled. The following table show draw weight to STR values.

Draw-weight (lbs) STR
NA 3-6
NA 7
NA 8
30 9-12
40 13
50 14
70 15
80 16
90 17
100 18
110 19
120 20


With so many variables in involved when shooting a bow and arrow it became clear early on that some serious simplification would be necessary to keep things under control. So after doing some calculations and looking up some references I came up with the bow table below that shows damage by range given a character's strength and the choice of arrow weight.

For example, my character with a 14 STR has basically two choices: a 200 grain arrow which will shoot surer or a 300 grain arrow which will hurt more. I can also equip both in the quiver so when precision is more important than damage my character can select the better of both arrows.

If my character fires the lighter 200 grain arrow the effective range given his STR is 100 yd. He gets full damage (2d6) at short range (30 yd.). At medium range (60 yd.) damage suffers a -1 penalty and at long range (100 yd.) a -2 penalty. Below the bow table is the range table. When shooting a lighter (flight) arrow my character enjoys a +2 at short range, +1 at medium and +0 at long range. The clearance row indicates how much roof clearance I need to use that range effectively and it is based on the arrow drop per range. My character can use direct fire at 30 yd. range, requires a 10 foot clearance at medium (maybe not possible in a dungeon) and high clearance (no roof, no tree line) for longer ranges.

If damage were more important I can switch over to the 300 grain arrow which has more momentum. The difference is that all ranges include a +1 to damage bonus at the expense of the to hit bonus. At short range my +2 bonus is gone, at medium range I get a -1 and a -2 at long range.

Stronger characters will be able to pull event higher draw weights and use heavier arrows more effectively.  This will increase the damage deliverable by each arrow and increase the effective range of the bow. Heavier arrows will have more momentum and be effective at longer range. The downside is that they require more energy to propel and thus have higher DynE.

DynE is a value used in Era's combat mechanism and relates directly to fatigue during encounters. More of this will be covered in the next part of this series. In subsequent parts I'll go over bows for smaller humanoids (dwarf and halfling sized characters) and I'll take a look at how this relates to attacks per round.


STR Human 32” arrow shaft
light arrow heavy arrow Arrow Weight (grains) 30yds 60 yds 100yds 150yds 200yds DynE
9-13 9-12 150 2d4+1 2d4


7
14 13 200 2d6 2d6-1 2d6-2

8
15 14 300 2d6+1 2d6 2d6-1

10
16-17 15 400 2d8 2d8-1 2d8-2 2d8-3
12
18 16 500 2d8+1 2d8 2d8-1 2d8-2
14
19 17 600 2d10 2d10-1 2d10-2 2d10-3 2d10-4 16
20 18 700 2d10+1 2d10 2d10-1 2d10-2 2d10-3 18

19 800 2d12 2d12-1 2d12-2 2d12-3 2d12-4 20



Range modifiers

30yds 60 yds 100yds 150yds 200yds
light arrow 2 1 0 0 0
heavy arrow 0 -1 -2 -3 -4
clearance direct 10 feet 30 feet + 30 feet + 30 feet +




Image source

http://disneysrobin.blogspot.mx/2009/04/jonas-armstrong-and-his-bow.html

Reading material


English Longbow Testing against various armor


Javascript Archery Ballistics Calculator V2.08


A New Artefact Typology for the Study of Medieval Arrowheads

EXTERIOR BALLISTICS OF BOWS AND ARROWS

On the Mechanics of the Bow and Arrow


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