Low-Tech Missile Weapon Range and Accuracy

[Icelander]

Originally Posted by DouglasCole

Interesting. I hadn't thought to vary draw weight multiplier with skill. Increasing ST is the functional equivalent at constant multiplier, however, although I suspect your numbers above have more granularity than just (say) +1ST at DX and +2ST at DX+2 or something.

All guides on the subject say that a new archer will find that he can draw a bow of about 10 more pounds once he's had a few days or weeks of practice. That suggests to me that even a single point in Bow ought to be worth something.

I also believe that a reasonably strong archer will have exercised different muscle groups than a very strong weight lifter. It seems fair to me that the archer could pull a bow more efficiently than the weightlifter.

Given that most hobby archers will be at DX+1 or lower (except the exceptionally dedicated ones), this also means that a normal man (ST 10-11) will use a bow of about #45-#75, with the higher numbers being reserved for thsoe who are fit and practise a lot.

Originally Posted by DouglasCole

If we "believe" (or really, we wish to stipulate) the equivalent of +4 to ST through skill - or if we say that you can pull, say +40% heavier bow with special exercises and +40% with technique, rather than +2ST for each, then you could easily, say, give +10% to allowable draw weight at DX, with a +10% more per point of skill higher, capping at +40% at DX+4 or DX+5 in realistic campaigns. Likewise, charge 4pts per +10% for "special exercises" or something. Easier would be allowable up to +2 arm ST with the special Exercises perk and +1 at DX and +1 more at DX+2 or something.

Net/net, though, once you've spent the points in archery, presumably that's worth something as you say.

People who practise sports that value upper body strength tend to develop a corresponding musculature. I find the Special Exercises (Arm ST) Perk reasonable and realistic. It's mostly whole body ST of 15+ that I find unrealistic, and that only because of the striking ST component.

Originally Posted by DouglasCole

It wasn't an "experiment." I took my stats from the very useful article "The Physics of Medieval Archery" [http://www.stortford-archers.org.uk/medieval.htm] which give physics-based estimates for the strength of bows of the period, as well as estimating the velocity and mass of the projectiles themselves.

From this, using bullet impact formulae I derived in my article on GURPS bullet damage in Pyramid, I can calculate the points of armor a projectile of certain cross section and energy would penetrate. For a "muzzle velocity" of 60m/s and a weight of 60g, and a 1cm diameter shaft, you get about 3.8pts (1d) calculated penetration. This is complicated by the arrowhead, which has a MUCH lower cross section than the shaft, but even a cross-sectional area more accurately calculated (say, a trapezoid 4mm at its thickest and 30mm wide as a broadhead point) won't be less than about half that of the shaft, which only changes damage by 10% higher. (3.8pts goes to 4.2pts). What MIGHT drive that number higher is if the arrowheads were hardened or forged or something much harder than the jacketed lead or mild steel my model was built around. That would usually add an armor divisor...with good steel (semi-armor piercing) usually being worth a 1.25 to 1.5 armor divisor. That would typically make an arrow from this bow penetrate like 1d+1 (4.5pts) to 2d-1 (6.3pts). Given how much oomph I think we can all agree is required for a draw of 180-200lbs, having THAT bow eke out no more than 2d damage as a "ST20 bow" upper end would be fairly OK. That's thr or thr+1 using the ST table AS IS. But, it also requires the assumption of hard arrowheads and smaller cross section...which frankly ain't that bad.

Crossbows, apparently, have the benefit of not requiring so many points to eke out that same damage.

So the best we can do is thr+1.

Question, what difference would composite bows make here? Enough for a +1 damage over a yew longbow? Another question, what if we postulate fantasy materials that are lighter, springier and better? Do we eke out more damage or are the limitations not related to the material used?

Originally Posted by DouglasCole

My impression, mainly from this forum, is that arrows would rarely punch through metal armor.

This is also my impression. But, then again, the same applies to single-handed swords. So at least a part of the problem is ST damage.

If we are not going to monkey about with that, we'd probably want to benchmark bow damage at ST 10 level and accept that high ST will give unrealistic results. Otherwise bows are artificially weaker than melee weapons, which monkeys with relative weapon power.