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Old 11-25-2008, 12:44 PM   #1
Icelander
 
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Default Bulk and ST for missile weapons

I know that there isn't a weapon design system in existence. I know that what I'm asking will more properly be answered if and when we get one.

But I need at least a provisional judgment call on it now.

I'm attempting to link crossbow size, weight and power with the poundage needed to draw it. That way, crossbows might be closer to reality than the current version.

Clearly, the more powerful a crossbow is, the stronger its construction needs to be. Some of that can come from better materials, but the most common method will always be a larger and heavier prod.

In addition, the longer the prod/lanth is, the more efficiency we get. That means a bow with a very small prod needs a very high draw weight to get the same initial velocity as a prod with longer limbs. It's therefore practical to have the prod of a dedicated war weapon be as wide as a man can easily use.

I can find the weight stats for crossbows of a given poundage in historical sources. I can also find their dimensions. Their capabilities can be estimated from testing data and the GURPS ST damage rules (which are faulty at high levels, but I'll use nonetheless to retain compatibility and relative power with other muscle-powered weapons).

But Bulk and ST for missile weapons do not correspond to any real world number that I can research. The best I can do is compare to similar weapons and guesstimate.

So, GURPS gives a Crossbow weighting 6 lbs. Bulk: -6 and ST: 7†. A Composite Crossbow weighting 7 lbs. has the same Bulk, but ST: 8†. A Repeating Crossbow of 10 lbs. is Bulk: -5 and ST 7†. A Pistol Crossbow weights 4 lbs. and is Bulk: -4 and ST: 7.

My questions are these:

a) What are the dimensions of these weapons?
b) How much does weight have to change in either direction before ST changes?
c) How much does Bulk change with increased size?

In other words, what Bulk and ST is a 18 lbs. crossbow with a lanth 4' wide? And so on and so forth.
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Old 11-25-2008, 01:40 PM   #2
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Default Re: Bulk and ST for missile weapons

You might find it easier to compare to the Bulk of modern rifles from High Tech. At least those are for set specific models, and you can look up the dimensions online or in a Janes reference manual.

Regarding ST: Do you mean the Minimum ST to wield the crossbow, or the ST the crossbow can exert?
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Old 11-25-2008, 01:48 PM   #3
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Default Re: Bulk and ST for missile weapons

Quote:
Originally Posted by Bruno
You might find it easier to compare to the Bulk of modern rifles from High Tech. At least those are for set specific models, and you can look up the dimensions online or in a Janes reference manual.

Regarding ST: Do you mean the Minimum ST to wield the crossbow, or the ST the crossbow can exert?
I mean MinST.

And rifles are not shaped even vaguely like crossbows. A rifle of equal length to a high powered crossbow will be much less bulky because it doesn't have to have a wide prod that extends to both sides.

We can see that the GURPS Crossbow in the BASIC SET is only 6 lbs., but still Bulk -6, whereas rifles of that weight are usually much more handy.

What I'm trying to figure out is how much bulkier is the crossbow? How much does the inconvenient shape affect Bulk?
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Old 11-25-2008, 02:21 PM   #4
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Default Re: Bulk and ST for missile weapons

Blah. Yes, of course there's a significant shape difference. My brain stopped working when it noted that rifles tend to be big, and well documented, and reached out and hit the reply button without further thought.

Regarding MinST, I don't think there are any hard formulas around at the moment, but I'm remembering a few "rules of thumb" which may or may not be as "helpful" as my rifle suggestion.

1) weight - to - MinST seems to scale linearly at a 1:1 ratio within the same group of weapons, for the same shape, judging from the Dungeon Fantasy rules for scaling up weapons for bigger barbarians. 1.5x the weight modifies the MinST by 1.5x

2) the "Combination weapons" box in Martial Arts (page 214) says, when talking about adding spikes, blades, and nasties to existing weapons (Which changes the balance!):
Quote:
Originally Posted by Martial Arts
Apply +1 to the weapon’s ST statistic per 1 lb. or fraction thereof added to a one-handed weapon, or per 2 lbs. or fraction thereof added to a two-handed one.
However, determining the MinST of a weapon can't be as simple as dividing weight by 1 if one handed and by 2 if two handed. It just doesn't return the correct numbers if you try that.

But that's a few clues, and the rule from Martial Arts will at least give you a way of "Fudging" the MinST for crossbows of a given weight by using one or the other rule to scale up or scale down.

If I had to guess, I'd say the Martial Arts scheme is probably more accurate because DF tends to lean in the direction of quick-and-dirty-and-cinematic.

EDIT: Although, on second thought, it may be erring on the side of higher MinSTs under the assumption that the weapon becomes more unbalanced the more geegaws you tack on.
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Last edited by Bruno; 11-25-2008 at 02:25 PM.
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Old 11-25-2008, 03:35 PM   #5
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Default Re: Bulk and ST for missile weapons

You know, Ive been thinking about this quite a bit myself as I continue to ponder the essential wood question and its effects on constructs.

Let me see if I can come up with a logic that can relate DR to HP of damge dealt or range. Essentialy, if DR is your ability to take damage with out loss of structural integrity and flexing the Bow/Crossbow is essentially the sort of non permenant damge that DR is meant to represent, could you draw a paralell?

Let me be more clear.

Can you define the min DR and HP of a crossbow as a function of its ability to impart Kinetic energy to a bolt?

Can you then take that DR and HP to let you know how much material is IN one so that you can then determine its apporpriate dimensions?

The reason I wonder is becaues Im curious to see if essential wood would make a bow/crossbow more or less useful for high strength creatures.

Get back to you soon....

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Old 11-25-2008, 03:46 PM   #6
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Default Re: Bulk and ST for missile weapons

Quote:
Originally Posted by Bruno
2) the "Combination weapons" box in Martial Arts (page 214) says, when talking about adding spikes, blades, and nasties to existing weapons (Which changes the balance!):
That last part is critical. The GURPS Martial Arts rules assume add-ons for the most part, and simplify the Min ST calculation. It's a good enough system for what it does, but it's meant to be a simplification. At the time, Sean and I discussed What Goes in Martial Arts and What Goes Elsewhere (mostly, Low-Tech). One of these was "rules for Min ST and weapon design" and they were to go Elsewhere.

So while I'll stand behind those rules, I'll only stand behind them for what they are: a simple way of dealing with customized and combination weapons, that gives close-enough results. A more detailed system was beyond the scope of the book.
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Old 11-25-2008, 03:46 PM   #7
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Default Re: Bulk and ST for missile weapons

Quote:
Originally Posted by Nymdok
The reason I wonder is becaues Im curious to see if essential wood would make a bow/crossbow more or less useful for high strength creatures.
More.

Essential Wood pretty much makes the wood stronger without reducing its flexibility or other wood-like qualities. And the stronger the material for your bow or prod is for its weight, the less stored energy from your bow is lost in accelerating the bowlimbs.

Using Essential Wood would also allow a much higher absolute draw weight. While that would be all but irrelevant for bows meant for normal humans, since longbows can already be built as strong as any archer can draw, it could very well matter for fantasy creatures of human size*, but greater ST.

Making crossbows out of Essential Wood means that it would be possible to construct a high draw weight prod out of wood instead of steel. That would likely mean higher efficiency and thus better range and damage than a bow for the same ST made out of steel.

I suspect that Essential Wood is even better than horn and other materials used in composite bows. A perfect fantasy weapon would be a laminated or composite bow that has all the wooden components subjected to the spell.

The weapon could be a very light reflex bow, apparently too fragile to be used for anything other than sport, but due to the much stronger magical materials in use it would actually draw almost 200lb.

*Note that creatures larger than humans can use bows with a much longer draw length than was done historically. Since stored energy is a function of draw length times draw weight, this means a stronger bow for the same ST. Given that a fantasy giant would also have higher ST than a human, it becomes easy to see why people are scared of giants. Of course, single staves of good wood large enough to construct a giant bow might be hard to find. In that case, Essential Wood could be used on inferior wood in order to make it suitable.
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Old 11-25-2008, 04:03 PM   #8
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Default Re: Bulk and ST for missile weapons

One thing worth mentioning is that Bulk doesn't correspond to just, well, bulk.

If you think of the instances where the penalty applies, there might be other factors involved. Penalty to hide is in the "bulky" factor, but "ease of fire while mobile" doesn't just depend on weight or dimensions, the trigger mechanism greately helps to fire while running, and since Bulk is used to determine the penalty to shoot while running, the number should be modified by that.

Mass is a factor (which translates to HP/weight);
Distribution of mass (how easily you can move it around, balance);
Ease of use (including firing mechanism);
Volume (how easy is it to hide?);
etc...

Take a pistol, for instance, no matter how light it is (in fact it can have a theoretical mass of zero) it still will have a non-zero Bulk number (probably still -2) because it's still tricky to hide. Same goes for bows and firing while running, the coordination is tricky, regardless of weight, size, etc (it requires a certain alignment of several moving parts: body, arms, bow, bow-string, hand, arrow... and they're all moving).
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Old 11-25-2008, 07:58 PM   #9
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Default Re: Bulk and ST for missile weapons

Quote:
Originally Posted by Gudiomen
One thing worth mentioning is that Bulk doesn't correspond to just, well, bulk.

If you think of the instances where the penalty applies, there might be other factors involved. Penalty to hide is in the "bulky" factor, but "ease of fire while mobile" doesn't just depend on weight or dimensions, the trigger mechanism greately helps to fire while running, and since Bulk is used to determine the penalty to shoot while running, the number should be modified by that.

Mass is a factor (which translates to HP/weight);
Distribution of mass (how easily you can move it around, balance);
Ease of use (including firing mechanism);
Volume (how easy is it to hide?);
etc...

Take a pistol, for instance, no matter how light it is (in fact it can have a theoretical mass of zero) it still will have a non-zero Bulk number (probably still -2) because it's still tricky to hide. Same goes for bows and firing while running, the coordination is tricky, regardless of weight, size, etc (it requires a certain alignment of several moving parts: body, arms, bow, bow-string, hand, arrow... and they're all moving).
This is very true.

And somewhat problematic. For example, a well-designed trigger for and the addition of a pistol stock to a crossbow (instead of a period nut and rifle stock) might make it easier to shoot on the move, but if the rifle butt isn't shortened as well, it won't make it easier to hide.

I'm thinking that the best Bulk I can hope for with a usable crossbow is -3. That would be one with a pistol grip, no stock and a compact prod. It could be quite powerful (historical examples exist in 760lb versions) and require a cranequin or windlass of some sort to reload, but for a single shot assassination, it would be ideal.

I'm still not certain what the maximum Bulk would be for a handheld crossbow. The largest would have more than a 4' prod and a stock of similar size, perhaps a little longer. A stirrup was fitted in the front of the weapon to help draw it. The heaviest crossbows would weight around 20 lbs. Any thoughts?
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Old 11-26-2008, 02:49 AM   #10
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Default Re: Bulk and ST for missile weapons

It's also weird that there aren't rules for modifying the weight of a bow, whether it be ST10 or ST20... like you said, increasing the limb length adds more material. One possible justification is that it's possible to pull this off with changes in angle of the cord, curved design, type of wood, and whatever else is relevant (I don't know much about archery or bow-making/fletching).

Of course, crossbows have additional parts that scale with limb breadth, so even if the difference of weight for limbs is negligible the rest of the paraphernalia will still increase the weight a little.

While crossbows in history could grow to human-size and needed to be cocked with a stirrup and your foot, I don't think the crossbows in Basic/Martial-Arts get into that, they're just the ordinary 2-handed variety.

I also think that the realistic resolution of these crossbows also reflect the lack of material about them. Sure, we can differentiate the subtleties between several types of rifles, pistols and SMGs, we know a lot about them, and they're produced in series that share common traits. X-Bows weren't and we don't know a lot about them. "Small", "Medium" and "Big" might suffice, and even if you change the statistics a little, it's pretty believable that a crossbow existed with those stats, as they probably varied a lot even in the same place, as crafting wasn't industrialized.

I realize that's not what you're looking for, but for now eye-balling is probably going to give you the best results, and even if they're not perfect, there probably were some crossbows around that could perform like that and you can get away with it, unless you're too optimistic (which I don't think is the case).

I think there are too many variables we don't know how to quantify in order to reach a weight, bulk and minST value. I suggest taking the smallest crossbow you can find historically and giving it the lowest weight, bulk and minST value in the rules, likewise for the biggest historical crossbow that could be held, cocked and fired with 2 hands only. Everything else fits in between.
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