When to use heavy war arrowhead or light? (Deadly Spring)

[Flyndaran]

In the deadly spring article in Pyramid, and the oh so needed spreadsheet, there is the option to use either a heavy war arrowhead vs. a light one.
But there is no game effects or requirements other than the lighter one is of course much cheaper.

Am I missing something?

[Icelander]

I can't speak for the design of the spreadsheet, but in real life, optimum performance for bows depends on having an arrow that fits the draw weight. A few grains off and you'll lose some percentage of performance, while much lighter and much heavier arrows basically make it a different bow.

Of course, the target type and its distance decides how you assess 'perfomance'. Do you go for range, which argues for very light arrows, or are you looking for stopping power?

Against unarmoured targets whose important organs are fairly shallow (like humans), terminal effectiveness will generally be best with the combination of the largest possible wounding head and the most possible energy, meaning that you'll want the lightest arrow you can get with the biggest head. Even so, if the arrow is too light, you'll lose more energy to the motion of the bow limbs than otherwise, so you'll run into a point of diminishing returns at which you should generally not lighten your arrows because it will make them all but useless as wounders. Extreme cases of that are competition flight arrows, which may fly far, but deliver less energy than slightly heavier arrows would and have almost no momentum.

Momentum is important for most arrow wounding. Arrows have poor energy, but penetrate because of their shape and because of momentum. Even without armour or a body with non-vital parts in the way, most of the energy in an arrow is wasted if it is not heavy enough to penetrate. Against any kind of armour, weight is the most vital characteristic that determines whether arrows are an annoyance or can be fatal.

Pretty much the only arrows ever to penetrate something called 'armour' in the real world are the absolute heaviest war arrows, heavier than hunting arrows for the same bow and shorter ranged. And they'd also need either a hardened Type 16 broadhead or some other lozenge formed broad-head or a hardened steel super-long bodkin point (which doesn't exist historically, but might be made ahistorically).

Even if a certain other arrow weight might give higher energy yields because of added velocity, the true optimum might be slightly slower and heavier arrows. This is true for all bows, but particularly true for the thickest and heaviest ones, i.e. warbows, because the heavier the limbs of the bow the heavier the arrow needs to be to prevent excessive waste of energy through their vibration.

[Flyndaran]

Arrowhead, not arrow in total. I'm keeping the total weights the same just with heavy or light war arrowHEADs.

[Icelander]

Originally Posted by Flyndaran

Arrowhead, not arrow in total. I'm keeping the total weights the same just with heavy or light war arrowHEADs.

Well, the reason to use a heavy arrowhead is that you are not looking to do that, but to get a heavier arrow that is still aerodynamic and equally long as the lighter one.

If all your shafts are 34" pine ones of the same diameter, the only way to get a heavy war arrow from them is to add a heavier arrowhead. Even if you are making the arrows from scratch (not usual in a warzone, which imported parts which were assembled there), you still can't make the shafts as thick as you want without affecting the aerodynamics and therefore range and accuracy. Also, keep in mind that shafts usually taper slightly at the front end to enable the head to be fitted, which means that you need the head to weight enough to more than counterbalance the shaft. It needs stability in flight and, in general, the heavier the front is compared to the rear, the better.

In real world terms, if the arrowhead is tiny and the shaft is thick enough, what you have is less an arrow than a toy, less likely to hit what you aim at than it is to do cartwheels.

[Flyndaran]

I understand that as a lawyer it pays to love arguing for argument's sake. But explaining real world physics that I already know and has nothing to do with my initial question isn't very useful.

[Icelander]

Originally Posted by Flyndaran

I understand that as a lawyer it pays to love arguing for argument's sake. But explaining real world physics that I already know and has nothing to do with my initial question isn't very useful.

My point is that I would not expect the system to differentiate between a heavy arrow with a medium weight broadhead and a heavy arrow with a heavy weight broadhead, because the two are functionally identical when it comes to anything GURPS models. The arrow weight determines the velocity and the wounding, right?

GURPS assumes that fletchers will choose arrowheads that don't give penalties to Acc and doesn't get much into the aerodynamics involved, beyond the fact that Fine (Balanced) arrows are available, presumably involving precise fitting and calibration of arrowhead weight, shaft weight and shape, rear tapering, fletching, etc.

The inclusion of arrowhead weight on the tables is presumably so that you can add heavy ones to shafts of fixed length and diameter, to get a slightly heavier arrow and hopefully, edge into better performance.

[Flyndaran]

Originally Posted by Icelander

...
The inclusion of arrowhead weight on the tables is presumably so that you can add heavy ones to shafts of fixed length and diameter, to get a slightly heavier arrow and hopefully, edge into better performance.

That makes sense for the article, but not so much with a spreadsheets' whose purpose is to tweak. Since wood is much less expensive than metal arrowheads.

[Icelander]

Originally Posted by Flyndaran

That makes sense for the article, but not so much with a spreadsheets' whose purpose is to tweak. Since wood is much less expensive than metal arrowheads.

I didn't make the spreadsheets. ;)

If it helps, rule that using shafts heavier than x without using a correspondingly heavy head has deterimental effects on hitting things at distance. Which it does in real life.

If you want to know desirable ratios, look up a real example of an arrow designed for the function you're wondering about. For example, for a pure war arrow, compare the weight of a wood shaft and a type 16 broadhead and state that using a much lighter head on that kind of shaft would probably give a -1 to hit penalty for every 100 yds of range or so. Extreme cases can get heavier penalties.

That ought to prevent heavier shafts than are practical combined with lighter heads, cheaper though it may be. That said, note that bodkins are essentially lighter arrowheads that at least sometimes were fitted to normal shafts, because this gave longer range at the cost of penetration. So you'd need to go to a very light arrowhead to get penalties with a normal shaft, but of course, if someone were gaming the system with the lighest possible head and heaviest possible shaft, penalties ought to accrue.

Beyond worse balance in flight, tiny arrowheads ought to do less damage than ones properly fitted. That's a function of wound channel modifier, which I know Doug wanted to incorporate into these rules, but don't recall if he did. I seem to recall resistance to the idea from officials arguing that imp damage was imp damage.

Personally, I'm in favour of there being imp and imp, if you know what I mean (and I think you do). War broadheads might have imp, hunting broadheads imp+ and an AD(0.5) and bodkins might be imp-. Or you could have a number between 0.5 and 5 that would differentiate between a massive glaive penetrating something and a small spike penetrating to the same depth in it (rescale for target SM in line with David Punch's article in Pyramid). Arrows would generally have lower Wound Channel Modifier (WCM) than spears, but still very high compared to, say, firearms. Low-tech missile weapons generally penetrate very badly, but wound very nicely.

Well, technically, the absolute best war broadheads at point blank from the heaviest draw bows and with broad shafts rate AD(1) and most war arrows are AD(2/3), with hunting arrows at AD(0.5) easy, but I don't know if others are prepared to fuss with that kind of fractions and math at the table (even if they'll crunch a spreadsheet before play). Also, it makes bows less effective, which fits reality, but plays havoc with Legolas and the 'heroic average'.

[Flyndaran]

Optimally I guess I would like enough information to pinpoint optimal arrowhead weights for a specific arrow.
But without getting the author to divulge possibly non-existent notes, I'm stuck with two types.
I suppose eye-balling it is the best one can do.
When in doubt, roll and shout. :)

[Ulzgoroth]

Originally Posted by Flyndaran

Optimally I guess I would like enough information to pinpoint optimal arrowhead weights for a specific arrow.
But without getting the author to divulge possibly non-existent notes, I'm stuck with two types.
I suppose eye-balling it is the best one can do.
When in doubt, roll and shout. :)

The benefit of a heavier arrowhead, from the article's formulas, appears to be that it lets you increase the weight of the arrow without increasing the diameter of the shaft. That boosts 1/2D range, as well as increasing the bow's efficiency, at the cost of max range.

You could get similar, though not the same, effect by increasing both the length and thickness of the arrow. (The difference being that your arrow weight would rise faster compared to your arrow weight/cross section.) I suspect there are practical limits on arrow length but so far as I can tell the article doesn't specify them. I'd generally keep arrow length around 1-3 inches longer than the draw length (as the only example that deviates from that is the medieval crossbow with its extremely short draw).