Why isn't better limb armor available at TL8?

[Varyon]

Originally Posted by Anthony

As is usual for GURPS armor figures, the weights are grossly underestimated. Modern level IIIa body armor (Dyneema, typically) is around 1.1 lb/sf areal density, or around 22 lb for full coverage (listed armor stats are generally for armor that covers 25-50% of the torso).

I can find Kevlar with that areal density, but am having difficulty finding such data on Dyneema (plenty of Dyneema blends, but those range from 0.89 to 1.2 for IIIa). Of course, that panel is only 7/32 inches thick, which using the values from the article indicate DR between 7 (Kevlar) and 9 (Improved Kevlar), while I think GURPS usually has IIIa as DR 12 (DR 7 is enough to stop .44 Magnum HP, however, which is apparently one of the benchmarks for IIIa). This implies proper WM's of around 0.15 and 0.11, respectively, but I'd really like more than one data point (and better yet, where Pulver calculated his figures from) before I'd be willing to change them.

[ericthered]

Originally Posted by Varyon

Another issue, which GURPS doesn't cover, is that weight carried on the torso (as torso armor, in a pack, etc) doesn't "feel" as heavy as weight carried on the arms and, especially, the legs.

As a tangent, if I wanted to mess around with this, what would be a good multiplier for 'effective' weight?

[Varyon]

Originally Posted by ericthered

As a tangent, if I wanted to mess around with this, what would be a good multiplier for 'effective' weight?

This is just off the cuff, but I'd say that things on the Torso, Head, Shoulders, Upper Arms, and Thighs probably don't need a multiplier. For Elbows, Forearms, and Hands, you can probably ignore any multiplier so long as the character can keep his hands more-or-less by his sides or supported by something; otherwise, maybe x1.2? This extra encumbrance is going to penalize skill use and cause additional FP loss, but shouldn't actually slow you down or drop your Dodge. In combat, it may be appropriate to add this extra encumbrance to the weight of any weapons for purposes of determining MinST (but not for purposes of determining MinST-based damage caps, breakage thresholds, etc), although that's probably too fiddly to mess with. For the Knees, Lower Legs, and Feet, not moving around (or simply being carried) let you ignore any multiplier, but typically you're going to have some issues - you have to shift any weight on the legs a lot more than weight anywhere else while moving. I'd be tempted to go with x1.2 for Knees and Lower Legs, x1.5 for Feet. This extra encumbrance is going to function just like normal encumbrance.

[Tomsdad]

Originally Posted by Varyon

Assuming the limb armor you're talking about covers the entirety of the arms and legs and is made of optimized fabric, 10 lb Dyneema gets you DR 20 and is nearly half an inch thick, meaning it's no longer GURPS Flexible. So, some loss of mobility isn't entirely unlikely there. Another issue, which GURPS doesn't cover, is that weight carried on the torso (as torso armor, in a pack, etc) doesn't "feel" as heavy as weight carried on the arms and, especially, the legs. A lack of tailoring to fit the individual soldier may indeed also factor in.

All of these taken together, combined with the fact that soldiers are going to be wearing such armor over fairly long patrols, means using it is going to be rather uncomfortable. This may be under GURPS resolution, just like getting hit in the face with a weak punch, but in real life it is going to cause soldiers to complain and likely opt to simply forgo such armor.

Yeah wearing armoured fabric almost half an inch thick is going to have an serious impact, Even if this stuff is light in terms of total over all weight.

Originally Posted by ericthered

As a tangent, if I wanted to mess around with this, what would be a good multiplier for 'effective' weight?

It's a tough one because that's not the only impact, as others have said weight on your arms make using your arms harder (but its not like it will make you walk any slower just because it's on your arms which is how increasing encumbrance mainly effect you in GURPS).

If I was going to do it I'd go with DX penalties more than extra encumbrance penalties. There is a vague precedent for this is the rules for firing guns in body armour in TS. And I's likely allow it to be compensated for in some way (or at least only have it kick it at some threshold).

Another way of doing it is if you use the AP system giving some kind of cost for gun attacks in such armour (which don't normally cost AP) but there a granularity issue there I think


Another way to do it is make it a skill based technique were the default penalty is based on armour, this at least will allow troops to especially train to improve the issue

[Tomsdad]

Actually I like the idea of leveraging MinST in some way!

[RyanW]

Regarding the one-size-fits-all issue, if there is any rigidity, one more or less inch on an arm or leg can be crippling in a way torso armor is not. I occasionally wear a knee brace, and if it slips down at all my knee is completely immobilised.

[Anthony]

Originally Posted by Varyon

I can find Kevlar with that areal density, but am having difficulty finding such data on Dyneema (plenty of Dyneema blends, but those range from 0.89 to 1.2 for IIIa).

Hrr.. checking around:
http://www.engardebodyarmor.com/technology.htm : 5.3 kg/m^2 or 1.09 lb/sf.
http://ballisticprotection.fi/wp-con...INSTRUCTOR.pdf : 4.7 kg/m^2 or 0.96 lb/sf. This link is interesting because it actually gives quotes for Kevlar as well -- at 4.76 kg/m^2, implying a difference between Kevlar and Dyneema of 1.3%.

Oh, the other reason for not wearing limb armor is that (GURPS stats notwithstanding) flexible armor is near-useless against rifles, so if rifles are your major threat, there's not much reason to wear it.