Pyramid armor building rules for for other armors

[hal]

Hi All,
I've got some players in an upcoming GURPS CYBERPUNK campaign, in which they (the players) are somewhat worried. I can't really fault them, as my motto as a Cyberpunk GM is "If the players aren't paranoid, I'm not doing my job."

That being said, the players are interested in buying armored "slats" for their walls. In some instances, I can see them even buying these armoring panels for their homes in lieu of drywall.

Now for the fun part - those of you who have purchased the GURPS PYRAMID articles for build your own armors in issues dated: February 2013, November 2015, and October 2016 - will know that the armor weight and costs are dependent upon armor material, armor DR rating, along with a weight per square foot of surface area, and a cost per lb of armor material.

It occurred to me that those tables could just as easily work for building say, an 8' x 4' x <insert thickness here> type of panel of a given armor material. For instance, Kevlar "Mats" that are 8' x 4' x 1/2" would have a surface area of 32 square feet, and because the DR is listed as providing a thickness of 1" per 33 DR, a 1/2" thickness (actually .48 inches) would provide a DR of 16. Said "panel" would weigh 41 lbs, and cost $16,000 (well, technically, 16,384, but with rounding to nearest 1,000, it becomes 16,000).

Now, my question is this:

Does it matter how thick these armored Mats are overall? They are all designed as "Rigid plate" and I can't help but think that I could for example, create a kevlar Pad that measures 8' x 4' x 2" and have a DR of 66. It would weigh 170 lbs, and cost $68,000 to be sure, but hey, if the players want to spend that kind of money to have that kind of DR rating for their homes - I'm all for it.

So - structurally - is there any reason that one can't have say, a DR 99 TL 8 Kevlar Rigid Plate armored pad, that is 8' x 4' x 3"? If players want to insure that the entire ground level floor has armed padding that covers their homes can simply use 8 x 4 pads for a house that measures 2 x 30' x 4' + 2 x 20' x 4' or roughly 800 square feet . Total weight added to the house will be 4,200 lbs and cost 1.7 million dollars just to have a DR of 16 at any given outside wall of their 30' x 20' house.

Chances are good the players may be better advised to buy cheaper armor, or only create a single "panic" room and cover all four walls of that room with Kevlar 8...


Thoughts?

[mlangsdorf]

In the US, at least, exterior walls are usually 3-8" thick (depending on location and building practices), framed with wood, and faced with some covering material on the outside (brick, stone, concrete panels, aluminium, etc) and drywall/sheetrock on the inside. The gap between the faces and framing studs is usually filled with insulating fiber. There's nothing stopping someone from using thicker studs to have wider gaps and then filling the extra space with armor plates, other than expense.

Interior walls usually don't have the insulation, so it's even easier to create a safe room by adding armored panels.

I'm pretty sure I've seen home improvement shows that detailed the construction of a safe room by adding kevlar panels.

So yeah, your approach seems pretty reasonable.

[RyanW]

If you place an armor block between the studs of a standard built home (2x4 studs 16 inches on center, at least where I'm from), you could roll 3d6. On a 7+, the armor protects. On a 6 or less, apply the DR of 3.5 inches of wood. Plus the DR of whatever lines the wall on each side.

You can increase the thickness of a wall by a few inches without much question. If anyone asks, the previous owner used it as a recording studio and added extra soundproofing.

[Varyon]

It seems like you should be able to build such walls as Solid armor without much issue. I think ballistic fabrics don't work quite as well as the rules indicate when really thick, but even if this is true, the default rules are probably fine for GURPS purposes.

[Anaraxes]

Typical US 2x4 stud construction, 8' high, 16" on center, can support about 2000 lbs per linear foot, half of which is taken up by the floor and roof above. (Details vary a lot and in reality depend on the building plan, which walls are load-bearing, and all that. This is an easy-at-the-table approximation I made up for guessing an upper limit in case the characters of thinking of repurposing that old tank armor, as opposed to lining the drywall with ballistic plates from vests. If you want to do this in real simulated reality, the characters should hire a structural engineer to do the math and figure out the load-bearing walls.)

The drywall itself is a lot weaker (about 40 lbs / sq foot straight out, like hanging from a ceiling; maybe around 100 lb if it's vertical shear along the wall.) The characters will presumably just tear out the drywall and install their armor plate, maybe putting drywall back on top of that just for aesthetics. (But hey, the DRs add! :))

[Pursuivant]

Take a look at websites which sell ballistic panels, ballistic glass, and similar materials. That will give you a sense of real-world cost, weight, and DR values.

I referenced some of these materials in my Random Things to Throw and Smash thread earlier this year. That will give you reasonable weights per square foot.

[Ashtagon]

The prices for body armour are probably a bit higher than they would be for wall (or even vehicular) armour, as body armour has complex curves and a need for articulation, things that are not a concern for armoured walls. If your source for armour prices is based on body armour, you should definitely discount it for armoured rooms.

[Rupert]

Originally Posted by Anaraxes

The drywall itself is a lot weaker (about 40 lbs / sq foot straight out, like hanging from a ceiling; maybe around 100 lb if it's vertical shear along the wall.) The characters will presumably just tear out the drywall and install their armor plate, maybe putting drywall back on top of that just for aesthetics. (But hey, the DRs add! :))

40 lbs/ft^2 is about the weight of steel plate, so that's DR70 right there, assuming you can get RHA plates.

[RyanW]

Originally Posted by Ashtagon

The prices for body armour are probably a bit higher than they would be for wall (or even vehicular) armour, as body armour has complex curves and a need for articulation, things that are not a concern for armoured walls. If your source for armour prices is based on body armour, you should definitely discount it for armoured rooms.

In the armor design rules being cited, there's a cheap slab option that should cover that issue adequately.

[Witchking]

I thought that was what reinforced basements with escape tunnels were for??