Layering Armor

[Anthony]

Originally Posted by WaterAndWindSpirit

Or would a Diaphanous layer (and a single one, not multiple) count as a "free" layer of armor?

RAW, yes. Realistically, GURPS overestimates both the benefits and the penalties of layering armor (because doing it right is hard); on the one hand, those layers probably wouldn't add much of a DX penalty; on the other hand, the sum of DR 18, DR 8, and DR 6 flexible armor should only be about DR 21, because flexible armor is actually really bad at layering.

[Plane]

Originally Posted by Anaraxes

Gambesons were around 30 layers of linen (1 or 2 cm thick). Remember that linen is a lot tougher than some fabrics, like the cotton in a T-shirt.

Since that's probably not -30 to DX, there might be diminishing returns, or maybe the DX penalty could scale to the amount of total DR acquired?

[roguebfl]

Originally Posted by Plane

Since that's probably not -30 to DX, there might be diminishing returns, or maybe the DX penalty could scale to the amount of total DR acquired?

the multiple layers were quilted together, so it count as one piece of armor, it just made of multiple layers of linen, not 30 layer of independently moving layers.

[DanHoward]

Originally Posted by Anaraxes

Gambesons were around 30 layers of linen (1 or 2 cm thick). Remember that linen is a lot tougher than some fabrics, like the cotton in a T-shirt.

We believe that 30 layers was the maximum amount and probably not typical. 15-20 seems to have been more usual. In Low-Tech, the 25-30 layer variants are Heavy Layered Cloth with DR4.

[DanHoward]

Originally Posted by ravenfish

There aren't any rules in the books that I'm aware of, but, as a GM, I'd be happy to give a character wearing enough clothing on a given location to equal the weight of cloth armor for that location the benefit of DR 1.

Low-Tech covers it (pp. 98-99). Winter clothing only gives DR 1 vs cutting attacks. For complete DR 1 you'd need to wear something like a parka or leather coat over that. The combination of clothing should weigh significantly MORE than the equivalent DR of proper armour because it is considered to be improvised and you suffer DX penalties like other types of layered armour.

[ErhnamDJ]

Originally Posted by Anthony

the sum of DR 18, DR 8, and DR 6 flexible armor should only be about DR 21, because flexible armor is actually really bad at layering.

Why is flexible armor bad at layering?

Is it only bad at layering with other flexible armor? What if you wear, say, maille underneath plate?

[Anthony]

Originally Posted by ErhnamDJ

Why is flexible armor bad at layering?

Two reasons. First of all, hard armors are actually nonlinear in thickness (doubling thickness more than doubles energy required to penetrate), flexible armors are at best linear, and GURPS generally measures in units of hard armor. Secondly, flexible armor is dependent on having space behind it to flex into (this mostly causes a problem with flexible on top of hard).

Originally Posted by ErhnamDJ

Is it only bad at layering with other flexible armor? What if you wear, say, maille underneath plate?

It will be less protective than the same weight in heavier plate.

[Rasna]

Originally Posted by Anaraxes

Gambesons were around 30 layers of linen (1 or 2 cm thick). Remember that linen is a lot tougher than some fabrics, like the cotton in a T-shirt.

Historical textile armor thickness varies between 0,5 cm and 5 cm. Most gambesons and aketons of rigid or semi-rigid construction worn as standalone armor are 2 cm to 3 cm thick. Textile armor or underpadding worn with mail or other kinds of metal armor is usually thinner and has flexible construction. Textile armor up 3 cm of thickness is rarer and can be pretty heavy (a layered linen cuirass with an average thickness of 5 cm weights 3,5 times a steel cuirass with an average thickness of 2 mm).

[Rasna]

Originally Posted by Plane

How many layers of everyday clothing (sweatpants, t-shirts) would someone need to wear to get the equivalent of the 1 DR from Cloth Armor?

For Low-Tech, Padded Cloth (DR 1*, 6 lbs.) is 1/4" (0,635 cm) thick.
So, Light Layered Cloth (DR 2*, 12 lbs.) should be 1/2" (1,27 cm) thick, Medium Layered Cloth (DR 3, 20 lbs.) should be 0,83" (2,11 cm) thick and Heavy Layered Cloth (DR 4, 28 lbs.) should be 1,16" (2,95 cm) thick.

Edit: there is also Paper, Proofed (DR 6, 45 lbs.); it should be 1,875" (4,76 cm) thick.

[DanHoward]

Originally Posted by Rasna

For Low-Tech, Padded Cloth (DR 1*, 6 lbs.) is 1/4" (0,635 cm) thick.
So, Light Layered Cloth (DR 2*, 12 lbs.) should be 1/2" (1,27 cm) thick, Medium Layered Cloth (DR 3, 20 lbs.) should be 0,83" (2,11 cm) thick and Heavy Layered Cloth (DR 4, 28 lbs.) should be 1,16" (2,95 cm) thick.

Edit: there is also Paper, Proofed (DR 6, 45 lbs.); it should be 1,875" (4,76 cm) thick.

There is a lot of data available for metal armour and modelling to determine the amount of protection afforded, but there is nothing like that for textile armour. There are at least four totally different historical ways to make textile armour (none of them involve using glue) and the methods are so variable that there is no way to use figures like these. The stats in Low-Tech involved a lot of estimates, approximations, and anecdotal evidence.

In addition, it isn't just the amount of layers that provide the protection; it is the heavy compression caused by dense quilting, which you can't get from clothing. Layered clothing is the equivalent of improvised armour; it is heavier and more cumbersome than properly-designed armour.