Retro-modern armour for alternate timelines

[Anthony]

Originally Posted by DanHoward

Think about why those plates are not made any larger. Hint: it has nothing to do with weight.

Hint: yes it does. There's also other issues (large plates need to be better fitted and thus you'd need either many more sizes or fitting specific people), which means most improved coverage models use additional plates rather than larger plates, but it's not because you can't put plates over padding.

On the other hand, the main reason plates are mostly over kevlar is because hits on ceramic armor (and high hardness steel to a lesser degree) tend to result in spalling and kevlar is quite good at dealing with that.

[Ulzgoroth]

I wouldn't even be confident in saying plates are mostly over kevlar - plate carrier harnesses that aren't made with any armor materials are not uncommon AFAICT.

I'm not sure whether plates under kevlar is a thing anyone does, though I wouldn't rule it out.

[Anthony]

Originally Posted by Ulzgoroth

I'm not sure whether plates under kevlar is a thing anyone does, though I wouldn't rule it out.

Impacts on hard plates have a tendency to send small bits flying around to cause secondary injuries, and an outer layer of soft armor is useful for catching those fragments. Flexible armor over rigid is otherwise a quite poor idea, as the performance of flexible armor is dramatically reduced if it's unable to flex (this same principle applies to low tech armor -- a layer of padding will catch fragments of arrows that would otherwise fly off and cause injury).

Note that the main reason for not layering hard with soft is that, GURPS notwithstanding, it's usually heavier for the same penetration resistance than just making the hard armor thicker and reducing the soft. A standalone plate is only barely heavier than an insert, even though the insert is DR +23 and the standalone plate is DR 35.

[Ulzgoroth]

Originally Posted by Anthony

Impacts on hard plates have a tendency to send small bits flying around to cause secondary injuries, and an outer layer of soft armor is useful for catching those fragments. Flexible armor over rigid is otherwise a quite poor idea, as the performance of flexible armor is dramatically reduced if it's unable to flex (this same principle applies to low tech armor -- a layer of padding will catch fragments of arrows that would otherwise fly off and cause injury).

Note that the main reason for not layering hard with soft is that, GURPS notwithstanding, it's usually heavier for the same penetration resistance than just making the hard armor thicker and reducing the soft. A standalone plate is only barely heavier than an insert, even though the insert is DR +23 and the standalone plate is DR 35.

However an upshot of the latter un-GURPSly layering issue is that if you're layering plates and flexible armor, the order probably doesn't make much difference to the total performance against main penetration.

The flexible layer might work better inside the plate, but it still probably won't stop a hit that penetrates the plate.

[Rupert]

Originally Posted by Ulzgoroth

The flexible layer might work better inside the plate, but it still probably won't stop a hit that penetrates the plate.

That's not really the case - unless the plate is badly over-matched it'll take quite a lot of the projectile's energy to get through the plate and it will also probably be deformed, if not coming apart as well. A kevlar backing (or other modern textile backing) of reasonable thickness could well stop such bullets. If the carrier/backing layer is thick enough to do much of anything for areas not covered by the plates, it should do something useful under the plates in cases where the plate was not quite enough, and unless you know that all you'll be facing are rifles powerful enough to need plates to stop them, having no meaningful protection outside of the plates isn't wise, as they don't cover everything, or even you core from all angles. Having flexible pistol- and fragment-proof armour with plates where you can is a decent compromise, given plates all over would be prohibitively expensive and heavy.

[Keampe]

One other thing to consider about this particular topic (Metal breastplate over kevlar) is that while gambesons were sometimes 2" thick kevlar vests are not. They are about 1/2" thick and far more flexible than a than a properly made gambeson.

You would still need to do something about the under arm and inside elbows, though. Kevlar vests might be more flexible, but they aren't that flexible. Most likely, you'd have weak points.

- Shane

[Say, it isn't that bad!]

Originally Posted by Keampe

Most likely, you'd have weak points.

- Shane

Which makes it the same as any other armour we've ever made, including full plate - which can't cover everything, either. ;)