Re: [OT]Not-Stupid question about sloped armour

>
>This has been bothering me for awhile.  How does sloped armour gain
>me anything?
>
>If I take the same mass of sloped armour and make armour perpendicular
>to the ground I gain the same thickness you would gain from the
>slope.  Space would remain the same (If I pivot the slope about
>the center everything I lose from the bottom reappears on the
>top.)
>
>The only thing I can think is maybe you increase your chance
>of a "glancing" hit.
>
>Where am I off? I'd think my reasoning would be obvious to
>any engineer.

>This has been bothering me for awhile.  How does sloped armour gain
>me anything?

As you surmised, Armour sloped at 60 degrees is effectively twice the
thickness
of armour at 0 degrees.  ( Multiply raw thickness by 1/cos(Slope) )
Trouble is, you need twice as much to cover the same vertical area. So
no gain,
right?

Except that almost no hits are exactly square-on. They're at about 15-20
degrees
or more. So a slope of 0 degrees becomes an effective slope of 15-20
degrees.
Not a huge gain (1.06). But a slope of 60 degrees becomes an effective
slope
of 70-75 degrees. And 75 degrees is about 4 times (3.86) as effective.

There are complications - conventional solid shells tend to veer in the
direction
of greatest resistance when they hit armour, so the formula is at best
an approximation.
OTOH at really high angles, they'll bounce off. OTOH Plunging fire at
long range
will also decrease the effective slope. For really high velocities you
can best
think of the collision as a slug of fluid hitting a sheet of fluid, so
the mechanics
are different again etc etc.

A reasonable rule of thumb would be to say that armour sloped at 60
degrees
weighs twice as much, but is 3.5 times as effective, as the same
thickness of
armour sloped at zero. 100mm at 0 degrees protects *in the field* about
as well
as 30mm at 60 degrees, and is about as effective as 106mm of armour at 0
degrees
in a lab experiment.