Plumbata

[ambrosius]

Well yes and no... and no. 8) All projectiles with a metal head and a wooden shaft will be front-heavy, and so land at an angle unless being shot/thrown at extreme point-blank range. That goes for arrows and pila as well as plumbatae.

Not all projectiles with a metal head are therefore point heavy - some arrows are not, most javelins that I held were not, and most stabbing spears certainly are not (before you correct me that these aren't projectiles - yes, they are described as being thrown regularly).

I think you'll find that they are. Weigh any of them at the mid-way point
and they'll be front-heavy. Even the smallest metal arrowheads will
outweigh the horn nock and feather fletchings at the back (though the
difference will be less, here, than with the heavier head of a javelin or
a spear, obviously. Try throwing a modern athletics javelin, and the
metal head will give it a downward trajectory at the end of its flight.
That's the whole idea of its design. The IAA don't want javelins flying
on a completely flat trajectory and skidding-off the grass to spear some
official or spectator. On the other hand, they do want the javelin to
stick in the ground, where it can A.) Do no damage beyond its point of
impact and B.) make a clear mark in the grass which can be measured.

The same principle goes in warfare. The primary function of the head
of any projectile (or spear) is to punch through the target, rather than
get blunted or split, as the bare wooden shaft might, on its own. But
with projectiles, especially, you desire them to be slightly front-heavy,
as this prevents them tumbling in flight and not hitting the target with
the point first. The fletchings on an arrow or a plumbata also help to
keep the flight straight, by acting ar rudders in the air and even by
imparting spin (arrow fletchings do this) like the rifling of a gun barrel.
You only have to see what happens to a cylindrical bullet fired from a
non-rifled barrel to realise how easy it is for projectiles to tumble or spin
(end-over -end) in mid-flight and either hit the target side-on or fly-off at an angle and miss it completely. So if you were just throwing a sharpened stick at the enemy, it coudn't even be guaranteed to fly straight. In fact, the act of sharpening a wooden stave would actually remove some of the weight from the point and make it 'back-heavy', meaning that it was
far more likely to tumble in flight or simply drop its tail way before it
reached the target and hit the taget side-on or even back-on. hock:

The difference between arrows and spears (hastae) on the one hand, and pila and plumbatae on the other, is that they are weighted. This weight gives them different qualities, and much more force is put on the joints betwen head and shaft.

They are all weighted. The plumbata most of all and the arrow least.
The arrow needs less of a weight in its head to keep it flying straight
as it has the added benefit of the fletchings, which, coupled with its
higher speed of flight, give it a large 'rudder' effect and a longitudinal
spin which prevents 'end-over-end' spin (the thing we're trying to avoid).
The javelin requires a larger weight in its head, to keep it flying front-
first, as it doesn't have the fletchings. The plumbata is an interesting
case. How do you throw yours? By holding it at the back of the shaft,
behind you, and pointing backwards? Right. And you fling it (either
over- or under-arm - it doesn't matter which) past your head with your
arm passing through 180 degrees. Thus the plumbata is also passing
through 180 degrees. You are thus not only giving it lateral motion but
imparting rotational kinetic energy to it. That is, if it did not have
the lead weight to over-ride its rotational momentum upon leaving
your hand, it would continue to spin, end-over-end in mid flight, losing
speed and either dropping short of the target or hitting the target at any angle other than head-on. Notice that slight 'wobble' as it first leaves
your hand and settles into its trajectory? That's the lead weight kicking-
in and correcting the rotational spin, which would otherwise cause the
problem mentioned above. 8)

It doesn't really matter what angle they land at, though, as long as the force of impact is straight through the head and into the shaft.

And this is exactly what happens with a plumbata - when the head hits the target (or the ground), the weight plus shaft will 'overtake' the head, thereby forcing it to bend or break. A well-poored weight should protect the shafted as well as the tanged joint from that force.

No, no. That's the point (the metal one ). So long as the projectile hits squarely (point-first) then the impact goes directly through the axis of the head and the shaft, lengthways, just how it's designed to do. The problem only comes when it hits at an 'angle-off' and imparts a lateral strain on
the joint between head and shaft. That's when it's liable to break. As we
discussed with tanged versus socketed heads, both will direct the force
of impact straight througn the head and shaft on target and force the
two together. But a slight 'angle-off' on the impact will tend to split the
shaft with the tanged head, while the socketed head actually provides
a uniform force on the shaft and compresses it inside the socket, which
helps to prevent the wood splitting. :wink:

I would very much like to test if tanged shaft break sooner than socketed shafts.

So would I :twisted:

So far however, I assume...

hock: You should never do that. 8)

Sure, but a plumbata is so much heavier than an arrow that the extra weight surely makes up for being slower.

Kinetic energy is proportional to the weight of a projectile but proportional
to the SQUARE of the velocity. E=m x v squared. (That's exactly
the same as Einstein's famous equasion, without the 'BANG' :lol: )

Ambrosius/Mike[/quote]