The ram is an instrument used to project the kinetic energy of the
attacker into the hull of the target. If the energy put into the
structure of the target exceeds the stress limits for that structure
then it is damaged. At sea a damaged structure fills with water to
the disadvantage of its crew.
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| Sometimes, one must improvise. |
Studies of ram function have accelerated since the discovery of the
Egadi rams. Previously there were only three known and only 1 in
perfect condition. Now we have many rams including some which show
battle damage which can be analysed.
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| Bent blades - from Egadi |
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What is surprising is the similarity of form the rams show. They are
similar across time from monuments in ancient Greece of 4th
century BC down to Rome of the first centuries AD. The found rams
also show great similarity between Roman, Carthaginian and Greek
examples.
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| Rams from Athens 4thcenBC?, on Arc de Triomph d'Orange 20BC, Egadi3(Carthaginian)241BC |
We know the ancients were no slouches in the technological sense. If
something could be made to function better then it would be adopted
if the economic situation allowed. Witness the use of mechanical
pumps, piped water, katapelta and the experimentation that produced
Hero's steam turbine, Archimedes steam cannon etc. The Antikythera
mechanism has been shown to be a wonderfully complex 'laptop' for
celestial time and place calculations. It cannot have existed in
isolation.
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| Not made by numbskulls |
The structural similarities the rams are showing us reveal effective
mechanical principles that had been developed from experience and
were held-to because they worked.
The earliest images we have of rams show – if they are true
military rams and not cut-waters – rounded spike-like forms.
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| Phoenician Ship ? From Nineveh |
These
would do the job of holing an opponent but the big problem with
ramming as a tactic is at once apparent. Once one has smashed the ram
into the opponent there is the problem of extrication. If the ram has
a uniformly increasing size then the point exerts massive stress and
will penetrate easily. As the point moves into the target the hole
is widened as the rest of the ram follows.
At some point, however,
the compressive and resistive forces counter the attacker's momentum
and the intrusion is stopped and the ram is gripped. This is nicely
illustrated by those of us who have energetically tried to split logs
which are too wet or tough and, even though one strikes along the
grain, they allow the blade of an axe in but grip it tight at some
point allowing no escape.
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| Stuck in a slightly different way... |
Boar spears and bayonets also have this problem – hence the
cross-piece use to prevent deep penetration and the standard advice
for bayoneteers to twist their weapon before attempting to pull it
out of their adversary.
The hull structure of ancient ships comprised planks laid
edge-to-edge that were joined with many mortise-and-tenon joints.
These were very tightly made. The resulting shell is very resistant
to splitting and to lateral disruption. This kind of structure would
grip a flat blade or a spike-formed penetration. A sheet of steel
will simply fail and be punched open but a composite wooden structure
will react elastically and grip the intrusion.
The solution to the problem of holing and disrupting a wooden hull of
the type used in triereis is rather more cunning. One must break the
planks to make gaps and one must also overcome some of the joints to
make recovery impossible and one must prise the hole wider to allow a
serious amount of water in.
Not surprisingly the ancient rams fit this purpose perfectly.
The form is at first somewhat disguised by the ancient aesthetics of
seeing the only appropriate device for penetrating an enemy at sea as
a trident. This is the weapon of Poseidon or Neptune, the lords of
the undersea. If one's maritime enemy should be smitten it is only
fair to call upon and to acknowledge the help of the earthshaker. So
when we look at an ancient ram we see a trident from the side
superimposed on the geometry of a technical solution to staving-in
the hull of a ship.
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| One of Poseidon's tridents on the sea floor at Egadi |
It is not accidental that the ram has the three 'blades'. A single
blade can wedge and be stuck. Two blades may penetrate but hold a
single plank. Three blades can strike across two planks and three
joint-lines giving a better chance of success. More blade are
superfluous and begin to dissipate the force applied.
The blades hit the target like chisels or axe-blades with their
blades entering along the grain. The widening profile splits the
wood. The vertical extent of the ram means at least one joint line
will be hit and, hopefully, burst. The strakes on ancient triereis
wer in the order of 20 to 30 centimetres wide. The separation of the
ram blades is of the same order thus ensuring a spread of attack
across at least one and probably two joint lines and three or four
strakes.
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| Side of hull impacted by ram (Oldfield2012) |
Once the blades have wedged open the target's planking then the
momentum of the attacker is transmitted across the whole of the ram's
cross-section – the so-called 'driving centre' – because the
blades have a vertical cross-piece which joins them and presses all
the wood in front into the target. This breaks the tenons out from their mortises. Once out of place they will never go back. There is no need to drive the ram deep into the target hull. It must just break the hull shell's integrity. (Steffy(1983) refers to this when
he says the ram 'pounded' rather than pierced the target).
The hull shell of the target ships has now suffered a devastating
blow from piston with sharp blades. The force developed by a triereis
of circa 50 tonnes hitting at 10 knots has been calculated by John
Coates as circa 66 tonnes. This is applied over the driving centre of
the ram which is less than 50cm square. Something will give !
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| Hole made in hull. Police are looking into it. |
Computer simulations (Oldfield 2012) have been run to discover how
much energy is needed to breach hulls in relation to woods used and
the relative velocities and inertia of triereis. The results confirm
that the concept of ancient warships as massive hulks engaging each
other like mastodons with rams instead of tusks and delivering
terrible damage to each other until one succumbs are completely
wrong.
The first point to be aware of that it is not speed we are discussing
here but relative velocity. It makes a big difference to the impact
if two ships are moving in the same or opposite directions. This will
also have big implications for how we imagine triereis to operate, as
we shall see. If the ships move towards each other the impact forces
are much greater than if one is stationary or the target is moving
away.
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| Luckily, this is not a head-on collision so the force of impact will be reduced. Somewhat. |
Oldfield discovered that the forces generated by a trieres ram are
more than sufficient to catastrophically damage a trieres hull so
long as the collision velocity was 0.5 knots ! No need for cries of
'ramming speed' and extra lashes for the galley slaves ! A smooth
approach at reasonable speed would result in a nice smooth impact and
busting of the target's flush. The best angles for attack were, as
may be expected, those closer to perpendicular. The strength of the
mortise-and-tenon hull is greater against acute-angled attacks. Also,
attacks with high closing velocities had a much greater chance of
success than those pursuing – but this has a downside we shall
discuss later.
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| Successful attacks can be made in the arcs shown -for set relative velocities and wood(Oldfield2012) |
These finding mean that the kybernetes would know he could count on
holing the target in a head-on attack and in an attack against a
fleeing enemy he had to strike a careful balance to deliver his
maximum effect which, if done correctly only need a 0.5 knot
advantage in speed to hole the target.
What we stand with now is a model for trieres battles which involves
combatants more like first world war stringbags than mastodons.
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| Gertcha...! |
The
opponents can easily damage each other if they are given the chance
but each also has a high degree of manoeuvrability to use in evading
being hit – or making a hit. Once hit effectively the game was
probably quickly up (see this blog entry - 'Get Down Ship' 20/08/14).
The weapon developed to equip the trieres was well suited to its
purpose. It is hard to imagine a better form. It was developed with
full knowledge of the hull construction techniques then in use and
exploited their weaknesses. These weaknesses would be well-known to
the commanders – kybernetes, pentekontarchos and trierarch, as
they stood anxiously on the poop-deck and sought to manoeuvre their ship to
ensure its survival and success.
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| "And all depends for its safety on one little old atomy of a man, who
controls that great rudder with a mere broomstick of a tiller! He was
pointed out to me; Heron was his name, I think; a woolly-pated fellow,
half-bald." -Lucian:'The Ship/The Wishes'(Sean McGrail in control of Olympias from Trireme Trust) |
