Mr Hines: A Favor, If You Please.

[Tiglath]

This is a dead serious history post… no politics or repartee.

I need to know how ship anchors work. My neighbor was in the navy but I think you can explain things far better than he did.

This concerns the Persian pontoon bridges over the Hellespont built in 480 BC. Herodotus' description (Hdt. 7.36.2) raises a few questions.

https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0126%3Abook%3D7%3Achapter%3D36%3Asection%3D2

I’ll give you the context and then a few questions, if I may.

Xerxes’ engineers build four bridges, the first pair didn’t work and were carried by a storm, the second pair held fast and worked as intended. Each consisted of hundreds of triremes parallel to the shore and secured by anchors, with a gangway build over them.

"After putting the ships together they let down very great anchors, both from the end of the ships on the Pontus [Sea of Marmara] side to hold fast against the winds blowing from within that sea, and from the other end, towards the west and the Aegean, to hold against the west and south winds." (Hdt. 7.36.2)

https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0126%3Abook%3D7%3Achapter%3D36%3Asection%3D2

I’ve seen the spot with my own eyes recently, the current is about 3-4 knots in the direction from the Black Sea to the Mediterranean. The depth at that point is about 85 meters, with the curious fact that in the lower half water is on the move in the opposite direction. There must be a shear effect, and surface disturbance is visible. The challenge of building floating bridges in such waters with ancient technology cannot be overestimated. Yet they did it.

Herodotus says that each trireme had two anchors to keep it in place. It sounds fishy. How can you keep hundreds of long lines so close together from tangling up and ruin the purpose? And the amount of iron to make such large number of anchors seems not feasible even for the Persian empire at its apex.

I dedicated a page to this. where I propose one way in which this could have been done, with a diagram at the bottom of the page, using fewer anchors. I am not shipwright, but neither was Herodotus.

The booksite is still under construction, but I have a Hellespont draft page:

http://xerxes-the-recount.com/sub/hellespont.html

The illustration at the top of the page accurately depicts, Herodotus description, with two anchors per ship. The page has further details, but what it is written above is sufficient context for these questions.

1. Do anchors need to rest at the sea bottom to serve their purpose or can be used also without reaching it, just dangling?
2. Do they need to dig into the ground or otherwise hook into something or can serve the purpose just by lying on the bottom?
3. If the anchor dig in or hooks on something, how do you free it when you want to lift it? By sailing in the opposite direction, or how?
5. Can you keep a ship firmly anchored in strong winds and currents, or do you need more or bigger anchors? The Hellespont has both, current and winds in either direction.
6. Would your answers apply to ancient ships? Triremes were light ships, not very strong. They were usually beached when not in use, as they took a beating and a leaking in the water.

Please add as you see fit. If you answer, I’ll give you proper attribution in the booksite.

According to the U.S. Navy’s Social Usage and Protocol Handbook, that should be: ‘Commander David Spencer Hines, United States Navy, Retired.’

Correct?

Many thanks and kind regards.

JS

[Ed Stasiak]

tiglath
And the amount of iron to make such large number of anchors seems not feasible even for the Persian empire at its apex.

Did the ancients use "hook" type anchors or simply large rocks with a hole bored thru it?

[Tiglath]

Post by Ed Stasiak

tiglath
And the amount of iron to make such large number of anchors seems not feasible even for the Persian empire at its apex.

Did the ancients use "hook" type anchors or simply large rocks with a hole bored thru it?

Both. Persian had the heavy stone type, which anchors by weight and friction, but the Greeks added teeth, which could involved metal, sometime as lead inside tree trunks. There was not much space in triremes for low density anchors. In the 5th century BC, the Persian empire included many Greeks. Persians used Phoenician, Egyptian and Greek navies, since they themselves were not a sea people. Herodotus doesn't say but in the Hellespont current would have required the firmer kind of anchor that had teeth. Bridge builders had every incentive to make sure the bridges held. It is possible however that heavy stones alone could work, because the lower half of the water moves against the current in the upper half so it may have made the stones less likely to drag along the sea bed. Someone should test this. Not me.

The amount of metal is not a big concern, we don't know how much metal anchors needed, if any. but the proximity of so many 100-meter long anchor lines, as triremes must have been spaced out a matter of tens of feet. I don't see that working.