The Dry Dock of Peter I

 

The legend that Russian czar Peter the Great copycatted all his innovations from the europeans is very popular among the “modern historians”. In particular, the navy and everything related to shipbuilding were taken from the Dutch.

 

One could believe or disbelieve the legends. Both do not involve brains. Well, for those whose brains have not rusted, there is a third way: check the reality.

 

Recently, a TV reporting on the Dry Dock of Peter I in Kronstadt caught my eye. Peter the Great saw a dry dock in Holland, which means he “copied” the idea. But was it a copycat as technically illiterate "intelligentsia" thinks? Let's see.

 

The shells and algae inevitably grow with time on the ship hulls. Unlike fish, most shells and algae need to “cling” to some hard surface. For them, the underwater surface of ship does not differ from stones and rocks. If they had not prevented the ship from moving, people would hardly have paid attention to this fact. But, alas, hull fouling increases the hydraulic resistance manyfold. Ship speed and maneuverability drops drastically.

 

What could be done? The hull should be periodically cleaned from these "uninvited guests". One could, of course, use divers, but even nowadays it is quite expensive.

 

There is another way: raise a ship and clean its bottom. When ship is relatively small, it is difficult, but possible to raise it ashore. But the larger the ships are, the more difficult it is to lift them out of the water.

 

Pirates of the Caribbean (and not only them) exploited a great ebb tide. The ship was aground. At low tide, the water left, the ship ended up ashore, and the pirates rushed to peel the shells and algae before the tide. This method is called “careening”.

 

But this is not always and not everywhere possible. Also, there was too little time for a quality bottom treatment.

 

And then the idea of ​​a dry dock was born. The ship is driven to the dock. The dock gates are hermetically sealed and water is pumped out of the dock. After that, slow and efficient cleaning and necessary repairs could be done. Then, the dock is filled with water by opening the gate. These are the dry docks that Peter the Great saw in Holland.

 

But he did not “just copycatted" this idea. Why? The dry dock had one serious problem. Water was pumped out at that time with manual pumps; their performance was very limited. And there was a lot of water in the dock. As a result, draining the dock could take a month. All this time the ship stood idle and occupied the dock. And there were not so many ships in the Russian fleet to allow the ship to stand idle for a month. Moreover, the dock also stood "idle" for a month. Ineffective, isn't it?

 

Let's formulate this as “Mission: Impossible”.

 

In order for the fleet to protect the country's sea borders, ships must be  in service. At the same time, high speed and maneuverability of each ship should be maintained. However, this is prevented by hull fouling with shells and algae.

 

This problem could be corrected by cleaning the hull in a dry dock. In this case, of course, it is necessary to ensure the effective use of dry dock. However, this is hindered by long drainage of the dock that took at least 3-4 weeks.

 

This story could be represented by the following model:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

So, the fleet ensures the protection of the country's sea borders. In order to accomplish this, ships must be in service.

 

However, an unsolvable contradiction arises: the service of ships is hindered due to hulls fouling with shells and algae. One could clean the hull in a dry dock, but drainage of dock takes an unacceptably long time, 3-4 weeks.

 

The mission is to ensure the protection of sea borders so that ships have high speed and maneuverability, and the dry dock used to service them is used efficiently. The contradiction that has arisen hinders accomplishment of this mission.

 

So what did Peter the Great invent? Let's try to figure out.

 

Consider the first opportunity to complete the “Mission: Impossible”:

 

I. Accomplish 'dock should be used efficiently', despite of 'drainage of dock takes 3-4 weeks'.

 

To take advantage of this opportunity, we should describe in detail the “story”: how cleaning the bottom in a dry dock ensures its efficient use, and how the long drainage of the dock interferes with efficiency.

 

A ship enters the dock. Dock is hermetically locked. Water is drained from the dock. When water is completely pumped out of dock, the bottom of the ship becomes accessible, and the workers begin to clean it of shells and algae.

 

In order for the dock to be used efficiently, time when cleaning of hull is not performed should be reduced. However, pumping water out of dock is slow, because hand pumps have low productivity. Therefore, pumping water from the dock takes a long time, from 3 to 4 weeks. During pumping, the bottom of the ship is inaccessible to the workers, and work on its cleaning is not performed. As a result, the dock is used inefficiently.

 

This story consists of several interrelated events (they are italicized in the text). The first opportunity can be realized if the connection can be broken:

 

Draining the dock takes 3-4 weeks hinders using the dry dock efficiently.

 

For this, it is necessary to prevent some of the events from the described "story":

 

Hand pumps have low productivity -> hand pumps pump water -> pumping water out of the dock is slow.

 

Productivity of manual pumps cannot be increased. Hence, water should be removed from the dock NOT by pumps.

 

This is what Peter I came up with: the water from the dock flows into the pool. It takes about an hour. And then people can start repair work! Water from the pool can be pumped out by pumps. Even if water is pumped as long as the repair of the ship lasts, it does not affect efficiency of using the dry dock.

 

"Wise" Dutch did not think of that!

 

Here is how it was:

 

At that time, it was an innovative hydraulic structure. At the beginning of the 18th century, docks for repairing ships existed in Europe, however, it was possible to start repairing a ship directly no earlier than 3-4 weeks later. That is how much time it took to drain the dock. Peter I did not like this situation! According to official history, Peter I personally designed the Dry Dock that could be drained in a few hours! Peter’s main idea was to place a drain tank (dock basin) below the level of the bottom of the dock, into which water would be drained by gravity through inclined channel. Water could be slowly pumped out of pool by a pump with a wind engine. Everything ingenious is simple! When did our tireless czar manage to do all these things?

The Dry Dock of Peter I is a grandiose building; it was built over 30 years. It was put into operation in 1752, and the last time when it was used is 2008. Over 250 years of service!

Could you call it a "copycat" now?

 

The following articles were used:

 

  1. Wikipedia, article Careening

  2. The Dry Dock of Peter I

 

| How to accomplish the "Mission: Impossible" |

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