# Why are dry docks (for ships) such a seemingly (relatively) rare thing? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [August 27, 2025, 11:49pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542 "2025-08-27T23:49:00Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [August 30, 2025, 4:45am UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/21 "2025-08-30T04:45:53Z")
> [@Whack-a-Mole](#): > > At the end of the day they are a big hole in the ground with a door and water pumps. While impressive in size nothing really remarkable. It’s not cutting-edge, technologically speaking, but still a pretty sizeable engineering project. I have heard of a few temporary dry docks that were used to good effect. When Boston was building the Big Dig, it required making a tunnel under Fort Point Channel. Ordinarily, the tunnel sections would be built in a shipyard and floated into position, but there were low bridges over the channel. The construction team dug a huge casting basin, and built the tunnel there. I heard it’s the most expensive section of highway ever built. Similarly, when Washington was replacing one of the floating bridges over the lake just east of Seattle, a temporary construction site was created on the coast, and bridge segments brought to the lake by tugboats. Size was limited by locks. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 30, 2025, 3:51pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/22 "2025-08-30T15:51:42Z")
One other complexity with drydocks: Ships are designed to be supported by their entire sub-waterline surface simultaneously. Obviously that’s not strictly necessary, and you have some margin to get away with a more concentrated force, but to support a ship with solid supports, you still need supports on a decent fraction of the ship’s surface area. And if you want your drydock to be able to service more than one model of ship, those many supports all need some sort of articulation. Lots of supports that can be articulated and support a lot of weight is an engineering challenge, and it’s an even bigger engineering challenge for a drydock that can handle larger ships. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [August 31, 2025, 12:48pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/23 "2025-08-31T12:48:29Z")
> [@Whack-a-Mole](#): > > And that doesn’t account for all the civilian ships that need drydocks. Most civilian ships are drydocked in Asia where labour is cheaper. And this has been going on so long that now not only is the labour cheaper, it’s more skilled. > [@Chronos](#): > > And if you want your drydock to be able to service more than one model of ship, those many supports all need some sort of articulation. Lots of supports that can be articulated and support a lot of weight is an engineering challenge I guess you can use “articulation” to describe a bunch of lumps of concrete and wood of varying heights and sizes that you move around to appropriate positions. But it seems a fancy term for what remains a very simple solution. ---
**Author:** ![TokyoBayer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tokyobayer/32/13989_2.png) [@TokyoBayer](https://boards.straightdope.com/u/TokyoBayer)\ **Post date:** [August 31, 2025, 1:07pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/24 "2025-08-31T13:07:47Z")
> [@Whack-a-Mole](#): > > At the end of the day they are a big hole in the ground with a door and water pumps. While impressive in size nothing really remarkable. And buildings are simply supports holding up a roof. Nothing really remarkable. There is a new drydock being [built in Hawaii](https://www.stripes.com/branches/navy/2024-02-16/navy-new-dry-dock-hawaii-13030318.html). > [@](#): > > The Navy has begun the most expensive building project in its history with construction of a $3.4 billion submarine-repair dry dock in Pearl Harbor, Hawaii. > [@](#): > > Padhi is commander of Officer in Charge of Construction, Pearl Harbor Navy Shipyard, a newly commissioned command by Naval Facilities Engineering Systems Command. “The amount of just material that goes into these projects alone is staggering,” Padhi said. “We’re talking about 250,000 cubic yards of concrete,” he said. “If that were delivered by truck, we’d be talking about 25,000 trucks.” The project will require about 63,000 tons of steel. “That’s enough steel to build eight submarines,” Padhi said. The length of utilities to be installed for the dry dock could “circumnavigate Oahu,” he said. The price tag for the project reflects “what it takes to build something of this magnitude in Hawaii,” he said. Building the dry dock on a speck of an island in the Pacific costs roughly twice what it would on the mainland because of the cost and complexity of getting materials to Hawaii, he said. ---
**Author:** ![motu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/motu/32/259_2.png) [@motu](https://boards.straightdope.com/u/motu)\ **Post date:** [August 31, 2025, 2:18pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/25 "2025-08-31T14:18:50Z")
A dry dock is not just the facility, it requires a large skilled labor force and hopefully, an experienced management team. The U.S. ship building/repairing industry has been declining for decades, as noted above, much of that business moved to Asia. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 31, 2025, 2:59pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/26 "2025-08-31T14:59:17Z")
> [@Princhester](#): > > I guess you can use “articulation” to describe a bunch of lumps of concrete and wood of varying heights and sizes that you move around to appropriate positions. And that you can move around into position around a ship that’s almost filling up the space, underwater. You can’t empty out the water until the supports are in place. ---
**Author:** ![scabpicker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/scabpicker/32/8268_2.png) [@scabpicker](https://boards.straightdope.com/u/scabpicker)\ **Post date:** [August 31, 2025, 3:07pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/27 "2025-08-31T15:07:03Z")
Every dry dock image I’ve ever seen of a warship is supported by wood propping it up. In the case of this image of the Nimitz, it’s pretty flat on the bottom, so there’s not even really much stacking necessary. [![](https://i0.wp.com/cms.sofrep.com/wp-content/uploads/2018/12/1000w_q95-1.jpg?w=1000&ssl=1) ](https://i0.wp.com/cms.sofrep.com/wp-content/uploads/2018/12/1000w_q95-1.jpg?w=1000&ssl=1) ETA in other images, it seems those might be concrete blocks it’s stacked on. Either way, not much in the way of articulation. [![](https://i0.wp.com/cms.sofrep.com/wp-content/uploads/2018/12/fd.jpg?w=667&ssl=1) ](https://i0.wp.com/cms.sofrep.com/wp-content/uploads/2018/12/fd.jpg?w=667&ssl=1) ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [August 31, 2025, 3:31pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/28 "2025-08-31T15:31:12Z")
> [@Chronos](#): > > And that you can move around into position around a ship that’s almost filling up the space, underwater. You can’t empty out the water until the supports are in place. The keel blocks are moved into place manually using cranes and fork trucks per the hull plan while the dock is drained, then the dock is flooded and the ship is towed in. Some minor amount of shimming can be done by divers to ensure consistent contact, and lateral supports are added while the dock is drained to keep the ship aligned but all of the hull supports have to be moved into place when the dock is evacuated.. There isn’t any kind of self-articulating system that automagically forms to the hull. [![](https://img.youtube.com/vi/_iZ9xW3w1lc/maxresdefault.jpg "The Impressive Process of Moving Gigantic Ships into Dry Docks") ](https://www.youtube.com/watch?v=_iZ9xW3w1lc&t=130s) As the link by @TokyoBayer illustrates, a dry dock is a massive civil engineering structure requiring enormous resources and power to operate. Describing it as [“… a big hole in the ground with a door and water pumps,”](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/20) is like describing the Hoover Dam as a big wall of concrete. And as @motu notes, a dry dock facility isn’t just the structure but all of the equipment, infrastructure, and skilled labor and expertise that makes it work. Bomb or otherwise disrupt that and your dry dock is nonfunctional until you can repair and restaff the facility. Stranger ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [August 31, 2025, 3:33pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/29 "2025-08-31T15:33:59Z")
That article also mentions a new one at Portsmouth, New Hampshire. ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [August 31, 2025, 3:41pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/30 "2025-08-31T15:41:08Z")
> [@Chronos](#): > > And that you can move around into position around a ship that’s almost filling up the space, underwater. You can’t empty out the water until the supports are in place. I always assumed that the supports in a dry dock were put in place before the ship even comes in. Pump all the water out, use a crane to swing blocks (concrete, wood, or whatever) into place, let the water back in, and sail the ship into place. That relies on a few assumptions. You have to know the shape of the hull, some means of measuring locations withing the dock, and then position the ship and hold it in place as the water gets pumped out and the ship settles onto the supports. Does anyone know if that’s how it’s done? I have someone I could ask. ETA: Ninjaed. ---
**Author:** ![Misnomer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/misnomer/32/14897_2.png) [@Misnomer](https://boards.straightdope.com/u/Misnomer)\ **Post date:** [August 31, 2025, 4:13pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/31 "2025-08-31T16:13:04Z")
> [@robby](#): > > my _Los Angeles_-class sub looked like a little guppy in a massive drydock built to hold _Ohio_-class SSBN missile subs I’m a federal contractor who recently started supporting USN SSP, and one of my training/orientation courses included images of a drydock with an SSBN in it – and some people, for scale. I was blown away by even just _that_! I’d love to get to GA/WA someday and see the facilities and a boat in person. I’m sure my head would hurt for days afterwards…in a good way. ---
**Author:** ![TheTyrant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thetyrant/32/19111_2.png) [@TheTyrant](https://boards.straightdope.com/u/TheTyrant)\ **Post date:** [September 4, 2025, 3:03pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/32 "2025-09-04T15:03:02Z")
Heh, be careful what you wish for. I’ve worked on boats for about 25 years (5 active-duty, 20 as an engineer) and I spent my first few years in the industry on the road and on boats at least 75% of the time. It gets old fast and I’d be fine never seeing a boat again haha. (Of course, it doesn’t help that having to go to a boat generally meant something was broken.) ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [September 4, 2025, 3:13pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/33 "2025-09-04T15:13:07Z")
> [@TheTyrant](#): > > (Of course, it doesn’t help that having to go to a boat generally meant something was broken.) In my experience, something is always broken on a boat. If there isn’t anything that seems broken it is just because you haven’t found it yet, and are likely to discover it at the most inconvenient time. They say that “The two happiest days in a boat owners life are the day they buy the boat, and the day that they sell it.” Now imagine that that magnified by a price tag of several billion dollars. Stranger ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [September 4, 2025, 3:26pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/34 "2025-09-04T15:26:10Z")
> [@Stranger\_On\_A\_Train](#): > > They say that “The two happiest days in a boat owners life are the day they buy the boat, and the day that they sell it.” Now imagine that that magnified by a price tag of several billion dollars. Also, “a boat is a hole in the water into which you throw money.” ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [September 4, 2025, 3:38pm UTC](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542/35 "2025-09-04T15:38:58Z")
> [@Elmer\_J.Fudd](#): > > But every new ship needs one. I was recently at an event on Mare Island right next to a dry dock and it’s one of the most impressive things I’ve ever seen. I think the OP underestimates what a complex and costly endeavor it is to construct one. It’s not just a concrete hole, it is massive cranes\* and gates requiring thousands of tons of steel and engineering expertise. This. It’s a significant bit of engineering that needs to be maintained. It’s basically a displaced Panama Canal lock with a large scale factory surrounding it. For repair work there is the option to use a [floating dry dock](https://en.wikipedia.org/wiki/Auxiliary_floating_drydock#/media/File:USS_Los_Alamos_(AFDB-7).JPEG) which can be moved as needed. [Previous page](https://boards.straightdope.com/t/why-are-dry-docks-for-ships-such-a-seemingly-relatively-rare-thing/1022542.md?page=1)