What **yoyodyne **said.
It’s a slipway not a drydock.
I’m going to guess they’re nothing more then piles of dirt. Judging by all mess of bricks between the tracks and all the guys standing around and the other piles of stuff further to the left and right, it looks like a small construction site. Like they might be building something. Actually, when I first saw the picture, I assume they were putting pavers between the tracks. Like someone dumped the pavers down the middle and those piles are leveling sand for setting them in place.
There are a lot of videos of the launch, but none give any clues about the dirt.
A similar launch of a different ship from 2002 shows similar piles of dirt. (lot more photos here)
Here is a photo of the construction which shows timbers with a wooden base being used to support the ship. They’re in the general area of the dirt piles. I wonder if before launch they just go through and cut the timbers and leave piles of sawdust? Seems like too much sawdust though.
I went ahead and emailed the photographer contact on the NASSCO site. If he replies, we can all get some sleep!
Much better pictures, looks like piles of dirt and sand left over from tidal wash and construction. Just making the site prettier for the big send off. Impressive. I want to go see one now.
This is not a dry dock in the sense mentioned above. It’s a slipway and it is entirely above water, as you can see looking at the ground either side and beyond the cranes. You can also see a distinct slope compared to the adjacent ground, which is needed for launching a ship but not in a dry dock.
I’d pick that the piles of dirt are sweepings, not spoil from channel digging. How do you dig channels out of concrete, which is what the base is?
The loose blocks in the centre are from the cribbing that is used to support the hull as it is being built. Once the launch cradles are constructed, the cribbing is removed to allow the cradle to take the ship’s weight. You can see similar blocks off to the side, beyond the piles of dirt.
This is a bow view. The bulge is a bulbous bow, common on large ships.
Thanks.
They seem a little tall and pointy to be sweepings. I couldn’t sweep anything into that shape. Of course I’m not a shipbuildin’ man so I may not know the tricks, but it looks more like they’re poured there than swept into a pile.
There’s a retired Naval Architect here who explains that ships are built on top of hundreds of blocks with a box of sand in the center. Before launch, the sand is released and the ship settles down onto the launch gizmo. That may not be exactly what’s going on with the OP photos, there’s not nearly enough sand for that, but I have a theory that it’s close.
Look at the Cesar Chavez photos. Here’s one that says it is ready for launch, although the launch wasn’t for another 11 days. There’s no dirt and no stacked blocks of wood on the sides, but there are vertical supports with blocks of wood under them (the brown ones, not the white ones). The water is some distance away, you can’t see it. Notice the railing on the right and how the dock with the railing comes level with the slipway somewhere near the end of the railing. The vertical supports under the ship also start near the end of the railing.
Here is a photo of the launch showing the dirt and stacked blocks of wood to the sides. Notice the railing, it’s on the left this time. Notice where it comes even with the slipway. They’ve partially flooded the slipway before launch.
That puts those piles of dirt almost exactly where those vertical supports were in the pre-launch photo, except the supports are on the third row of eyelets and the piles of dirt are between the second and third rows of eyelets. I bet the blocks the vertical supports are on have sand in them and it’s poured out before launch. How else would you get those vertical supports out?
That’s a theory anyway.
I have seen pictures of them being launched sideways.
That is a slipway.
In the 19th century wooden ships were built on the slipway resting on piles of wooden timbers. When the ship was to be launched workers with sledgehammers would take out the supporting piles of timbers and the ship would put its weight on the greased skids of the slipway and slide out. Sometimes they got stuck and needed some help.
With the huge ships today this is just not practical. The support piles needed are wider and could not be taken out with a sledgehammer. Furthermore, ships today have very flat bilges and you could not get a man under them except crawling.
The solution is that instead of a pile of timbers you have a timber on a sandbox which can be disassembled. Fill the box with sand and put timbers on that as needed. Build the ship. When launch time comes you just disassemble the sand box and the whole thing comes apart. You can see the boxes very clearly at http://www.nassco.com/news-center/news_ctr_images/hi-res/9-1-11-T14-Prog-1565.jpg . Note also that the separation of the slipways is adjustable. They can be separated or moved closer as needed for the ship being built.
The disassembled boxes can be seen to the right of the piles of sand in the OP photo.
Very interesting and not a technique I’d heard of. One minor quibble:
I’ve been under ships in drydock and the supports are more than man-high, so you can walk under quite easily.
Yes, the main issue is that it is not practical to support directly only using timbers. After I posted I thought that many ships of the age of sail also had very full bilges. It is just that they could be supported with smaller piles of timbers which could be knocked out by a man with a sledgehammer but today you need bigger piles which could not be knocked out like that. A disassemblable sandbox makes it very easy because you just disassemble the box and the sand falls out. It is sort of like a “sandraulic” support.
Spent ages hunting youtube but this was the best I could find. No sandboxes, just a lot of guys with sledgehammers.
That link popped back as unallowed by my company’s webfilter for “incidental nudity”.
Must be a blanket site ban or something…
The shape of the piles makes me think they were dumped there. That’s just the sort of shape I get when dumping a wheelbarrow load of dirt, though I suspect these were dumped by a dump truck or front loader just from their size.
Fubaya’s first picture makes me think the piles of dirt were used to even the surface under the launch rails (and what you see now is just what’s left over from that process).
As for going in butt-first: I can think of a few reasons for that:[list=*]
[li]They might want to get the props and rudder in the water first so the ship can pull itself out of the ramp if necessary. [/li][li]They were laid out that way in the shipyard (for whatever reason) and you can’t really turn one of these monsters around on land. [/li][li]They want to make sure some smartass didn’t install a reverse movement indicator (to make it go “beep-beep-beep” when backing up)[/li][/list]
There’s also the higher drag in the water going stern-first - you don’t want the hull to slide too far out in the water or it might hit something, and be a nuisance to retrieve. And, it lets the lady swing the bottle of champagne against the more-photogenic bow, since the hull will slide away from the reviewing stand instead of into it.
Michael S. Sanders’ book The Yard, about building destroyers at Bath Iron Works in Maine, is a great read. BIW now uses the floodable-drydock method of launching, since it allows the ship to be built level instead of always forcing the slipway angle to be accounted for. Plus, there’s no longer a danger of the ship sliding all the way across the Kennebec River and grounding in the opposite bank - that gets embarrassing, especially with Navy brass present. A slipway launch could be dangerous as hell, too, with all that weight being transferred via just a bunch of blocks of wood.
The ship is actually assembled in Lego-like blocks on the ground, including all piping and most of the wiring. Each block is lifted by crane and welded onto the blocks below it, until the whole hull is ready for launch.
Though I’m sure #3 was tounge-in-cheek, I have seen a half dozen sliding launches of submarines at Electric Boat in Groton, CT (back when they used to slide them - now they are launched from a drydock) - each one had the boat sounding its horn the entire time it was moving in reverse into the Thames River. I don’t know if it’s a maratime convention, or just something they do at EB.
No answer from the email I sent to NASSCO’s photographer contact. The only other contact listed is the Manager of Public & Government Relations and it’s phone only. I wouldn’t have time to call during business hours, plus that title sounds like it’s a little above “researching questions about dirt.”
You might be surprised - people in obscure professions like that love to talk about their jobs. He/she’d probably be thrilled and somewhat amused that a few folks online were wondering about the art of launching multi-ton ships.