Ro/Ro Question

[kalos72]

So what can one of these bad boys carry anyways? I aint got a clue on how to accurately determine the vehicle capabilities of one of these things.

http://www.globalsecurity.org/milita...pe-d-specs.htm

[StainlessSteelCynic]

Here's some general information on RO-RO ferries http://en.wikipedia.org/wiki/Roll-on/roll-off
However I believe that vessels meant to carry heavier vehicles (e.g. construction vehicles, military vehicles) are reduced by about a quarter or more capacity due to the need for reinforced decks



And I found this too, I thought it was interesting because it mentions trains can also be carried http://www.ship-technology.com/projects/skane/

[kalos72]

Ive read those links, thanks. I guess I am just curious about how many tanks/APC's a good sized ro/ro could fit.

Using the 130000sqaure feet listed on the example I gave and say an over exaggerated 500sqft size for a MBT. But that leaves us with 250 MBT's? That seems high. Are my guesstimates that off?

[StainlessSteelCynic]

Reading through the links again, they didn't really offer a lot of information did they?
However I have a vague recollection that a typical large civilian RO-RO could carry about 30 heavy armoured vehicles (tanks, SPGs), around 100 (or less) lighter armoured vehicles (APCs, armoured cars) and anything up to 200-300 non-armoured vehicles (trucks, trailers, field cars and so on). They wouldn't carry more armoured vehicles because of their collective weight but it's probably also to stop the loss of say 100 tanks in one shot should the ship get sunk.

[kalos72]

Perfect that will work fine then. Thanks.

[Targan]

Originally Posted by StainlessSteelCynic

However I have a vague recollection that a typical large civilian RO-RO could carry about 30 heavy armoured vehicles (tanks, SPGs), around 100 (or less) lighter armoured vehicles (APCs, armoured cars) and anything up to 200-300 non-armoured vehicles (trucks, trailers, field cars and so on). They wouldn't carry more armoured vehicles because of their collective weight but it's probably also to stop the loss of say 100 tanks in one shot should the ship get sunk.

This thread reminded me of the sinking of the Atlantic Conveyor during the Falklands War. I thought I'd offer this link for anyone else wanting a refresher:
http://en.wikipedia.org/wiki/Atlantic_Conveyor

[chico20854]

A (lot of) thoughts about ro/ros. (First, my job consists of financing ships, the Ro/Ro you linked to belongs to my agency and I’ve been aboard a few of them, and I worked in military sealift planning before moving to finance).

First, as far as civilian ro/ros, there aren’t that many. They were quite popular in the late 70s and early 80s as a way to more quickly service ports in the developing world, as they didn’t require much port infrastructure and they were massively quicker in cargo handling than break-bulk cargo carriers. They were envisioned to carry both wheeled and containerized cargo, the containers on chassis (wheel sets) or loaded onto chassis at the port. Unfortunately, the ships (like the Atlantic Conveyor) had larger vehicle capacity than was usually required, which was usually filled with containers. Unfortunately, they were not as efficient (time and volume wise) as container ships, and the continuing trend towards containerization (and ever larger container ships) in more developed markets meant that there was always additional containership capacity coming into competition with ro/ros, and the costs were low enough that installing container handling cranes made sense. So by the late 1980s the ro/ro market was in pretty bad shape. Desert Storm was a boom for the ro/ro market, but it collapsed completely after 1991, especially when the market was flooded with former Soviet merchant ships coming onto the market. The US military bought up most of the militarily useful ro/ros that came on the market. The ones that remain are typically smaller (designed for “project cargos”, things like relatively small lots of construction equipment, locomotives, large pressure vessels for chemical plants, and other oversize and overweight cargos), ferry vessels, with relatively low strength decks, passenger facilities (many of which are strictly day facilities, so berthing troops would be difficult) and limited endurance, or car carriers.

As for capacity for military vehicles, it depends on a bunch of things…

First, the strength of the decks. Most commercial car carriers have decks capable of holding about a ton per square meter. Tanks and armored vehicles require a little over 2.5 tons per square meter of deck strength.

Second, the height between decks. If you want to stow CH-47 helicopters below decks, you’ll need 6m minimum deck height. Tanks and most other armored vehicles need about 3.5-4 meters. Commercial car carriers in the 1990s were frequently under 2m in height; there was considerable disruption in the industry when SUV sales volume exploded in the late 1990s and huge portions of the car carrier fleet were unable to carry SUVs, causing massive amounts of scrapping relatively new ships and new construction. (And due to the deck strength and height issues, the military wasn’t interested in picking up the ships on the cheap).

Third are things like loading facilities (ramps, cranes and so on). During the Falklands war, there were issues with some of the ro/ros having only a few small, low doors, ramps that were too lightly built, or not enough chain to lower the ramps all the way to the water level. The overall size of the ship matters too, I’ve got a study around here somewhere about the small percentage of ports worldwide that the large ro/ros the USN built in the 90s will fit into, which means they’d have to be unloaded “in stream” – in middle of the harbor via floating causeways, landing craft or barges and susceptible to the weather.

As a guideline, in 1991 following Desert Storm, DoD issued a requirement for ro/ros with 220,000 sq feet of cargo space at 525lbs/sq ft and 13.5 ft of deck height.

Ok. On to cargo capacity itself. First, a stroke of luck… in 1993 the Cape Douglas (about 167,000 square feet of useful cargo space) loaded prepositioning cargo in Antwerp: 123 M1A1, 126 M2, 24 M-109, 9 MLRS, 445 other vehicles and a 300-bed field hospital. For a deployment they might cram some more cargo aboard – the prepositioning mission requires a little more space between cargo for ongoing maintenance of the vehicles, and there might also be cargo space taken up with preservation equipment (dehumidifiers and the like). In general, it seems like a good rule of thumb might be that a generic “military vehicle” takes about 10 square meters of ro/ro space. We have a whole staff of naval architects that spend a significant portion of their time determining what the carrying capacity of ro/ros are…

Sorry that this has turned into a mini-novel. Send me a PM if you want some more info…

[StainlessSteelCynic]

No need to apologize Chico, your information was a fascinating look into 1. a job most of us will never encounter 2. the quite significant vehicle carrying capacities of RO-RO ships and 3. the massive difference between those ships designed for civilian use compared to those needed for military use.
I did not realize that some of these ships can carry nearly 300 heavy armoured vehicles

[kato13]

Originally Posted by chico20854

Sorry that this has turned into a mini-novel. Send me a PM if you want some more info…

In general if you have the time to type it, I have the drive space to hold it