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Cargo is not well defined - but Joe says in the end it must come down to tons.

But what is a ton?

For oil and fuel I decided it is deadweight. This slightly reduces the capacity of tankers (by 2/17ths - just more than 1/9th but less than 1/8th). And it is a uniform standard. Combining this with higher fuel requirements - either because ships had too low a fuel requirement - or because we are changing the cruising speeds for many - may help. A gasoline tanker carries slightly less than its deadweight rating if it carried oil, but not by much - and we don't do gasoline anyway - just fuel oil and crude oil - which are pretty similar - and allow almost exactly deadweight loads.

For dry cargo, the measure is space - cubic space. But while this is usually given in gross tons - that is a TAX concept - NOT a cargo concept!
Everything in a ship not exempt is taxed - wether it carries cargo or not!
What REALLY matters is NET tonnage - the gross tonnage minus all those spaces that don't generate revenue - carry real cargo. That is - for a Liberty ship - 47.8% of the gross tonnage and 40% of deadweight tonnage. [The ship can carry more weight than it can carry volume - a heavy cargo might get the ship near its deadweight limit - but on the average you don't get close.] This provides a basis for a rational standard of cargo definition: use Net Tonnage and you get values about half the GRT (always available) and 40% of deadweight (often available) - since half is easy to do in your head - I propose to use half of GRT - which is more often available anyway.

This way we don't have to greatly reduce the number of ships - preserving the research that put them in - but we do get a major reduction in cargo efficiency. Reducing the ranges in some cases as well, and increasing fuel requirements in a few cases (where they were not right) - also helps.

Another related issue - it will take forever to implement - is ships appearing even before they are built! Or before they went to the Pacific.
This is being done - by a volunteer - but it will involve updates - not all will be done up front. There are many thousands of lines to look at! And each one is being looked up in databases of historic ships.

It does, indeed, all come down to tons.

Whether we're talking about oil, phosphate, manganese, or dry break bulk cargo, the capacity of any ship, in those days, was measured by Net Deadweight Tons (long tons). It's somewhat confusing in the literature because there is a Net Tonnage figure often given that refers to Net Register Tonnage and is, just like the Gross Register Tonnage, a measure of internal volume used to define port and canal fees (yes, taxes).

The International Maritime Organization defines Gross Tonnage (before 1969 refered to as GRT) as the total moulded internal volume of a ship. Net Tonnage (the old NRT) is the total moulded volume of the "revenue bearing" spaces (includes passenger space as well as the holds and a certain amount of deck space). Both definitions are in terms of 100 cubic feet per 'register' ton and both are fee (tax) determinant quantities.

It's a very misleading measure of break-bulk capacity, however. A cargo of 500,000 cubic feet of pingpong balls (500' x 35' x 35' is over 600,000 cubic feet) is 5000 register tons. So is 500,000 cubic feet of sheet lead (711 pounds/cubic foot); which results in 158,700 long tons.

The Deadweight Tonnage is everything a ship can load (typically to the summer loadline) and includes cargo, water, fuel, crew, passengers, clothing, kitty litter, spare parts, etc .. It is calculated by taking the difference between Displacement Loaded and Displacement Light (the raw empty ship weight). It's in long tons (2,240 pounds).

Net Deadweight (or Cargo Deadweight, or Net Cargo) is the Deadweight minus water, fuel, crew, passengers, clothing, kitty litter, spare parts, etc .. Problem is that this quantity is not often documented.

The biggest hit (apart from cargo) is fuel and water. Water is about 2.9 long tons per register ton; Bunker C is about 2.4. The deadweight standards tables suggest that fuel (liquid fuel only; coal is another issue entirely) is approximately 28-31% of deadweight. Water (I’m also taking food, crew and passengers as having substantially the same density) generally occupies an additional 14-18% of deadweight, accounting for about 42-49% of deadweight tonnage.

So, if you can find a vessel’s dwt, her actual physical cargo capacity should be in the range of between 51% to 58% of dwt. I performed these calculations on the ship specifications of the vessels comprising the various national AKs and found that 55% of DWT corresponds closely enough to about 60% of GRT as to make little appreciable difference; although 55% of DWT is likely more defensible.

Replenishment vessels are similar. Even modern fleet AORs and AORLs, put 8,900 tons of fuel, avgas, food, ordnance stores on 15,000 DWT. Dedicated tankers are a bit different. The largest modern ULCC, Jahre Viking (ex Seawise Giant) has a capacity of 78% of DWT (at summer). A typical 1930s tanker design (US Maritime Commission T2) would come in at about 57-62% of DWT.

Please also note that the 60% of GRT analysis is not valid for either warships or ‘true’ passenger vessels. Passenger ship deadweights can be as little as one half the GRT because of the large volumes given to relatively low density ‘freight’.

To conclude; I guess the best way to determine actual capacity is to use 50% of DWT for the ‘dinks’ (less than 300’ and around 2000 tons grt) 55% of DWT for the remaining break-bulk vessels and 60% of DWT for tankers, AOs and the like.

I hope this is helpful. If you need references and a more rigorous analysis, please PM me. Ciao.

JWE

Thanks - will do more analysis.

Something that might help. Post war studies and analysis showed that 1 ton of "Average Military Cargo" occupied 2.36 deadweight tons of cargo space.

ORIGINAL: Mike Scholl

Something that might help. Post war studies and analysis showed that 1 ton of "Average Military Cargo" occupied 2.36 deadweight tons of cargo space.

A bit more like 100 cubic feet (1 register ton) of "Avg Mil Cargo" weighs 2.36 long tons. Makes sense though, because the three major components were food, fuel, & ammunition, all with densities in the 2.2 - 2.9 Ton/cubic range (taking packaging into account).

JWE

ORIGINAL: Mike Scholl

Something that might help. Post war studies and analysis showed that 1 ton of "Average Military Cargo" occupied 2.36 deadweight tons of cargo space.

Trouble with the above "average" is that outlyers can distort the "average", and I would rather like to see this in the standard deviation with any outlyers removed. In an analysis done by the Army Transport Command in 1946 it appears that the effeciency in loading cargo vessels was approximately 75% for bale volumn and 79% for tonnage. This value varied form year to year and from port to port. If we use JWE's percentages and then modify by some number between 75 to 80% would be a reasonable way to caculate load capacity for supplies in the game and then determine which standard to use, volumn or weight. For transporting LCU's and such, the cost for transport is determined by the setting in the device database. Maybe this needs a good examination as to the current veracity of the values used.

ORIGINAL: JWE

ORIGINAL: Mike Scholl

Something that might help. Post war studies and analysis showed that 1 ton of "Average Military Cargo" occupied 2.36 deadweight tons of cargo space.

A bit more like 100 cubic feet (1 register ton) of "Avg Mil Cargo" weighs 2.36 long tons. Makes sense though, because the three major components were food, fuel, & ammunition, all with densities in the 2.2 - 2.9 Ton/cubic range (taking packaging into account).
JWE

NO..., I meant exactly what I said. One ton of "Average Military Cargo" occupied 236 cubic feet. Stop and think a second. Military equipment may seem fairly heavy, but it is also generally bulky and oddly shaped. 100 cubic feet of cargo space is only about a yard and a half cubed. A one-ton Jeep (crated) easily fills 300 cubic feet.

Now that's for US usage. The Japanese, who did without a lot of things (and suffered accordingly), would undoubtedly do somewhat better.

Something that might help. Post war studies and analysis showed that 1 ton of "Average Military Cargo" occupied 2.36 deadweight tons of cargo space.

(in

This is very valuable information for simpulation purposes. Average is what we need to know to get things "right" - on the average! Design your sim with average data rates and you get pretty close - mostly.

Something that might help. Post war studies and analysis showed that 1 ton of "Average Military Cargo" occupied 2.36 deadweight tons of cargo space.


A bit more like 100 cubic feet (1 register ton) of "Avg Mil Cargo" weighs 2.36 long tons. Makes sense though, because the three major components were food, fuel, & ammunition, all with densities in the 2.2 - 2.9 Ton/cubic range (taking packaging into account).

I understood this eactly as you do - a "ton" to shipping being 100 cubic feet. [As a sailor, I am trained to think of a ton as a cubic meter, because a ton of water weighs approximately 1 metric ton - based on the definition of density itself - but modified by impurities slightly. A ship floats or sinks based on displacement - and you can do this in your head - figuring how many meters are flooded - the actual weight of the ship - etc. 100 cubic foot tons, on the other hand, are wierd - and not exactly a ton - flooded or otherwise. But I know that is the standard of the industry - for revenue rather than damage control reasons.]

Trouble with the above "average" is that outlyers can distort the "average", and I would rather like to see this in the standard deviation with any outlyers removed. In an analysis done by the Army Transport Command in 1946 it appears that the effeciency in loading cargo vessels was approximately 75% for bale volumn and 79% for tonnage. This value varied form year to year and from port to port. If we use JWE's percentages and then modify by some number between 75 to 80% would be a reasonable way to caculate load capacity for supplies in the game and then determine which standard to use, volumn or weight. For transporting LCU's and such, the cost for transport is determined by the setting in the device database. Maybe this needs a good examination as to the current veracity of the values used.

I understand your concern with the tata "integrity." The database was very approximate - and then got modified by committee operating with few definitions to guide them. But I have no idea what you are talking about. I would think the average value would be the average value. Are you talking about inefficiency because of (a) returning empty; (b) waiting for docks - stuff like that?

NO..., I meant exactly what I said. One ton of "Average Military Cargo" occupied 236 cubic feet. Stop and think a second. Military equipment may seem fairly heavy, but it is also generally bulky and oddly shaped. 100 cubic feet of cargo space is only about a yard and a half cubed. A one-ton Jeep (crated) easily fills 300 cubic feet.

I see. So you are saying this is really a cubic measure - not a weight measure at all. That is, a ship is volume limited - and its grt or nrt value is more of an indicator than its deadweight value. This is consistent with my understanding. My first ship was the last APA ever built - and it certainly seemed that way.

But note that we must deal with other cargos besides military ones. We need to have a value for resources and for oil as well as for supplies and fuel. I think we need two values - since a ship generally either carries supplies/resources or oil/fuel. [An AK can carry fuel, but at a 50% penalty, which I not only approve of - it was my idea (in ancient UV days BEFORE we could carry fuel on AKs]. I still think oil is weight defined while other cargo is mostly space defined. If NRT is about half of GRT, then 236 cu ft per nominal ton is about 4.72 GRT per ton - or with some slop for enefficiencies - call it 5. If we know the GRT rating of a ship, it carries 1/5 of that in terms of military tonnage. THAT should help prevent the apparent gross overcapacity of the supply system!

ORIGINAL: el cid again

NO..., I meant exactly what I said. One ton of "Average Military Cargo" occupied 236 cubic feet. Stop and think a second. Military equipment may seem fairly heavy, but it is also generally bulky and oddly shaped. 100 cubic feet of cargo space is only about a yard and a half cubed. A one-ton Jeep (crated) easily fills 300 cubic feet.

I see. So you are saying this is really a cubic measure - not a weight measure at all. That is, a ship is volume limited - and its grt or nrt value is more of an indicator than its deadweight value. This is consistent with my understanding. My first ship was the last APA ever built - and it certainly seemed that way.

But note that we must deal with other cargos besides military ones. We need to have a value for resources and for oil as well as for supplies and fuel. I think we need two values - since a ship generally either carries supplies/resources or oil/fuel. [An AK can carry fuel, but at a 50% penalty, which I not only approve of - it was my idea (in ancient UV days BEFORE we could carry fuel on AKs]. I still think oil is weight defined while other cargo is mostly space defined. If NRT is about half of GRT, then 236 cu ft per nominal ton is about 4.72 GRT per ton - or with some slop for enefficiencies - call it 5. If we know the GRT rating of a ship, it carries 1/5 of that in terms of military tonnage. THAT should help prevent the apparent gross overcapacity of the supply system!

Remember that oil and other liquids are generally shipped in tankers and measured in "barrels". This average in generally concerned with "dry" military cargo, though it does include various liquids like gasoline when being shipped in containers like barrels. The point was that few cargoes (like iron ore pellets) actually weigh more than 1 ton per 100 cubic feet---the great majority weigh less. And that having 100,000 tons of "shipping" does not generally allow you to move 100,000 tons of "cargo" (unless your a Great Lakes Ore Freighter like the EDMUND FITZGERALD).

Boy oh boy, lots of interesting considerations in the thread.

To keep the kinds of "tons" straight, I'll use the term "cubic ton" to refer to the volume or register tonnage (the 100 cubic foot volume); and "long ton or metric ton" to refer to the weight measure (2,240 pounds). This will tag the volume measurements to the gross and net register tonnage figures, and the weight measurements to deadweight and displacement tonnage figures.

Using either one as a basis for capacity is quite valid. If you were loading asphalt or sheet steel for airfield construction, one basic pallet (assume 5'x5'x4' to give 1 volumetric or "cubic ton") would likely come in at about 21.8 "long or metric tons" (sheet steel is about 489#/cubic foot), ignoring the holes, of course. For this manifest, the ship capacity is weight limited so its capacity would depend on a percentage of deadweight tonnage.

Conversely, a basic 5x5x4 "cubic ton" pallet of winter jackets would very likely weigh less than 2,240 pounds, so that this manifest would mean the ship was volume limited and its capacity would depend on a percentage of register tonnage.

I think that Don's 60% of "GRT" corresponds closely enough to the 55% of "Deadweight" figure, that either one can be used as a base figure (at least for break-bulk, cargo-type vesels). The different measures just define the outside corners of the capacity calculation.

A ship's manifest is tabulated, with each "pallet" of cargo listed as to its "cubic tonnage" and its weight in "long or metric tons"; two "tonnage" figures next to each piece of cargo. If it's palletized, it's easy, 1 pallet = 1 cubic; an odd piece, like a truck, has an imaginary volume assigned, 1 truck = 4.7 cubics, for example. Then, it's just a pencil and paper operation to load the maximum amount of weight into the maximum amount of volume.

If the Cargo Master or Port Agent have their heads screwed on straight, the loadout will end up at max deadweight capacity AND max volumetric capacity. The ship's manifest will put the sheet steel and ammo into the bottom of the hold, and then pile the toilet paper on the deck up to the kingposts. Thing is, if you grossly exceed deadweight, you sink; you can exceed volumetric, so long as you are careful with metacentric height; 20-25% volumetric overload was not uncommon on the North Atlantic run.

Of course, combat loading was just the opposite; you do NOT put the toilet paper on top of the ammo. This changes the metacentric height and substantially reduces the "metric or long tonnage" capacity. A good Cargo Master just might be able to fill out the available volume, but, as has been mentioned in many other threads, assault ships very commonly float high.

Beats me what the answer is. I still think a percentage of deadweight is the more practical solution as a capacity "base", for AK types of ships; it covers the range from 200' to 550' a bit better than a % of GRT. However, for passenger and passenger/cargo types (i.e., APs) perhaps a % of GRT would be better, since their passenger volumetric tonnage spaces are being utilized in substantially the same manner with troops.

Once the "base" calculation is made, the different ships would, at least, be consistent (at baseline). Then an efficiency "fudge factor" reduction, like AlaskanWarriors 75-79% could be applied across the board.

Does this make sense?

JWE

Once the "base" calculation is made, the different ships would, at least, be consistent (at baseline). Then an efficiency "fudge factor" reduction, like AlaskanWarriors 75-79% could be applied across the board.

Does this make sense?

Yeah it does. But we are TIME limited. Please recommend a base figure.

Okey dokey. 55% of Deadweight tonnage. If deadweight isn't listed, take the difference between Navy Light or Maritime Commission Light and Full Load Displacement = Deadweight.

This next is extruded right outta my butt, but is lubricated by posters on this and other relevant threads; a 75% reduction for efficiency for combat loading for assault landings; a general 80/20% split between "normal" voyages and "combat" loadouts.

DWT[.8(.55) + .2(.55)(.78)] = DWT[.44 + .086] = .5256 DWT, or 52 - 53 % DWT. For tankers, I still hold with 60% of Deadweight.

JWE

ORIGINAL: JWE

For tankers, I still hold with 60% of Deadweight.

JWE

Why 60%? There is plenty of data out there givig the capacity in barrels for tankers. Why not just convert barrels to tons. I do not any ineffeciencies in liquid transport as opposed to dry.

USS Guadalupe on 1944.06.26 (Beans, Bullets, and Black Oil, Page 143):
7470 tns light, 24,830 tns full = 17000 capacity
90,139 Barrels of Fuel Oil (heavy) = 13,850 long tons
7, 840 Barrels of Diesel (marine)= 1060 long tons
391,202 gals Aviation fuel = 1078 long tons
Total load: ~16,000 tons of petro products

Although not listed here, tankers and AO's also would usually have a deck load of compressed gasses (propane, acytelene, oxygen, CO2, nitrogen, etc)

I can give other examples, they are not that hard to find.

Tankers Built in U.S. During World War II

The T1 type were named after major oil fields in the United States. The T2 types were named after monuments, national parks, forts, battles, historic settlements, trails, lakes, swamps. Later T3 type were built for private companies and named by the company. Many tankers were built for or taken over by the U.S. Navy and named after Native American names of rivers and lakes. The Navy AO designation indicates Fleet Oilers.

Tankers were developed around the turn of the century to carry liquid cargo: gasoline, oil, or molasses. During World War II, American tankers made 6,500 voyages to carry 65 million tons of oil and gasoline from the U.S. and the Caribbean to the war zones and to our Allies. They supplied 80% of the fuel used by bombers, tanks, jeeps and ships during the War.

T2-SE-A1 was the workhorse of the tanker fleet (481 built):

* 523 feet long overall
* 68 foot beam
* 30 foot draft
* 10,448 Gross tons
* 21,880 Loaded displacement tons
* 6,000 shaft horsepower Turbo-Electric propulsion
* Speed 14.5-16 knots
* Liquid capacity 141,200 barrels (42 gallons or 162 liters per barrel). [nearly 6 million gallons]

T3-S2-A1 (All became Fleet Oilers and several were converted to Escort Carriers CVE):

* 553 feet long overall
* 75 foot beam
* 32 foot draft
* 11,335 Gross tons
* 24,830 Loaded displacement tons
* 4 Steam turbines geared to twin shafts
* 13,500 shaft horsepower
* Speed 18 knots
* Capacity: 146,000 barrels

T3-S-A1

* 501 feet long overall
* 68 foot beam
* 29.6 foot draft
* 9,880 Gross tons
* 2 Steam turbines single-screw
* 7,700 shaft horsepower
* Speed 15 knots
* Capacity: 133,800 barrels

Okey dokey. 55% of Deadweight tonnage. If deadweight isn't listed, take the difference between Navy Light or Maritime Commission Light and Full Load Displacement = Deadweight.

This next is extruded right outta my butt, but is lubricated by posters on this and other relevant threads; a 75% reduction for efficiency for combat loading for assault landings; a general 80/20% split between "normal" voyages and "combat" loadouts.

DWT[.8(.55) + .2(.55)(.78)] = DWT[.44 + .086] = .5256 DWT, or 52 - 53 % DWT. For tankers, I still hold with 60% of Deadweight.

JWE

This is useful but it would be more useful if we could write code. The oil/fuel value is useful directly - no combat loading and, since I have already rated for dwt, 60% is going to be easy to implement. But we do NOT have the ability to write code - so whatever the penalty is in the code (and there is one) - we have to accept it. We must use a value for civil cargo and, when there is a landing, let the code penalize it further. Regretfully, we do not often have dwt for a non-tanker, but we have grt - so that means we must say 55% of that is dwt, UNLESS we happen to have the dwt value. But we must remember the CODE will take care of combat loading - so we only care about normal voyages. In that case - do we want a further reduction for inefficiency? IF we went with about 10% (9% actually) - we would end up at 50% of grt - and that is what I already did - so I am home free in that case.

Why 60%? There is plenty of data out there givig the capacity in barrels for tankers.

Three reasons:

1) We already have dwt data. It is universally available for tankers. And it is entered already.

2) It is NOT universally available. Getting the data would require using materials we do not have - if you want to run down every class - and still you would not get it all. Then you would have to estimate bbl from dwt anyway for those cases.

3) The result should be statistically the same. That is, if you understand how to convert, you could convert dwt to bbl, and you would find that adding up all the bbl ratings and converting them from dwt would produce a result well under 1% different.

That is way to much work for the time available - and too much even if time were unlimited - since it would cause no increase in accuracy within the scale of the system. I will use anything better than what we have, but not if the cost is excessive. This is a very sensible proposal.

USS Guadalupe on 1944.06.26 (Beans, Bullets, and Black Oil, Page 143):
7470 tns light, 24,830 tns full = 17000 capacity
90,139 Barrels of Fuel Oil (heavy) = 13,850 long tons
7, 840 Barrels of Diesel (marine)= 1060 long tons
391,202 gals Aviation fuel = 1078 long tons
Total load: ~16,000 tons of petro products

Although not listed here, tankers and AO's also would usually have a deck load of compressed gasses (propane, acytelene, oxygen, CO2, nitrogen, etc)

I can give other examples, they are not that hard to find.

The problem is not examples - it is that we need comprehensive data for ALL classes - even the most obscure - and for military vessels never rated in bbls at all.

Also, we cannot do deck cargo. AOs make fine cargo ships - Japan shipped a rare ore from Malaya to Japan containing both uranium and thorium (Mozanite) - the only time it was ever exported from that country - on tankers! But it is not a factor in this system. Maybe WITP II.