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View Full Version : The Incredible (Shrinking) Hulk - How?

Hornblower
2012-Jun-07, 01:33 AM
I am referring to variations in the claimed gross tonnage of the ocean liner S.S. United States. Gross tonnage is defined as a measure of the volume of enclosed space, at 100 cubic feet per ton. In various references I have seen it listed as having changed from 51,988 gross tons originally to 38,216 in the late 1960s. My rough estimate from the appearance of the ship is that such a difference amounts to almost the entire superstructure. Does anyone have any explanation for this? My recent browsing has turned up no plausible explanation other than the possibility of initial exaggeration with the aid of an "antiquated" measuring system, whatever that is supposed to mean. It makes me wonder about the accuracy of the gross tonnage figures of any of the great liners in those days.

References can be found by Googling "SS United States 38216."

Solfe
2012-Jun-07, 02:37 AM
Tonnage appear to be a taxation and fee calculation unit. Wikipedia shows the formula for Gross Tonnage (http://en.wikipedia.org/wiki/Tonnage)as GT=K*V where V is the volume and K is a decimal between .22 and .32. A ship of a GT of 52,000 and a K value of .32 has a volume of 162,500. For a GT of 38,000 and a K of .22 the volume is 172,727. That is "only" 10,000 m^3 difference just playing with ball park numbers and extremes.

Hornblower
2012-Jun-07, 02:34 PM
Tonnage appear to be a taxation and fee calculation unit. Wikipedia shows the formula for Gross Tonnage (http://en.wikipedia.org/wiki/Tonnage)as GT=K*V where V is the volume and K is a decimal between .22 and .32. A ship of a GT of 52,000 and a K value of .32 has a volume of 162,500. For a GT of 38,000 and a K of .22 the volume is 172,727. That is "only" 10,000 m^3 difference just playing with ball park numbers and extremes.

Yikes! I had naively assumed that the published numbers were simply calculated by means of reasonably accurate numerical integrations of the linear measurements of the ship. Now I smell fudge cooking, with formulas that can be manipulated into exaggeration for boasting about having the biggest ship, or into understatement for the purpose of a tax dodge.

mike alexander
2012-Jun-07, 02:42 PM
Having vague memories of that era, I recall rumors that the United States was actually a testbed for revolutionary new naval technologies. Given that, plus Cold War boasting, it would not surprise me that prolonged immersion in cold water caused some shrinkage over time.

Hornblower
2012-Jun-07, 03:44 PM
It is my understanding that the ship was built to U. S. Navy specifications, and that the hull design carried over to the hulls for the USS Forrestal and subsequent supercarriers.

Nicolas
2012-Jun-07, 06:59 PM
Ah, the incredible hull.

In various references I have seen it listed as having changed from 51,988 gross tons originally to 38,216 in the late 1960s.

Wow, that puts my current problem at work in perspective. I'm looking for 56 tons difference. Metric tons that is, because we work with real physics and not some measurement of payment in a rogue unit system. ;) Oh, and with this precision we're no longer talking about box factors but about calculations of the actual hull geometry. 56 tons on a large ship is next to nothing, so it's a hard task to find where it's coming from. 14000 tons on the other hand shouldn't be too difficult. :)

Solfe
2012-Jun-08, 01:44 AM
Actually it doesn't appear to boasting. The K value range is used to calculate tonnage for the purposes of harbors, docks and canals. It is a commercial value. The ship owner would likely prefer that the smaller K value be assigned to the ship while the operators of docks, harbors and canals all use a higher value as a means of assessing how many resources X ship requires of the facilities.

Displacement might be a better value of actual size, but even then you are only talking about how much water the ship shoves out of the way. Net tonnage is the measure of how much cargo space a ship has, while TEU and FEU measure how many cargo containers a ship carries.

Nicolas
2012-Jun-08, 04:34 PM
Displacement might be a better value of actual size, but even then you are only talking about how much water the ship shoves out of the way.
Which, thanks to Archimedes, is at least in a static situation equal to the total weight of the ship. On the money side of things, net tonnage/passenger capacity/TEU are the more interesting figures indeed.