7 JAN 44
Princeton's 20 knot journey southwest across the Pacific continued on January 7th, the monotony of the vast oceanscape broken only by the occasional “Plan 6” anti-submarine zigzag scheme. The day’s log entry is only a few dozen words of typically minimalist navalese, terse but detailed times of course and speed changes.
Undoubtedly training was being conducted throughout the ship that goes unmentioned in the log. So it seems appropriate that we should take the opportunity to do some training ourselves.
As most of you know, we have an “Enginerd" in this email group, who shall remain anonymous.
So anyway, after the first email in this thread Steve messaged me about the 120,000 gallons of fuel oil, and didn’t it seem a small number? I agreed.
In fact, one of my lasting memories of my very first cruise comes to mind. I was laying in my rack in USS Constellation while the ship was “unrepping” — that is, the ship was conducting an “underway replenishment” from an oiler. I distinctly recall the Captain coming on the 1MC (Ship’s Public Address communication circuit) and announcing that the unrep was complete, great job to all hands involved and then, and this is what astonished me, providing details which included the fact that we had taken on some tens of millions — yes, MILLIONS — of gallons of fuel oil. The number seemed incomprehensible to me and is something at which I still marvel.
I now had a hankering to find out exactly what Princeton’s actual specifications were. Fortunately, I have a book titled “The Independence Class Light Aircraft Carriers” which seemed a good place to start.
Appendix A of said book contained the technical data I was looking for, sort of. It states that this class of ship carries a maximum fuel oil capacity of 2,632.6 tons. The obvious question of course is how many gallons is 2,632.6 tons?
🤔
Before investigating that datapoint, a brief but hopefully instructive diversion…
In the aviation world, we measure fuel not in gallons but in pounds because gallons matter not when the consideration is the four forces of flight:
Whether concerned with launching a rocket to Mars or a rubber band-powered balsa wood airplane, these four forces are immutably linked and critical. At least where flight is concerned. Which is a long way of saying that the Navy’s shipboard aviation fuel (known as JP-5, which has a lower flash point than JP-8, the fuel used by the US Air Force) weighs in the neighborhood of 6.8 to 7 pounds per gallon. An easy calculation when given a gallon amount, simply divide by…wait…whut…no…uhhh…multiply by 7 to get pounds. For example: 100 gallons of JP-5 x 7 pounds per gallon equals 700 pounds of fuel. And that 700 pounds is a key factor when creating enough thrust to overcome drag in order to create the proper amount of lift with which to defy gravity.
I am an arithmetic genius*.
So! Where were we?
Oh yes. How much did World War II era marine fuel oil weigh per gallon? Because we live in an amazing time in history, after a little searching I was able to find a website dedicated to this information. And much, much more. For instance, a page titled "War Service Fuel Consumption of U.S. Naval Surface Vessels FTP 218” provided not just the information I sought, but specific charts and data outlining how to operate an Independence Class ship’s engines in the most, or least, efficient manner.
Right about now, I sense that Steve-O is getting aroused.
But we still haven’t answered our initial question: What is the relationship between the 120,044 gallons of fuel oil Princeton took on on New Years Day, and her maximum fuel oil capacity of 2,632.6 tons?
Behold!
So here are our givens:
- 1 ton of Fuel Oil equals 277 gallons.
- Capacity of ship is 2,632.6 tons of fuel oil
- Ship took on 120,044 gallons
Ergo:
2632.6 tons x 277 gallons = 729,230.2 gallons, which is the fuel capacity of USS Princeton. Which means that on New Year’s Day in 1944 she took on 16.5% of her maximum fuel capacity (120,044 ÷ 729230.2 = 16.46%).
I would assume that her tanks were already full or close to full, considering she was about to get underway for the roughly 2,800 mile trip to Hawaii.
Speaking of which, if we look at this chart...
...and assume (accurately based on the War Diary bridge logs) that Princeton averaged 20 knots on the crossing, with full tanks she would have had roughly 14 days before running out of fuel. The chart also indicates that Princeton would be able to travel approximately 8,000 miles before her tanks ran dry.
So … since 20 knots velocity converts to roughly 550 miles per day and 2800 miles ÷ 550 = 5.1 days, how did “The Peerless P” do on the crossing? We know that she departed Bremerton at 1003 on January 3rd and we know that she was pier side in Pearl Harbor at 1619 HST/1819 PST on January 8th which, measuring from her departure from the West Coast time zone, calculates to 5 days, 8 hours and 16 minutes.
5.18 days!!!!
One can only assume that the extra .24 of an hour is due to all that zigzigzagging and it’s negative effect on the boat’s downrange travel. ;-)
Thank you all for indulging my wannabe nerdness!
Steve, please check my work.
*I took Business Calculus 4 times in college.
Update: 7 JAN 44 Mistakes & Corrections:
I awoke in the wee hours this morning with concern about a few typos and at least one larger mistake in yesterday's email. The typos and small grammatical missteps I will leave to each of you to ponder.
But the time zone conversion error I will remedy. In calculating the time of Princeton’s departure from the west coast to her arrival at Pearl Harbor, I subtracted 2 hours when I should have added. Therefore, I have determined that her journey took 5 days, 8 hours and 16 minutes, which is 5.34 days vice the 5.18 I initially figured. So all that zigzagging seems to have added an additional .24 of a day to the nominal 5.1 days a routine 20 knot crossing would have taken. Whew! I feel better.
Steve, check my work.
One other item I was thinking about was the digression into fuel gallons and the conversion of liquid measures into weight. We determined what Princeton’s fuel tank capacity was in gallons (729,230.2) but we didn’t convert that to pounds. From the website (here is the link by the way: https://www.ibiblio.org/hyperwar/USN/ref/Fuel/Fuel-CVL.html) we know that Independence Class boats could hold 2632.6 tons of Fuel Oil so we simply multiply 2632.6 x 2000 to convert those tons to pounds, which is 5,265,200. A big number.
Which reminds me — WARNING! DIGRESSION AHEAD! — it stands to reason that all that weight, in sloshing liquid form no less, had to have a rather significant effect on how the ship rode in the water. Just as ancient wooden sailing vessels used stones as fixed ballast and cargo as dynamic ballast, so modern vessels use a complex system of pumps and piping to move fuel fore and aft and port and starboard in order to trim* the ship so it rides evenly and efficiently in the water.
I know this because, in the 8 years of my Naval career that I spent as an LSO (Landing Signal Officer) I got to experience the system on occasion. On the LSO platform, port side aft, we had a small inclinometer gauge, maybe the size of a 50 cent piece, which we could reference to determine the ship’s trim. For example, during the initial “fly on” prior to departing on a cruise, the flight deck would be empty of aircraft. Our inclinometer would confirm that the bridge watch standing team had the ship trimmed out and riding nice and level. As aircraft, each weighing anywhere from 30,000 to 60,000 pounds, would come aboard and be tied down, it stands to reason that this weight would effect the center of gravity of the ship. And it did. As aircraft were parked, usually forward on the flight deck, the bow would begin to ride lower in the water. More importantly to me as an LSO, the aft end of the ship, where the aircraft were crossing the “round down” just prior to landing, would elevate in direct proportion. Why did this matter you might ask? It mattered because the aircraft were generally flying a fixed angle “glideslope” as they came aboard, and the bow down/aft up trim of the ship acted to decrease the distance of the aircrafts’s clearance, it’s safety margin, from the round down as it flew that fixed glideslope. Which again, is a long way of saying that when this occurred, I would simply pick up the LSO Platform handset, buzz the bridge and ask them to trim the ship. A good bridge team would have been doing this without prompting — they had much better gauges and indications than we did and trimming the ship was literally in their job description — at which point they would proceed to move fuel around in order to make the ship ride level. Problem solved! And I must admit it was always fun to claim that I was actually controlling the ship with my mini-inclinometer and my handset.
Thank you for listening. Onward!
* trim (noun )
1 additional decoration, typically along the edges of something and in contrasting color or material: we painted the buildings off-white with a blue trim | suede sandals with gold trim.
• decorative additions to a vehicle, typically the upholstery or interior lining of a car: refinements such as air conditioning and leather trim.
2 [count noun] an act of cutting off part of something in order to neaten it: his hair needs a trim.
• a short piece of film cut out during the final editing stage.
3 the state of being in good order or condition: no one had been there for months—everything was out of trim.
4 the degree to which an aircraft can be maintained at a constant altitude without any control forces being present: the pilot's only problem was the need to constantly readjust the trim.
5 the difference between a vessel's forward and after drafts, especially as it affects its navigability: ships' masters had to check trim and stability before departure.
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