Trial from 1985

I'm writing to comment on the series of "Speed Thrills" essays on this site, specifically, the ones dealing with the Iowa class battleships. In the essay "Speed Thrills II," Mr. DiGiulian writes: "The Iowa's power/speed curves are reportedly classified and are not available for calculations of this nature."

This is no longer true. While the World War II data (from an October, 1943, sea trial off Rockland, Maine), had been restricted to some degree (a different category from today's classifications, if I remember correctly), most of that information was released to the public at the time of the publication of William Garzke's first battleship book in 1976. That book was used often among Navy designers as plans for the reactivation ramped up.

I have been exposed to this controversy for a long time. Early on in my career as a naval architect, I met a former XO of USS New Jersey from the Vietnam period. He swore that she had made 35 knots on her way back to the US after the famous deployment. When I questioned this number and cited some of the sources, he deferred to my engineering knowledge but offered a theory: That the cold water temperatures in the Northern Pacific basin could have improved condenser vacuum, resulting in more than rated power being developed by the engines. It is a fact that naval condensers are slightly undersized compared to merchant ship practice for similar steam conditions in order to make engine rooms more compact, and therefore, vacuum may be slightly less at full power because enough heat can't be transferred away from the exhaust steam. Of course, this is a limit on power, but if you look at the steam tables, the difference is not large enough to boost power by 19%, which is about what it would need to be in order to advance from 32 knots to 35 knots. So, ever since that time (1980), I have doubted the myth of the 35-knot battleships, and later on I had occasion to see the proof for myself.

I was working as a hull design and performance naval architect at NAVSEA when the battleships were re-commissioned. I was assigned as the task leader for that project, so I had access to all pertinent data. I analyzed the 1943 data and found that it was questionable for a number of reasons. The trials were hastily done and did not provide believable numbers for performance; whether they were adequate for fuel consumption was doubtful. Accordingly, I requested a new trial. My request was granted and in August, 1985, I drove to Norfolk to join Iowa, which had just been re-commissioned, for a week of speed and maneuvering trials off the Virginia Capes. (It was the high point of my professional career as a naval architect, and I'll never forget it). Later, a comparison of the 1943 and 1985 trials was created as a David Taylor Model Basin Report, written by the Trials coordinator who was also on board for the 1985 trials, Dick Stenson.1 That report has already been "Approved for Public Release, Distribution Unlimited," so the entire story may now be told without any security concerns.

The original trials results from 1943 (on New Jersey, BB 62) were:

Table I
Average Speed (knots) RPM SHP (total 4 shafts)
24.9 147.2 78,000
27.92 168.9 126,400
29.3 183.2 163,400

Extrapolating the last point to 212,000 SHP, the rated power for the ship's engines, assuming the speed-power curve was a perfect cubic (power proportional to the cube of the speed), according to theory, leads to a predicted top speed of 31.956 knots at rated power. This trial was conducted at a displacement of 56,550 long tons (averaged over the several days required to take the data). This would be in accord with the basic assumptions in the sources, and in Tony DiGiulian's Speed Thrills II. The top speed of an Iowa class battleship was approximately 32 knots at rated power and 56,000-plus long tons displacement, which is a little under the designed full load displacement.

In the August, 1985 trials, we were favored by excellent weather (sea state 2 and 20 knots of wind, which for a ship Iowa's size was within acceptable limits), and had no problems with our equipment. In those pre-GPS days it was necessary to put two transponders in fixed, known positions - on fixed towers as described in the report, far enough apart that the computer could triangulate and solve the speed-time-distance equations to give us a speed and, for maneuvering, a complete navigational trace. The report gives the following numbers at an average displacement of 56,900 long tons, barely different from the 1943 displacement.

Table II
Average Speed (knots) RPM SHP (total 4 shafts)
8.56 50.2 3,300
13.17 75.5 9,800
17.45 99.7 21,400
22.52 130.5 50,000
24.96 144.2 66,000
28.08 166.9 109,700
29.41 180.4 141,500

As the ship was turning to line up for the next runs at higher speed, a boiler room fan failed and higher speeds were no longer possible. This stopped our speed trial cold, but of course, our 29-knot point was nowhere near 212,000 SHP, so we still needed additional points to define the curve as full rated power was approached. One of the problems with the 1943 data was that they didn't extend to a high enough speed to define the shape of the curve at top speed, where variations in ship resistance from the theoretical cubic, or even smaller variations in propeller efficiency, could affect the results by several tenths of a knot.

Fortunately, on a previous night there had been a high power fuel economy run. While only power and RPM data had been taken since at that time the ship had been off the range, speed readouts from the speedometer on the bridge had been taken. That speedometer had been calibrated against range speeds during the standardization trial, and accordingly, the model basin trials crew was able to reconstruct an additional data point at 31.0 knots of 198.2 RPM and 186,400 SHP. This being substantially closer to full power than the World War II data, extrapolating it as a cubic is correspondingly more accurate. The result is 32.36 knots, in very good agreement with the classic design number of 32.5.2 Since this trial was run 71 days after the last drydocking, suggesting there could be some hull fouling, I am inclined to believe that 32.5 knots at 212,000 SHP is within experimental error of what actually happened on the sea trial in 1985.

I would hope this essay can put to rest all of the speculation about the maximum speed of the Iowa class battleships. They achieved their design performance at a displacement of 56,900 long tons, slightly less than their design full load.

Personal Memoir of the Sea Trial

While the main purpose of this article is to convey the results of the standardization trial, which has been accomplished in the preceding section, I consider the Iowa sea trial to have been the most important week of my career. It was full of interesting incidents and possibly some of them would amuse readers from the NavWeaps site.

At the beginning it didn't look like the week would go well. I drove to the familiar Navy base where I'd picked up several ships on previous trips. I had no trouble with security, but when I got to the deep draft piers, Iowa was not there. I asked around to no avail. Finally I saw an information booth with a long line of people waiting to ask questions of the lady inside. I got on line, hoping she could help me. A Chief Petty Officer got on line behind me and seeing his authoritative look and beginning to suspect a problem, I asked him if there was an "industrial area" in the base where maintenance was performed.

"Well, no," he answered. "Were you maybe looking for the Norfolk Navy Yard? This is a different base." I realized he'd given me the golden key so I asked him to show me on my map, and sure enough it was on the other side of town.

After driving across town and across a bridge as it got to be rush hour (although Norfolk's rush hour is bush league compared to the one I'd been fighting regularly in Washington), I arrived at the Navy Yard and stopped at the security checkpoint. I showed them my orders and asked where I could find the Iowa. This time there was no hesitation: "Sorry, you missed it - it left half an hour ago." I guess the guard at the gate could tell by the look on my face that things were bad. Fortunately, he knew a lot more than he needed to know. "You can still catch it - they'll be anchoring out tonight so they can load ammo tomorrow. Can't go to sea unarmed without an escort. You didn't know that?" I didn't. "I suggest you just go to a restaurant and have dinner. By the time you're done, the ship will have been through the channel out of the river and anchored in the Roads. Then you can find some way to get out to it. It'll be near the operating base."

So, I had to drive right back where I'd come from. I found a restaurant on the waterfront in Virginia Beach, east of the base, and had a leisurely seafood dinner. As I was finishing my meal, the unmistakable silhouette of an Iowa class battleship glided majestically eastward along the waterfront, then almost immediately to seaward of my position, did a stately pirouette into the westerly wind and anchored. With a puff of black smoke from No. 2 funnel, the ship settled into position for the night.

Back I went to the base, and I went to the same information booth as before. This time I knew exactly what I wanted. "I'm riding the Iowa on trials. Is there somewhere I can get a 26-foot motor whaleboat or something to take me out to the ship?" I was visualizing having to talk a coxswain into taking me out to the ship in solitary splendor, possibly having to wave my orders around. That was not at all what happened. The information lady told me there was a place called the Fleet Landing where returning liberty parties would be taken out to the ship by much larger boats. She described where it was and indeed, no one even asked me for my orders - I just lined up with about 600 other young men in civilian clothes and when I got to the head of the line, out I went to the ship in a 50-foot personnel boat.

On board, I was assigned a berth - an upper of a triple stack in a deckhouse at the base of the aft director tower. This room had a porthole, a rarity, but lockers - I was assigned one of those too - were outside in a passageway. It was mainly occupied by engineering ratings and a few of the trials crew berthed there. We had one female member in the trials crew; since this was before mixed gender ships, she was relegated to the only totally private quarters on board - the Admiral's suite, where she got to bathe in the bathtub that had been specially installed in 1943 for the use of then President Franklin D. Roosevelt when he rode the ship to Casablanca on his way to the Teheran conference of Allied leaders. She had her own cook and steward as well. Since I hadn't met her previously, I was never able to find out if she liked having the red carpet treatment or found it boring and isolated (there was no admiral on board during our trial, needless to say). Mr. Stenson had an officer's cabin, but the rest of us berthed with the enlisted men.

The next day we took on quite a lot of 5-inch ammunition from a barge; Navy rules say no warship may proceed to sea unarmed and unescorted. There is also a prohibition against ships being drydocked with ammunition on board (battleship experts might recall that on February 26, 1942, the German battleship Gneisenau had her bow practically blown off by a secondary explosion of her own ammunition when hit by an air attack in drydock). So, that's why Iowa needed ammunition before proceeding to sea on the trial.

Once at sea, the trials crew turned out to be just a little short on manpower. This was partly because one of them, who was in his 60’s, had also been assigned an upper berth and he rolled out of it in the middle of the night, falling about 5 feet. Wandering around the ship bleeding from a cut in his scalp, he finally found someone to take him to sick bay and appeared at breakfast the next morning with a bandage around his head. Anyway, I was "drafted" to help take the data. The computer station was on the level below the navigation bridge, which had been the flag bridge originally, and the computer was placed so that it could be run from the Admiral's chair, where Willis Lee and William Halsey had sat in World War II. The chair was either new or re-upholstered in a rather kitschy vinyl, but it was fun to think about sitting where a famous admiral had once sat.

Another advantage of my position on the bridge was I got to watch (through the panoramic windows at the front of the deckhouse) the deckhands applying a clear liquid to the teak deck each morning, which transformed it instantly from weathered gray to a golden brown that would have done credit to the most elegant yacht. (No holystoning, and it was just as well since the crew wasn't big enough to grind that big an area with abrasives). However, there weren't even enough deckhands to apply the liquid with a mop to the whole deck in one morning, so throughout my time on board the deck had a patchwork appearance with approximately ten by ten foot squares each a slightly different color. However, by the time the ship appeared on TV the following year at some event in New York Harbor, the deck was a uniform, perfect golden brown.

The trial triggered at least one unfortunate dispute between the ship's crew and the trials crew. This was reported to me at one of the meals in the crew's mess, which was on the second deck in the same space as the barbette for No. 3 turret. One of the older trials people, who must have remembered the ship from World War II, chipped away paint from a brass fitting, apparently believing the ship would look better if all brass was polished. The crewman who reported this to me was responsible for keeping that compartment shipshape and didn't have the manpower to polish brass. He had the numbers at his fingertips, which I remember as approximately 1,550 men total in 1985 compared to something over 2,200 in 1945. He wanted me to get Mr. Stenson to issue "cease & desist" orders to the offender. I told him I understood the problem and would talk to Mr. Stenson, but I don't know what, if anything, the latter could have done, short of giving his subordinate a can of battleship gray and ordering him to repaint the fitting to match the compartment.

After the trials, I plotted the results on graph paper using drafting instruments provided by Mr. Stenson; I drew a smooth curve through the points using ships’ curves, very likely the ubiquitous K + E No. 60 (this was before Microsoft Excel). I don't think the curves shown in the report are the same ones, because at the time I created mine, analysis of the fuel consumption trial was not complete and my curve ended at 29 knots. We also did not attempt to calculate what might happen with the additional "design overload" power, which I was not even aware of at the time. Because the results needed to be presented to the Captain before we left the ship, I was still drawing at the time the XO gave the other trials crew members a tour of the ship, which I later found out included the President's bathtub and the barely visible dent made in the armor on one of the turrets by a glancing blow from a Japanese shell during World War II.

In retrospect, the crew was new to the ship and that probably had a lot to do with the boiler room problem. Having an experienced engine room staff was important in getting the best out of this complicated steam plant, and had the engineering division had a chance to drill a bit more before we sailed, it might be that numbers between 32 and 33 knots were possible, especially if they were aware of the overload capability. Also, the Atlantic off the Virginia Capes in August is relatively warm, so we did not have the advantage of maximum condenser vacuum cited by the New Jersey's former XO. However, the bottom line is that the myths of extreme Iowa class speeds are untrue. The conclusions of this "Speed Thrills" series are correct. Also, as is pointed out in one of these articles on the Tech Board site, the Iowas were nevertheless extremely fast for battleships, as well as having excellent combat capabilities and also were blessed with relatively smooth, vibration free operation even at top speed, except in hard turns.

My return to land was in a CH-47 helicopter that flew out from Oceana Naval Air station to pick up the trials crew and return us to land. I don't recall how I managed to get back to my car, which was on a different base, but I did return home that very day without needing to stay overnight either in Norfolk or on the road.

About the author

Mr. Toby is currently employed as a Naval Architect at Alion Science & Technology. He has a BA in Archaeology as well as BSE and MSE degrees in Naval Architecture and Marine Engineering from the University of Michigan and an additional MSE in Mechanical and Aerospace Engineering (aerodynamics) from Princeton. He has written numerous technical articles, many with a historical slant, notably a series on interwar destroyers in the Naval Engineers' Journal. He originally contacted NavWeaps in January 2009 to ask some questions about one of the "Speed Thrills" essays which conflicted with his own expert knowledge of the subject. Recognizing an opportunity when I saw one, I took the opportunity to take advantage of Mr. Toby's expertise to cadge a longer, more detailed work that could be added to the Technical Board files. Mr. Toby also generously supplied the attached First of Class Trials on USS Iowa Report (2 MB) mentioned above which contains many details on the speed capabilities of the Iowa Class Battleships.


  • ^Richard J. Stenson, "First of Class Trials on USS Iowa (BB 61) - Past and Present," DTRC 89/027, Oct. 1989, also presented at the STAR Symposium, New Orleans, April 1989.
  • ^In the trials report, the data point is extrapolated using some different method, arriving at a result of 32.25 knots; possibly the Model Basin crew corrected for water temperature, wind, or displacement as the ship burned off fuel during the trials period. I will rely on my own extrapolation since it is mathematically simple and easily verified.

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23 June 2011