Full Speed Ahead and Crash Stops on Iowa Battleships
Well, I've been on a couple of sea trials where we cranked her up 10 rpm every ten minutes.
That's each shaft increasing another 10 rpm. That's each 18-ton propeller increasing another 10 rpm.
The skipper usually held out at a maximum of 200 rpm for the required 2-hour hold. However, the machinery was capable of kicking up another 10 or 15 rpm. But 31 to 32 knots was sufficient for the high-speed tests.
When the ship got up to 26 knots, a rooster tail would start to appear. Vibration was reported, but only aft of frame 166 (where the aft transverse armored bulkhead is). Chief's quarters were pretty bouncy and the Nixie room was like standing on a jackhammer. I set my notebook down on a table to record some data and you can barely make out my handwriting.
Walking forward, the vibration almost totally disappears as soon as you cross the threshold at frame 166. By the time you get up near the anchor windlass room, you can feel a slight torque to the bow. An almost imperceptible twisting that can only be felt by people with excellent sense of balance. I think it was that twisting that caused hairline cracks in the upper outboard corners of bulkhead 36 and allowed fuel to leak into the storeroom. Identical cracks were found on 3 of the 4 ships.
Once the crew accidentally hosed me down when I stepped out onto the weather deck. They were washing down the teak and I was within range. But I just walked up to the bulwark on the bow, forward of the anchors, and let that 30+ knot headwind dry me off in a few minutes.
The high speed turns can shake you up a bit. New Jersey was riding very light and heeled quite a bit. Missouri was ballasted a little better (plus having bilge keels in better shape) and heeling was almost unnoticeable.
A full crash back is almost a non-event. That's where all four screws are reversed from full ahead to full astern. It takes a little over a mile for the ship to come to a stop before going in reverse, but there is no feeling of inertia throwing you forward - unless you turn the rudders inboard toward each other to close off the passage of water between the twin keels. That is called a "Barn Door Stop" and only the Wisconsin has ever tested it. A former XO of Whisky said that when they threw a piece of wood over the side from the bow at the onset of that maneuver, the ship came to a stop with that wood no further aft than turret III. That's stopping a 57,000 ton ship traveling at 33 knots in about 600 feet, which means that anything that is not tied down winds up on deck or against a forward bulkhead.
Of the four BB's we reactivated in the 80's, the Wisconsin had the most problems with loose rudders. I wonder why. But Philadelphia did a great job of tightening them back up again.
- 6 January 2000