The carrier that interrupted my oatmeal came down on me like a speed boat. Didn't time it but on radar she shot from a lazy 8-10 to a not so lazy 25-27, it seemed like almost as fast as she made her turn into the wind.
Grand old ship...new life?
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Originally Posted By: Astro14
Great question, Supton, I honestly don't know. I do know that the shaft is the limiting factor. The reactor can make far more steam, and the turbines more torque, than the shafts can handle.
The top speed is limited by that torque.
Though, I have to say, I've seen phenomenal acceleration from a Nimitz-class carrier when a simulated torpedo attack took place directly astern during training. The speed difference alone (from before the flare in the wake simulating the attack to final speed) was greater than the top speed to which the Navy admits.
We added nearly 30 knots to our speed in just a few minutes. The prop wash coming from the stern was amazing as well...a huge swell of whitewater. You could feel vibration from the ship itself, which I'm told comes from cavitation of the props. Just think about the torque needed to make props that size cavitate...
My dad was on a boomer and he said at least in the sub world cavitation is what limits your speed.
They spent a lot of time tuning their prop.
On a surface ship it doesn't really matter, everyone already can see/hear you.
Great question, Supton, I honestly don't know. I do know that the shaft is the limiting factor. The reactor can make far more steam, and the turbines more torque, than the shafts can handle.
The top speed is limited by that torque.
Though, I have to say, I've seen phenomenal acceleration from a Nimitz-class carrier when a simulated torpedo attack took place directly astern during training. The speed difference alone (from before the flare in the wake simulating the attack to final speed) was greater than the top speed to which the Navy admits.
We added nearly 30 knots to our speed in just a few minutes. The prop wash coming from the stern was amazing as well...a huge swell of whitewater. You could feel vibration from the ship itself, which I'm told comes from cavitation of the props. Just think about the torque needed to make props that size cavitate...
My dad was on a boomer and he said at least in the sub world cavitation is what limits your speed.
They spent a lot of time tuning their prop.
On a surface ship it doesn't really matter, everyone already can see/hear you.
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Just some numerical messing here, taking a 4' (solid) shaft and 360 degree twist over 100m.
Yes, the shaft is entirely well within it's elastic range, and will return to normal should the torque be removed.
To get that deflection over 100m lenght of shaft requires 1.4MNm (mega Newton Metres) of torque.
260,000 shaft horsepower would require a speed of 1330 RPM to transmit...and I'm very positive that it's not going that fast...couple hundred max would be my guess.
So I'm quietly positive that if it's a 4' shaft, it twists some number of times down it's entire length.
My turbines have 21" maximum shaft diameter in the bearings between the LP and the generator, and have moved just under a million horsepower...but at 3,000RPM, the applied torque is massively lower.
Yes, the shaft is entirely well within it's elastic range, and will return to normal should the torque be removed.
To get that deflection over 100m lenght of shaft requires 1.4MNm (mega Newton Metres) of torque.
260,000 shaft horsepower would require a speed of 1330 RPM to transmit...and I'm very positive that it's not going that fast...couple hundred max would be my guess.
So I'm quietly positive that if it's a 4' shaft, it twists some number of times down it's entire length.
My turbines have 21" maximum shaft diameter in the bearings between the LP and the generator, and have moved just under a million horsepower...but at 3,000RPM, the applied torque is massively lower.
Originally Posted By: hattaresguy
Originally Posted By: Astro14
Great question, Supton, I honestly don't know. I do know that the shaft is the limiting factor. The reactor can make far more steam, and the turbines more torque, than the shafts can handle.
The top speed is limited by that torque.
Though, I have to say, I've seen phenomenal acceleration from a Nimitz-class carrier when a simulated torpedo attack took place directly astern during training. The speed difference alone (from before the flare in the wake simulating the attack to final speed) was greater than the top speed to which the Navy admits.
We added nearly 30 knots to our speed in just a few minutes. The prop wash coming from the stern was amazing as well...a huge swell of whitewater. You could feel vibration from the ship itself, which I'm told comes from cavitation of the props. Just think about the torque needed to make props that size cavitate...
My dad was on a boomer and he said at least in the sub world cavitation is what limits your speed.
They spent a lot of time tuning their prop.
On a surface ship it doesn't really matter, everyone already can see/hear you.
Cavitation (and the ensuing vibration) breaks parts. Old liners would, at full power, actually move up & down 3-4" at the stern from it. And this is a 30,000+ ton liner! It chewed up propellers, and could damage shaft bearings.
Originally Posted By: Astro14
Great question, Supton, I honestly don't know. I do know that the shaft is the limiting factor. The reactor can make far more steam, and the turbines more torque, than the shafts can handle.
The top speed is limited by that torque.
Though, I have to say, I've seen phenomenal acceleration from a Nimitz-class carrier when a simulated torpedo attack took place directly astern during training. The speed difference alone (from before the flare in the wake simulating the attack to final speed) was greater than the top speed to which the Navy admits.
We added nearly 30 knots to our speed in just a few minutes. The prop wash coming from the stern was amazing as well...a huge swell of whitewater. You could feel vibration from the ship itself, which I'm told comes from cavitation of the props. Just think about the torque needed to make props that size cavitate...
My dad was on a boomer and he said at least in the sub world cavitation is what limits your speed.
They spent a lot of time tuning their prop.
On a surface ship it doesn't really matter, everyone already can see/hear you.
Cavitation (and the ensuing vibration) breaks parts. Old liners would, at full power, actually move up & down 3-4" at the stern from it. And this is a 30,000+ ton liner! It chewed up propellers, and could damage shaft bearings.
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