Jacob Gunnarson

Physical oceanography PhD student at the University of Hawaii. I also write things about submarines.

[Jacob Gunnarson @JacobGunnarson]

@USN_Submariner The control surfaces appear to remain unchanged as the longer moment arm provides enough additional control authority and stabilization. However, the dihedral stabilizers will not be on the VPM boats.

[Jacob Gunnarson @JacobGunnarson]

@JohnBru67272436 @USN_Submariner Nothing remotely sensitive in this photo.

[Jacob Gunnarson @JacobGunnarson]

@USN_Submariner That’s an Ohio, presumably the Louisiana given the date. The spherical array is much smaller and does not have the conformal and active hemispherical arrays of the Seawolf class (see photo).

[Jacob Gunnarson @JacobGunnarson]

@DJSnM From “Instruction Book, USS Albacore (AGSS 569) Phase III Maneuvering Systems, Part 3”

[Jacob Gunnarson @JacobGunnarson]

@DJSnM A lot of nonsensical answers here about hydrodynamics. It is entirely a mechanical consideration. Some European and Japanese subs with X sterns have individual stocks for each plane and thus do not have this asymmetry.

[Jacob Gunnarson @JacobGunnarson]

@USN_Submariner Oh, then it’s probably just someone’s idea of what the Ohio replacement would look like. I do recall seeing one old NAVSEA render without fairwater planes, but it looked different (eg, no dihedral stabilizers).

[Jacob Gunnarson @JacobGunnarson]

@USN_Submariner The submarine to the left is the Dolphin (AGSS 555) (at some point someone misidentified her; I’ve seen the error elsewhere)

[Jacob Gunnarson @JacobGunnarson]

@Aeroengineer1 @USN_Submariner They look just like the Phase I Albacore bow planes, angled at 45 degrees for tilting and rigging. But honestly this render looks very conjectural; the torpedo tube shutters seem way too far forward

[Jacob Gunnarson @JacobGunnarson]

@CovertShores @USN_Submariner @Saturnax1 @USNavy @AlexLuck9 @TheSubHunter1 @R_P_one @jonsrennie @BobKoonce @mikeplunkettuk @KingNeptune767 @EmbersOfSuns @jeffreybailey7 @Robt_VC @steve_thephotog @metabolicmike It’s a scoop for the polymer ejection system. The ram pressure from the scoop would pressurize the polymer stowage tanks and eject it into the boundary layer via perforated manifolds. The Albacore has a similar scoop in her sail (blanked off because it is a classified system).

[Jacob Gunnarson @JacobGunnarson]

@ShipsOfLegend @stoa1984 What is this nonsense lol?

[Jacob Gunnarson @JacobGunnarson]

@ShipsOfLegend @stoa1984 That’s a myth I’m afraid; such decoy propellers do not exist. A big tarp is much easier and cheaper to put over a propeller than casting a decoy propeller, installing it, removing it, and putting the real propeller on.

[Jacob Gunnarson @JacobGunnarson]

@CovertShores @Saturnax1 @AlexLuck9 @SubBrief @USN_Submariner @TheSubHunter1 @mikeplunkettuk @IBallantyn @The_Lookout_N @RSS_40 @FPSchazly In addition to the excellent photos from @Saturnax1 here's a drawing (the more detailed profile and plan drawings published in the Tayfun magazine don't show much detail on the doors or their operating mechanism)

[Jacob Gunnarson @JacobGunnarson]

@heatloss1986 Yeah, he's pretty infamous in the submarine community for spreading absolute nonsense. Even on the narrow subjects he should be qualified to comment on (sub sonar), he is often way off base. To say nothing of the subjects he's not qualified to comment on, but does so anyway.

[Jacob Gunnarson @JacobGunnarson]

@thegeneralboard @battleshipnc @BattleshipAL @BattleshipCove @ussiowa @USSMissouri @BattleshipNJ At least to first-order, certainly there can be other secondary causes of vibration (imbalances, singing, etc.)

[Jacob Gunnarson @JacobGunnarson]

@thegeneralboard @battleshipnc @BattleshipAL @BattleshipCove @ussiowa @USSMissouri @BattleshipNJ In regard to vibration, it is actually caused by oscillations in thrust instead of waves. The blades move in and out of slow and fast areas of the wake (slow wake=more thrust), resulting in thrust oscillations that travel up the shaft to the thrust bearing.

[Jacob Gunnarson @JacobGunnarson]

@thegeneralboard For example, this excerpt from a 1954 BuShips memo entitled "SSN571, propellers and vibration problems"

[Jacob Gunnarson @JacobGunnarson]

@thegeneralboard You’re right that the interaction between the wake and propeller(s) is very important to vibration, but the no. of blades alters the blade-rate freq. and harmonics, which can be important to avoid critical (resonant) frequencies of the shafting and machinery

[Jacob Gunnarson @JacobGunnarson]

@USN_Submariner Interestingly this mockup is of the Grayback as an attack submarine (improved Tang class). She was nearly complete on the ways at MINSY when her design was modified to become an SSG. Same story with the Growler: laid down as a Darter-class SS, converted on the ways to an SSG.