Submarine Question: Diving plane configuration

**tmasi** · 26 Feb 10,, 18:41

Hi, I've got a rookie question...

I've noticed that the diving planes on submarines are sometimes mounted on the sail, sometimes low on the forward part of the hull, or sometimes high on the forward part of the hull.

During WWII, it seemed most subs had them on the hull, and US nuclear subs up until the 80s/90s favored the sail.

Can someone explain in layman's terms what are the design advantages and disadvantages considered when choosing where to station the diving planes?

I'm guessing it's a balancing of submerged speed, noise, and the boat's responsiveness to the diving commands?

Thanks.

**dundonrl** · 26 Feb 10,, 20:12

well, I know the early 688's (Los Angeles class) fast attack submarines have their diving planes mounted on the sail.. it wasn't till they went to the 688i (improved Los Angeles) that they were moved to the hull.. the reason is when surfacing through ice, you don't have to worry about them when they are mounted on the hull..

USS Hawkbill with sail mounted diving planes..

USS Alexandria with hull mounted diving planes..

Originally Posted by tmasi

Hi, I've got a rookie question...

I've noticed that the diving planes on submarines are sometimes mounted on the sail, sometimes low on the forward part of the hull, or sometimes high on the forward part of the hull.

During WWII, it seemed most subs had them on the hull, and US nuclear subs up until the 80s/90s favored the sail.

Can someone explain in layman's terms what are the design advantages and disadvantages considered when choosing where to station the diving planes?

I'm guessing it's a balancing of submerged speed, noise, and the boat's responsiveness to the diving commands?

Thanks.

**TopHatter** · 26 Feb 10,, 20:20

Originally Posted by dundonrl

well, I know the early 688's (Los Angeles class) fast attack submarines have their diving planes mounted on the sail.. it wasn't till they went to the 688i (improved Los Angeles) that they were moved to the hull.. the reason is when surfacing through ice, you don't have to worry about them when they are mounted on the hull..

That's correct, the early 688's couldn't surface through ice with their sail-mounted fairwater planes...which the earlier Sturgeon-class could do.

**tmasi** · 26 Feb 10,, 22:17

Okay, that makes perfect sense.

But I'd still wonder what was it that prompted designers to move them to the sail in the first place, given that the WWII subs and prior models seemed to have them on the hull.

I don't recall ever seeing diving planes on the sail/conning tower in photos of submarines prior to the 50s.

Of what I've seen, I think it was the Skipjack subs that first had it.

I just checked, and interestingly enough, the USS Albacore which I think pioneered the tear-drop shape hull-form didn't have any forward diving planes at all!

**dundonrl** · 26 Feb 10,, 22:20

"Once the boat is trimmed to more or less neutral buoyancy, the depth of the boat is controlled with the hydroplanes. To use the hydroplanes the boat requires speed to create a force on the tilted planes. At slow speeds, the fore hydroplanes are exclusively used to keep the boat at the required depth. The fore planes can be located on the hull near the bow or on the sail of the boat. Because bow mounted hydroplanes are located further from the center of gravity, the depth control is more accurate with these types. Arguments for locating the fore planes on the finn of the boat are (a) improved performance of the spherical sonar array in the bow because the fore hydroplanes generate noise and (b) bow mounted hydroplanes can be damaged during docking of the submarine. Penalties for placing the fore planes on the fin are (a) the operating gear takes up space in the fin where room badly is needed for the masts, (b) the ice breaking performance is decreased, (c) at periscope depth the planes are close to the surface so their performance is adversely affected by the surface turbulence and finally (d) the hydroplanes are closer to the center of gravity and are thus less effective. Note that while improving the Los Angeles class submarine (688I) the US Navy relocated the fore planes from the sail to the bow. At sufficiently high submerged speed (more than 12 knots), the fore planes are no longer needed to control the depth of the submarine. At these speeds, they are rotated in a neutral or slightly dive position. Because the fore planes generate noise, many submarines are capable of retracting the forward bow planes at high speeds. All this considering, we may conclude that (retractable) bow planes are more favorable. It may be added that the author is not aware of boats having both dive planes on the bow and on the sail. "