Submarine questions

  1. For the fore and aft dive planes on a submarine, do they work like elevators (as in airplanes) or do they work like ailerons?

If able to work like ailerons the sub can then make a banked turn. Or the sub can be trimmed to "reverse" bank so as to remain vertical while making a sharp turn underwater.

  1. Do the dive planes work in tandem, that is both are defelected at the same angle at the same time, or do they work independently?

If working in tendem the hull would be able to remain horizontal while going deeper in a dive I presume. If the front dive plane is steeper than the back planes the sub would move forward and dive in like a fish. On the other hand having the front and rear dive planes work independently would allow the sub to be dynamically trimmed should the stern happen to dip lower during underwater maneuvers.

I had never though of asking these questions until I thought of motorizing the Revell 1/72 U-Boat. And come to think of it I am surprised that no one has motorized this model yet. The model's size certainly lends itself to such a conversion. The ROBBE U-boat

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has already done it.

Reply to
PaPaPeng
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"PaPaPeng" wrote in

All that I know of work like elevators. There are/were some subs with X rather than + plane configurations that probably used independent action, plus some experimental types.

KL

Reply to
Kurt Laughlin

They work like elevators.

The rudder causes this anyway.

There is neither need nor desire for this to happen. In a full-sized vessel, what you propose would result in every portable object within the boat to be flung outboard away from the direction of the turn, including the crew. This causes things to break, which really ruins your day.

Yes. : ) They are operated independantly, and thus may be operated together or in opposition.

Yes.

Yes.

Yes. All of this is why the Diving Officer's job is much more difficult than it appears at first.

Good luck with your project.

Reply to
Jeff C

Jeff C wrote in news: snipped-for-privacy@4ax.com:

That's interesting. I never suspected any of that. So, what's this "angle on the bow" I always see in movies? Das Boot, for example.

TF

Reply to
TForward

Angle on the bow is used in calculating the firing solution for the torpedoes. I don;t know the exact math for it, but it involves the angle between the submarine and the target's location at the moment of torpedo impact I believe. I could be wrong on that. I know it is a difficult concept and saw it explained in a book once a long time ago. Steve

Reply to
SMarsh3807

AOB is that angle measured from the target ship's bow to the point where the observer's line-of-sight intersects the target. Imagine that you are looking thru a periscope and you see the full broadside of a target. If you're on the left side, you'd have a left 90-degree AOB; on the right - a right 90-degree AOB. If you were looking at the starboard (right) quarter, you'd have about a right 120-degree AOB.

Reply to
jmt

Like elevators.

Not from what I understand. And I've been told (or read somewhere) that rolling during turning while submerged was a BIG problem with the fist test subs which had hulls shaped like bodies of revolution - the ones more circular in cross section. From what I'm told the shape of the conning tower (also referred to as the "sail") on a modern sub counters the roll in turn effect.

Independently, to dynamically trim the boat.

Yes.

From what I've read, some are trying...though I myself think the 1/72 kit is a bit small for this. But I don't see why it couldn't work.

Check out this FAQ, if you haven't seen it:

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Reply to
Rufus

Thanks for the great link, especially useful on Sub basics.

Reply to
PaPaPeng

Heard of the looping story before, which was countered with statements that most sub decks aren't bolted down. The weight of equipment and the deck itself is more than adequate to hold it in place.

Looping sounds near impossible given the amount of "altitude" required, decks suspended by gravity sounds dubious but possible.

Reply to
The Raven

"Sean" wrote

Well . . . A little context and physics is in order. It has really only been since WW II that submarines could dive deeper than their own length. A Los Angeles class sub is 362 ft long and the official depth capability is "greater than 800 feet". Even if you double that, the D/l ratio is only

4.4. The Albacore was 203 feet long and built for speed, not depth, using HY-80, 80 ksi YS steel to allow weight reduction while maintaining the same strength as a typical sub of the era. So, one could posit that the Albacore could dive to about 4 or 5 times it's own length, say 1000 feet. (This assumes its design basis is more or less the same as other subs, which is reasonable. If you don't accept that assumption, pick a number, like the 2000 - 4000 feet claimed for some deep-diving Soviet subs, and go on.)

Now figure out just how tight of a loop a submarine could make. The tighter it is, the more Gs it will have to pull. The limit on a sub would be 2, maybe 3 Gs. (It's been too long since I figured this sort of thing out.) With that, you can figure out how tight of a loop it could take at 50 knots. I'm nearly certain that the minimum diameter would be much larger than 1000 (or even 4000) feet, meaning that the sub would have to go below crush depth to keep from breaching at the top. For an even more detailed check, consider the bending stresses on a 200 ft long tube going around a circle

4000 feet in diameter at 50 knots.

Most rumors like this fail after even less scrutiny. The problem is that most people are so "gee-whizzed" by the whole thing that they take it as truth.

KL

Reply to
Kurt Laughlin

Ship's decks most definitely ARE welded down but access covers, furniture, equipment and portable items are not. I don't buy the looping story.

Reply to
Jeff C

Why 50 knots? No sub has ever been that fast, and if you're going to do a loop, a low speed will give you a tighter loop.

Reply to
Harro de Jong

FWIW I'm with Kurt, I think the looping story is just an "urban Myth" type thing. Now rolling a submarine through 360 degrees might be possible, but I hate to think of the clean up afterward!

Bill Shuey

Reply to
William H. Shuey

"Harro de Jong" wrote

The Albacore was claimed to go 50.

I'm not sure about the speed vs. radius relationship being as you state. There must be sufficient flow over the planes for them to provide a hydrodynamic force to turn the sub. A higher velocity means more force and a tighter turn, while a lower velocity means less stress on the sub and crew for a given radius of turn. So, for example, if you wanted to hold 2Gs in a

300 feet radius turn, 5 kt might be better than 25 kt, but I'm not sure that 5 kt would allow the sub to make the 300 feet radius turn in the first place. Granted, you could rotate about a transverse axis at full stop using the auxiliary propulsion motor, but is that really a loop?

Another factor making the loop dangerous would be possible changes in buoyancy due to the sudden release of trapped air or other materials. A sudden, unexpected, breaching could fail the hull because of cantilevering part of it out of the water.

KL

Reply to
Kurt Laughlin

Can I ask an ancilliary question ???

Why do most modern US subs have the foreplane on the sail - while most non-us subs have it on the bow ???

I would have thought that the non-US solution would work better - the diving plane is already in the water and would therefore be effective immediately.

The plane on the sail needs time before it enters the water - and is therefore ineffective until a few minutes into the dive.

I know that there were experiments done on the USS Daniel Webster with bow-mounted diving planes - but the idea was not adopted.

Also - most modern non-US subs with bow-mounted diving planes have them retractable (Russian) or foldable (UK).

Any ideas anyone???

Ken

PaPaPeng wrote:

Reply to
Ken Duffey

Actually, the newest classes, 688-I, Seawolf and Ohio do have bow planes, which are retractable. Originally, planes were moved away from the bow when more effective and large bow sonars were installed. The plane hydraulic equipment caused noise issues. A downside is that planes on the sail make the submarine more difficult to handle at periscope depth, as wave action from the surface can have an effect. With advanced sonar signal processing, and the desire to give the later classes of Los Angeles submarines (the so-called 688-Is) the ability to surface through ice. The short Los Angeles class sail made it impossible to have the planes rotate to the vertical as in the earlier Sturgeon class. Hence, the retractable bow planes were introduced on the 688-I, along with a reinforced sail and propeller protection. The Seawolf and Virginia have the same bow planes design. Tom Dougherty ( snipped-for-privacy@aol.com)

Reply to
Ives100

Albacore was not built with HY-80, and her test depth was 700 feet. She ended up going deeper (>1200 ft) on at least two occasions. She was basically built, with equipment and materials very similar to the contemporary Tang class diesel boats. She even got the execrable "pancake" rotary diesels to charge her batteries.

Ballast tanks have vents which are open on the bottom at all times. The upper vents are opened to release air to submerge, and then closed. To surface, high pressure air is introduced and the water is forced out through the bottom, open vents. If one were to loop and invert a submarine, you would lose the air bubble in the tanks. This would lead to a rapid trip to the bottom, and you would have to upright the submarine and quickly put an air bubble back in the ballast tanks. BZZZTT.. Time's up! Total inversion would be a very bad day.....

Albacore's top speed, in her Phase IV configuration of twin contraprops and silver zinc batteries was just over 32 knots. Nowhere's near fifty. Tom Dougherty ( snipped-for-privacy@aol.com)

Reply to
Ives100

Actually, IIRC, the sail causes the roll, not counters it. With the rudder over, the submarine banks into the turn, and the sail acts as an airfoil, exerting uneven forces on the hull. The submarine can then abruptly take a more sharp angle where it is rolled over onto the side.

The length to beam ratio is a big factor in the "snap roll" problem, also. The narrow, longer hull (33 ft beam and 360 ft long) LAs had particular problems early in the program. Seawolf was shortened and widened (42 ft vs. 33 ft) over the LA class, which in turn was much longer than the preceding Sturgeons (a round 300 ft). The new Virginia class returns to a narrow beam, long hull, so they will have to work out the performance characteristsics.

I've been told that with reasonable handling and experience, the roll can be controlled by coordinated actions by the two planesman. The big problem with the roll is that when a submarine goes over on the side, the rudder now acts as a "stern plane", driving the submarine deeper. Fast turns near test depths early in the LA program caused a few tense moments. In addition, the LAs test depth was reduced over the preceeding Permit and Sturgeon classes, due to the much heavier reactor leading to the need to reduce total submarine weight (to keep the displacement to the point where the submarine coul still surface). Hence the HY-80 hull thickness was reduced, costing depth performance.

Then there's all the loose stuff when you suddenly roll sideways.... Tom Dougherty ( snipped-for-privacy@aol.com)

Reply to
Ives100

No problem. Let us know how your R/C effort turns out!

Reply to
Rufus

I'm thinking that by "loop", they actually mean a "roll" though 360 degrees. I was talking about subs with a friend of mine that is an ex-submariner some weeks ago and this subject somehow wandered into the conversation.

He mentioned the Albacore specifically, and some of the things they discovered about hulls shaped from bodies of revolution in testing it. One of the things he mentioned was the trendancy to roll during a turn when submerged...and that is was a BIG problem. He said that part of the solution was in the sizing of the conning tower - also called the "sail" on a modern boat, and now I wonder if this is why.

I'll have to ask him if the planes on the sail also play a part in the dynamics of a turn.

Reply to
Rufus

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