why not a sail like a shark fin ?? streamlined and able to have sensors ?

sharks are very well adapter for slide through water during millions of years...:hmm:

What about sensors on floating platform connected by cable ? Some of such sensors are already researched .. like that floating up-looking fish-eye scope with computer corrected image. Radio wires and buoys are used even today. Sure .. snorkel is a
problem, but you don't need it that much.

Or something like UUVs equipped with cameras, RWR or Radar masts. Or even better, UAV (unmaned airborne vehicle) inside UUV, with both radar and cameras.

Or just long mast supported with wires .. like snorkel on german subs - folded backward on the hull (or inside hull cavity). With non-penetrating masts this is no problem.


I think the most important reason for sail is that there must be some place for watchmen in harbors. And sub-hull is not suited for that at all.

The sail is needed. Not only for placing sensors, but because without it, the sub would rotate on its longitudinal axis without control.
That's why all long-traveller fishes have the upper fin (don't know the name in English :damn: ).

You could say:" Whales haven't got one". Well, whales are not fishes but mammals, some whales have it and the whales without it have to compensate this with the movements and bodyshape.

Thus, the sail is the best design at this time... removing it implicates changing the design of the whole sub... maybe even the propulsion system.

Despite this, the submarine on the photo is horrible!!

why is it important for you to remove the sail in the future?

It is more like subs without a sail were disadvanced.

Um.. no. The metacentric height would prevent that. The center of gravity is below the center of bouyancy then ensuring a righting movement that would keep the top side UP.

When a sub is at PD it tends rock due to the forces acting on the vertical sail surface. Actually, I believe that a sub without a sail would be more stable at PD as the rounded surface would not be as effected by wave action.

But....

One reason for the sail is that the boat can be deeper and still pierce the surface interface. Thus the boat is less affected by wave action and surface tension/ducting.. If you place these masts and sensors in the hull, you have to have a MUCH longer mast, which will vibrate as it travels thru the water. Since you are talking a long, fairly stiff shaft, this means that you will have low frequency harmonics which travel better in the water. Also, you will be REALLY speed limited with this extra long mast supported from just one end. If you make the masts short so that these are not issues, then think of how close to the surface you will have to be. It would mean that anything over a state 2 or so sea would be impossible due to wave action.

So so far the advantages/disadvantages of the sail-less-ness are:

Sail-less
Good
-Less prone to wave action per say (mostly caused by the sail)
-Less drag = quieter and higher top speed
-Less draft = more manueverable in littoral waters
Bad
-Extremely long mast = slower and noiser 'mast up'
-If short mast used then shallower PD
-port transits complicated by no bridge (PD dependent)

Sail
Good
-Deeper PD
-shorter/stronger mastup's
-visible in surface transits
Bad
-worst in higher sea state (wave action on the sail)
-more drag = more self noise and slow speeds
-shallow water limitations

Modified sails (in picture)
Good
-more internal volume
Bad
-more drag
-Ugly as sin (induces intractable vomiting):doh:

I've got a solution! Retractable sails!:|\\

Just suck the whole sail into a chamber when in shallow waters are high speed transits :yep: :)

See, i knew somebody would say that...

Right, and when you need it and don't have it, how would you feel about it then? Pretty chagrinned that you let the bonehead engineers back on land sell you a sub with no snorkel, after you suffer a major power plant casualty, battery runs low, and you with no diesel generator...

and how do you propose to control it without radio masts? ;)

More drag and self-noise. Not an option. This is why submarine designers (including the Germans, with the Type XXI sub) removed external projections, such as guns and railings, and moved antennas and sensors into a protected, streamlined sail.

Much better technical explanation than mine.... typical nuke... :roll: :up:

TG

That's ok when the sub is stabilized, but when turning at a speed the submarine would be much harder to control without a sail.

Not true as it goes reading some time ago a thesis on submarine hydro dynamics it turns out the higher the sail the more prone to snap roll the submarine is, as ive been told the "skipjacks were the worst".

Without a sail the submarine is just as stable, if you have noticed the russian submarine sails are small (you cant even break a leg if you jumped), the akulas sail is about a foot taller than the bullet at the back end its also longer and more sleek looking.

The quote "Skipjacks were the worst" came from xabbarus a while back he got that from an acctual skipjack submariner.

I'm not saying the sail must be big, I'm saying that is good for stability when navigating. Of course can have cons, everything is good for something and bad for another things.

And, please, what does "Skipjacks were the worst" means? My English is not as good :hmm:

So perhaps the best thing to do would be to have two classes of submarine, one with a sail for those that are expected to stay near the surface often, and one without a sail for those that will almost always be deep (countering other subs, tapping underwater cables, that kind of stuff).

Well, the mast can easily be telescoped into the depth of the pressure hull. 30ft base telescope half extended with a 30ft interior telescope half extended would give a 30 ft reach. If strength and resonance is an issue one could choose high strength composite materials (modern day composites have 2-3 times the strength of titanium) which would provide more strength and decrease resonance. With 30 ft mast, periscope depths would be 30 ft mast + 33 ft to keel = 63 feet PD, roughly the same as some PD depths now if I understand correctly... and if BH is right the sail-less hull would be less prone to wave action. The captain would just have to except the fact that the design doesn't allow him to drive as fast with 'mastup'. Its the trade-off for better littoral maneuverability, shallower draft, less drag...

... And it sounds like the US Defense Science board recommendations believes its worth the tradeoff

He's saying that its the sails that's causing the snap roll effect when turning (the sub turns, and the water pushing on the sail makes the sub roll). From what I read, at higher speeds, the sail also tries to pitch the nose of the sub up and also causes flow irregularities at the aft control surfaces.

http://navysite.de/ssn/images/ssn592_2.jpg

This is a Skipjack class SSN (The USS Snook to be precise), take a look at the height of the sail....almost the size of my house! This would make the sub aquadynamics a nightmare, and prone to snap-rolls. Hence the "Skipjacks were the worst".

I think the Russians come onto a good thing with their sail designs, short and streamlined is the way ahead in my opinion. Even the US has realised that now, the short slope at the base of the Virginia and Seawolf's sails are surely to improve the flow and stability of the sail. It probably won't be long before they slope it up like the sub at the start...I once designed a sub with a sail like that....long time ago....I also made the front sharp and pointed...which, now I realise, severely reduced the maximum depth for the design. Subsequent redesigns removed the pointed bow in favour of a more conventional shape, but kept the sloped sail. Looks like I wasn't alone in thinking that kinda sail might be something worth looking into...

So...if you're looking for other ideas US Navy? Drop us a line.... ;)