Submarine questions

"Ives100" wrote

That's all I could find with 5 minutes on Google. . . It said HY-80 and maybe 50 kt.

Speaking of ballast, why don't we use solid propellant gas generators in the tanks for emergency blows? I could see one negative, the fear of them being ignited by enemy action, but that's manageable I'd think. We already use SPGGs in the missile launch tubes, and in the missiles themselves.

KL

That's a new and interesting factoid and very common sensical. In novels we read of blowing the fore or the aft ballast tanks. How many ballast tank compartments are there?

Now the Revell U-Boat has quite a few details on the lower side of the hull. that don't make sense yet.

1. The keel is rather thick, enough for the model to sit upright on it. Is this keel shape the same on the real U-Boat? If not what's the shape.
2. There are hull bottomside vent holes just behind the foreplanes and in the arear of the rear planes and rudders but none in between. Wouldn't that cause unbalanced water ingress when venting the ballast tanks?
3. Right in the middle of the keel is a recessed symetrical semi circular groove which I haven't seen in other models or noticed in any photos or drawings. Is that a scale rendition of the real thing and if so what is its function? If not why would Revell put it there?
4. There are 3 rectangular panels on either side of the ballast tank above the recessed groove in 3. What do these represent?

The fore and aft can be deflected differentially, but not each individual plane at a given location. Tom Dougherty ( snipped-for-privacy@aol.com)

The outer hull was HY-80, the frames were the high tensile 50,000, so she had a test depth of 700. The fastest any submarine has been credited with going was a Soviet Papa class that hit 44 knots. No way that Albacore even hit 40.

Google is fine for fast answers, but hardly the last word in accuracy. I'm using the books by Polmar and Friedman as my sources. Tom Dougherty ( snipped-for-privacy@aol.com)

On Modern US Subs, there are fore and aft ballast tanks, plus trim tanks. Most of the length of the hull you see is the pressure hull, so the ballast tanks are in the relatively small double hull sections fore and aft. US WWII Fleet submarines had multiple ballast tanks fore and aft and along the side flanks, trim tanks, negative tank ("down express") and safety tanks. Tom Dougherty ( snipped-for-privacy@aol.com)

Limited number of dive/surface cycles per sortie?..

Active ballast works as long as you have power. And wastes less space.

From what I read, a Type VII has four diving tanks, located in the saddle tanks - compartmented two per side. The rectangular features you see on the lower of the saddle tanks are the inlet valves for fore/aft compartments of these "diving" tanks (numbered 2 and 3 on the starboard side, Tank 2 being aft). Revell for some reason did not model the outlet valves on the top of the saddle tanks. The boat also has a main internal diving tank, bringing the total to at least five.

I can only assume (but I won't swear to it) that since my reference calls these "diving tanks" that the boat may have also been equipped with trim tanks fore and aft. Or it may have been dynamically trimmed, or it may have been trimmed using a combination of flood state of the saddle tanks (since they are compartmented) and/or set of the diving planes fore and aft.

Yes - that's the true shape. I was probably ballasted, but I haven't encountered a reference to that effect...yet...

These are actually what are refered to as "spill" or "flood" holes. The basic design of the Type VII (and most German U-boats) was/is a cylindical, single walled pressure hull with somewhat conical end caps fitted fore and aft. To the basic structure was welded an "outer casing" more the shape of a surface vessel - it is the fore and aft outer casings (and the port and starbord saddle tanks) which make up the external profile of the boat. The space between the deck(s), pressure hull, and the outer casing needs to be open to the sea to more easily trim the boat - so the holes you see fore and aft are there simply to flood these spaces.

This the main ballast intake. Yes, it is there on full scale boats.

The rectangular features you see above the the recess in the keel are the inlet valves for main internal diving tank. Revell also did not model the outlet valves for this tank either.

I can HIGHLY reccommend the book on the Type VII U-boat from the Naval Insititute Press, in their "Anatomy of the Ship" series to you. Lots of drawings from the original plans of all of the Type VII variant, with promenent features numerically referenced/keyed and notated.

This book provides lots of answers to just such questions, and I personally wouldn't build the Revell Type VII without it (and I plan to bild at least two...more that likely, three...). It's just the best reference on the subject I've seen so far. I think I paid $27 for my copy, from Amazon.

Thanks.

"Rufus" wrote

Like I said, these would be used in an emergency, like the Thresher where the air lines froze up due to Joule-Thomson throttling (from what I've been told) The SPGGs would be inside tanks themselves and outside the pressure hull. It's also my understanding that the Russians used them.

Which reminds me. . . More than once asked a NAVSEA cheerleader why we didn't try to adapt some things off the Russians like this, or smaller crews, or more automation, or whatever. The standard, glib answers were "Well that's great if you want our sailors to glow", and "Russian subs are junk." Self-preservation instincts have kept me from asking the obvious follow-ups, "Are you saying we couldn't engineer it any better?" and "If they were so horrible, why were you so afraid of them?"

KL

"Ives100" wrote

Agreed, however looking at my copies would require lifting my ass off the chair and going to the basement, then making sure I did not accidentally inject my own knowledge into my transcription; all-in-all much longer than a Google search. Besides, it was perfectly adequate to bound the physics/hydrodynamics problem of looping and show it to be bunk.

KL

snipped-for-privacy@verizon.net (Kurt Laughlin) wrote in :

A bad case of NIH syndrome. It's pretty widespread in the US.