Re: [OT] Navy releases photos of U.S.S. San Francisco

From: Mr Jim (nospam.mrjim_at_cox.net)
Date: 01/29/05 

Date: Sat, 29 Jan 2005 13:17:15 -0800

"Reed Snellenberger" <rsnellenberger@houston.rr.com> wrote in message
news:rZrKd.76906$_56.5477@fe2.texas.rr.com...
> Pat Flannery wrote:
> >

snip

> Question for anyone who knows... there is what looks like a "hump" right
> where the lubber lines are located... is that normal? I've never seen a
> picture of a sub from this angle -- usually it's from below (if under
> construction) or this area's covered by the bow wave when they're
> underway. I imagine that the bulge here could act sort of like a
> regular ship's breakwater when traveling on the surface... if the bulge
> wasn't there before the collision, then I'm even more amazed they made
> it to the surface.
>

As a former crew member of two 688 submarines, from two of the 4 different
"flights" (the Portsmouth was the same flight as the San Francisco), I can
tell you that by design, there is no "hump" on this part of a 688 boat. The
appearance of one in the referenced photo appears to be an optical illusion,
enhanced by the curved shadows of the lifelines. Laying a ruler along the
joints (the joints running fore to aft) between the anechoic tiles, one can
see that there is no evidence of deformation. That the capstan (the small
squat cylinder about 2/3 of the way between the two people) is extended
above the deck, and the reversible cleats (the horn shaped objects in two
pairs outboard of the guy walking at the bow) are rigged out is further
evidence the molded fairing is not bulged.

The pressure hull forms the visible outer hull of the boat right up to about
the point where the aft-most person is. From that point forward, the mold
line begins to curve towards the ogival bow dome. The visible hull surface,
from that point forward, is actually a light outer hull. It fairs the
forward end of the pressure hull, which is a truncated cone extending
forward to a point just about directly below the forward-most person, who is
seen walking past the underwater telephone fairing (the fin-like vertical
structure his left hand is on). An elliptical bulkhead closes the forward
end of the pressure hull. Both bow and stern of a 688 are faired with
structures called molded fairings; relatively light streamlined steel outer
hulls which are subdived into main ballast tanks, sonar domes, etc.
Truncated cones (the mold line of the aft one is a complex curved shape,
vice the forward one's simple conical mold line) and elliptical bulkheads
enclose both ends of 688s pressure hull, whose outer surface makes up the
entire cylindrical section of the boat's overall form.

The sonar sphere is located beneath the blue tarp. It is about 15 feet in
diameter, normally unmanned, but part of the pressure envelope, and extends
forward from the elliptical bulkhead on a "stalk", a meter-wide tube through
which people roll themselves along a little rope-towed trolley. A
normally-closed hatch at the elliptical bulkhead serves to protect from
flooding. The sphere is directly behind the ogival bow dome, suspended in
that flooded volume far enough from the noisy main hull to "hear" external
noises (via a huge number of transducers studding the sphere's surface)
through the acoustically-transparent done over a very wide aspect. If the
sphere was breached, crushed or simply knocked too far out of dimensional
tolerances, then the scope of the repair job will be vastly increased.
Obscuring the extent of this damage is probably the principal reason for the
tarp.

When running on the surface at any speed over a few knots in very calm seas
the main deck is not habitable; the bow wave flows down the forward hull,
often a couple feet deep, past the sail and down the length of the boat.

The feasibility of repair may be controlled by the damage to the torpedo
tubes and the torpedo room. If the dimensional tolerances of that room, or
the tubes, have been altered too much, it may not be economical to retain
the ship in commission.

> --
> Reed Snellenberger
> GPG KeyID: 5A978843
> rsnellenberger-at-houston.rr.com

Relevant Pages

  • Re: New Hudson Great White 1X
    ... The sales pitch says 'Hull volume moved toward bow, ... Otherwise the inwales would have to be twisted or machined with progressively increasing bevel along the full length of the boat - which complicates life. ... There are good fluid-dynamic arguments for a distinctly V cross-section to the bow, giving a deep but fine entry into the oncoming water, & blending this out to a U as you move astern. ...
    (rec.sport.rowing)
  • Re: Fin shapes
    ... the hull's intrinsic tracking ability - a hull with a deeper bow may naturally track straighter than one with more rocker and hence a smaller skeg may ... Slightly off-topic, but now that you mention hull shape, I'd like to ask this question: ... And as waterline length increases speed, the bow is designed to be perpendicular. ...
    (rec.sport.rowing)
  • Re: Fin shapes
    ... the hull's intrinsic tracking ability - a hull with a deeper bow may naturally track straighter than one with more rocker and hence a smaller skeg may ... Slightly off-topic, but now that you mention hull shape, I'd like to ask this question: ... This half metre seems useless at that point and thus dead weight, and just before the catch when the boat speed is at its maximum, you probably need all the waterline length you could get! ...
    (rec.sport.rowing)
  • Re: How close do you have to be to benefit from drafting
    ... The mistake people make is to assume that Froude's formula for hull speed actually represents a meaningful number for analysis or design. ... In real vessels, if you tow them and measure the bow wavelength and then determine the speed at which it equals the waterline length, you will find that is is not likely to be precisely 1.34. ... Vessels do not climb their bow wave - you cannot climb a wave that you create. ...
    (rec.boats.paddle)
  • Re: Fin shapes
    ... the hull's intrinsic tracking ability - a hull with a deeper bow may naturally track straighter than one with more rocker and hence a smaller skeg may ... Slightly off-topic, but now that you mention hull shape, I'd like to ask this question: ... This half metre seems useless at that point and thus dead weight, and just before the catch when the boat speed is at its maximum, you probably need all the waterline length you could get! ...
    (rec.sport.rowing)