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Duncan Gibbs
08-19-2016, 09:18 AM
https://c5.staticflickr.com/8/7053/6805661876_29723cc03c_b.jpg

Gerarddm
08-19-2016, 09:34 AM
Real pr0n! Yay!

Fabulous photo. Weirdly airship erotic, too, LOL.

Vince Brennan
08-19-2016, 02:52 PM
Illuminating.

mmd
08-19-2016, 02:55 PM
Try to imagine the complexities in trying to make 3/8" (or thicker) steel plate take that shape...

Paul Pless
08-19-2016, 02:57 PM
Fun with explosive hydroforming. :D

Paul Pless
08-19-2016, 03:00 PM
Schwing

https://upload.wikimedia.org/wikipedia/commons/9/92/Passenger_ship_Zaandam_in_drydock.jpg

mmd
08-19-2016, 03:16 PM
"Fun with explosive hydroforming." Paul

Probably so, but not a process that many shipyards I know about can do.

I read a paper a few years ago that described a process that Hyundai Heavy Industry uses, where they put an electric arc tool (basically a TIG welder with no shield nor wire feed) in a 3D CNC tool and 'draw' loops and designs on a steel plate in a very precise pattern. As the metal cools it shrinks at the arc path and draws the plate into the proscribed shape. Pretty interesting...

P.I. Stazzer-Newt
08-19-2016, 05:00 PM
Donn's hat
http://englishplus.com/grammar/00000294.htm

I've seen some film of Koreans using gas torch and cold water to form those curves.

Rob Hazard
08-19-2016, 08:35 PM
The bulb in the OP makes visual sense to me, but the one in post#6, on the Zaandam, has me stumped. Is it supposed to reduce drag or make the ship's motion more comfortable or what?

mmd
08-20-2016, 12:56 PM
Reduce drag, Bob. It is actually more efficient than the one in the OP, but more difficult (read, expensive) to build.

Rob Hazard
08-20-2016, 03:02 PM
I see by the waterline that the bulb breaks the surface at rest. Then it slopes downward before the stem rises. Is this a shape that is more efficient over a wide range of speeds, or is it aimed at a specific cruising speed and wave length?

mmd
08-22-2016, 08:01 AM
It is most likely optimized for the 'standard' loading and cruise speed of the ship. Most merchant ships are terribly underpowered for their mass, when compared to other ship types, so they can operate as efficiently as possible. Dollars-per-nautical-mile is a merchant ships' nemesis, and everything possible is done to reduce the dollar consumption. Optimizing route, propeller, hull condition, speed, and yes, the shape of the bulb are all items closely considered to enable a ship to make a profit for her owners in a very, very competitive trade.

Canoeyawl
08-22-2016, 08:07 AM
http://farm1.static.flickr.com/148/393486499_850aecaf47.jpg?v=0

mmd
08-22-2016, 08:21 AM
I think that is a bulb with a slightly different purpose, Canoeyawl...

Peerie Maa
08-22-2016, 08:27 AM
I think that is a bulb with a slightly different purpose, Canoeyawl...

It is pertinent though. Admiral Taylor noticed that warship ram bows were less resistfull than the conventional fore foot, and so developed the original onion bulb bow.