5 ms·

Lessons from shipbuilding productivity

85 points by worldvoyageur 5y ago

DennisP 5y ago
At the risk of derailing discussion, this is why Seaborg and Thorcon plan to use shipyards to mass-produce molten salt reactors. https://thorconpower.com/production/ https://thorconpower.com/production/ https://www.seaborg.com/ https://www.seaborg.com/ Seaborg presentation: https://www.youtube.com/watch?v=x-Dz9sfBKEg https://www.youtube.com/watch?v=x-Dz9sfBKEg
mLuby 5y ago
IIRC, Liberty ships were of fairly poor quality due to their rushed construction and welding vs riveting, but that they only had to complete a single Atlantic cargo crossing to be worth the construction cost. Sounds a bit like fast fashion in that regard. Also because there were so many Liberty ships left over, many became privately owned, possibly tramp freighters? Easy to see parallels to the "space trucker" sci-fi trope of a (relatively) small, armed, independently owned and operated cargo vessel. Good 7min video on Liberty ships: https://www.youtube.com/watch?v=8qDxqBvK3NA https://www.youtube.com/watch?v=8qDxqBvK3NA
- hef19898 5y ago
  Being an industrial engineer, a suuply chain and logistics guy with a prdound interest in history, the Liberty ships are one of my favorite subjects. So many lessons to be learned from that! EDIT: I also have a special place in my heart for Star War's tramp feighters and their captains, legit or otherwise.
- sandworm101 5y ago
  They were planned to be bad, but after a while they became rather good. The factory approach results in incremental improvements all around, including build quality. Many continued to work long after the war.
  - gumby 5y ago
    > They were planned to be bad, but after a while they became rather good This is the very definition of the (misunderstood) learning curve.
    - a9h74j 5y ago
      In this half-fraught context, I'd like to raise the question of a potential new era of "liberty ships" -- i.e. proposal(s) to build modular nuclear plants using shipbuilding technology and scales. Presumably high standards of quality control could be maintained from the start.
      - mLuby 5y ago
        On the other end, one wonders how large freighters might become were the Panama and Suez canals not constraints.
mandevil 5y ago
One thing about his hours comparisons: it is not clear that British and American yards counted hours the same. This matters for office work like accounting, materials received, etc.- was that counted or not? Which of them was counted, for what contracts? The most that D.K. Brown (in _Nelson to Vanguard_) felt could be said was that the data was suggestive that the British shipyards were more efficient, not that they actually were.
owenversteeg 5y ago
>The Liberty Ships, on the other hand, would be welded. Not only could welding be done faster, but unskilled workers could be trained to do it far quicker than they could be trained to rivet - it took just 10 days to train a welder I'm very skeptical that it took more than 10 days to train someone to rivet. Riveting is very simple and I seem to recall I taught myself how to rivet with a cheap Harbor Freight blind rivet gun in a matter of minutes. I've shown several non-technical people rivet guns as well and they've been able to use them easily. Drill hole, put rivet in hole, squeeze. That said, ships did not use blind rivets, they used a two-person rivet setup where one person would put in the rivet and the other would hammer it on the other side, but that would still be far easier than welding to teach - it certainly would not require 10 full training days like welding apparently did! I suspect that riveting was just slower per steel joined per person-hour (much due to the use of 2 people instead of 1), in addition to the excess material used by overlap required by riveting. Training time wouldn't even matter much - if one process took 10 days longer but was 10% faster, then it would pay off over about a half a year of work. I have no figures for how much faster either was in use or training time. That said, I imagine the steel saved (in both rivets as well as overlap) was probably the main component. Apparently the HMS Ark Royal, a British aircraft carrier during WW2, saved 500 tons of its total 22,000 tons by using welding, so about 2.2%. A Liberty ship is about 10,000 tons, so you'd save about 220 tons by welding. The USGS's data puts a 100 lb hot rolled steel bar at $2.15 in 1944, so very very roughly that's $43/ton or $10,000 per ship saved. A Liberty ship took 592,000 man-hours to build, at $0.30/hr (1944 minimum wage) that's $178k; so the steel reduction could pay for an extra 6% more hours, even if welding was slower, which is significant if you're churning these things out. [0] https://pubs.usgs.gov/sir/2012/5188/sir2012-5188.pdf https://pubs.usgs.gov/sir/2012/5188/sir2012-5188.pdf
- lmilcin 5y ago
  Riveting is not simple. There are various types of rivets and riveting procedures for different occasions. It is simple if you just need two things to stay together, but on a ship there is a lot other considerations. But I am surprised that welding was deemed simpler. Welding seems to me even more complex than riveting.
  - 5y ago
einpoklum 5y ago
> And while the new assembly methods resulted in improved productivity, ... levels remained below what the British could achieve ... using their more traditional methods ... were able to produce ... at lower cost and fewer labor hours than the US was able to Tell your boss this whole story when management next decides to introduce some new methodology :-)

85 points by worldvoyageur 5y ago

At the risk of derailing discussion, this is why Seaborg and Thorcon plan to use shipyards to mass-produce molten salt reactors. https://thorconpower.com/production/ https://thorconpower.com/production/ https://www.seaborg.com/ https://www.seaborg.com/ Seaborg presentation: https://www.youtube.com/watch?v=x-Dz9sfBKEg https://www.youtube.com/watch?v=x-Dz9sfBKEg

mLuby 5y ago

IIRC, Liberty ships were of fairly poor quality due to their rushed construction and welding vs riveting, but that they only had to complete a single Atlantic cargo crossing to be worth the construction cost. Sounds a bit like fast fashion in that regard. Also because there were so many Liberty ships left over, many became privately owned, possibly tramp freighters? Easy to see parallels to the "space trucker" sci-fi trope of a (relatively) small, armed, independently owned and operated cargo vessel. Good 7min video on Liberty ships: https://www.youtube.com/watch?v=8qDxqBvK3NA https://www.youtube.com/watch?v=8qDxqBvK3NA

hef19898 5y ago
Being an industrial engineer, a suuply chain and logistics guy with a prdound interest in history, the Liberty ships are one of my favorite subjects. So many lessons to be learned from that! EDIT: I also have a special place in my heart for Star War's tramp feighters and their captains, legit or otherwise.
sandworm101 5y ago
They were planned to be bad, but after a while they became rather good. The factory approach results in incremental improvements all around, including build quality. Many continued to work long after the war.
- gumby 5y ago
  > They were planned to be bad, but after a while they became rather good This is the very definition of the (misunderstood) learning curve.
  - a9h74j 5y ago
    In this half-fraught context, I'd like to raise the question of a potential new era of "liberty ships" -- i.e. proposal(s) to build modular nuclear plants using shipbuilding technology and scales. Presumably high standards of quality control could be maintained from the start.
    - mLuby 5y ago
      On the other end, one wonders how large freighters might become were the Panama and Suez canals not constraints.

mandevil 5y ago

One thing about his hours comparisons: it is not clear that British and American yards counted hours the same. This matters for office work like accounting, materials received, etc.- was that counted or not? Which of them was counted, for what contracts? The most that D.K. Brown (in _Nelson to Vanguard_) felt could be said was that the data was suggestive that the British shipyards were more efficient, not that they actually were.

owenversteeg 5y ago

>The Liberty Ships, on the other hand, would be welded. Not only could welding be done faster, but unskilled workers could be trained to do it far quicker than they could be trained to rivet - it took just 10 days to train a welder I'm very skeptical that it took more than 10 days to train someone to rivet. Riveting is very simple and I seem to recall I taught myself how to rivet with a cheap Harbor Freight blind rivet gun in a matter of minutes. I've shown several non-technical people rivet guns as well and they've been able to use them easily. Drill hole, put rivet in hole, squeeze. That said, ships did not use blind rivets, they used a two-person rivet setup where one person would put in the rivet and the other would hammer it on the other side, but that would still be far easier than welding to teach - it certainly would not require 10 full training days like welding apparently did! I suspect that riveting was just slower per steel joined per person-hour (much due to the use of 2 people instead of 1), in addition to the excess material used by overlap required by riveting. Training time wouldn't even matter much - if one process took 10 days longer but was 10% faster, then it would pay off over about a half a year of work. I have no figures for how much faster either was in use or training time. That said, I imagine the steel saved (in both rivets as well as overlap) was probably the main component. Apparently the HMS Ark Royal, a British aircraft carrier during WW2, saved 500 tons of its total 22,000 tons by using welding, so about 2.2%. A Liberty ship is about 10,000 tons, so you'd save about 220 tons by welding. The USGS's data puts a 100 lb hot rolled steel bar at $2.15 in 1944, so very very roughly that's $43/ton or $10,000 per ship saved. A Liberty ship took 592,000 man-hours to build, at $0.30/hr (1944 minimum wage) that's $178k; so the steel reduction could pay for an extra 6% more hours, even if welding was slower, which is significant if you're churning these things out. [0] https://pubs.usgs.gov/sir/2012/5188/sir2012-5188.pdf https://pubs.usgs.gov/sir/2012/5188/sir2012-5188.pdf

lmilcin 5y ago
Riveting is not simple. There are various types of rivets and riveting procedures for different occasions. It is simple if you just need two things to stay together, but on a ship there is a lot other considerations. But I am surprised that welding was deemed simpler. Welding seems to me even more complex than riveting.
- 5y ago

einpoklum 5y ago

> And while the new assembly methods resulted in improved productivity, ... levels remained below what the British could achieve ... using their more traditional methods ... were able to produce ... at lower cost and fewer labor hours than the US was able to Tell your boss this whole story when management next decides to introduce some new methodology :-)