David G. Brown wrote:
Mark--thanks for an excellent and useful post.
Thanks. I am glad you found it useful.
With regard to the cracking in the superstructure, I neglected to define it as "small." What I was referring to is the normal stuff that develops in square corners of anything that moves and vibrates. The only unusual thing is that it was mentioned about a ship so new as Olympic. None of this was structural and at wors nothing more than cosmetic. It had no direct bearing on Titanic's loss.
I do not know if you’ve seen my article yet, but if you have then you’ll be aware from the diagrams that this is precisely the sort of item I am referring to. You’re quite right to say that this was not structural, given the light scantlings of the areas we’re discussing. Following the December 1911 and January 1912 storms, I suspect that they had an influence — for obvious reasons.
If there was a panting problem I suspect it was in the single skin of the sides above the tank top; and, it would have occurred mostly when moving through a running sea. This is the sort of panting often seen where the sides warp from the straight midbody to the tapered shapes of stem and stern. Typically, frames are more tightly spaced in view of this problem.
It seems rather a big ‘if’ to me, but thanks for clarifying what you’re thinking.
One thing I disagree with Mark is his comment about Harland & Wolff being "generally very conservative." In a way, yes.
It’s a partial disagreement, then.
But, with regard to the hull plate scantlings of the Olympics they were hardly conservative. The one-inch hull plate chosen for this class of vessels was not up to then-applicable standards for 650-foot vessels.
If you have specific, primary source documentation for that, then I’d be interested to see it.
This did not mean a yard could not build a large vessel over 650 feet, just that member companies of the classification society would not have insured a larger vessel because it was "outside" the allowed scantlings simply by being too large. In that era, a 620 footer required 1.125-inch plate. Extrapolating to a ship of Olympic class size, the thickness would have been 1.25 or 1.3-inches.
Given that Aquitania was constructed to the highest of Lloyd’s standards, and that her plating was thinner than even your stated requirement for a 620 footer, I’d appreciate it if you could clarify your source.
By that measure alone, you could say that Oceanic,
Lusitania, Mauretania and Aquitania were ‘not up’ to the standards to which you refer. (I have details of their hull plating to hand right now, so my comments are not intended to be a comprehensive assessment.) I think it’s a rather narrow to focus on the general thickness of the hull plating in isolation, although I realise you may be using it as a brief illustrative example.
Aquitania was built to Lloyd’s highest standards. Her approved scantlings were compared to Olympic by a naval architect at the time, and he found the two ships extremely similar. His conclusion was that Olympic was ‘somewhat lighter’ with the main differences being found in the shell and deck doublings. Somewhat seems to be generally defined as ‘to a small degree or extent.’ His comments seem entirely accurate, from my research into the two ships, and my examination of Aquitania’s midsection. In fact, by the 1920s Lloyds were re-examining their rules as part of their process of keeping them updated, and in several regards they reduced the scantlings for such large vessels based on shipbuilders’ experiences.
This by no means proves weakness. The tables were designed to protect insurance companies and not to build the most elegantly engineered vessels. Again, the latest History Channel computer analysis showed Titanic's hull held together beyond its designed strength.
That finding did not really come as a surprise to me. You might find it interesting just how similar the standards were. For instance, although the Cunard ships were being designed to Lloyd’s rules, when
Lusitania, Mauretania, Aquitania and Olympic were being designed the naval architects worked to precisely the same standard in terms of stress. On the basis of mild steel construction, it was the practise — and it’s clearly documented — to ensure that the structure was not subjected to a stress greater than ten tons per square inch. The figures for all four ships bear this out, although in the case of Lusitania and Mauretania there are some higher figures which were tolerated owing to the use of high-tensile steel. Similarly, when we examine the HAPAG trio, in many ways the German designers seem to have been working to exactly the same standard in that regard.
The one thing H&W seems to have been good at was learning from its own history. In that sense, the company was conservative.
Agreed. You don’t get to be such a success in shipbuilding without learning from your own past experience.
After Titanic the design office had information about water entering places like boiler room #4 with no apparent source of ingress. They also had information about panting issues (not problems--issues) with the hull design.
The first seems evident from the Mersey testimony. As regards the second point, I don’t agree with that — as I’ve explained in my post above. I await the evidence.
Mark says he does not see evidence of a modification to correct panting. I do. It was the addition of the inner hull to Olympic.
I have been advised that the inner skin, as constructed, would merely pant with the exterior shell. It was not designed for the purpose of preventing panting. The cure for panting requires substantial longitudinal structural members, fixed to the hull frames and the side shell plating.
It is erroneous to assume that a relatively lightweight inner skin would not have greatly improved the sides of the ship.
I think that, itself, is assumptive on your part. You seem to be assuming that you know what another researcher knows.
Adding a double skin to Olympic was hardly innovative. Ships have been reinforced with inner skins for thousands of years.
I have not seen any primary source documentation to demonstrate that the inner skin was added as a reinforcement measure.
What I do know is that it was described as an improvement upon the ship’s watertight subdivision. It was about the best measure that could be taken with an existing hull, and it proved its worth the only time Olympic’s hull was penetrated amidships by a torpedo, as it contained the damage and kept the boiler rooms amidships dry.
I also know that the possibility it would be used to store oil in the future was being considered, at the time it was being designed. In fact, I have a document from 1912 that clearly outlines a discussion between Lord Pirrie and
Bruce Ismay regarding the storage of oil fuel in the inner skin. When the time came to convert Olympic to oil, the ‘tanks’ of the inner skin followed a useful pre-determined pattern.
None of this had anything to do with the expansion joints. If H&W had any second thoughts about the joints it had to be in relationship to the breakup.
As I said earlier, I am not sure if you’ve read my article on the subject. If you have not, you would find that there is a case to be made that Harland & Wolff already had grounds to improve Britannic’s design before Titanic was even completed.
Best regards,
Mark.