Was the enclosed A-deck included into the Titanic's Gross Tonnage?

[Johan Björklund]

We all know that the Titanic had gross tonnage of 1,004 more than the Olympic had, as built. As we also know that gross tonnage (GT) only includes the enclosed spaces of a ship. So the question is, what spaces did the Titanic have enclosed that the Olympic had not to count for in the raised GT?

A naïve assumption would be that the enclosed forward part of the A-deck plus the Café Parisien and the extended A la carte restaurant on the aft end of B-deck would sum up to these approximately 1,000. But then again, after the Olympic's refit in 1913, she got a GT even higher than the Titanic's, more precisely 1,017 more than the Olympic's original GT. The 1913 refit did add a Cafe Parisien and and extended A la carte on the Olympic's B-deck but she did not get her A-deck enclosed. (The remaining rebuilding of the Olympic in 1913 took place inside her hull and would not have counted for any change of her GT.)

So, my assumption here is that only the enclosure of the B-deck promenade spaces (Parisien, A la carte) actually did count into Titanic's higher GT, whereas the enclosed A-deck actually did not. Maybe because it was not fully enclosed, it did not have any wall or doors in the aft part of it. Could this assumption actually be the case?

 

[Michael C Brady]

It is my understanding that the largest contributor to her increased GT would be the inclusion of suites along the outboard sides of B-Deck, eliminating the promenade on that deck almost entirely - as well as the Cafe and extended restaurant, as you noted. The question of the enclosed A-Deck space is a very interesting one though - I hope one of the many experts on this forum can enlighten us!

~Mike

 

[Johan Björklund]

But if the B-deck cabins where the main contributors, where did the Olympic's 1,017 tonnage increase come from in 1913? She did not get any cabins installed on B-deck at that time.

 

[Michael C Brady]

But if the B-deck cabins where the main contributors, where did the Olympic's 1,017 tonnage increase come from in 1913? She did not get any cabins installed on B-deck at that time.

Hi Johan,

That increase in tonnage could be attributed to the addition of the inner 'skin' of Olympic's hull at the engineering spaces, the heightening of her selected bulkheads as high as B-Deck and an extra bulkhead at the Dynamo Room. All of this steel would surely contribute greatly to her additional tonnage? On top of that add the Cafe Parisienne, extended Restaurant, additional B-Deck suites etc.

~Mike

 

[Johan Björklund]

Gross tonnage is not a measure of weight, its a volume measure. Any inner works, no matter how heavy, would not affect gross tonnage. Only enclosed space, volume, counts.

 

[Johan Björklund]

Hence, inner skin, higher bulkheads etc. would make no difference to the GT.

 

[Michael C Brady]

Oh apologies, I follow you! I need a coffee

Its an interesting question you raise since it stands to reason, as you pointed out, that Olympic's GRT should have still been lower than that of Titanic even with the addition of the Cafe and extended restaurant. I wonder if her B-Deck promenade was considered an enclosed space after the aforementioned additions to that Deck and therefore included in the GRT measurement? (Since the after end ended in a bulkhead on both sides post-1913.) I suppose adding the restaurant and cafe aft "sealed off" the promenade area, as there was a bulkhead forward at the stairs.

You have a good eye to have spotted this discrepancy. I am curious to see what others think.

~Mike

 

[Michael C Brady]

Here's a bit of a rough diagram showing my theory.
What could be deemed 'open' promenade - that is, a promenade space not enclosed by bulkheads - I have coloured white. Green is enclosed, interior space. You can see that, in 1913, the inclusion of extra interior space at the Cafe and Restaurant creates an area of promenade enclosed on both forward and aft with bulkheads (coloured light blue).
This would at least bring GRT for Olympic's B-Deck spaces in line with those of Titanic - less 31 GRT.

~Mike

 

[Michael C Brady]

Apologies for 3 posts in a row!
As for the extra 31 GRT Olympic had over Titanic post-1913 refit, there is an area on A-Deck at the port side of the No 3&4 Boiler Casing which, if these plans are to be believed, was enclosed at the time of the refit for the inclusion of additional cabins;

All this considered, it would stand to reason that Titanic's A-Deck was not included in her GRT as, given the fact the promenade was not 'walled-off' at both ends as was Olympic's B-Deck Promenade post-1913, it could have been considered an open space and therefore not counted in her GRT.

~Mike

 

[Johan Björklund]

Hi Michael

Great reasoning. After consulting Olympics's original B-deck plans, I think you are spot on right. I previously tended to believe that the B-deck on Olympic was walled off at the aft end but as you point out, it was not until after the 1913 refit.

 

[Michael C Brady]

Thanks Johan!
Hopefully I have made up for my silly displacement-GRT mix-up earlier.

~Mike

 

[Johan Björklund]

Indeed you have made up for it! I realise that I mistakenly throughout have used the term GT, when GRT of course is the one to use, as you do. (GT being the more modern, slightly different measure was not used in 1912, whereas GRT was.)

Here is a good picture of the Olympics B-deck promenade, pre-1913 clearly showing that its aft end was open and hence the space was not counted into her GRT. Consequently, the corresponding promenade on A-deck of the Titanic wasn't either.