That is an interesting calculation. One has to suppose that the people on board the
Titanic came in all shapes and sizes and there must have been many men and maybe a few women who weighed over 10 stone. But since most boats were
initially loaded with women and children, the average weight was probably well under 10 stones per person to start with. IF men had been then allowed to fill the empty spaces, the mean weight would have moved closer to and maybe even slightly over 10 stone.
Taking those possibilities into consideration Jim,
how many people in your estimation would it have been safe to launch via the davits - The standard wooden lifeboat
- The two emergency cutters
- The 4 Englehardt Collapsible boats?
The size of the boat has nothing to do with it - It depend on the circumference of the manila rope used. Normally this would be common to all boats.
Deck Officers use a number of formulae depending on the construction and material used for ropes.
In the case of
Titanic the lifeboat fall would have been of best Manila three strand RH lay. The strength of a rope is determined as follows:
SWL = Safe Working Load:
1: for continuous use.
2: for occasional use.
3. Ultimate Breaking strain.
4. Maximum shock load.
Due to the method of lowering - i.e. 'surging the lifeboat fall around a bollard -It is the fourth one we are concerned with - because any interruption of the lowering process causing a sudden jerk on the fall imposes a shock load at the point of restriction equal to the weight of the boat and it's contents. Seamanship Manuals recommended 1/6 of Ultimate strength of a manila rope to avoid breaking due to shock load.
To find the fourth, you must know the circumference of the lifeboat fall, how it is layed, and what it is made of.
Let us assume that
Titanic's falls were 2.5 inch diameter Manila ropes. This means they had a circumference of 4.98 inches,. The formula for ultimate strength is Circumference squared divided by 3. This mean that in our example a 2.5 inch diameter manila rope would have an ultimate strength of 4.98 x 4.98 divided by 3 = 8 tons. However, to be safe against sudden jerks, the load should ideally be 1/6th of that = 1.3 tons which is totally impractical.
You could, of course increase the diameter to compensate, but then you would need mooring tope size falls which is nonsense, The designers of the lifeboat launching systems knew this as did the Officers on ships.
In 1912, lifeboat launching systems were still based on those designed for ships with single decks.
Consequently, the officers on passenger ships like
Titanic were gambling if they lowered a fully loaded boat from any great height.
As for the answer to your question?
"How long is a piece of string?".
The same Seamanship Manual gives the safe working load of the rope in our example for continuous use as three times the circumference divided by seven
It might surprise you to know that shock loads were breaking lifeboat fall on vessels with modern wire systems as recently as the 1970s.