I have just had another look at my plans and applied the evidence of Mr. Wilder and QM Rowe to them.
Titanic did not raise her stern much more than 6 degrees before she sank. here's why:
The ship's stern was 12 feet 8 inches out of the water and she was 4 degrees down by the head when the water line was from the forward end of the forecastle head (fore end of deck 'B') to the top of the bulkhead between boiler room 5 and boiler room 4. That was just before it spilled over into boiler room 4. This would be about 1:15am according to Trimmer Dillon.
Also according to him, the last real lifeboat boat would leave about 15 minutes later at 1:30am so the trim by the head was not all that significant at that time either.
According to QM Rowe, he left Titanic on collapsible boat C. At the time, he noted that the forward well-deck.. deck C was awash. In other words Titanic had sunk to a level whereby the sea was just washing over the surface of the forward end of 'C' deck. This seems to have been at 2pm..45 minutes later.
Plotting Mr. Wilding's water line for Dillons time of the water coming into boiler room 4, points to Titanic having submerged her bow by 26 feet by 1:15am.
Plotting Rowe's evidence, suggests she had sunk it by a total of 29 feet by 2am.This meant that her draft at the bow had only increased it by 3 feet during the previous 45 minutes.!
Obviously the angle of tilt by the bow had not increased significantly!
The small change in bow-down angle is to be expected.
Because of the position of boiler room 4 in the hull, Titanic would not trim much more by the head after 1-30am and increasingly, Titanic would be sinking bodily.
What is more, the wt doors from boiler room 4 right aft to the stern were wide open. At that time, the water in boiler room 4 would have started flowing aft as the depth in that boiler room increased. It is significant that at that time, there would be no appreciable moment causing the vessel to tip more by the head i.e. increase the angle therefore there could never have been a break angle much more than 6 degrees.
However, the small change in bodily sinkage between 1:15am and 2:am is puzzling. Could one or either of the witnesses have got the times wrong?
Up until 1:15, Titanic was sinking bodily at a rate of about 13.5 feet per hour. If this rate had continued, the forward well deck should have been awash by 1:45 at the latest! What slowed-down the rate of sinkage?
Perhaps it was Dillon who got it wrong? He said the last proper lifeboat was leaving when he arrived on the aft well deck some time between 1:15 am and 1:30am . However other sources state this did not happen until 20 minutes later, at 1:50am!
Dillon said the engine room clocks had been set back 20 minutes! Could this be the source of the problem?
20 minutes from 1:50am gives us a Dillon launch time of 1:30am.
What about the break-up itself?
As Mr Wilding said, a ship is considered as a girder. The main strength members are the topmost line (strake) of side shell plating at the main deck.. deck C .. the shear strake...and...the Keel and the plating on either side of it.
But these longitudinal strength members have their greatest strength in the vertical plane. I.e. up and down the way. Titanic was heeled over to port!
This would mean that there would be a bending moment caused by gravity acting downward on the partially upward -facing starboard side of the vesssel which was suspended in the air. In this way a sort of twist would be imposed on the section. The result would be an opening up of the aft expansion joint in the superstructure while the submerged starboard side of the ship at the round of bilge at wt bulkhead 'J' ... just ahead of the main engines bed plate ... where the height of the double bottom tanks is reduced... would be put in tension.
If that particular area failed catastrophically, the sides of the ship in that area would spring apart and the water would pour into both exposed internal parts of the hull. The hull would separate vertically, possibly on both sides of 'J'. Finally breaking away completely to form two separate parts. This would cause the stern portion to briefly right itself before the weight of the main engines in the forward part would cause it to tip over, before finally sinking while twisting away to the left and downward. The front portion, having lost the centre of flotation, would tilt rapidly, wounded end upward, then sheer left then right, and head bow downward into a spiral.
On the way down, any water tight or airtight enclosed spaces such as Double Bottom Tanks would be increasingly effected by the pressure. Initial stress damage would be agravated and become distorted.. even breaking free from secure mounting etc.
When the bow hit the sea-bed, it dug-into the mud and the flat bottom behind it crashed down onto the sea bed
All the top-hamper above the flat bottom tried to telescope but only succeeded in bellying-out the side plates and buckling any stanchions or fashion plates.
It possibly came to rest straddling a sub- mud ridge. Over the years, the hull sagged on each side of the ridge leaving it bent as we see it today!
You saw it here ladies and gentelmen. James Cameron; eat your heart out!