It Would Take a Titanic Raft of Flotsam to Float Two Actors

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Assumptions and Physical Constraints for the Titanic Flotsam Raft

This article confines itself to the mathematics of buoyancy: would they sink or float? We will ignore other considerations, such as exposure and hypothermia.

The calculations are in metric:

  • Kg = Kilogram = 2.2 pounds = 2.2 lb
  • M = metre = 39 inches = 39″ = 3.28 feet = 3.28′
  • Kg/M^3 = Kilograms per cubic Metre

Simulation of Rose and Jack – yep, they’d both fit! Image courtesy of imgur

Let’s assume calm winds and no waves on the Atlantic, with salt water at a density of 1025 Kg/M^3. Water is more dense when it is colder, reaching maximum density at +4C. Sea water is also denser than pure, due to the dissolved salt. Pure water at about 4 degrees Centigrade has a density of 1.000, and weighs 1,000 Kg/M^3 .

The density of wood used for lumber depends, in part, on the type of tree. Let’s assume they are floating on Canadian spruce, with a density of 450 Kg/M^3.

Pine’s density is somewhat over 500, while oak’s is well over 700; ebony would sink in fresh water, with a density of about 1200 Kg/M^3.

Let’s also assume that the door upon which Rose floats is 78″ x 31″ x 0.5″, or 2M x 0.8M x 0.0127M, based on an actual fragment of a door from the Titanic which was one-half of an inch thick.

Since 1″=2.54cm=0.0254M, the door would be 0.127 metres thick.

Let’s also assume that Rose weighed 134 pounds, or 61 Kg, and that Jack weighed 158 pounds or 72 Kg.

Will Rose and Jack sink or float?

Titanic Buoyancy Calculations: Image by Mike DeHaan

A Realistic 1-Door Raft Sinks Under Kate’s Weight

If the door is 2×0.8×0.0127 metres, its total volume is 0.02032 cubic metres. At a density of 0.45, its weight is 9.1444 Kg. If fully submerged at the surface, it would displace 0.02032 cubic metres of water weighing 0.02032M^3 X 1025Kg = 20.828Kg. The net buoyancy is 20.828 – 9.1444 = 11.6836Kg.

Since Kate weighs 61Kg, she and her makeshift raft would sink until her body displaces about 50Kg of water. While this would spare her some swimming effort, it fails to provide for her safety under the conditions this article requires, and she certainly wouldn’t be floating on top of the water.

Click to Read Page Three: Building a Raft Large Enough For Kate (We don’t want her to sink, even though the general consensus is that she should have just stayed in the lifeboat to begin with!)

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© Copyright 2012 Mike DeHaan, All rights Reserved. Written For: Decoded Science


  1. Mike DeHaanMike DeHaan says

    For Will, Stooge & Moioci, who pointed out that the door was probably much thicker…
    “Arghh, you’re all extremely likely to be correct”.
    Assume 1.5″ rather than 0.5″? So we only need 1/3 the number of doors that I had calculated?
    Thank you for taking the time to let us know.

  2. moioci says

    Wait a minute. The NYT site describing the 1/2-inch thick piece of door says, “This relic was once a **thicker block** that years ago was cut up into tiny pieces, which sold for four figures each.” Think about it. Even in today’s world of very cheap construction, a half inch would be very flimsy, even for a closet door, let alone a stateroom door. I vote the actual door was at least an inch thick, possibly more.

  3. Stooge says

    Your assumption about the thickness of the original door is wrong: as the blurb for the Titanic door fragment clearly states, the piece being sold is 0.5 inches thick, but it “was once a thicker block that years ago was cut up into tiny pieces”.

  4. says

    For the door to support their weight it would have to weigh approx. 560 lb. to float level with the sea surface and more to keep them above. Take some strength to launch it!

  5. Paul DunneNara says

    I guess neither Jack, nor Rose (and she was smart, too) were aware of Archimedes principle…too bad, maybe Jack could have lived a day longer or so…but then, the ending had to be gut wrenching, after all.

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