Pouring oil on water to calm waves

[Jon]

Perhaps you've heard the saying about pouring oil on water, in reference to calming a problematic situation. Turns out that this expression has considerable history, rooted in the physical phenomenon (only a phenomenon to non-physicists, of course) that a small amount of oil, poured onto the surface of a roiling sea, can significantly reduce waves.

In action:

This effect appears in ancient writings, as well as, more famously, in a 1773 letter by Benjamin Franklin, in which he recounts his oil-on-water experiment, reproducing an original experiment by Pliny the Elder (AD 23-79).

"At length being at Clapham, where there is, on the Common, a large Pond, which I observed to be one Day very rough with the Wind, I fetched out a Cruet of Oil, and dropt a little of it on the Water. I saw it spread itself with surprising Swiftness upon the Surface, but the Effect of smoothing the Waves was not produced; for I had applied it first on the Leeward Side of the Pond where the Waves were largest, and the Wind drove my Oil back upon the Shore. I then went to the Windward Side, where they began to form; and there the Oil tho’ not more than a Tea Spoonful produced an instant Calm, over a Space several yards square, which spread amazingly, and extended itself gradually till it reached the Lee Side, making all that Quarter of the Pond, perhaps half an Acre, as smooth as a Looking Glass."

What's happening here? There is considerable mumbling about "surface tension" and "friction" (concepts no doubt invoked in all online discussions involving physical effects). Both are reasonably applicable; it looks like it might be an example of Kelvin-Helmholtz instability, which occurs at an interface between two fluids of different density. More details on page 115 of this paper by MIT professor Erik L. Mollo-Christensen.

This effect is especially useful for ships in stormy seas, or lifeboats. Old sailing ships were sometimes equipped with large containers that slowly dispensed oil over the sides to calm the seas. In fact, even today, US law requires that certain lifeboats carry a supply of storm oil, detailed here: 46 CFR 169.529 - Description of lifeboat equipment.

(x) Oil, storm. One gallon of vegetable, fish, or animal oil must be provided in a suitable metal container so constructed as to permit a controlled distribution of oil on the water, and so arranged that it can be attached to the sea anchor.

This legally-required storm oil dispenser looks like this:

[Jon]

I remembered this thread when reading about Undaunted, the 42-inch craft whose builder, 33-year-old Matt Kent, is attempting to set the record for the smallest boat to ever cross the Atlantic.



Said Kent in an interview with Yachting World:

My diet consists of nuts, dried fruit, protein powder, nutrition bars, a variety of soups, stews, pasta, peanut butter, Nutella and so on. I have a huge variety as well as 64,000 extra calories in the form of two gallons of olive oil to add to my food.

I'm not sure that olive oil would be the best choice here, if caloric value was the the only criterion. Keep in mind how little oil is necessary to calm waves. 2 gallons of olive oil nicely doubles as a good supply of oil to calm waves on an Atlantic crossing, and would likely be especially valuable in a 42-inch boat.


More:

https://littleboatproject.org/
https://www.yachtingworld.com/extrao...tlantic-107559

[mklotz]

Sounds like some drunken bar bet gone horribly, horribly wrong.

[ranald]

Sounds like some drunken bar bet gone horribly, horribly wrong.

Yes, it does Marv. Then again that is how we got "King of the Mountain" race in Pomona Qld: a bored drinker went out for a run up Mount Cooroora and the bar bets & all the rest is history.

Don't think we will see a race across the Atlantic in metre long vessels soon though.

Cheers

[suther51]

I can only expect that the draft of this boat is many times deeper than the length as per the mast. Must gain stability over the masts hight in some manner. Slow boat to China as they say. New type of meditation chamber. Lots of time to think things over.
Eric

[stillldoinit]

When I was still in the work force, there was a Gardener double disc grinder processing cast iron parts for hydraulic pump castings that was cooled with synthetic concentrate mixed with water at 130 gallons a minute. Sometimes when the anti foam additives would get weak in coolant return tank and start foaming over the sides, the guys had a spray bottle of WD40 which would knock it right down. The chemical composition of the coolant apparently changed with age and mixture of cast iron grinding swarf. The grinding wheels were 30" diameter as close as .200" and were vertical with parts fed on a rotary carrier coolant fed through center of spindle.