SailNet Community banner

1 - 14 of 14 Posts

·
Registered
Joined
·
41 Posts
Discussion Starter #1
I was reading a short biographie of Jean Gau and came across this

Quote:
"Before Carrie struck, he had furled sails, lashed the helm, rigged a can of oil to drip over the side, and gone below to read, paint, and sleep."

Now remember I havent handled a sailboat yet, but Im getting there. I just wanted to ask yall what the "oil dripping over the side" is all about ? Thank you
 

·
Registered
Joined
·
41 Posts
Discussion Starter #2
Well I should say Im not really sure there's actual "oil" involved. There's the "oil can" and there's something that "drip"s . Is it some sort of system to keep water out of the cabin? Im not trying to make a scene here, but this is really diggin into me head !
 

·
Bombay Explorer 44
Joined
·
3,619 Posts
50 years ago used engine oil.

Nowadays biodegradable fish oil of course.

Seriously the use of an oil bag to "calm the seas" was a standard passage in all heavyweather sailing books 50 years ago.
 

·
Telstar 28
Joined
·
1,000 Posts
Oil tends to form a protective slick and reduce the chance of breaking waves, by calming the seas within the slick. BTW, this would be illegal nowadays...
 

·
Registered
Joined
·
3,070 Posts
Hopefully that "Oil" is either Fish, vegetable or animal... Because it major fines and jail time if it lube, mineral or diesel oil.
He probably did this in the belief that oil spread on stormy waters will calm them down. What it really does is create a surface tension that prevents most seas from breaking. Notice I said most seas, not all of them. The waves are still there, but just not breaking.
 

·
Registered
Joined
·
1,174 Posts
Oil actually reduced the surface tension of water. I did a research study of the environmental impact of oil on water as it related to aeration rates and we were quite surprised to find that an oil slick actually reduced surface tension. If mariners actually did this in the old days, it would have either been totally ineffective or made a bad situation worse.

This may seem counter-intuitive to some but, unless someone found a way to effectively disperse a thick layer of bunker oil over a huge area upwind of a boat, this is just another myth.
 

·
Registered
Joined
·
1,297 Posts
Oil actually reduced the surface tension of water. I did a research study of the environmental impact of oil on water as it related to aeration rates and we were quite surprised to find that an oil slick actually reduced surface tension. If mariners actually did this in the old days, it would have either been totally ineffective or made a bad situation worse.

This may seem counter-intuitive to some but, unless someone found a way to effectively disperse a thick layer of bunker oil over a huge area upwind of a boat, this is just another myth.
I wouldn't be so quick to dismiss the 'wisdom of the ages' -- it is true that many, many of the older books on heavy weather talk about this tactic. I doubt that it "made a bad situation worse" if so many old salts recommended it. Perhaps it's something that should be put to the "Mythbusters" on Discovery Channel.

The Pardeys have a theory about reducing the force of breaking waves by disturbing the surface of the water with the "wake" left by letting the boat drift very slowly down wind while lying to a sea anchor. They swear by it. My guess (and it's only that) is oil works on a similar principal -- disturbing the surface dynamics of moving water.

As for the legality of it..... believe me, if I found my boat in extremis and needed to calm breaking seas, the last thing I'd worry about was being written up for discharging a few gallons of oil. I'd let the lawyers argue the merits of the action once the boat and crew were safe.
 

·
Registered
Joined
·
1,174 Posts
I too would resort to whatever worked if the need ever arose, however, on it's face, this makes no sense unless you can also explain how one would manage to disperse sufficient oil, of sufficient viscosity far enough upwind to effect the surface of the water. Rather than being "wisdom of the ages", it's just another myth of the ages.
 

·
Telstar 28
Joined
·
1,000 Posts
The boat drifts when hove-to... the oil slick remains behind... and forms a protective slick upwind of the boat, as it drifts downwind... It works better on old shoes than newer, more modern designs, as they tend to forereach more than the older designs.
I too would resort to whatever worked if the need ever arose, however, on it's face, this makes no sense unless you can also explain how one would manage to disperse sufficient oil, of sufficient viscosity far enough upwind to effect the surface of the water. Rather than being "wisdom of the ages", it's just another myth of the ages.
 

·
Registered
Joined
·
1,297 Posts
I too would resort to whatever worked if the need ever arose, however, on it's face, this makes no sense unless you can also explain how one would manage to disperse sufficient oil, of sufficient viscosity far enough upwind to effect the surface of the water. Rather than being "wisdom of the ages", it's just another myth of the ages.

Have a look at YouTube - Oil-on-Water Calming Effect for a less than scientific demonstration of the effect.

Re methods of disbursement -- if memory serves, putting a small hole in an oil can (or plastic bottle) might be all thats necessary. (I've never tried it because, after all, it's illegal :D ). I've also read that putting a wad of cloth rags well-saturated with oil in a container and hanging it over the windward side works. Apparently, you don't need a big thick slick, only a film of oil to disrupt the motion of the surface water.
 

·
Registered
Joined
·
1,297 Posts
For the scientific explanation see:

The calming effect of oil on water

American Journal of Physics -- May 2007 -- Volume 75, Issue 5, pp. 407-414

Issue Date: May 2007

Abstract:
The<SUP> </SUP>calming effect of oil on water has been known since<SUP> </SUP>ancient times. Benjamin Franklin was the first to investigate the<SUP> </SUP>effect, but the underlying mechanism for this striking phenomenon remains<SUP> </SUP>elusive. We used a miniature laser interferometer to measure the<SUP> </SUP>amplitude of surface waves to a resolution of ±5 nm, making<SUP> </SUP>it possible to determine the effect of an oil monolayer<SUP> </SUP>on the attenuation of capillary waves and the surface dilational<SUP> </SUP>modulus of the monolayer. We present attenuation data on pure<SUP> </SUP>water, water covered by olive oil, water covered by a<SUP> </SUP>fatty acid, and a water-acetone mixture for comparison. From the<SUP> </SUP>attenuation data at frequencies between 251 and 551 Hz, we conclude<SUP> </SUP>that the calming effect of oil on surface waves is<SUP> </SUP>principally due to the dissipation of wave energy caused by<SUP> </SUP>the Gibbs surface elasticity of the monolayer, with only a<SUP> </SUP>secondary contribution from the reduction in surface tension. Our data<SUP> </SUP>also indicate that the surface-dilational viscosity of the oil monolayer<SUP> </SUP>is negligible and plays an insignificant role in calming the<SUP> </SUP>waves.

---------

Those ol' salts of yester-year weren't so dumb afterall. :)
<!-- end abstract_title_info.jsp -->
 

·
Registered
Joined
·
5,491 Posts
The older narratives frequently discuss "bags" of oil, which argues for a thick or rubber-lined sack from which oil would drip fairly slowly. We've all seen how even a teaspoon of spilled diesel can cover a bedroom-sized surface of a calm harbour, but how this would work in a foaming sea is beyond my experience.

The forereaching boats hove-to in the older stories (pre-1970!) actually describe their hulls as leaving a "slick", so the connection between a upwind zone of relative calm and the quasi-Biblical injunction to pour oil over troubled waters seems to have a long pedigree.
 

·
Registered
Joined
·
4,647 Posts
Thanks for the tip. I might try it.
 

·
Swab
Joined
·
825 Posts
The boat drifts when hove-to... the oil slick remains behind... and forms a protective slick upwind of the boat, as it drifts downwind... It works better on old shoes than newer, more modern designs, as they tend to forereach more than the older designs.
As usual SD - right on the money. I have never spread oil on the water because I doubt its effectiveness and don't carry any oil or means of spreading it (Although we could probably rig something up to spread what little cooking oil we do have) but I can attest that the Pardeys are correct about the effect of a boat drifting downwind while hove to and it is obvious to me that hanging an oil bag over the windward side would, indeed, spread a slick up wind.


Latest videos
 
1 - 14 of 14 Posts
Top