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The posting of my experimental results has generated several responses (and
thank god it wasn't as many responses as an anchoring or computer nav post).
I'll try to reply here en mass.
<Garrett and Jim Donohue had comments about the advisability of inspecting
<fuel before purchase.
And my response to both: If you are getting fuel that is being hand carried
to the boat in jugs then it makes a lot of sense to look at it before you
pour it in. BTW: You don't have to go to Mexico or the third world to find
this type of delivery. According to "Exploring Vancouver Island's West
Coast" by Don Douglass, Snuggery Cove has this type of fuel delivery and
it's only about 50 miles WNW of Victoria BC.
OTOH: If you're getting fuel at the more common pump & hose type of fuel
dock then the choice is not the same. Between 1 and 20 seconds prior to
arriving at the nozzle the fuel you're buying went through a powerful high
speed pump. Any contaminates are temporarily very well mixed into the fuel.
Maybe a trained eye could discern whether there is a serious problem, but I
know that I couldn't and I've been dealing with petroleum products (first
hand) for about 25 years now. Diesel straight from the hose typically looks
cloudy (due to entrained air), just as does diesel that is contaminated with
water. The way that you tell the difference between the two is to wait until
they separate which could take a while. An alternative method is called the
"crackle test" but it involves an open flame which is generally frowned upon
at the fuel dock.
The simplest way of avoiding worry about your fuel quality is to buy from a
fuel dock that you trust and having a good filter/separator in your fuel
system. Look for a local fuel dock that's busy. The faster they turn over
their inventory the cleaner the product will be. If you're planning a trip,
ask around about fuel sources on your route. IMHO you'll get more useful
information by asking about bad experiences (and avoiding those places) than
you'll get from other's good experiences (which could mean that they just
got lucky).
<Paul Kruse expressed the hope that one of the scientists on the list could
<give us some insight as to why a layer of petroleum would have such a
<drastic effect on the evaporation of water underneath such a layer.
I'm not a trained scientist but I'd like to offer the following conjecture:
Most of us have seen a cartoon animation of water evaporating. In it, water
molecules are depicted as little balls that are continually bouncing around
and colliding with each other. As energy is added to the system the
collisions become more violent and occasionally there is the right
combination of force and direction to knock a molecule out of the liquid and
into the atmosphere. Now imagine a thin layer (Even one molecule thick) of
diesel fuel between the water and the atmosphere. The molecular weight of
water is 18 while the molecular weight of diesel is at least 142 (both
numbers have been rounded off). A water molecule with enough energy to break
free of the liquid water would meet a barrier of molecules that weigh almost
eight times as much. It seems to me that this would be analogous to trying
to throw a baseball through a heavy blanket; It can be done but you have to
throw many times harder to do it.
<Bob Conrich pointed out that this phenomenon is used to reduce water
<consumption in certain wet cell batteries and George Geist suggests that
<one could cut potable water consumption by using a layer of oil on top of
<the boats drinking water supply.
My response: Bravo! It's just this kind of "Thinking outside the box" that
has made America great!
Yes, I know that George is from Canada and Bob is from the British West
Indies but, by God, Exxon is American and one of their ships was
experimenting with this technique over ten years ago. They weren't just
fiddling around with a couple of Mason(tm) jars, or a ni-cad battery, or
even a vessel's drinking water; No sir, they used Prince freaking William
Sound and if it hadn't been for a bunch of tree huggers insisting that the
protective layer of crude oil be "cleaned up" I'll just bet that the results
would have showed a major reduction in evaporation from that body of water.
Optimistically yours,
Alex
