wrote:
On Aug 3, 5:48 am, "Marc" wrote:
Looks like a great article. THX!


You are welcome. I notice the the link I posted is broken in my
browser so if anyone else is interested they might want to go to
http://www.proboat-digital.com and look for the june/july issue.
Professional Boat Builder is an usually good rag. There were a couple
of points that I thought were interesting about the article:

1) despite the fact that Calder is somewhat famous and well connected
he obviously had trouble shaking real numbers out of the d/e folks and
in the end resorted to a good deal of hand waving and extrapolation.
We mortals may have trouble getting enough disinterested information
on small d/e setups to do any valid engineering.

2) thermodynamics version 3.0 for the new digital age (tm) as brought
to you by Solomon Technologies is still pretty much the same old stuff
we learned back in the steam age. You still have to balance the
equations and there ain't no such thing as a free lunch.

3) the inefficiencies in small boat propulsion systems are primarily
the result of propeller inefficiency at slow rpms which result in
lightly loaded engines which are inefficient producing a vicious
circle. The logical place to break the circle is at the propeller.
Attempts to break the circle at the transmission are very likely
become exercises in moving the problem around rather than fixing it.



A nice summary. I read the 2nd article as basically saying "there
ain't no free lunch and the D/E folks are having a hard time
justifying their systems".

On a cat a SIMPLE D/E system would almost seem to work rationally
(like Glacier Bay "do away with the batteries philosophy"), but I LIKE
the redundancy of twin engines instead of a more complex
genset/motor/controller system

Evan Gatehouse