[Alberg30] props

[Don Campbell]

Jim Mennucci has said that he has added some BS to the heap, but what he
has outlined is a much more realistic approach to prop blade design than
he is willing to back-up, that willingness apparently limited  because
he wrote it from memory in 5 minutes! There is a whole other bit he left
off about energy transfer to and away from boundary layers by turbulence
from waves, but suffice it to say, designing prop blades is only as good
as the computer programme that spits out the numbers. That programme  is
only as good as the engineer who developed the algorithms, or the
programmer (if different) who did the code. It is still a compromise!
    While the suggestion to ask others of their success may be valid,
the problem is most have not measured performance or tried a number of
props, so how do we know?  We still need the tank. Kevin Blanc has
suggested relative improvements with the indigo prop, but without
measurements. I know my 2 blade is more fuel efficient than the 3 blade
was, but again, I have only compared individual trips, not every mile
motored. I have also not measured the differences in the prop blades.
although I did increase the pitch ( but should not have) by 1" because
of lack of supply at the time I wanted to change.
Don Campbell

 +---------------------------------------------------------------+
 |                This Old Boat by Don Casey                     |
 | http://www.amazon.com/exec/obidos/ASIN/0071579931/alberg30-20 |
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