First a re-howdy. I haven't posted here in ages though I still read some
digests. I just returned from the Reno Air Races where I shot everything
with my old OM1 and the 65-200/f4 that I got on recommendation from this
list, and from a list member. It worked very well. I will post links to
pics when I have scanned a few.
Subject: [OM] Info on Vivitar 135/f2.8
I'm thinking of bidding on this lens. Could someone kindly give details of
its performance.
Many thanks.
John.
I have had one of these for ages. I think I got it really cheap. It's
been very useful for me, especially as a Macro.
Cavitation is a phenomena associated with operating in fluids such as water.
When the local pressure drops low enough, the liquid changes state to gas -
it boils, with bad results with regard to noise, performance, and hydrofoil
longevity. Can't happen in air, air is already a gas. So, no, Cessna
drivers (and Cessna's designers) aren't interested in cavitation. Cavitation
is primarily of interest in high speed watercraft propeller (screw) design.
The big flap a dozen years ago over Toshiba's illegal sale of computer
controlled milling machines to the Soviet Union was based on the fact that
that technology allowed them to better build complex, non-cavitating (thus
quieter) submarine screws.
They talk about props 'cavitating' at Reno all the time. I have wondered
at times what they mean. I assume it is something like complete flow
separation from the prop blades resulting in near vacuum. I'm curious if
anyone knows more. Of course, their problem is that they are trying to put
3500HP into a prop built for 2000HP. Someone said that they don't bother
with nitrous because the prop is already cavitating at full boost, which is
something like 120-130 inches. Of course, this is a realm that no Cessna I
know of plays in.
DMcG
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