Galvanic corrosion or cavitation problem?

I watched Richard Hammond (Hamster) on the goggle box the other night - This reminded me about a program transmitted last week. It was the first of Richard Hammonds - Invisible Worlds series on the BBC.



The series is built around an intriguing collection of high speed filming clips, which lets us see things we don't normally perceive. The clips detail things that happen way beyond our sight limitations. Letting us see for the first time secrets hidden in every element of our planet. A secret world where thin air can be seen to shatter rock and water can tear through metal.

There is a little section in the first program of interest to boaters. The clip is based on the cause of pitting found on propellers running at high speed for long periods.

Depending on the rotational speed of the propeller and the length to the blade tip, there is the possibility that the formation of super heated water vapour at a temperature exceeding 4000 degrees can occur. These vapour bubbles that are produced then immediately collapse, releasing their latent energy and this can cause a cavitation burn on propeller blades. Often called tip erosion.

Have a look at the clip (Propeller cavitation - 37 mins in) or the whole program.

http://www.bbc.co.uk/iplayer/episode/b00rmrln/Richard_Hammonds_Invisible_Worlds_Speed_Limits/

Call me old and cynical if you must.....

You would think that most people would be aware of personal safety issues. We teach our children how not to put themselves at risk by not making eye contact, not displaying valuable items, not talking with and not accepting sweets from strangers.

However, in this techno-savvy world that we live in today. The latest thing in "personal protection" being hawked is "KamAlert" an iPhone application.


http://www.kamalert.com/protect-yourself/


[Nicked from their website]

Protect yourself

There are many areas of personal protection. The most obvious are at our homes or out in unsavoury neighbourhoods. There are particularly vulnerable times such as when we are on holidays or in unfamiliar situations - rushed or stressed or in crowds. Each example requires the same basics of personal awareness of the surroundings and ongoing events, and an adapted awareness for the individual circumstances. Too often, in the most relaxed and secure environments such as our homes, our antennae for recognizing danger is least active. It is therefore important to have additional security take over for us.

In the streets a lot depends on how familiar you are with the area, times of day and any particular danger spots. In any case always be vigilant, even if it is a daily routine. If you carry any self-defensive items such as KAMALERT, be sure to have them “at the ready”, and if you are in a danger area or a potentially vulnerable situation, have “your finger on the button”.

Be sure to have your KAMALERT “Contacts” and local emergency and police and numbers entered correctly.

Stay safe and well, Randolph von Gans

Randolph - I am going to give you a bit of daddies friendly advice usually shared with the little vulnerable ones…. First don't go out in unsavoury neighbourhoods. But, if you should ignore the advice and one day find yourself out in an unsavoury neighbourhood. One way to reduce the chance of a mugger taking interest is not to be seen to brandish your expensive iPhone in the first place. KamAlert is no match for a club, fist, gun or a knife.

Give me strength….

Later….