Reply
 
Thread Tools Search this Thread
 
Old 01 October 2012, 12:45   #11
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
That was my point, albeit not maybe posted as clearly...

The "implosion" of the bubbles would destroy the hull in the same way the effect destroys propeller blades and pump impellers.
__________________

__________________
9D280 is offline   Reply With Quote
Old 11 October 2012, 05:28   #12
Member
 
Country: Other
Town: Stanley, Falkland Is
Boat name: Seawolf
Make: Osprey Vipermax 5.8
Length: 5m +
Engine: Etec 150
Join Date: Mar 2006
Posts: 3,688
Prince Charles talks to plants, but I view chemicals as more effective than putting something under the boat to shout at them.

Whole-hull cavitation would be a phenomena worth filming as the boat disappeared from under you
__________________

__________________
A Boat is a hole in the water, surrounded by fibreglass, into which you throw money...

Sent from my Computer, using a keyboard and mouse
BogMonster is offline   Reply With Quote
Old 11 October 2012, 10:49   #13
DGR
Member
 
Country: UK - Wales
Town: Barmouth
Boat name: Blue Marlin
Make: Ribcraft
Length: 7m +
Engine: Yanmar 315/Bravo 2X
MMSI: 235020218
Join Date: Jun 2003
Posts: 827
Quote:
Originally Posted by 9D280 View Post
That was my point, albeit not maybe posted as clearly...

The "implosion" of the bubbles would destroy the hull in the same way the effect destroys propeller blades and pump impellers.
No it won't!! I looked into this a couple of years ago - the idea is that the unit puts tiny vibrations into the hull structure at ultrasonic frequencies - which causes cavitation in the single-celled critters that are the first things to set up camp on your hull - 'bursting' them. In theory, if that bit of the food chain gets interrupted, the next thing that feeds on the single celled stuff won't bother staying/growing, etc etc - so nothing grows on your boat. Most of the units I looked at were multi-frequency, and claimed to work on some larger stuff too.

Anyway - I was unconvinced - and the lack of proof that it had much effect......... so I bought a petrol jetwash instead.
__________________
DGR is offline   Reply With Quote
Old 15 October 2012, 12:08   #14
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
Ultrasonic vibrations ain't cavitation... I'm on phone here so when i get back to a pc I'll post a rib of the destruction it causes

The effect of the vibrations might cause that effect but i would debate the use of the word cavitation- you need to have boiled them to do that!
__________________
9D280 is offline   Reply With Quote
Old 15 October 2012, 12:29   #15
RIBnet admin team
 
Poly's Avatar
 
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: 2 stroke YAM 20 HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 10,114
It is possible to induce cavitation using ultrasound. Whether it is possible at the power/frequency used, all over the hull from one or two transmitters might be a bit more controversial.
__________________
Poly is offline   Reply With Quote
Old 15 October 2012, 16:25   #16
Member
 
Country: UK - England
Town: Dorset
Length: no boat
Join Date: Mar 2012
Posts: 19
Not wishing to blow my own trumpet (!), but guess what anti-foul the founder and owner of NRG Marine (manufacturer of Sonihull) uses on his own boat? That's right - Coppercoat!

Though I must assume he's fitted his own electronic gizmo as well. Two anti-foul system should work better than one. And hopefully the sonic vibrations will protect the bits that Coppercoat can't be applied to (i.e. the running gear).
__________________
Ewan Clark.

Aquarius Marine Coatings Ltd.
(www.coppercoat.com)
ewan clark is offline   Reply With Quote
Old 17 October 2012, 11:14   #17
DGR
Member
 
Country: UK - Wales
Town: Barmouth
Boat name: Blue Marlin
Make: Ribcraft
Length: 7m +
Engine: Yanmar 315/Bravo 2X
MMSI: 235020218
Join Date: Jun 2003
Posts: 827
Quote:
Originally Posted by 9D280 View Post
Ultrasonic vibrations ain't cavitation... I'm on phone here so when i get back to a pc I'll post a rib of the destruction it causes

The effect of the vibrations might cause that effect but i would debate the use of the word cavitation- you need to have boiled them to do that!
Cavitation is a reduction of pressure sufficient enough to vaporise a fluid. There are several ways of doing this - with a prop, too much shear stress is placed on the water around the prop, pressure plummets, water vaporises - cavitation. I KNOW that it damages boats and props - but the severity is directly proportional to the mount of power you are putting into the process/water to cause the cavitation.

If you make a single celled algae cell vibrate at a certain frequency, you can cause the internal fluid to vaporise (cavitate) with very little power/energy - which will kill it - and the structure it's sat on will just vibrate at that frequency, without damage.

Theoretically it's a brilliant idea, just really difficult to get to work properly, as most boat hulls have too much stuff in them that damps out the vibrations - internal structures etc.
__________________
DGR is offline   Reply With Quote
Old 19 October 2012, 03:47   #18
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
Ok i will admit i am a couple of beers down here but algae are a relatively complex organism and so a single frequency might obliterate one flavour but realistically what are the chances of destroying all on yer hull?

And as the single cell critters are on the hull do you not think the damage seen on props & pump impellers would be seen on the hull?

Posts above comments notwithstanding...
__________________
9D280 is offline   Reply With Quote
Old 19 October 2012, 11:31   #19
Member
 
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,653
Quote:
Originally Posted by ewan clark View Post
Two anti-foul system should work better than one.
Well, that's the question, isn't it? Does adding the electronic thingie work better than one?


jky
__________________
jyasaki is offline   Reply With Quote
Old 19 October 2012, 11:50   #20
DGR
Member
 
Country: UK - Wales
Town: Barmouth
Boat name: Blue Marlin
Make: Ribcraft
Length: 7m +
Engine: Yanmar 315/Bravo 2X
MMSI: 235020218
Join Date: Jun 2003
Posts: 827
Quote:
Originally Posted by 9D280 View Post
Ok i will admit i am a couple of beers down here but algae are a relatively complex organism and so a single frequency might obliterate one flavour but realistically what are the chances of destroying all on yer hull?
The one that I looked at (the Aus one) went through a range of frequencies - so it wasn't aimed at a specific flavour of critter.

Quote:
Originally Posted by 9D280 View Post
And as the single cell critters are on the hull do you not think the damage seen on props & pump impellers would be seen on the hull?

Posts above comments notwithstanding...
I think the idea is that it damages the algae sufficiently to kill it, rather than obliterate it completely.

As for the damage - that's related to the power used. The ultrasonic cleaners that people use to clean their carbs (and jewellery etc) uses cavitiation to remove the dirt, but at such a low power levels that it doesn't damage the thing being cleaned itself.

It's similar to the US having an ultrasonic weapon that can render a person immobile - but we don't worry about ultrasound scans for unborn children. It's all about the power used to generate the effect.

Same for military radar and a mobile phone - both use radio waves - but I definately wouldn't put one of them anywhere near my head (or in my pocket!!)...
__________________

__________________
DGR is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 01:58.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.