Elctronic device to keep growth off the hull

[redthunder]

Has any body got any experience of these devices. I am looking at a sonihull gadget that keeps the growth off the hull. Looking for an alternative to antifoul. Opinions? http://www.nrgmarine.com/sonihull.html

[Rokraider]

Interesting. It apparently only weighs 3 Metres??!

It would be good if it works, I guess we wont know until someone puts their hand in their pocket and does a before and after comparison.

A season on a mooring in Chichester Harbour would be a good test for it, most boats start growing beards in a couple of weeks.

[willk]

"Will i still need to paint my boat with antifouling paint?
Painting the hull is not only for purpose of antifouling. it is also an important waterproofing barrier, protecting the gel coat from the effects (and immense cost) of osmosis. Therefore we would still recommend that the boat is protected under the water line. In some cases to maximize performance some yacht owners who have installed the sonihull system have opted to use a harder grade of antifouling paint, as apposed to the soft self polishing versions which have a higher drag factor through the water. So although there is still a need for painting below the water line, when using the sonihull system the need to do so will be greatly reduced."

LOL - buy our kit but keep using the Antifoul!

Snake Oil, IMO.

[Starovich]

it is also an important waterproofing barrier, protecting the gel coat from the effects (and immense cost) of osmosis.

um, is it not the case that anti foul is porous anyway, to facilitate the leaching of the active ingredient to prevent growth?

I am seriously looking at copper coat instead of traditional anti foul.

[martini]

There's a few of these types if device around now and also a few independent tests by boaty mags etc.

General consensus is that they're all s**te and do next to nothing to weed growth

Sent from my portable speaking device using Rib.net

[Cookee]

Originally Posted by martini

There's a few of these types if device around now and also a few independent tests by boaty mags etc.

General consensus is that they're all s**te and do next to nothing to weed growth

Sent from my portable speaking device using Rib.net

There has been some discussion on this topic over at YBW forums and the results have variable success just like antifoul paints working in some areas better than others, one thing is for sure - you'll need a mains supply!

[Steve_B]

I considered this option and as they were based just down the road, they even offered a "good" price.

However, unlike other products, they could not let me have the details of an existing user so that I might talk to them or observe the product in use. This might have changed now(?)

My decision therefore was to go elsewhere. Have used CopperCoat and have NO regrets

Steve

[9D280]

*in a phenomenon known as "cavitation."*

That will be the effect that destroys propeller blades & eats chunks out of pump impellers...

[willk]

So why doesn't it clean the antifoul paint off then?

[jyasaki]

Originally Posted by 9D280

*in a phenomenon known as "cavitation."*

That will be the effect that destroys propeller blades & eats chunks out of pump impellers...

Cavitation is caused by reducing pressure of water to the point where it allows gas to form (essentially evaporating water within the liquid itself.) Once pressure is restored, the bubbles collapse, and the resulting pressure waves cause the destructive force that eats props.

So how does this magical thingie cause cavitation? Magnetically affecting water? Good luck...

jky

[9D280]

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.

[BogMonster]

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

[DGR]

Originally Posted by 9D280

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.

[9D280]

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!

[Poly]

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.

[ewan clark]

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).

[DGR]

Originally Posted by 9D280

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.

[9D280]

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...

[jyasaki]

Originally Posted by ewan clark

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

[DGR]

Originally Posted by 9D280

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.

Originally Posted by 9D280

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!!)...