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10 minutes ago, magnetman said:

I meant anti ventilation plates. 

 

Of course you did. The trouble is that those who know the difference between cavitation and ventilation on props are not as numerous who think both are the same thing.

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24 minutes ago, Tony Brooks said:

 

Of course you did. The trouble is that those who know the difference between cavitation and ventilation on props are not as numerous who think both are the same thing.

 

 

I'd imagine with a cavitation problem, welding on anti-ventilation plates would make no difference or could make it worse, if anything. 

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18 minutes ago, MtB said:

 

 

I'd imagine with a cavitation problem, welding on anti-ventilation plates would make no difference or could make it worse, if anything. 

 

I agree, but not sure how it could make things worse because cavitation air/gas bubbles are caused by the prop itself making low pressure areas, not drawing air down from the surface.

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47 minutes ago, Tony Brooks said:

 

I agree, but not sure how it could make things worse because cavitation air/gas bubbles are caused by the prop itself making low pressure areas, not drawing air down from the surface.

 

 

I was thinking they might marginally further restrict the flow of water into the prop, making cavitation slightly worse.

 

 

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4 minutes ago, MtB said:

 

 

I was thinking they might marginally further restrict the flow of water into the prop, making cavitation slightly worse.

 

 

 

That is certainly a possibility, but if it restricted much I think it would ventilate because that means water would have been drawing down from the surface.

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Well I'll show my further ignorance by asking; What is an anti-ventilation plate, and how does it differ from an anti-cavitation plate?

Where is it fitted, what does it do?

The correction needs an explanation. (At least for me it would appear).

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Ventilation is when air is drawn down from the surface into the propellor, spoiling  its thrust.

 

Cavitation is when the pressure at the front face of the propellor blades is low enough for tiny steam bubbles to form ( boiling )   in spots.  When the bubbles collapse there is often damage to the propellor, and a lot of underwater noise.

 

Anti ventilation plates  as seen on many converted butties e.g. Renown, stop air drawing down and are a substitute for the motors counter plate.

 

Anti cavitation plates do not exist.  Cavitation is dealt with by extra immersion and careful propulsion system design

 

 

N

Edited by BEngo
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The motorised former horse Boat I owned briefly had anti ventilation plates. 

 

The Raven butty had a very similar arrangement but I don't think it had the flanged edges so if you fell in at the wrong time it would cut you in half. 

 

This was the Boat I had:

 

 

 

https://www.nationalhistoricships.org.uk/sites/default/files/data/nrhv/vessels/2087_ORIANNE_5.jpg

 

 

Edited by magnetman
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41 minutes ago, magnetman said:

The motorised former horse Boat I owned briefly had anti ventilation plates. 

 

The Raven butty had a very similar arrangement but I don't think it had the flanged edges so if you fell in at the wrong time it would cut you in half. 

 

This was the Boat I had:

 

 

 

https://www.nationalhistoricships.org.uk/sites/default/files/data/nrhv/vessels/2087_ORIANNE_5.jpg

 

 

 

Enlarged picture of Raven from the other end to my previous picture showing the plates being discussed.  Actually it looks to be more of a single plate as it wraps around the stern but whatever :lol:

 

Screenshot2024-04-16095957.jpg.18398ab0fe2c5d02d5e8170b519ab1a5.jpg

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On 16/04/2024 at 08:18, BEngo said:

Ventilation is when air is drawn down from the surface into the propellor, spoiling  its thrust.

 

Cavitation is when the pressure at the front face of the propellor blades is low enough for tiny steam bubbles to form ( boiling )   in spots.  When the bubbles collapse there is often damage to the propellor, and a lot of underwater noise.

 

Anti ventilation plates  as seen on many converted butties e.g. Renown, stop air drawing down and are a substitute for the motors counter plate.

 

Anti cavitation plates do not exist.  Cavitation is dealt with by extra immersion and careful propulsion system design

 

 

N

Photo from here: http://nurser.co.uk/index.html

Henry Grantham.jpg

Edited by Ray T
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  • 3 weeks later...
21 minutes ago, Admiral said:

Gort for sale

Gort

We accompanied Gort up the Grand Union after the Diamond Jubilee Parade on the Thames in 2012. The owner is a lovely chap, and from spending a few days boating, and a couple of evenings in the pub with him, I would never have guessed he was a Peer of the Realm!

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Gort was Mike H's first boat as captain.

I met the owner and boat a few years ago now at Sutton Stop.

I was privileged to be allowed in the cabin. 

A beautifully maintained boat.

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6 hours ago, Ray T said:

Gort was Mike H's first boat as captain.

I met the owner and boat a few years ago now at Sutton Stop.

I was privileged to be allowed in the cabin. 

A beautifully maintained boat.


We let Gort past us last year round Wolfhampcote, lovely engine noise and a beautiful boat. I hope someone who appreciates and can look after her is tempted. 


Re an anti ventilation plate - does this one count? 

 

IMG_2024-05-14-193405.thumb.jpeg.cada26f25a98fd9bdfc45c58e91da27d.jpeg

 

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13 hours ago, Stroudwater1 said:


We let Gort past us last year round Wolfhampcote, lovely engine noise and a beautiful boat. I hope someone who appreciates and can look after her is tempted. 


Re an anti ventilation plate - does this one count? 

 

IMG_2024-05-14-193405.thumb.jpeg.cada26f25a98fd9bdfc45c58e91da27d.jpeg

 

I used to moor next to that boat lol. 

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12 hours ago, Admiral said:

James Henry bantock for sale on the duck

 

James Henry

 

Phil and Margaret Dowling's old boat, so would have been well looked after at least until he died a few years ago.

 

They were a lovely couple who used to manage the Black Prince hire base at Northwich. It was one of the better moorings for our shareboat.

 

 

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