Video of the prop cavitation

[Burtox]

My significant other half bought me a aquapac type waterproof camera case for around £16. So armed with this and my compact camera I set out to do some underwater filming The prop has been making a noise and i thought it might be cavitation. What do you think?

Well I thought I would hold the camera underwater and gentle increase the speed, this didn't go to plan and the second attempt my mate opened the throttle fully which took me by surprise good job I had my arm through the A frame

The language is a little bit descriptive so turn down the sound down if you are a miner or a sailor

YouTube - ‪Rib Boat Honda 90 Underwater filming of propellor‬‏

[Pikey Dave]

......and this years nominations for the Darwin awards are........

[NeilH]

Excellent! I was expecting the water to suddenly turn red!

[Jizm]

Like that

[Boats&Outboards]

Originally Posted by NeilH

Excellent! I was expecting the water to suddenly turn red!

Me too, perhaps attaching it to a pole for the next attempt may be wiser...

Peter @ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[Burtox]

Originally Posted by NeilH

Excellent! I was expecting the water to suddenly turn red!

Yes, I agree it does look a bit dangerous but the camera was held against the tube and never any lower than the hull of the boat. The film that you see was the results of many trials to get to this point. I was on a short harness and my arm was through the A frame. My hands were more than a metre short of the prop. So to summerise reasonable precaution were exercised, the only thing that was unexpected was my mate suddenly opening the throttle which was not part of the plan. This resulted in me getting wet.

I would not recommend any one else doing this with out fully assessing the potential dangers. Kid don't do this at home moment come to mind.

I hope you enjoy the video.

[Burtox]

Originally Posted by Boats&Outboards

Me too, perhaps attaching it to a pole for the next attempt may be wiser...

Peter @ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

Isn't that comment a touch rascist

[Max...]

Originally Posted by Burtox

...reasonable precaution were exercised, the only thing that was unexpected was my mate suddenly opening the throttle which was not part of the plan...

Something 'unexpected happening' (ie an 'accident' or a careless 'mate') is surely why there are guidelines (common sense??) for keeping away from props whatever you're up to...

[Burtox]

Originally Posted by Max...

Something 'unexpected happening' (ie an 'accident' or a careless 'mate') is surely why there are guidelines (common sense??) for keeping away from props whatever you're up to...

I do agree with you

I did realise that it wasn't the brightest thing to do. Therefore I would not recommend anyone else doing it.

[Boats&Outboards]

Originally Posted by Burtox

Isn't that comment a touch rascist

Lol, Depends on the pole I guess

Let me rephrase, perhaps next time attach it to a short pole.... Now I'm being discriminative instead, is that better ?

Peter @ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[Burtox]

Originally Posted by Pikey Dave

......and this years nominations for the Darwin awards are........

Oh no don't tell me that the pikies can afford boats as well as new transits and caravans. What has the world come too

[jyasaki]

Safety notwithstanding, I doubt you'd be able to tell if you're getting cavitation from a handheld video camera on a through-hub exhaust outboard.

Cavitation is caused by the lower pressure area on the prop blades turning the liquid to a gas. The collapse of the resulting bubbles is what causes damage.

With a through-hub exhaust, there is so much gas being put into the water from the engine exhaust that you'd never see the formation of the smallish bubbles on the prop blades.

My $.02;

jky

[Pikey Dave]

Originally Posted by Burtox

Oh no don't tell me that the pikies can afford boats as well as new transits and caravans. What has the world come too

Do you want to buy a dog??

ee lad, tha can't educate pork

[Burtox]

Originally Posted by Pikey Dave

Do you want to buy a dog??

ee lad, tha can't educate pork

Yes I'm in the market but no more than ten bob

[rik_elliott]

Impressive shots but really not something to repeat. Props are seriously dangerous.
On a lighter note, the first run you doesnt look to cavitate too bad, most of the bubbles look to be from the exhaust. The second run looks to cavitate a bit - take it that's when he opened the taps? A bit of slip under hard acceleration is likely normal however.
Still, a good set of concept shots, but really do find a less dangerous way of repeating it if you must - I work just up the road from you and don't fancy sewing your arm back on!

[Courageous]

Hi Burtox - I'm probably looking for further info for me as much as anything here but your anti cav plate looks quite high up above the keel on your boat. Is that so or is it an optical delusion? I ask mainly because I am having problems with my setup at the moment with ventilation for that very reason. Yours doesn't seem to be affected by that from the video shots out of the water.

[Burtox]

I have a feeling that the prop is spaced too far from the gear box. I will reduce the thickness off the spacer and increase the washers thickness behind the castlelated securing nut. This mod should reduce the exhaust gasses escaping in front of the prop.

I also agree that the engine could go down another bolt hole as it does cavitate whilst doing a tight turn. Also the cavitation sound worse when I am travelling in the same direction as the waves.

Thanks you for all your comments.