Blueskying - silicone on a prop

N

Neeves

Well-Known Member
Joined
20 Nov 2011
Messages
14,073
Location
Sydney, Australia.
Visit site
Having a badly fouled prop, well 2 actually, I was pondering prop treatment. Top of the options are Velox and Prop Speed. I've tried them both, they are not as good as the best AFs used on our hulls thus the props determine the AF schedule.

My first thought was drivers of racing cars (it was the Bathurst 12 hour last week (first 3 cars Mercedes, fastest Audi) and this made me recall those with open cockpits where they used disposable covers for the visor of their helmets. They were/are simply tear off strips, when the outer one is fouled simply tear it off - offering a new exterior.

So I wondered about a bag, made from polythene, that would be blade shaped. There would be another cover, Hub shaped and a further made for the Saildrive. You would clean and prepare the prop etc and simply slide the various pieces on (( did not get as far as how they could be secured). Might need oil, lubricant, to slide on the covers.

My thought developed - latex rubber gloves, I believe, are made on mouldings of hands, simply dipped and left to 'set'. They are elastic and they are not overly difficult to put on. I then thought why not make the mouldings from silicone - that's what Prop Speed is. So silicone moulding 3 for a three bladed prop, one for the hub (with appropriate gaps) and one for the sail drive - with appropriate holes for the water intakes etc. Maybe just latex.

I'm thinking disposable, though maybe the silicone could be cleaned, weak acid???

I know nothing about silicone mouldings (nor about welding polythene) nor whether there might be better polymers - and whether my idea is simply ....daft. I also don't know of anyone with expertise or manufacturers.

Any manufacturers of silicone gloves out there.....

Jonathan
 
[/QUOTE]
AntarcticPilot said:
My immediate thought is that there must be outward forces perpendicular to the blade of a propeller on the forward side of the blade. So a coating that isn't adhering to the blade will balloon away from it, a) reducing the efficiency of the propeller and b) destroying itself PDQ.
Click to expand...

To say nothing of the additional risk of even more ‘plastic’ pollution in our Seas/Oceans.
 
I imagine the manufacturing problems would be huge, but top marks for lateral thinking. Some of the greatest inventions are a result of not following the norm.
 
I did something similar in the past...well sort of. Primocon followed by a couple of coats of Trilux and two of ordinary antifoul without any prep to the Trilux. Worked really well as the regular antifoul fell of about half way through the season taking the fouling with it. I chickened out when I bought a more expensive feathering prop though.
 
Nice idea, sounds a bit like using plasticote. If you applied that in different coloured layers you might be able to peel one off at a time.
Can't see anything loose staying put under the enormous pressures on prop blades.
 
Johnathan, you quite often mention that you can and do dry out, so as far as you're concerned, it shouldn't be too difficult to clean your prop then. Maybe you're just being altruistic for the benefit of those of us with keels? ?
 
NormanS said:
Johnathan, you quite often mention that you can and do dry out, so as far as you're concerned, it shouldn't be too difficult to clean your prop then. Maybe you're just being altruistic for the benefit of those of us with keels? ?
Click to expand...

Unfortunately due to Australia's awful weather, at least on the east coast, where we have had 2 years worth of rain in a month and my laziness we have not used the cat much - and obviously not enough.

The hulls are quite good, need a wipe down, but the props are badly fouled.

We are waiting for the next high tide that allows us to dry out sufficiently - not till mid June. Our tides are small - even the best tide in June only offers a 1m tide.

I could dive but I find the water temp a bit too bracing. It is winter here, 11 deg this morning. Yes - I'm a wimp.

But I was being altruistic. Prop AF is a recurring theme, along with exhaust elbows, AF by itself, and - dare I mention it ground tackle.

So I was blue skying for my own selfish reasons but with the hope maybe a bit of brain storming amongst 'US' might pay dividends. I have been reminded copper electro plating (which Vyv did) is one answer, Distantshores, but this has additional logistical issues. I need to take the blades off but if the blades are off the cat becomes difficult to move.... I could tow it back to the mooring but then I need to tow it back to beach - my altruism has limits (as the nearest YBW member, Coopec, lives 5,000 miles away....:(. )



To say nothing of the additional risk of even more ‘plastic’ pollution in our Seas/Oceans.
[/QUOTE]

If there was an answer and needed testing I'd be willing to have a small additional amount of plastic in the sea - if the answer worked and long term the amount of pollution was reduced. There is a cost - I think the cost worth it.

AntarcticPilot said:
My immediate thought is that there must be outward forces perpendicular to the blade of a propeller on the forward side of the blade. So a coating that isn't adhering to the blade will balloon away from it, a) reducing the efficiency of the propeller and b) destroying itself PDQ.
Click to expand...

This may be the issue that kills the idea. Maybe with further thought the issue can be engineered out - reinforcing set in the silicone - which is how kitchen utensils are made.

I have no idea of silicone manufacture - I'm just floating a different approach....


DanTribe said:
I imagine the manufacturing problems would be huge, but top marks for lateral thinking. Some of the greatest inventions are a result of not following the norm.
Click to expand...

Thank you for looking at it the same way I am - De Bono is not to be forgotten.

We have a pair of silicone oven gloves - they are very loose fitting but I though of using the blades as a mould - but this would give a perfect fit but how do I ensure the outer surface is smooth - and reinforce the inner surface to over come the Pilots comment - fibre glass battens?....


An answer is not to make the assembly, including sail drive, from aluminium etc but to make the whole lot from carbon reinforced plastic or sealed with a carbon reinforced plastic coating - this would remove the need for anodes and for fancy AF - you could AF the whole yacht with one component (again Distantshores and the Kiwi prop). However this is not something I can do - it needs Volvo et al to do it - and there must be a reason it is not done....


Jonathan
 
Neeves said:
This may be the issue that kills the idea. Maybe with further thought the issue can be engineered out - reinforcing set in the silicone - which is how kitchen utensils are made.

I have no idea of silicone manufacture - I'm just floating a different approach....
Click to expand...
I'm afraid you have two opposing requirements for the material. First. you want it to be elastic enough to fit over the propeller blad, like a surgical glove. Second, you want it to be rigid enough to resist forces perpendicular to the blade surface - and, like "swigging" up a halliard, these will be magnified by the geometry. These two properties are diametrically opposed to each other! I wonder if you could find a material that would go on like a surgical glove and then cure, possibly adhering to the blade as it does so? Perhaps like heat-shrink?

A personal recollection reminds me of how difficult it is to resist aero- or hydro-dynamic forces such as those on a propeller. Back in 1983, I was on a survey expedition to Svalbard, and we were operating with a Twin Otter - hardly the most high-performance aircraft in the world (the air-mech, an RAF guy on secondment, referred to it as being "a bit agricultural" in a Welsh accent!). Anyway, we had designed and had made up some self-adhesive mission patches, and we placed a couple of these on the exterior of the aircraft, on the fuselage side, so not in a location particularly exposed to aerodynamic forces. After the first flight, there was no sign whatsoever of the patches; though thoroughly well adhered to the skin of the aircraft, and only the thickness of paper, they had succumbed to the tiny turbulence round their edges. This on an aircraft only capable of 160kt! Moral of the story is, don't underestimate the forces on anything you want to stick to a propeller.
 
Last edited:
yotter said:
Kiwi prop, got me thinking, I wonder if they could add an antifouling material (copper oxide?) to the plastic material before molding the blades? Thinking out of the box also:)
Click to expand...

Just add copper to the epoxy - maybe that has been done before...... :).
AntarcticPilot said:
I'm afraid you have two opposing requirements for the material. First. you want it to be elastic enough to fit over the propeller blad, like a surgical glove. Second, you want it to be rigid enough to resist forces perpendicular to the blade surface - and, like "swigging" up a halliard, these will be magnified by the geometry. These two properties are diametrically opposed to each other! I wonder if you could find a material that would go on like a surgical glove and then cure, possibly adhering to the blade as it does so? Perhaps like heat-shrink?
Click to expand...

Heat shrink was an idea - I was constrained in my focus :(

Maybe those shrink fit packs for food....

Its an easier one to try. Heat shrink bag on the hub....?

Part of my thinking was that silicone is 'non stick' or said to be so, for fouling - does silicone heat shrink

Jonathan
 
Stemar said:
If you forget to replace your anode, that will happen anyway. Unfortunately, it tends to end expensively.
Click to expand...
Mine is still bright after 22 years. I have tried to paint it. The first time was with Silic One, but there was no trace of it or its primer at the end of the season. I had more luck with Trilux last year but there were still some bare patches to re-prime. I think that different metals take more or less kindly to being primed.
 
Neeves said:
Just add copper to the epoxy - maybe that has been done before...... :).


Heat shrink was an idea - I was constrained in my focus :(

Maybe those shrink fit packs for food....

Its an easier one to try. Heat shrink bag on the hub....?

Part of my thinking was that silicone is 'non stick' or said to be so, for fouling - does silicone heat shrink

Jonathan
Click to expand...
Silicone generically is not non-stick as far as marine organisms are concerned - specially formulated, carefully designed silicone is what is used. Deterring fouling organisms is the subject of extensive academic research; it's big money in the commercial world and a major economic factor in shipping. The silicone-based treatments for propellers that we have access to are spill-over from the treatments used on commercial ship's hulls. But anything non-slip like that ONLY works if it is frequently in motion; any lengthy period at rest will allow organisms to get established. What the silicones do is provide a surface to which juvenile organisms can't adhere strongly enough to resist the drag forces when in motion. But once said juvenile organism has got established, it's stuck and won't be dislodged by motion. That's why such treatments are only useful on vessels in regular use, and (in the case of hull treatments) move at a speed above a threshold - 8 knots is usually quoted.
 
Again, trying to 'think out of the box' without necessarily hatching a whole, complete solution.....

Perhaps part of the difficulty lies with the work involved in cleaning the props in situ. Perhaps part of an answer might lie in having a replacement set of props, offering the opportunity to 'hot swop' swiftly and take away the fouled props for cleaning - e.g. sat overnight/weekend in a weak solution of something that dissolves crustaceans.

Yes, that might prove to be ruinously expensive - but the industry might invent an advanced engineering composite suitable for such use, and bring to market props in matched pairs, which attach/detach easily, at a suitably attractive price.

That wouldn't stop fouling of immobile outdrive/outboard props, but could address the cold, wet inconvenience of standing knee-deep in cold seawater for an hour or more per side.

A similar approach to swift 'hot swopping' of anodes might emerge.

A composites engineering firm such as IGUS.EU might be just the sort of innovative specialist to approach.
 
Plenty of canal barges have a well to allow access to the prop for cleaning purposes, though I suspect the kind of cleaning they have in mind may be removal of old bicycles and supermarket trolleys. Maybe some kind of lift-out lazarette to reduce turbulence from the hole?
 
You must log in or register to reply here.

Share this page

Top