Propeller mystery

[BruceK]

forensic fingertip test

That's what Matt Hancock said after groping his aide

 

[Bouba]

I know it’s hard to see, but if you compare my polished part to the encrusted part there is a slight ridge. But if you compare my polished part to one of the small patches of unencrusted blade then there is no ridge.

 

[BruceK]

? we believe you, trying to mirror polish a curved surface is an art. The light throws up every imperfection and is highlighted in gory detail. If you were testing for pink we'd forgive you but as a first pass polish up for comment it deserves some schtick! Vas of course is just jealous ?

 

[Bouba]

? we believe you, trying to mirror polish a curved surface is an art. The light throws up every imperfection and is highlighted in gory detail. If you were testing for pink we'd forgive you but as a first pass polish up for comment it deserves some schtick! Vas of course is just jealous ?

The problem is, Vas is the smartest guy on the forum, so if he says something then I worry?

 

[BruceK]

True.


In times like these I find a hearty lunch helps settle the stomach, followed by a few glasses of a robust red and a nap. Best way to call it a day on a job imho

 

[Bouba]

True.


In times like these I find a hearty lunch helps settle the stomach, followed by a few glasses of a robust red and a nap. Best way to call it a day on a job imho

You know, I wasn’t even going to polish the prop, just acid wash to remove barnacles, but everyone insists on pictures now days.
I’m going to a beach restaurant tonight for some fine dining and beer.............I’ll post some pictures.......

 

[BruceK]

Think of it this way, no pink, 5 dings, maybe a bit of paint. You were expecting to have to replace the prop. I'd say thats a win. Why wait for dinner? Celebrate now

 

[Mr Googler]

The problem is, Vas is the smartest guy on the forum, so if he says something then I worry?

Doesn’t say much for the forum that ??

 

[Portofino]

I,am with vas with this you have taken far too much metal off .
Just acid wash agitation with a brush is all that’s needed.
If you are not snake oiling them ie leaving them naked any polish in the med does not work as a accretion grows back which you just prior hand scape off .



Top pic the “accrections “
Bottom pic simply acid + brush - water rinse .No aggressive machines .

You gonna end up with a micro rippled surface as to regain the OEM shine you have no control over the thickness of material removed .If it’s not restored like my bottom pic then it’s new found roughness you have iatragenically created is gonna make matters worse .
For such a low revving , low speed ( none planning ) boat I would have thought the various snake oil prop AF s would stand a better chance on your boat than mine .As 700 Hp per side shoving 20 tonnes at 30 knots ....props the surface contact with water will be battered more than your one prop @ 8 knots turned by 1/2 the Hp pushing 1/2 the weight ??

Thus far the yard stuff seems to work .
I believe it’s all in the prep and attention to following the instructions to the letter ?
Ie resist the Stone Age man , just figure it out a d slap it on

Your props look like a Neanderthal s had a go

 

[Bouba]

I,am with vas with this you have taken far too much metal off .
Just acid wash agitation with a brush is all that’s needed.
If you are not snake oiling them ie leaving them naked any polish in the med does not work as a accretion grows back which you just prior hand scape off .

View attachment 118135
View attachment 118136
Top pic the “accrections “
Bottom pic simply acid + brush - water rinse .No aggressive machines .

You gonna end up with a micro rippled surface as to regain the OEM shine you have no control over the thickness of material removed .If it’s not restored like my bottom pic then it’s new found roughness you have iatragenically created is gonna make matters worse .
For such a low revving , low speed ( none planning ) boat I would have thought the various snake oil prop AF s would stand a better chance on your boat than mine .As 700 Hp per side shoving 20 tonnes at 30 knots ....props the surface contact with water will be battered more than your one prop @ 8 knots turned by 1/2 the Hp pushing 1/2 the weight ??

Thus far the yard stuff seems to work .
I believe it’s all in the prep and attention to following the instructions to the letter ?
Ie resist the Stone Age man , just figure it out a d slap it on

Your props look like a Neanderthal s had a go

Ok, I do have some snake oil. But I was saving it for another thread. I read about plastilube being an effective anti foul for stern gear. So I bought two spray cans of
TEROSON VR 500

 

[vas]

I'll agree with previous posters (except for the fact that I'm the smartest in here which is plain silly -seems that you are impressed with a bloody foreigner who touchtypes fast...)

If you go through all the threads on sterngear and Med, you'll find two suggested/working (to various extends) solutions:

A. clean with acid, polish (or not) and leave
B. clean with acid, primer, antifoul

solutions like oil, snake oil, lanolin, udder whatever doesn't seem to work (not particularly surprising tbh)

So, either acid and don't bother
or go the full monty, which is more work and more expensive and most importantly have to choose and apply something in a way that works (else you just waste your money).

I went through all the options and have devised one that works for me and the filthy port my boat spends most of the year:

• acid clean and wash thoroughly
• rub with 60-80grit, lightly with my hand no tools just to make sure there's key to apply primer (again wash)
• get either spray cans with primer for ss and galvanised metal (it's semi transluscent greenish generally) or get Velox plus primer transfered into spray cans (any paintshop will do that for you)
• finally get Velox plus a/f again transfered into spraycans

Apply spray from circa 200mm in a few consecutive layers on a dry day with no wind.
I leave 15mins between coats for the primer and around the same for the a/f
BTW, that's for bronze props and p-brackets, same applies to ss shafts, rudders and tabs

The approach above means that a/f stays on, doesn't flake.
Since I lately lift every two years, means that it will survive (any) scrapping of bits that may be on it after one year at the beginning of the second season.

TBH, if you lift every year and use the boat on a Med like 4-5m season, I wouldn't really bother a/f, stay at the acid clean and wash, don't even polish, you may keep them clean for an extra fortnight, is it worth the effort?

cheers

V.

 

[Bouba]

So, after my forum bollocking, I went and reinspected my work! There is not a grain of propeller dust on the ground or on my polishing disk, and not a grove, indentation, ridge, scratch on any of my work.......it’s all perfectly smooth

 

[BruceK]

So, after my forum bollocking, I went and reinspected my work! There is not a grain of propeller dust on the ground or on my polishing disk, and not a grove, indentation, ridge, scratch on any of my work.......it’s all perfectly smooth

You lie worse than Roy when his mates are on the scavenge.

Got anything to drink? Noooooooo (eye starts twitching)

 

[vas]

honest? specs on? (right specs on I mean, not shades!)
if so fine by me

mind still have refrained from mentioning rpm of angle grinder as well as pad/flapdisk/whatever you used.
No mention of grit either, don't you think that's suspicious mr Bouba?

 

[Bouba]

honest? specs on? (right specs on I mean, not shades!)
if so fine by me

mind still have refrained from mentioning rpm of angle grinder as well as pad/flapdisk/whatever you used.
No mention of grit either, don't you think that's suspicious mr Bouba?

I haven’t forgotten, but I had a little set back today, so I will do it honest?

 

[Hurricane]

@Bouba
I don't think you are far off.
What are you using to polish the prop?
Firstly, I acid wash to remove any barnacles.
Then I use a 4" angle grinder with felt pads.
Something like this - 10PCS 100mm 4 Inch Wool Buffing Angle Grinder Wheel Felt Polishing Disc Pad Kit | eBay
I think the ones that I use are slightly different.
Then , I use a polish - one of these.
500g POLISHING COMPOUND Hard Soft Metals Steel Coarse Fine BUFFING Bar Block | eBay
Actually, I have two angle grinders on the go - one to "wax on" - one to "wax off"
After a bit of time and patience, you can get a really nice shine.
I don't put anything on the props - after polishing, just pressure washing and acid washes.

 

[penfold]

What is this acid wash you refer to?

 

[Hurricane]

What is this acid wash you refer to?

In Spain we buy a household product called "Agua Fuerte" (translates to Strong Water)
In Spain, we buy it in the local supermarkets.
This is the stuff:-


I use a paint brush and a pot with this acid.
I dunk the paint brush into the Agua Fuerte and then rub the props with the brush.
The object is to keep the acid on the surface of the prop changing.
I keep dunking and painting the acid using a circular motion.
It is "kind of" like having a small angle grinder - as you rub in a circular motion, the barnacles dissolve.
Two of us can clean both our props, shafts, rudders and trim tabs in the time it takes for our boatyard staff to pressure wash the rest of the hull.
Usually around an hour and we are done.

 

[Bouba]

For Vas




And my Bosch cordless angle grinder does 11,000 rpm

 

[Bouba]

You can see where my polishing with the disc meets just an acid wash, while shinier, there is no difference to the surface, both areas are smooth and the same level