Cast keel treatment

pete

pete

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Hi

Has anyone removed cast iron bolt on keels on a twin keeler, taken them to be sand blasted and galvanized ? instead of the usual treatments.
Just a thought.

Pete
 
It is my understanding that the nobility of galvanised bolts would be different from that of cast iron. water can get into the cavitys occasionally/rarely but possibly. This causes the bolts to fail. Even different grades of stainless can corrode quickly or at different rates in a lead keel and particular attention should be paid to the combination of keel/bolt.
 
I think the question was about galvanising the keels not the bolts.
I don't know anyone who has had it done but you would need to prevent the galvanising from getting in the bolt threads and use steel bolts to refix it. Stainless steel bolts are not a good idea as they can corrode and fail even when sealed in, without you seeing them. Steel bolts will only corrode if water or air get to them and this rarely happens inside the thread.
Interesting idea - I'm having mine sand-blasted and then I shall immediately treat it with Kurust or Jennolite before priming and anti-fouling. That should last a few years.
Boats would be so much easier to maintain if it wasn't for all this damn water!
 
The usual methods seem to work if done properly... Clean to base metal and apply a decent paint system. I have found Primcon from International does all I want on Westerly keels.

John
 
Whilst on the keel/rust subject ,has anyone any ideas/experience of a thin grp/epoxy encapsulation,hopefully to deal with the problem on a longer term basis?
I wonder wether a good enough bond can be achieved!
I have a cast lifting keel which takes some hammer in the slot aperture when either lift/lowering or if left unfixed at all.
This takes off any conventional coatings in certain areas almost immediately!
 
Galvanising equals dipping in molten zinc. Zinc is the stuff we use as an anode. Surely if you galvanise the keel the coating will simply act as an anode, and be wasted away by electrolytic action? Even if it is painted before antifouling, any scrape in the paint will expose it to rapid localised loss. I think conventional treatments of rust removal and painting with suitable waterproof primer and antifouling are probably better and cheaper.
 
G'day Michael (jmp)

Yes epoxy will bond very well, however you need to go a little further to fix your problem of:

<<'This takes off any conventional coatings in certain areas almost immediately!>>

You need to grind this problem area back about 10 mm and fill it with a mixture of epoxy and Micro-Fibres to act as a wear plate, or better still fix a stainless steel rubbing plate and back with Micro-Fibres.

But first, you must ensure the keel is very dry, Cast Iron is porous and will hold some moisture, it will also flash rust, this means any coating must be added as soon as the blasting is completed, now I don't mean wait till the whole thing is done, or even one side, I mean follow the blaster with a long handled roller and coat as he goes. Don't worry about getting a pretty finish, just get it covered and fast, you can sort out any runs or dags later.

Let's know if you need more info, hope this helps.

Avagoodweekend......
 
What about sand blasting or needle gun in an oxygen free enviroment, biuld a tent around the keel/hull, pump in enough nitrogen to displace the oxygen (well most of it) and then treat the keel? Of course you would have to hold you breath for a while. But has it been done?
 
For what it is worth, I made half inch STEEL plate bilge keels for my Macwester Rowan a good few years ago. Had them galvanised at Scottish Galvanisers (excellent firm). I used half inch stainless nuts and bolts. Primed them with red oxide and then antifouled.
I had no problems whatsoever. I inspected several of the bolts after 5 years, and there was no discernable(?) wasting. The boat was hauled each winter and occupied a half tide mooring in the season.
Cheers, Dave
 
[ QUOTE ]
Galvanising equals dipping in molten zinc. Zinc is the stuff we use as an anode. Surely if you galvanise the keel the coating will simply act as an anode, and be wasted away by electrolytic action? Even if it is painted before antifouling, any scrape in the paint will expose it to rapid localised loss. I think conventional treatments of rust removal and painting with suitable waterproof primer and antifouling are probably better and cheaper.

[/ QUOTE ]

That's exactly how galvanising works - by the coating acting as a sacrificial anode. It is, however, a long lasting system and one which protects adjoining bare areas. We have a pre-war galvanised watering can which has lived outside for decades and is still fine. Alright, it doesn't see sea water. You would need to establish whether any local galvanisers could cope with such big, heavy items as keels.
 
I disagree, I do not think galvanising is intended to act as a sacrificial anode at all. I think it is intended to bond to the steel or maybe cast iron beneath, and act as an impervious and non rusting barrier. Many yacht builders use cast iron for their keels, and I have not heard of any who routinely galvanise them. I think that this is precisely because in a seawater environment the galvanising would act as a sacrificial anode. Instead the keels are painted, and a replaceable anode fitted to them. If galvanising keels was really effective, surely some manufacturers would take up the idea?
 
Hi All
Thanks for the replies.
I don`t think the galvanizers would have any trouble with them as they do large boat trailers!
I can`t see them acting as large anodes being two much of a problem as I replace my shaft anode every year and it is only ever half worn and could normally last another season.and even if they did act as anodes there would be a lot of them.
The boat lives on a drying mooring and is only wet around 6 hours a day

Pete
 
Pete you asked about a thin coating of resin and GRP on a keel. Sorry thin coating of fibreglass on anything are a bit of a distaster. The glass tends to peel off with any disturbance underneath (rust or moisture) If you are going to put GRP on naything I reckon it needs to be thick enough to be structirally rigid so it will maintain position and shape regardless of under distubrance. ie at least 4mm. Epoxy alone on the other hand will tend to stick fairly well and only fall off the actual rust or other disturbabce.

As for the idea of removing bilge keels for sandblasting it may be OK but I would always warn against major projects on boats. (And I reckon this might be a major project)
I reckon you would be better off grinding or sandblasting and paint treating the keels as suggested in a manner that is adequate but will get you sailing again ASAP. I have seen boat projects laid up for years due to owner being over fussy and biting off more than he can chew. good luck olewill
 
Hi olewill
Thanks for the reply It wasn`t me who said about encapsulating the keels as I appreciate the problems with that. its just that I prefer to do jobs myself as much as possible I have access to a boat lift The boat is a Hunter 27` The keels are causing me no problems but the bolts are clean and accessable It would be cheaper to take the keels to a sand blaster than for him to come to me.
Every year I Clean off the keels as best as I can but They soon look a mess again although they are coming to no harm (cleaning them in situ is hopeless as the paint/rust is ingrained and then putting on multiple coats of expensive paints such as"Primacon" in marginal conditions outside seems a waste of money)
It is just an idea to have them galvanized as that should last quite a few years but I don`t know what the cost of that would be.

Pete
 
Re: Cast keel treatment (Oldsaltoz & Will)

Hi Brian & Will,
Thanks for your responses! I will think on! there is not much (about 1/4") gap around the keel in the apperture which has thick stainless plates around the slot both inside the keelbox and outside under the bottom, bolted together with the 4" hull thickness between,and no small job to remove.These are the culprits in the abbrasion .I am now thinking of a possible way to line the fixed apperture to make it more friendly! I have struggled with a rusty mess each year in the full depressing knowlege of what to expect when she comes out.The forward and trailing edges (gap about 1") are particularly bad with quite some abbrasion to each side at the max chord points,at the full down and full up points.
You have both been helpful to me in the past on several occasions for which I thank you again.
Regards Michael.
 
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