Drilling holes in bilge keels for anodes

[tolhurstorganic]

I am posting this on behalf of a friend at our boat yard, hope the forum allows that! His boat is a Moody 29 (approx. 1980) bilge keeler. It is kept in a mud berth and has recently suffered severe corrosion to the bilge keels. He has been advised to attach anodes to each of the keels, simple enough one would think, until trying to drill the keels. It was assumed that they were made of cast iron so easy enough to drill. But no they are of something very much harder than that and no ordinary drill bit will make any impression at all.
Anybody know what type of cast material this would be and offer any advice as to what type of drill would allow holes to be drilled right through?

 

[David2452]

Tell your friend that cast iron is a lot harder than mild steel to drill as it is... well, a lot harder. Good quality bits (preferably cobalt) and some cutting fluid should help greatly.

 

[langstonelayabout]

Although you should be able to get away with HSS, cobalt drills will help (either way, make sure they are sharp) and a suitable cutting fluid to keep the drill cooler.

AND remember to use the correct drilling speed for cast iron. (and of course adjust for your diameter of drill). It'll usually be communicated as a formuls (such as: 1000xS over PIxD for mild steel...)

 

[CoVianna]

Try this:

http://www.ollivier.nl/html/drillspeedchart.htm

 

[Tranona]

Won't make the slightest bit of difference to cast iron keels. They are rusting because - well they are cast iron in water. Keels of that era were often very poor quality and full of muck and imperfections and if not properly protected with a coating will rust.

The only thing to do to stop it (or at least reduce it) is to blast the keels clean coat with epoxy. Even then the chances of sealing it completely are small and it will still need regular attention to deal with any new rust. This is clearly not cheap and you will find many people clean it up the best they can with grinders, wire brushes etc, paint with rust protector such as Fertan and then prime and antifoul.

 

[tolhurstorganic]

Won't make the slightest bit of difference to cast iron keels. They are rusting because - well they are cast iron in water. Keels of that era were often very poor quality and full of muck and imperfections and if not properly protected with a coating will rust.

The only thing to do to stop it (or at least reduce it) is to blast the keels clean coat with epoxy. Even then the chances of sealing it completely are small and it will still need regular attention to deal with any new rust. This is clearly not cheap and you will find many people clean it up the best they can with grinders, wire brushes etc, paint with rust protector such as Fertan and then prime and antifoul.

The corrosion is not like anything I have seen before, huge chunks of material gone from the leading edge over just a short time very little rust present. The material is definitely not any cast iron I have seen before which is easy enough to drill with decent bits. Material looks very dense no grainy porous texture like you get with CI, really hard.

 

[Tranona]

It will be cast iron - just poor quality and what you are seeing is the impurities creating voids. Very common in keels of that era. It is not galvanic corrosion as there are no dissimilar metals so adding zinc will not make any difference. Best you (or owner) can do is have it blasted, fill and fair the voids with epoxy and apply a protective coat.

 

[bert49uk]

Won't make the slightest bit of difference to cast iron keels. They are rusting because - well they are cast iron in water. Keels of that era were often very poor quality and full of muck and imperfections and if not properly protected with a coating will rust.

The only thing to do to stop it (or at least reduce it) is to blast the keels clean coat with epoxy. Even then the chances of sealing it completely are small and it will still need regular attention to deal with any new rust. This is clearly not cheap and you will find many people clean it up the best they can with grinders, wire brushes etc, paint with rust protector such as Fertan and then prime and antifoul.

+1
Friend of mine has the same boat when he got it it had anodes fitted to keels he has since removed, not a bit of difference
Cast iron keels are a maintenance item and require attention every year

 

[Seajet]

Either this was a pretty specific time period when cast iron was so dodgy, or I have been lucky; my 1977 cast iron ballast bulb is good as new - same with the rest of the class.

The galvanised keel plates above do corrode ( and we have spares ), but the cast iron bits seem to last forever.