Cast soft spots

PabloPicasso

PabloPicasso

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I was helping a mate dry out his fin keeler any his cast iron keel seems to have 3 or 4 round soft spots about an inch in diameter. Initially they looked like rust spots but on gentle prodding they were defiantly soft. The rest of the keel seemed sound.

Boats refloated now, and I didn't take any pictures, not that they would have revealed much. Boat is A 32 footer GRP construction from late 70s I think,with cast iron keel that is not encapsulated.

Any ideas on what the soft spots were. One a third of the way up near the front of the keel, another couple in other places one higher up, another lower down?
 
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PabloPicasso said:
I was helping a mate dry out his fin keeler any his cast iron keel seems to have 3 or 4 round soft spots. Initially they looked like rust spots but on gentle prodding they were defiantly soft.

Boats refloated now, and I didn't take any pictures, not that they would have revealed much. Boat is A 32 footer GRP construction from late 70s I think,with cast iron keel that is not encapsulated.

Any ideas on what the soft spots were. One a third of the way up near the front of the keel, another couple in other places one higher up, another lower down?
Click to expand...

were they "slots" for the stud nuts
 
Were these all on the same side of the keel?

I've encountered a few keels which have clearly been cast on their side, and have areas with bubbles on one side. In one case a big patch that could best be described as iron froth, 2+ cm deep. Eventually pin holes in the surface grow to open up the top layer of bubbles. First time we saw this, we noticed that directing a jet washer onto one bubble produced little jets of water several cm away.

We ground away to open up the soft bits, descaled as well as we could with a needle scaling gun, filled, faired and painted with epoxy and it looked good for the next five years, till the boat moved on.

A.
 
Almost certainly casting defects. As suggested many keels are cast on their side as it is easier to make patterns and they use poor quality iron for the castings. They are either bubbles just below the surface or pockets of impurities. Grind them out and fill with epoxy. However recognise that cleaning sufficiently to ensure the epoxy stays in is not easy.

BTW the keel will be attached to the boat with threads cut into the keel and either studs and nuts or bolts through the hull.
 
Tranona said:
Almost certainly casting defects. As suggested many keels are cast on their side as it is easier to make patterns and they use poor quality iron for the castings. They are either bubbles just below the surface or pockets of impurities. Grind them out and fill with epoxy. However recognise that cleaning sufficiently to ensure the epoxy stays in is not easy.

BTW the keel will be attached to the boat with threads cut into the keel and either studs and nuts or bolts through the hull.
Click to expand...

So nothing to lose any sleep over then? It must be some sort of soft sealant rather then epoxy filler. It wasn't coming out anyway and none of us were inclined to go poking it out while awaiting the return tide.
 
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Cast iron is the cheapest and nastiest material used for keels, full of contamination, porous, and when grit blasted to a silver grey will start flash rust in minutes.

I have seen pockets of sand trapped in them and voids you cal almost get your fist in.

So not much doubt that what you saw was just another typical cast iron keel defect.

Nothing get excited about, **it happens.

Good luck and fair winds. :)
 
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