Repairing Cast Iron Keel

[ArkTinkerer]

My cast iron keel from a sailboat has broken. It is about 18"x72"x1.5". The break is across the 18" dimension and revealed a void in the casting. I have looked at building up a new keel from steel plate but the materials alone will hit $1000 even if I try and use what I can haul from the scrap metal yard.

I have gas and stick welding equipment. What I have read about welding cast talks about heating and allowing for a slow cool of the material. I can't imagine trying that with such a big mass of metal. There are some lower temperature brazing materials that will work at temps below 600. Anyone have experience with these? I am considering trying some sort of mechanical joining followed by that.

The casting is of very low quality. Lots of small voids. I removed it for other repairs to the boat and was going to fill the voids and repaint it while it was off.

Any suggestions greatly appreciated.

ArkTinkerer

[torker]

I'm thinking that keel is a pretty important thing to have on a boat. Any kind of welding could be a disaster...no? Meaning...you say it is a poor casting...those are very hard to weld with any success.
I think if you did...the first time you hit a rock with your welded keel...you may hear that funny "tink" sound that welds make when they crack.
I've welded lots of cast iron...but I'd be very wary of taking this on.
Surely there has to be some scrap plate around that would be an awful lot cheaper than $1000????
I'd far rather fab up a new one from mild steel than take a chance on it cracking when I needed it most.
Just sayin...
Russ

[J. R. Williams]

Casting

Does it have to be repaired? I thought the part is mainly for ballast . There are some repairs for castings that use a series of drilled holes and soft stainless steel keys that are driven into the holes. The holes are drilled with a template and a chisel is used to remove some material between the holes. I have seen this used on a large diesel engine (approx 1000 hp.) driven pump. It did not leak oil after the repair.

[lalatheman]

Some thoughts on repair/ replacement

18" X 72" = 9 sq ft area X 1.5" thick yeilds roughly 540 Lbs if it is rectangular. First street Recycling in Dayton Oh where I buy most of my steel will sell it at 50 cents a pound.

Would a single piece perhaps torch beveled on the leading edge work ?

Just for fun and to see how it would take bronze how about building a nice big wood fire get half of it good and red and ( having previously ground an area shiny with the disk grinder) , flux it up and just see how it takes bronze rod.
Probably would want a shop vac blowing into a steel pipe available , a chain on it to drag it out when about ready a long handled shovel to make a nice bed of coals away from the main fire etc.

David

[J Tiers]

CI has the benefit of rusting fairly slowly.... steel not so much.

[The Artful Bodger]

Depending on the design the keel on a sail boat can be a pretty important thing. If it drops off the boat can be in real trouble so you probably want to get it right.

My thoughts would be to scout around for a bit more scrap cast iron and have it recast, is there a foundry in your area?

[Weston Bye]

Is the keel part of the structural integrity of the hull, or primarily ballast?
If the latter, you might consider a composite solution. Take a casting of the keel and mold an epoxy keel filled with lead shot, enough to provide equal weight of the iron. Include a bronze or stainless steel runner along the bottom for wear resistance in case of grounding. Don't forget the zincs. Mold in structure for fasteners.

Does all the foregoing hassle makes a welding solution sound attractive?

[ArkTinkerer]

Its a swing keel. I've been watching the scrapyard but no joy on steel near the right size. No foundry's nearby that I know of. Someone suggested covering it with fiberglass. I think I might try that whether I fab a new one or repair this one.

[bob_s]

How about a ferro-concrete replacement?

Basically a whole lot of rebar with vinyl-concrete filler, all dolled up with a really
coating of epoxy ester paint. Try to maintain average density of about 380 lb/ft3.

I've seen ferro-concrete hulled sail boats up to about 15 meters, ketch rigged.

[The Artful Bodger]

I think concrete is much lighter than cast iron?

[Bob Ford]

Fab a new one out of 1/4 - 1/2 plate. Two sides with a hollow center and the top open. In the hollow center pour Epoxy with lead shot for weight. Plates and edge could be Mild or stainless.

Bob

[HWooldridge]

Oy...braze it back together and get back to sailing. Another good method is to lay steel straps across the break then braze or weld (with cast iron specific electrodes).

[derekm]

My cast iron keel from a sailboat has broken. It is about 18"x72"x1.5". The break is across the 18" dimension and revealed a void in the casting. I have looked at building up a new keel from steel plate but the materials alone will hit $1000 even if I try and use what I can haul from the scrap metal yard.

I have gas and stick welding equipment. What I have read about welding cast talks about heating and allowing for a slow cool of the material. I can't imagine trying that with such a big mass of metal. There are some lower temperature brazing materials that will work at temps below 600. Anyone have experience with these? I am considering trying some sort of mechanical joining followed by that.

The casting is of very low quality. Lots of small voids. I removed it for other repairs to the boat and was going to fill the voids and repaint it while it was off.

Any suggestions greatly appreciated.

ArkTinkerer

I 'm assuming the keel joins on to boat along a 72" by 1.5" surface
get a 72" of 1" by 1.5" steel bar profile to match top 1" of joining surface of cast iron
machine 1" off the joining surface of cast iron. drill & CSK 1/2" holes through bar to mating tapped holes in cast iron every 6"
on bottom of the keel cast iron machine recess for a 3/8 by 3/4 steel strap for a much of the length as practible drill ck & tap 3/8" every 6".

This should help in case are there any more voids

[mark61]

Braze it.

Build a fire under it then when it is good and hot braze it then throw a little more wood on the fire. Let fire go out-if you can cover the keel with something to slow the cooling fine it not just drop it right into the ashes and keep it from getting rained on until it cools down.

mark61

[Weston Bye]

Its a swing keel...

Knowing that, I would now be concerned with just welding or brazing, lest the weld fail in deep water and you loose part of your keel. You might want to add strapping in addition to the weld so that if the weld fails you don't loose the broken off piece. The strapping might have to be thin or recessed into the keel so that the keel isn't too wide to fold up into the keel trunk in the hull.