Welding 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 cost makes repairing this look like something I really need to pursue harder.

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

 

[kbs2244]

Think about brazing.

 

[Jagmandave]

Since that's not really a structural part of the boat, rather it's to balance the forces on the mast and for ballast, I'd think just about any way you can rejoin it will work.

How did it break in the first place? I know you said it was a poor casting, but did it hit something? How did you recover the part that broke, were you in dry dock?

Does steel plate weigh as much as cast iron?

did it have a tapered shape or a bulb on the bottom? What kind of boat?

 

[ArkTinkerer]

Took it to a friends shop to grind the edge for a bit less drag, was going to sandblast, fill and paint. They moved it with a forklift and it broke when they put it down. I trust them to have been gentle with the forklift. The void at the crack was large relative to the other voids.

Boat is a SouthCoast 24' I think.

It is a bit larger on the ends than the middle. To fab I looked into a flat sheet of steel with .25" plates added on both sides top and bottom. If I recall, metal alone approached $1000. If I can't repair this, I may look at doing my own design. It is a swing keel so I can't really change the outside dimensions much though. Maybe more mass at the bottom and just enough at the top to keep it tight at the pivot and in the box.

I'm looking hard at low temperature brazing. I think its worth gambling $100 of materials to try and get this fixed. Just don't have a good feel for the strength of this repair. Void was scary looking so maybe thats not really that much of a concern!

 

[MoonRise]

Sometimes the keel actually is a structural part of the ship.

The ballast is just there as, well, ballast.

Poor castings are almost always trouble. Trouble to work with, trouble to fix, trouble to get to be 'right', then trouble to fix again when they aren't 'right', etc, etc.

Cast iron can sometimes be welded without preheating it. Sometimes. It usually can be welded better with preheat though. Got a big enough and controllable enough heat source to heat the completely removed and dissassembled keel to 600-800F (sometimes spec'd as 500-1200F) or so? Then weld it with some $$$$ nickle filler? And then put it back into the heat source and let it slow cool down over 12+ hours back to room temperature?

http://www.lincolnelectric.com/en-us/support/welding-how-to/Pages/welding-cast-iron-detail.aspx

So maybe doing a welded steel keel isn't all that far out now after all, is it?

For most purposes, the weight/density of cast iron and steel are close to each other. That doesn't count any possible porosity in poor castings though.

 

[ArkTinkerer]

Heating/cooling is a big part of why I'm interested in some lower temperature brazing material.

This is an older boat. This keel worked for years even with a void in this center section. When it was moved the stress would have been across the flat of the keel so I would expect it to be much weaker there.

I don't usually deal with such large metal parts. Don't have a good feel for cast iron strength of such an object or relative strength compared to a brazed joint. So.. I'm asking!

Is brazing enough? What if I "tinned" the crack with brazing material, cut the front/rear edges, and bolted bar stock tinned with brazing material there. Reflow like one would with silver solder but just on a much larger scale.

Second option would be to grind to open the break, mechanically join as above and do a proper fill with brazing.

 

[Bronson]

Is that keel not encased in fibreglass? My 1976 Catalina 27 had a broken keel from a hard grounding. I didnt want to attempt the repair, as I had a second boat. The new owner was going to keep Me informed, but I havent heard any more from Him. Good luck!

 

[Jagmandave]

Ah...a swing keel, that makes a little difference.....

And that explains why it broke, I'll bet they were carrying it flat and it's designed to be vertical - that and the voids of course.

Don't have any great ideas, but if you could figure out a way to join the halves mechaincally (Ie nuts, bolts and straps and such) then JB weld over it I'll bet it will hold.

 

[NASTYZEN]

A picture would help a lot.

 

[ArkTinkerer]

Don't have a photo. You can see the keel shape here:
http://www.permasite.com/SouthCoast/sc22flr3.jpg
Yeah the boat may only be a 22 or 23. Don't have a spec plate for it but it looks like the drawing. Break is about 1/3 of the way down. Keel was not fiberglassed but that would not be a bad idea after repair or even if I build a new metal one.

 

[BWS]

Don't know chit about keels.Have done enough CI welding/machining to last me for awhile...its usually a PIA and dirty.But it is doable.....patience,probably the biggest asset after deciding on which process.

BUT...would be tempted to fab up a new "gauge" metal Keel....and fill it with concrete.Even if it had to be a bit bigger to get the weight.Like a big azz Pita bread samwhich.BW

 

[ArkTinkerer]

"Bigger" is limited in a swing keel. Has to rotate up into a box inside the boat for trailering. Cant get much bigger without cutting up the hull to enlarge the box...

 

[NASTYZEN]

Brazing with Oxy- Ace is one alternative. Preheat with a rose bud or cutting torch. Then braze with a coated rod. First champher edges and clean of scale, paint ,whatever, back 1/2 or so from edge.

Arc welding is another. Prepare the same way and lay in Nickel based welds.
You must peen the weld area with a ball peen hammer afterwards however to take away the brittleness. Be prepared to pay anywhere from 4 to 6 bucks per electrode.

This may help.http://www.garagejournal.com/forum/showthread.php?t=120122

Good luck!

 

[Lotek]

Given the downside if the weld fails under way, I would look around for a doner first, maybe a Macgregor/Venture, the V222 keel looks similar and a whole boat can be found in your budget range. Glassing the keel may cause more problems than it solves, the early Ventures were built that way and when water got inside it would swell up and jam in the trunk.

 

[MoonRise]

As I mentioned, poor quality castings are always trouble.

And that keel is at least 'semi' structural to me. Not structural as in hull integrity, but structural as in If/when it fails under-way, you are likely going over.

Although brazing can be as strong or stronger than some ferrous materials (cast iron and plain low carbon steel) and is often times 'plenty good', on a large poor-quality cast iron piece I think you will have 'issues' getting a good brazed joint done without some general preheat overall and then some BIG torch(es) to get the joint area hot enough to flow the brazing material. Although "brazing" is a lower temperature process (generally, we won't get into aluminum brazing and such) than ferrous welding, it is still pretty darn hot. Hot as in ~1200-1600F for 'common' brazing fillers.

Or you may be able to do a mechanical type of repair (Lock-n-Stitch is a 'big' company there, they also have some info on welding and brazing of cast iron)

http://www.locknstitch.com/CastIronWelding.htm

Also not some info from them on repairing cast iron, including brazing and welding and mechanical stitching

http://fulltorque.com/pdf/GMRC white paper.pdf

More than one way to fix it, and also more than one way to ****** things up even more. Duct tape ain't gonna work there!

YMMV.

Please post follow up info/pics about this repair endeavor. It sure sounds interesting and just a little bit out of the ordinary.

 

[Buckgnarly]

As I mentioned, poor quality castings are always trouble.

And that keel is at least 'semi' structural to me. Not structural as in hull integrity, but structural as in If/when it fails under-way, you are likely going over.

Although brazing can be as strong or stronger than some ferrous materials (cast iron and plain low carbon steel) and is often times 'plenty good', on a large poor-quality cast iron piece I think you will have 'issues' getting a good brazed joint done without some general preheat overall and then some BIG torch(es) to get the joint area hot enough to flow the brazing material. Although "brazing" is a lower temperature process (generally, we won't get into aluminum brazing and such) than ferrous welding, it is still pretty darn hot. Hot as in ~1200-1600F for 'common' brazing fillers.

Or you may be able to do a mechanical type of repair (Lock-n-Stitch is a 'big' company there, they also have some info on welding and brazing of cast iron)

http://www.locknstitch.com/CastIronWelding.htm

Also not some info from them on repairing cast iron, including brazing and welding and mechanical stitching

http://fulltorque.com/pdf/GMRC white paper.pdf

More than one way to fix it, and also more than one way to ****** things up even more. Dcut tape ain't gonna work there!

YMMV.

Please post follow up info/pics about this repair endeavor. It sure sounds interesting and just a little bit out of the ordinary.

That metal stitching is interesting, never heard of that before!

 

[Jagmandave]

Metal stitching is fine for cracks, but I don't see how it would work for rejoining two broken pieces....

I think contacting some boat forums would be a good move, maybe you can find a replacement or a place that has experience fixing these, or even casting a new one that's better made.

Now that I saw the drawing, maybe steel plate would work after all, it would sure be easier to weld. I just thought the cast iron was heavier, and weight matters in a keel.

 

[Buckgnarly]

Metal stitching is fine for cracks, but I don't see how it would work for rejoining two broken pieces....

I think contacting some boat forums would be a good move, maybe you can find a replacement or a place that has experience fixing these, or even casting a new one that's better made.

Now that I saw the drawing, maybe steel plate would work after all, it would sure be easier to weld. I just thought the cast iron was heavier, and weight matters in a keel.

Not so...

http://www.locknstitch.com/Repair pdf files/Custom truck with cracked 5.9 block.pdf

http://www.locknstitch.com/Repair pdf files/Ingersol Rand compressor cylinder.pdf

 

[Steve from Socal]

If you don't think it will weld perhaps a mechanical fix. Several steel dowels glued into both pieces and the crack glued as well. This would be using devcon AKA JB weld as the glue and the pins to add more grip and positive location of the two parts.

Steve

 

[gt40mkii]

An option worth at least investigating is having a shop experineced with cast iron welding look it over and give you a quote.

Around here, we have several shops that specialize in rebuilding cylinder heads that are used on stationary Diesel engines ou in the oil fields (imagine a straight-six engine who's head is about 8 FEET long and you'll get the idea...)

These guys heat the entire head to cherry-red, weld up the cracks between the valve seats with a cast-iron rod and borax flux, and then put the head back in the oven to slowly cool over a few days. Then they bring the machine shop over (they try not to move the heads around all that much,) and machine them.

If anyone could weld up your keel, these guys can.

 

[sharkytm]

How about trying to find a donor boat? I can't imagine that that boat is a one-of-a-kind (it was a kit anyhow), and I'll be someone has one rotting in the backyard.

 

[ArkTinkerer]

This is a swing keel so the whole thing hangs by a pivot point on a narrow end.

Center of Arkansas is not a place with lots of donor sailboats let alone a specific type from about 30+ years ago!

Gonna try welding a couple braces to the front/back edges maybe a side strap or two (lots of short welds to keep temp down) and then low temp braze the center. We'll see how it goes. Success or failure I'll try and get some pics and post the results. If I fail, then its time to pry open the wallet and buy some materials. Thanks for all the input!

ArkTinkerer

 

[Brutl67]

Check out the Royal 44-30 MIG wire from www.crownalloys.com, i believe its still featured on the front of their page. They are claiming easy welding on difficult iron projects. I'm actually waiting on some of this wire to show up as I'm doing a Ford 8.8 Rear End Hybrid for my 98 Camaro and the Center section is Nodular Iron, while some bracketry is Steel.