Suitable metal for replacement keel bolt in cast iron keel?

[sailr69]

I would just use waterproof grease in assembly, pack it full and seal it in. better yet is pack it full of tuf-fil. no corrosion at all. any good steel bolts would be enough if they fit.

[bobconnie]

Go to a machine shop, and have tapers cones made to fit the cone in the casting, slip them over the hex head bolts and you will have a flat spot for the head of the hex head bolts! real simple and you can get all the galve bolts ya need ! Cheap to !! Just an old cheap sailors way of fixen stuff.

[Sandero]

Has anyone heard of a keel dropping off from bolt failure/corrosion?

[Stumble]

The problem you are facing is one that is pretty common. Everyone knows that stainless is a terrible option for keel bolts, but the same can be said for HS steel. Different designers tend to fall on one side of the debate or the other, and there really isn't a single solution that is agreed on by the industry. There are as many experts that use steel as there are that use stainless, and frankly if what you have has lasted this long, I wouldn't be in a hurry to switch.

We have been working with a few designers on titanium keel bolts, but to date I don't know of any that are currently being used except for on some maxi race boats (open 60's, ect...) that have very different requirements than a standard cruising boat. Ideally titanium would be the best option, but until it becomes more common in the industry it is hard to recommend for a end user.

As for switching to hex heads. Unless you are rebuilding the whole area (which it doesn't sound like you need to) making the switch is a terrible idea. The fit between the bolt head and the mating parts is critical in maximizing strength and spreading loads. In addition, the well that the existing bolts are designed to fill would become a perfect place for stagnant water to collect even if the rest of the sump is dry. This is guaranteed to accelerate corrosion problems.

[Stumble]

Originally Posted by defjef

Has anyone heard of a keel dropping off from bolt failure/corrosion?

Yes. I can think of a number of boats that have lost their keels from corrosion in just the last few years.

[sww914]

There's no question that I would buy the black oxide bolts and send them out to be galvanized. Cold galvanizing spray is about like a Band-Aid on a bullet wound. Grease won't stay grease for another 3 years, let alone 23. Stainless won't work, and you could buy titanium bolts for a lot less than the machine shop quoted for the 4 custom made bolts. Sealant around the bolts? It isn't even completely reliable on ports or stanchions, I certainly wouldn't trust in on keel bolts. It's only reliable where it's well sandwiched.
I like to think that I'd go ahead and pull & replace the other 4 bolts too.

[Freerider]

Originally Posted by Stumble

Yes. I can think of a number of boats that have lost their keels from corrosion in just the last few years.

I would love to hear about these examples of failure from corrosion. The more info we can share about this issue, the better.

I've read a bunch on info on this subject and its seems its usually a hard grounding/collision or an extreme race design that is the cause of the failures.

A few member's here on CF have recently dropped their keels for inspection and its turned out the bolts were fine and they just needed a re-bed.

[OrangeCrush]

I can get behind your suggestion to galvanize, Sww. I might as well get the bolts as good as they can be before I put them in again. But would I really want to galvanize over the black oxide finish? I think the place that had zinc plated bolts (Fastenal) also had uncoated Grade-8 steel. Wouldn't that be a better thing to start with rather than galvanize an oxide finish?

Any idea what type of shop will hot galvanize a few bolts for me, and how much it should cost?

[sww914]

Yes, uncoated would be better and it might save you a couple bucks because the platers would need to remove the black oxide first.
When I was still doing Porsche restorations I saw many many fasteners replated in several different finishes. The results were usually better than buying new hardware when it was available.
If you can find somebody having a chain galvanized and you can throw your bolts into his batch it probably won't even cost any more than it would have without yours.
If not, see if you can find some more of your own stuff that needs it. The more you do at once the less it costs per piece.

[OrangeCrush]

I found someone that can galvanize them for $75. This seems fine to me, although he said something to the effect that regular hot dip galvanizing would thicken the threads too much for the existing nut, but that he could use more nickel to make the coating stronger and thinner, and that would be my best bet. Not sure about this... should I insist on 'regular' hot dip galvanizing? What should I be asking for exactly?

Before I completely abandon the idea, what if I just used West Systems epoxy with high density filler to create a taper on the bolts below the hex head? It seems like this would spread the load out properly and fill in the gap to prevent water from pooling up. If it's strong enough to support the washers on top, it should be strong enough to support the bolt heads below, no? I already have the bolts, which are "Ultra-coated" Grade-8 steel, made for marine environments. (see picture) Is there some problem with this approach I'm not thinking of? Maybe this "ultra-coating" is not going to be as good as a simple galvanized steel bolt anyway?

[Cheechako]

Originally Posted by Benz

Have you considered looking for cast iron bolts? They might just exist, and it would keep your metals similar. Or you could find a blacksmith somewhere (they still exist in various nooks and crannies) and have some iron bolts forged to order. I'd want to research possible brittleness in grade 8 bolts; sometimes extreme hardness or tensile strength come at the cost of more brittleness or more content of some corrodable alloy. I know this all sounds expensive, and probably is--boating is always a tightrope walk between affordability and quality. Good luck

Yes I was wondering if Cast iron were available. I wonder if you can get what you need in Monel in small quantity? Here's one place that sells them: Monel 405 Bolts | Buy Alloy Hex Bolt Nuts Studs & Fasteners

300 series SS would be the very last on my list to use... Galvanizing is going to leave the threads all gummed up. You will have to chase the threads and that will expose the raw steel in places. Might be the best plan you can do though. I would suggest coating the threads with Lanocote liberally.

[Ocean Girl]

Originally Posted by defjef

Has anyone heard of a keel dropping off from bolt failure/corrosion?

Keel failures prompt call for oversight

http://www.cruisersforum.com/forums/...two-25006.html

I could go on, and on.

Hope you work out your keel bolt conundrum. Please keep us posted

Erika

[OrangeCrush]

I would rather not experiment with anything like cast-iron since the original galvanized steel bolts did so well for the first 25 years of use.

Does anyone have an opinion on making the conical necks on the bolts myself out of epoxy/filler as I described? Is this a bad idea?

Otherwise, I'm going to get the plain Grade-8 bolts and have them galvanized, and hope for the best. If the threads are scraped bare, at least it will be on the part that is visible in the bilge.

Thanks again for all the help!

[Stumble]

Orange,

Epoxy could work but to get a good seal will take some work. The holes need to be roughed up, filled, then redrilled to get a decent bond. You wouldn't though have to fill the entire old bolt hole, just the neck area.

[Cheechako]

Originally Posted by OrangeCrush

I would rather not experiment with anything like cast-iron since the original galvanized steel bolts did so well for the first 25 years of use.

Does anyone have an opinion on making the conical necks on the bolts myself out of epoxy/filler as I described? Is this a bad idea?

Otherwise, I'm going to get the plain Grade-8 bolts and have them galvanized, and hope for the best. If the threads are scraped bare, at least it will be on the part that is visible in the bilge.

Thanks again for all the help!

Well, there is nothing "plain" about grade 8 bolts! Sounds like you have a good plan.
Isnt it true that higher grade bolts are more prone to corrosion due to the added carbon? Again,...... you can protect those threads long term with Lanolin or Lanocote. It's impervious to water.