Sealing keel bolts in epoxy
- Thread starter MightyMike
- Start date
I really don't want to seem argumentative here, but isn't 5200 a flexible adhesive? Would you really want a flexible layer between your keel and the boat? One would think it better to have a hard, solid connection which wouldn't allow any movement at all. I certainly wouldn't count on any glue to hold under the stresses a keel is put under, especially one that flexes.Well, the purpose that I have read is that encapsulating the keel bolts in the bilge prevents bilge water from seeping into the joint between fiberglass and bolt. I have read in at least one of the mags that keel bolts should be protected in the bilge, as it is almost impossible on most boats to keep the bilge dry. I'd guess that the advise on what to do is more varied than for just about any boat component. I've never heard universally that they should be tightened every year, or even periodically. I've also heard that a good bond with 5200 at the keel joint would effectively keep the keel on without need for bolts at all. Honestly, I've heard and read so many different things about keel bolts, that I am effectively paralyzed about doing anything until I see an obvious need to do something. That may come at the wrong time, I realize. I figure my time is gonna come when it's gonna come and there isn't much I can do or worry about it!
I've also read that some keel bolts aren't even SS, which doesn't make any sense at all. I think I have read that Beneteau has particularly troublesome keel bolts. Mine are definitely SS and they must be one fantastic grade of SS because they appear as if they are brand new.
As for encapsulating any bolt and nut in epoxy, especially stainless ones, isn't there a problem that develops when stainless is in an airless environment? Also, getting a good bond between the bilge and the poured epoxy would be almost impossible unless the bilge area was cleaned thoroughly, which would be pretty difficult if the vessel was anything but new. Therefore, I think in time, moisture would seep between the epoxy and the bilge fiberglass, creating much worse problems than exposed keel bolts and nuts.
Cast iron. Or lead. Which ever you have. Expands at a different rate than fiberglass. So hunter and others use to attach keel. And it really holds. Watched at boat yard a 84 Hunter 37 in for rebed. They attached keel to a huge forklift and travel lift pulling up boat. They must have checked for missing nuts 10 times picking 25,000 lb forklift off ground. I think they soaked with acidtone for another week till got apart
Yes, 5200 is a flexible adhesive, but less flexible than 4000, Polysulfide, or silicone. 4000, polysulfide, and silicone are more flexible and less adhesive in that order.
As @Whatfiero1 said, the differential expansion of lead, cast iron, and fiberglass requires the use of an adhesive that can flex. While 5200 is a very strong adhesive and can support the static weight the keel, it alone is insufficient to keep the keel attached to the boat when sailing. See the link to the Cheeki Rafiki story posted earlier.
There are a lot of different opinions out there regarding the "proper" way to attach a keel. There are also lots of opinions about why keels fail. I personally think that crevice corrosion is blamed many times when repetitive stress fatigue or inadequate surface passivization is actually the root cause. Somehow, crevice corrosion got publicity from a few articles that were written a while ago & a lot of people picked up on the phenomenon as something that they could brag about being in-the-know about, so it gained further popularity as a commonly diagnosed cause of failure as reported by people who wished to show others how well informed they were. It does happen sometimes. People are often correct is calling it as a cause, but stainless has several other modes of failure & that is not the one that I have seen most often in post failure inspections of stainless that I have been involved with.
Uncovered stainless bolts often work well.
Different grades of SS next to each other can be a problem waiting to happen.
Galvanized bolts have been used successfully on many boats.
painted alloy bolts have been used successfully on some boats
Many different coatings, resins, sealants & potting compounds have been tried over the years. Results have varied.
Different conditions make different options a better choice. It is possible that embedding bolts in epoxy, sealant, wax, or some other compound, may be an excellent choice in some situations & it may accelerate failure in other situations.
Uncovered stainless bolts often work well.
Different grades of SS next to each other can be a problem waiting to happen.
Galvanized bolts have been used successfully on many boats.
painted alloy bolts have been used successfully on some boats
Many different coatings, resins, sealants & potting compounds have been tried over the years. Results have varied.
Different conditions make different options a better choice. It is possible that embedding bolts in epoxy, sealant, wax, or some other compound, may be an excellent choice in some situations & it may accelerate failure in other situations.
Hello, Roy.
I actually sold the Hunter last fall. I have just replaced it with the Pearson.