View Full Version : Keelbolts

Sailmaker Jim
12-20-2003, 02:39 PM
We need information on keelbolts?We have a 1964 Mariner 35 all wood ketch.We had her surveyed 3 years ago and 2 surveyors said the keelbolts were good but we worry.Can keelbolts be sistered and how?Has anyone heard of a keel falling off a mariner?

12-20-2003, 03:45 PM
No, keelbolts cannot be sistered, they must be replaced. Yes, keel do occasionally fall off due to bolt failure. Simon LeBon's (of rock group Duran Duran) boat "Drum" suffered a massive keelbolt failure resulting in a capsize. Fortunately all aboard were rescued, I believe.

Bob Cleek
12-20-2003, 04:34 PM
YES, keelbolts CAN be "sistered." You simply put more of them in and leave the old ones be. On an iron keel, this is probably a more daunting task than anyone would want to tackle. Replacement of existing bolts would be much less arduous a task.

YES, keels have been known to fall off, but the circumstance is extremely rare, which is why it gets notice when it occurs. Most all keel bolt scantlings are overengineered so that the last thing that is going to go are the keelbolts. No question, keelbolts sometimes do deteriorate, but generally, they are not a major concern.

NOW, if TWO surveyors told you the bolts were fine only three years ago, not to worry. Don't you trust the experts you PAID, or do you think some know-it-all in here is going to give you better advice for free? LOL Under the circumstances, a recently surveyed 1960's built boat, I can't imagine worrying about keel bolts, unless, of course, you've wired them to a grounded 120VAC line and let them sit for a year or two! If you find this "worry" detracting from your enjoyment of the sport, perhaps you might consider taking up tiddlywinks instead.

Enjoy your boat. Take it easy.

12-20-2003, 05:28 PM
Ahh, Mr. Cleek, you have shone a bright light upon one of my dark prejudices! ;) I do admit that you can sister a keelbolt in some circumstances, but IMHO, most times the space for an additional bolt or two through the original load-bearing floor is unavailable, and when there is room, I don't like to see so much of the "meat" of the floor being drilled away (don't laugh - I've seen this done!). The alternative exists to place the new keelbolts in adjacent floors to the original locations, but one must look at the supporting structure carefully as sometimes the non-bearing floors and adjacent framing are of smaller scantlings. It is also my opinion that if you are concerned about the condition of your keelbolts (heedless of what surveyors say, apparently), you should be concerned about the structure supporting it, and the easiest - not the cheapest - way to check is to haul the boat, draw the old bolts, drop the keel, clean, inspect, and reinstall the keel with new bedding, bolts, & necessary repairs. Of course, one wouldn't go to such lengths unless one has reasonable indications that there is something wrong to begin with.

Horses for courses, of course.

Andrew Craig-Bennett
12-20-2003, 07:36 PM
Well, Bob and I will disagree on this one.

Boat was built in '64 and the keelbolts were last replaced....when?

You don't know?

Did the two surveyors three years ago actually pull a sample bolt or did they just rely on X-ray vision?

Keels DO fall off; they fall off quite ordinary boats, like Mariners, and they do so more often than you might imagine.

I've had my boat for 20 years; I have replaced the (iron) keel bolts twice in that time. Bob is right in saying that there is a massive safety factor in keel bolts, but that is not the point!

The point is that if keel bolts are allowed to corrode seriously they become very difficult to drive out, hugely increasing the cost of renewal.

Pull a bolt and set your mind at rest; new bolts are not expensive.

I do not understand the mentality of just waiting until the keel falls off.

Frank E. Price
12-20-2003, 07:52 PM
The schooner Blackfish was lost in the early sixties when her ballast keel fell off. She was built in the late thirties. Her keel bolts were a fraction of the number/scantlings rule of thumb in Chapelle's design book.


Lucky Luke
12-21-2003, 08:22 AM
Yes, you can sister keel bolts, but surely not on every boat. Hereafter schooner Morwenna:

In this boat, the keel (wood)was very wide 1'6", and the keel bolts did not go through the floors. Floors were riveted to the keel. When replacing the original iron floors by S.S. ones, as I would not remove the ballast, and 1 1/2 " bronze bolts were almost disintegrated, I had new keel bolts, going through floors / keel / ballast. They are not there yet on this picture.

[ 12-21-2003, 08:43 AM: Message edited by: Lucky Luke ]

12-22-2003, 02:25 PM
I lost track of every response, but would recomend replacing one and see what you find.

Pick one with good access, and make your self more comfortable knowing what you find.

I recently replaced 3 out of 11, in my 46' Casey yawl. they were iron, they had been replaced in the early 90's (10-12 years ago).
The nuts had corroded as the boat was tied to a bad wharf, with bad extension cords, and bad electrons floating in the bilge water!.

As I expected, the bolts were "as new" once into the wood and iron, but the top 1" was gone. luckily floors are okay, and fasteners checked out okay.

I replaced w/SS as the keel is iron, floors have iron bolts. Yes SS is expensive, but not compared to the labor. Iron is okay, could have threaded myself instead of a machine shop for SS, but, bronze not good w/iron around.

Someone above mentioned "don't wait til they are hard to get out" I agree, mine came out easily, and were rebed in roofing tar, with cotton on both ends, and a big backing plate on keel timber.

Now I know the keel won't fall off, and i have an idea of exactly what it looks like, and the type of workmanship done previously, besides it was a great picture to share with: cutting torch, sledge hammer, big pipes, driving rods, and such tools of destruction all in proximity to lovely delicate mahogany trim, and clean cabin!