Keel bolts

[Sailfree]

Just wondering - how easy is it to withdraw the keel bolts without dropping the keel?

Thinking whether checking just the first and last keel bolts would be sufficient to check whether we need to investigate further.

Obviously thinking of CR but if the rear nut had been undone as a check would the sealant/GRP interface have held the bolt sufficiently tight for the sheared bolt to be still undetected.

Sorry if it's a silly question but I have no experience in undoing keel bolts.

What torque are they?

 

[Rigger Mortice]

You haven't said what type of boat or keel you've got.

FWIW I removed all the bolts to replace the backing plates of my stub keel (GRP boat) a few years ago. The boat was resting on the keel and I did only one or two bolts (depending on whether it was a one or two hole backing plate) at a time. No problem at all.

The bolts were bloody tight. I needed a four foot tommy bar to undo them. But it's impossible to say what torque you should go for on yours. Maybe the manufacturers have a specification.

It's a job I would prefer to not do on the water. Only because the keel would be hanging and therefore putting tension on the join. But I don't know if it really matters.

However, as you mentioned both bolts and nuts. I'm not sure if you are really talking about studs and nuts. If you are talking about studs then, yes, the sealant could hold a broken stud fairly firmly. Some kind of leverage on it would soon show that up, though it is more likely that trying to undo the nut would simply mean the broken stud and nut would come off together.....unless it is broken a little further down.....The only thing to do is to give it a try.

 

[Billjratt]

Beware of over-tightening the nuts on a modern boat - I've seen one with a broken keel flange due to being over torqued against an uneven hull moulding.
They may be hard to crack open due to age and sealants, but that doesn't mean they were tightened to "creak plus 1/2 turn" originally.
Spanners are the right length for the foot-pounds required when used by an average person.

 

[oldsaltoz]

It's a pretty common practice to remove and then refit one bolt at a time in the water.

However I would not advise this on a boat with than eight keel bolts.

Good luck and fair winds.

 

[jwilson]

Unless you have knowledge or suspicion of grounding damage or obvious signs of corrosion (rust streaks outside keel/hull joint), on a typical GRP boat it is sometimes a bad idea to mess about with keel bolts. It's the sort of job that can either be easy and simple, or really difficult. It is certainly not anything I'd do unless ashore in a boatyard, so that if you do have problems you have the backup of yard facilities.

I'd also want to know in advance whether the keelbolts were studs threaded into the keel casting a la http://www.pbase.com/mainecruising/image/148059726.jpg or whether there were nuts in filled cutouts in the keel eg http://www.angelfire.com/tn/santana525/cal92/keel_01.jpg

 

[Tranona]

Your boat will almost certainly have studs screwed into the keel and lock nuts on top. No reason at all to ever touch them unless you suspect a grounding or other damage. Such damage is obvious from external observation of movement in the keel/hull joint or damage to the surrounding area of the hull. Replacing them is virtually impossible without removing the keel as no way can you unscrew the studs from inside the boat. Just check the joint and inspect the nuts and surrounding area internally.

The big bogy about inspecting keel bolts is a hangover from wooden boat days when keel bolts went through the ballast keel and the flexible wood structure. Water could get in the joint or up the bolt pockets and it was common to find corrosion, often waisting around the interface between the wood and metal keel, particularly if it was mild steel bolts through oak. I have a set somewhere in garage from my wooden boat that perfectly illustrates what happens. An erstwhile colleague gained his PhD from his study on the phenomenon (many years ago - like me long retired).

 

[Iliade]

If you are worried about them get some 'repo man' to x-ray them on the drying grid. It could be a lot cheaper than snapping a stud off in the keel while afloat.

(I'm assuming that the elves still allow such behaviour?)

 

[Fergus]

Don't do anything unless the boat is on the hard with the keel supported!

 

[Jamesuk]

I can see the keel bolts but that's about it.

 

[Tranona]

Waste (sorry for the pun) of time with studs in a cast keel. Is a reasonable approach for wooden boats or if through bolts are fitted as I described above. If a stud has sheared it will be obvious, as will any significant corrosion by inspection of the keel hull joint, the internal nut and the structure surrounding the keel.

 

[Slowtack]

I have removed and reinserted keelbolts on three boats now. 24ft, 27ft, 33ft - all grp with cast iron keels ranging from early 1970s to mid 1980s in build date. The only problem I have found is corrosion of the washer plates and some of the nuts in the two younger boats. For that reason I would do this in any boat more than 10 years of age or earlier if visual inspection suggested it. If the nuts and washers are covered with grp or filler type material corrosion may be present but not obvious until the covering material is removed.

 

[30boat]

I must disagree a bit here.I found on my two boats,one after the other,that the nuts weren't all that tight.I believe it's not impossible for them to loosen up a little over time.On my Fulmar I made a gizmo for removing a keelbolt because I was a bit paranoid.When I took it out it looked as if it had been machined that very morning,There was even a bit of engine oil at the bottom of the hole.It had been put there at the factory 30 years before.Needless to say I just nipped upt the rest of the nuts and that was all.

 

[Rigger Mortice]

Waste (sorry for the pun) of time with studs in a cast keel. Is a reasonable approach for wooden boats or if through bolts are fitted as I described above. If a stud has sheared it will be obvious, as will any significant corrosion by inspection of the keel hull joint, the internal nut and the structure surrounding the keel.

I'm not sure that it will necessarily be obvious. On my boat there is plenty of Sikaflex between the hull and keel, and also plenty on both sides of the backing plate. I suspect that even if there were a breakage it would still be held firmly in place even though it wasn't doing anything.

I'm not even sure that a single broken stud would always be revealed by corrosion from the joint and, in any event, the join can often only be seen at the end of the season when the boat is hauled out.

 

[Sailfree]

I posed the question as lots of conflicting statements being made.

Imagine you have bought a boat with a bolted keel like CR. You don' know whether it's been grounded or hit anything.

Let's say like CR the rear bolt has sheared. What winter maintenance/survey will reveal it?

From many other posts from what appear to be knowledgable people X Ray or Ultrasound is not a tried and proven method with cast iron keels.

I was wondering whether undoing a nut (if it had been CR) the top part of the stud would have turned with the nut revealing the sheared stud?

Just trying to sort my ideas of what a prudent owner of one of these modern boats with unknown history could easily do.

Looking for constructive answers not buy boat X instead. Let's face it 1000's of us own these modern boats.

In my particular case it's a Jeanneau and I think the nuts are easily accessible.

 

[Rigger Mortice]

If a stud has sheared then undoing, or attempting to undo, the nut mat well reveal the problem. If the stud is merely cracked then it's anyones guess.

 

[jwilson]

The most obvious signs of grounding are usually not in the keelbolts, but in the GRP structure at the aft end of the keel, both inside and outside. Most accidental groundings happen when going forwards, and that pushes the bottom of the keel aft and the top rear edge of the keel upwards into the hull. There is also some tension downwards on the front edge of the keel, though often the most obvious signs of damage at are at the aft end.

Not uncommon to see cracks in the GRP floor web or grid structure around the aft end of the keel: some boats such as Westerly Fulmars are notorious for it, the original build being slightly weak at this point - many Fulmars have had to have this area reinforced even without suffering accidental groundings.

Older GRP boats usually had timber or GRP webs laminated in to the hull, newer ones often have egg-box inner mouldings, that make looking for these cracks inside much more difficult, and make it more important to look externally. This is (inter alia) the sort of thing surveyors particularly look for, especially if keels are deep and iron. Lead keels are nice shock-absorbers, cushioning the worst of impacts as the softer lead dents.

Lead keels usually also mean definitely a more expensive boat construction in the first place, and hopefully stronger hulls.

 

[Tranona]

I'm not sure that it will necessarily be obvious. On my boat there is plenty of Sikaflex between the hull and keel, and also plenty on both sides of the backing plate. I suspect that even if there were a breakage it would still be held firmly in place even though it wasn't doing anything.

I'm not even sure that a single broken stud would always be revealed by corrosion from the joint and, in any event, the join can often only be seen at the end of the season when the boat is hauled out.

If it is a grounding severe enough to shear a stud - typically 20-30mm in diameter there will be visible damage somewhere in the keel area - have a look at Snook's photos on other threads. If you read the reports on keel failures, rarely is shearing studs an issue (although sometimes it is ) but the supporting structure failing. Leaking hull keel joint is common but not always visible, and not always the result of damage to the bolts - just an indicator that further investigation is required.

You are right though that damage often goes undetected until the boat is out of the water. In rocky parts of the Med charter companies often dive to inspect the keel after every charter. When I had my charter boat we regularly carried out underwater inspections using a camera.

 

[TimBennet]

Let's say like CR the rear bolt has sheared.

Let's start by saying there is no evidence that the aft bolt on CR was sheered prior to the failure that caused the keel loss.

"Rusty' staining in the proximity of stainless steel is no real indicator of problems.
Similarly, a lack of rust staining in the proximity of stainless doesn't mean things are okay either.

Whilst the area of the aft keel bolt on the high res photo looks discoloured, the area is also covered with a slight depth of seawater, and what's more, turbulent seawater with ripples on it. The optical distortion makes it impossible (in my eyes) to see if there is the fractured remains of a keel bolt in the aft hole, or whether we're seeing just the dark, discoloured keel bolt hole through the hull.

Much has been said about the rear keel bolt being failed in a prior 'grounding'. Well, the classic outcome of a grounding where the bottom of the keel strikes something solid whilst going forward is to see upwards, compression damage to the hull area around the aft end of the keel/hull junction. Usually there is displacement of the reinforcing structure and possibly furniture on the inside of the boat. The aft keel bolt itself would be subject to no additional load and I have never seen a grounding incident where the sheering of the aft bolt has been the only damage.

Again if there had been a classic 'grounding', you would expect any damage (even unnoticed) to have resulted in at least the weakening of the laminate around the hull at the aft end of the keel. This would then be the likely area for the hull to subsequently fail, but again in the photos we see quite the opposite - that area of the hull is intact.

We have precious few 'facts' to go on with this incident but any 'theories' about what might have happen need to be at least commensurate with what little we do know.

So if I had one of these boats with an unknown history, the first thing I would do is take a good look. If I had the slightest suspicion about anything, I would strip the gel coat from the outside of the hull around the keel joint (and the flowcoat from the bilge) and use a powerful light on the inside at night to try and 'see' through the laminate from the outside. Any suspicious looking 'features' might require surgery for a definitive answer.

In addition, if I suspected there had been 'movement' in the hull/keel joint and sea water penetration, I would be concerned about crevice corrosion of the stainless keel bolts, especially if the boat had spent time in the Med or tropics. Dropping the keel might then be warranted.

Once the bolts and hull checked out, I would replace the gelcoat with a heavy layer of biax/epoxy on the outside and similar on the inside well lapped up onto the grid frames. The thickness would depend on the 'spare' thread length on the keel bolts. I would then well round the corners and bottom edges of the flat plate backing strips, use use plenty of 3Ms 5200, bolt it back together and go sailing.

 

[30boat]

Let's start by saying there is no evidence that the aft bolt on CR was sheered prior to the failure that caused the keel loss.

"Rusty' staining in the proximity of stainless steel is no real indicator of problems.
Similarly, a lack of rust staining in the proximity of stainless doesn't mean things are okay either.

Whilst the area of the aft keel bolt on the high res photo looks discoloured, the area is also covered with a slight depth of seawater, and what's more, turbulent seawater with ripples on it. The optical distortion makes it impossible (in my eyes) to see if there is the fractured remains of a keel bolt in the aft hole, or whether we're seeing just the dark, discoloured keel bolt hole through the hull.

Much has been said about the rear keel bolt being failed in a prior 'grounding'. Well, the classic outcome of a grounding where the bottom of the keel strikes something solid whilst going forward is to see upwards, compression damage to the hull area around the aft end of the keel/hull junction. Usually there is displacement of the reinforcing structure and possibly furniture on the inside of the boat. The aft keel bolt itself would be subject to no additional load and I have never seen a grounding incident where the sheering of the aft bolt has been the only damage.

Again if there had been a classic 'grounding', you would expect any damage (even unnoticed) to have resulted in at least the weakening of the laminate around the hull at the aft end of the keel. This would then be the likely area for the hull to subsequently fail, but again in the photos we see quite the opposite - that area of the hull is intact.

We have precious few 'facts' to go on with this incident but any 'theories' about what might have happen need to be at least commensurate with what little we do know.

So if I had one of these boats with an unknown history, the first thing I would do is take a good look. If I had the slightest suspicion about anything, I would strip the gel coat from the outside of the hull around the keel joint (and the flowcoat from the bilge) and use a powerful light on the inside at night to try and 'see' through the laminate from the outside. Any suspicious looking 'features' might require surgery for a definitive answer.

In addition, if I suspected there had been 'movement' in the hull/keel joint and sea water penetration, I would be concerned about crevice corrosion of the stainless keel bolts, especially if the boat had spent time in the Med or tropics. Dropping the keel might then be warranted.

Once the bolts and hull checked out, I would replace the gelcoat with a heavy layer of biax/epoxy on the outside and similar on the inside well lapped up onto the grid frames. The thickness would depend on the 'spare' thread length on the keel bolts. I would then well round the corners and bottom edges of the flat plate backing strips, use use plenty of 3Ms 5200, bolt it back together and go sailing.

Pretty much what I would do.

 

[jwilson]

Pretty much what I would do.

The problem with this is that to see the inside of the actual hull, on many modern boats with an egg-box inner moulding, you have to cut away a fair bit of interior moulding and with that some of the overall hull stiffness and strength. And you are quite possibly doing substantial destructive work to find nothing wrong at all.

All ultimately fixable though, and perfectly possible to put back significantly more strength than when the boat was brand new, but the job will be obvious and if you ever come to sell the boat many buyers will run a mile if they see a cutaway section of the interior moulding round the keel area.

Personally I prefer the old-fashioned web stringers and floors, but not many production boats have that any more, as inner mouldings are the cheap way to build. My present 2005 Jeanneau 35 is one of the last Jeanneau built before switching to inner mouldings: Beneteau went to inner mouldings about ten years earlier.