Cast iron keel problem! Urgent help needed...

[timothygrifits]

Hello All,

I really need your advices or suggestions from experts...

Last year in May 2022, I bought a Dufour Gib Sea 33 from 2000 and during the survey, the surveyor just noticed that my boat needs to be sanded till gelcoat and do the antifouling from scratch. (Previous owner did the antifouling by himself and did it very badly...)

Yesterday I took the boat off to do antifouling, and while observing the keel, I saw a crack and with little force the part just came to my hand. (Please see the photos..)

I am now truly worried if this is a big problem or not. For now, the paint company did only one layer antifouling and covered the broken part with epoxy. Asking me to come in October after the summer and fix things properly. I am also attaching the photos of fix...

I am not sure what to do now, according to people in the yard the boat has an electrolysis problem and it resulted in this and advicing me to do a check when the boat is again in the water. And I dont know what to do, my biggest horror is that the keel goes off one day while sailing....

Could you please have a look at the photos and advice what to do! Thanks from now...

I also add photos from the bilge, there are 10 stainless steel screews holding it, 1 from the in the setup 1-4-4-1

 

[Bilgediver]

Can you scrape bits of the cast iron off the section you are holding. If so I suspect your keel has suffered from graphitisation. The keel needs to be checked over to see to what extent it is affected. One of my keels on my Westerly suffered this at the forward lower corner and I just removed the affected material and applied Primocon and antifoul. There has been no further repeat in 30+ years.
Unfortunately in your case the damage is in a critical area . I would remove the keel and check the mounting flange and upper keel areas if your sample is easily damaged uby a chisel or screwdriver..A hammer test will probably produce a dull sound at affected areas.

 

[Daydream believer]

The broken part appears to be the aft part of the keel. When I grounded my Hanse & lost the rudder, I spoke to the supplier Inspiration Marine as I had some minor gel crazing internally. They told me that the trailing edge of the keel had a short section just like yours & in serious hits a few Hanse models had broken the lip off as the keel was flexed back & up. I would suggest that following on from your pictures your boat has grounded at some point.
I was then told that the designer had been consulted about this & it had been determined that the piece was only there as a fairing to the keel & of no structural significance. So if I had found any crack in the keel I should not worry.
Upshot was that there was no crack in the keel & an independant surveyor felt that the gel crazing was because the yard at Inverness had chocked the boat badly & flexed the hull. ( it had forced the floor board joint up .5 inches as the stern was forced down)

Looking at your photo the section is very thin & a good wack from a grounding could flex the hul & push that but upwards & cause that crack & start it off. It has broken at a high stress point of a bolt hole. After all it is only cast iron & probably not very good quality. The bedding looks a bit poor as well

So unless there is further cracks, you need not worry too much. You can check by cleaning off the paint & having a good look.
Just make sure you always wear your life jacket

 

[Tranona]

Certainly looks like the boat has been grounded heavily and that thin bit of the keel casting has cracked. However from your photos no sign of serious interior deformation. Almost certainly nothing to do with electrolysis - the conditions don't exist for that. More likely just a rubbishy bit of casting. suggest first you get a surveyor to look at it. If ot were my boat I would also have the keel blasted back to bare metal and epoxy coated, independent of what the surveyor recommends as a repair for the broken bit of casting. The corrosion on the surface of the keel is good old fashioned rust.

Your internal photos don't show the single stud at the rear but obviously that is no longer securely screwed into the keel. The strap from the mast to the keel is a ground to water in the event of a lightening strike hitting the mast. Very, very rare in northern waters, but builders fit it anyway as they sell boats in parts of the world where strikes are more common. Has no connection with the corrosion on the keel.

 

[timothygrifits]

hello, I have forgot to mention that the broken part is in the aft. Very interesting when looking at the replies because while I bought the boat in last April, I did a survey and we did not see any crack, nothing. And by then I sailed the boat no one else and I have never grounded. Could it be because while i lifted of the boat yesterday, the guys in the lifting area did not put it properly and that thin part is cracked?

 

[michael_w]

I'd get your surveyor back pdq.

 

[Obi]

Cannot help on the structural stuff, there is clearly already some good advice above. What is the photo No 3352 showing?
Is that where the back of the keel meets the hull? I cannot tell from the photos. Is that an anode? If it is an anode, great, if that is your keel splitting in two it is a worry.

As for the electrolysis, again I support Tranona's comment. What would I do about that? Just get new anodes, ensure connections are solid and that the circuit is doing it's job. Probably a couple of hours of my time in total to do that.

Then I would monitor the situation by checking the anodes, possibly even waiting until the next lift out . It looks to me like the anode that has corroded has just done it's job with gusto! Lovely little things.

 

[timothygrifits]

Cannot help on the structural stuff, there is clearly already some good advice above. What is the photo No 3352 showing?
Is that where the back of the keel meets the hull? I cannot tell from the photos. Is that an anode? If it is an anode, great, if that is your keel splitting in two it is a worry.

As for the electrolysis, again I support Tranona's comment. What would I do about that? Just get new anodes, ensure connections are solid and that the circuit is doing it's job. Probably a couple of hours of my time in total to do that.

Then I would monitor the situation by checking the anodes, possibly even waiting until the next lift out . It looks to me like the anode that has corroded has just done it's job with gusto! Lovely little things.

Hi Obi,

Photo 3352 is showing the back of the keel splitting into two. You can see what that part has broke off and came to my hand and photo 3358 shows what is seen after. My anode was totally corroded and I replaced it with a new one...

 

[Tranona]

hello, I have forgot to mention that the broken part is in the aft. Very interesting when looking at the replies because while I bought the boat in last April, I did a survey and we did not see any crack, nothing. And by then I sailed the boat no one else and I have never grounded. Could it be because while i lifted of the boat yesterday, the guys in the lifting area did not put it properly and that thin part is cracked?

The crack in the casting looks very old so the grounding (if any) could have been years ago. It could also have been caused by the boat being dropped at some time in the past. There does not seem to be any deformation of the hull around the aft end of the keel and it could be that the weak link was the weak casting cracking. Such cracks are not uncommon in thin castings with a large stud tapped into them - there are many well known examples in other designs of boats that have those long fairing extensions on the mating flange of the keel to the hull. It is very difficult to cast such shapes in the low grade iron used for keels and impossible to tell from outside what the casting is like inside.

I note in your first photo that there seems to be the remains of an anode on the keel. There is really no need for anodes on a cast iron keel. They do nothing to stop corrosion which is rust - iron and seawater, not galvanic action. They will, however give the appearance of doing something because there will be traces of other metals in the casting that have different potentials which will cause the anode to erode. However without an anode the only thing you might see is some localised pitting where these impurities are near the surface. The best treatment for cast iron keels is to blast them to get rid of all the corrosion and surface impurities then immediately coat with epoxy. Not 100% foolproof but if done properly can be very durable.

Can't really help on how to repair the broken casting. First you need a surveyor to check for any internal structural damage and he may be able to suggest what to do with the keel.

 

[earlybird]

Agree that the problem is definitely not one of electrolysis. The cause may well lie with either a poor casting, physical shock or a combination of both. I also wonder if the original crack could have been caused by forcing the keelbolt into a slightly undersized threaded hole, the surrounding cast iron section is not robust. In any event, a knowledgable assessment is required before the boat is sailed again.

 

[debenriver]

^Yes - not electrolysis. Probably not a recent grounding or poor strap positioning when lifting. Most likely one or more of:

Impurities in the casting or a poor casting
Crack emanating from original hole for keel stud being too close to the end of a very thin section
Keel stud forced in, or screwed too deep originally
Keel stud corrosion
An old grounding or drop

It's likely not very structurally significant, depending a bit on where the next pair of studs are located, but it absolutely should be checked by an expert surveyor. It may be considered necessary to drill and tap an additional stud towards the aft end of the keel if the next studs are too far away.

Provided it's not structurally significant, I would be thinking about removing that stud altogether, filling and glassing over the hole in the hull and simply fairing the back end of the keel with epoxy filler.

Anodes on a cast iron keel don't serve any useful purpose. Grit blast the whole keel and epoxy prime and coat as suggested above #9

George

 

[Obi]

Hi Obi,

Photo 3352 is showing the back of the keel splitting into two.

I am out of my depth and better not comment but leave that to those who know. I can only wish you good luck with getting it fixed and hope it turns out to be nothing expensive. Sorry for not adding any value.

 

[timothygrifits]

Thanks to all, just to update, tomorrow a survery will come and check... I will keep this topic updated with surveyor's advice.

 

[Blueboatman]

I have seen that before on flange keels
Horrid discovery but the internal structure and floorboards look undisturbed , what do I know ?
No leaks, no creaks when sailing ?
you will of course be getting the surveyor back for peace of mind
Maybe see if torque on all the remaining keel bolts is the same
What to do with the broken bit ? What your surveyor recommends and thus what the insurer is unworried by
Horrid, best luck
Edit : cross posting , surveyor coming , great

 

[timothygrifits]

I have seen that before on flange keels
Horrid discovery but the internal structure and floorboards look undisturbed , what do I know ?
No leaks, no creaks when sailing ?
you will of course be getting the surveyor back for peace of mind
Maybe see if torque on all the remaining keel bolts is the same
What to do with the broken bit ? What your surveyor recommends and thus what the insurer is unworried by
Horrid, best luck
Edit : cross posting , surveyor coming , great

Hello Blueboatman,

There is no leak nor crack when sailing... I will ask the surveyor to check if torque on all the remaining keel bolts is the same, good idea...

I will keep this post updated.. Thanks