Keel / Hull join - cause for concern?

[Hamma]

Hi,

With the boat out of the water I took the opportunity today to have a good poke around underneath her. I noticed that the joint between the keel and the hull has opened slightly - or more likely, that the filler material has cracked and fallen out.

The discolouration of the hull suggest to me that there is some water ingress which is gradually leaking back out - thought the freezing weather seems to have put a stop to it. Am I right about that?

I will be getting it looked at next month - but in the meantime - should I be worrying about this? Am I looking at a major repair or is it something more pedestrian?

She's a S/O 35 if it makes any difference.

Thanks for any input.

 

[tom_sail]

My boat has a little crack around the keel join where the sealant is starting to degrade. I have scraped it out thrown some rust fixing liquid in there and at the moment I'm just letting it dry out. I'll run a bead of sealant or Sikaflex around the join.

Are your keel encapsulated? From the photos it looks like they might be? As long as the keel bolts aren't leaking I would dremel the join out clean it up and re-Sikaflex the join.

I'm sure a knowledgable person will be along soon. But that my two pennies worth.

 

[Martin_J]

I think a photo (and close examination) of the forwardmost keel stud/nut inside the boat would be most useful.

Has the plate washer perhaps disintegrated or not been tightened correctly from the initial build...

 

[Bobc]

Looks to me like it just needs scraping out and re-filling.

 

[ghostlymoron]

Is the boat resting on the keel?
I'd check the keel bolts. Withdraw them if possible (one at a time) using two locked nuts, a big socket, plenty of WD40 (other brands are available) and plenty of grunt. If bolts are suspect, replace. If OK, make sure they're really tight.
Don't forget that if the boat is resting on the keel, the joint will be compressed. When it's floating the joint will be stretched.
Rake out the joint, wire brush, apply kurust or similar and run in Sikaflex

 

[30boat]

I'd say your forward keel bolt(s) needs tightening.As suggested it could be that the plate washer has desintegrated but unless it was made of mild steel I think that's unlikely.Since the bolt has been loose for some time it would be a good idea to withdraw it and refit with sealant if in good condition.If not have another one made(or it could be that a length of threaded rod wil do).At the same time retighten the remaining bolts.

 

[rbcoomer]

Sorry for what is perhaps a silly question, but as a boating 'newbie' (and a mobo at that), how do you know that when you re-seal it that there is no water trapped within?

 

[30boat]

Sorry for what is perhaps a silly question, but as a boating 'newbie' (and a mobo at that), how do you know that when you re-seal it that there is no water trapped within?

It usually drains out when the boat is on the hard.

 

[Hamma]

Are your keel encapsulated? From the photos it looks like they might be? As long as the keel bolts aren't leaking I would dremel the join out clean it up and re-Sikaflex the join.

I'm not sure! What's an encapsulated keel bolt. Are they in "sockets" in the keel? If so - yes. There is rarely more than a couple of tea spoons of water in the bilge which I had previously attributed to condensation.

I think a photo (and close examination) of the forwardmost keel stud/nut inside the boat would be most useful.

Has the plate washer perhaps disintegrated or not been tightened correctly from the initial build...

I will photograph and report back next week. I don't think there has been any disintegration but I feel the need to check now!

Is the boat resting on the keel?
I'd check the keel bolts. Withdraw them if possible...

Don't forget that if the boat is resting on the keel, the joint will be compressed. When it's floating the joint will be stretched.
Rake out the joint, wire brush, apply kurust or similar and run in Sikaflex

It's hard to say from memory. I'll go and assess. She is in a metal cradle the keel has a piece of wood under it but I don't know whether she is standing on it or it is hanging from her.

I'd say your forward keel bolt(s) needs tightening.

I will go back, take a look and take some pictures.

Thanks for all the help so far.

 

[sailorman]

[t's hard to say from memory. I'll go and assess. She is in a metal cradle the keel has a piece of wood under it but I don't know whether she is standing on it or it is hanging from her.
]

she will be sitting on the timber to stop movement ( metal on metal will slip) & its kinder for the keel
the boat weight will be on that wood with the cradle legs just supporting the hull

 

[30boat]

The joint won't necessarily be compressed when on the hard .As the hull settles on the keel the weight of the engine could lift the bow and open the forward part of the joint. That happened on my Fulmar and after tightening the forward keel bolt the problem disapeared.

 

[PeterGibbs]

Looks to me like it just needs scraping out and re-filling.

This is the best step one approach. Keels move more than owners would like to imagine (watch when the boat is in the hoist!) and the sealant is there to absorb some of this movement. It should be regarded as a replaceable item, certainly it will not last the life of the boat.

You are unlikely to have problems with water ingress into the hull - it is solid by way of the keel. But a close watch on the keel bolts from the inside is v important. Sustained weeping or heavy rusting (not from water already in the bilge) is a first stage warning.


PWG

 

[SAMYL]

Could I suggest that you do not use Sikaflex as it has a poor record underwater.

Use CT1 instead as it seals well especially underwater and actually sticks to wet surfaces, is flexible and can be painted over.

I used it four years ago now on my bilge keels, with similar probs as your keel, and it is still good, whereas I had to replace Sikaflex every year before.

 

[ghostlymoron]

Could I suggest that you do not use Sikaflex as it has a poor record underwater.

Use CT1 instead as it seals well especially underwater and actually sticks to wet surfaces, is flexible and can be painted over.

I used it four years ago now on my bilge keels, with similar probs as your keel, and it is still good, whereas I had to replace Sikaflex every year before.

Sikaflex 291i is recommended for sealing above and below waterline (by Sika!) data sheet Although it's expensive and has a poor shelf life once opened, I prefer it to builders products. I always save up my sealing jobs so that I can use a full cartridge in one go. (Not always possible I know). This would be a good subject for a PBO review article. (Sarah please note!)
OTOH CT1 does appear good and can be applied to wet surfaces CT1 datasheet so maybe I'm mis-judging it. (The man on the promotional picture does look more like a builder than a mariner though)

 

[SAMYL]

Sikaflex 291i is recommended for sealing above and below waterline (by Sika!) data sheet Although it's expensive and has a poor shelf life once opened, I prefer it to builders products. I always save up my sealing jobs so that I can use a full cartridge in one go. (Not always possible I know). This would be a good subject for a PBO review article. (Sarah please note!)
OTOH CT1 does appear good and can be applied to wet surfaces CT1 datasheet so maybe I'm mis-judging it. (The man on the promotional picture does look more like a builder than a mariner though)

I understand that Sikaflex was initially developed for glueing sheets of marble together edge-to-edge on the sides of modern buildings to allow slight movement in the stone in different weather conditions so it is a 'builders product' as you put it. It doesn't matter who uses it as long as it works.

I was advised to use CT1 on my keels purely for its water resistance properties and it turned out to have been excellent advice. It has worked exceptionly well for me whereas my old favorite Sika did not.

 

[Mistroma]

The initial pictures look very similar to the keel on my SO42DS though I didn't have rust streaks.

I noticed the small gap when on the hard at the end of the first season. I showed the dealer closeup pics. and he said that it just needed a little filling and wasn't anything to worry about.

Never grounded or hit anything in my care and no sign of anything unusual in the bilges. Delivery crew might have hit something but doubt it as trip was all in deep water and no sign of any scratches to antifoul anywhere when lifted.

However, being paranoid, I cleaned out the loose sealant at the hull and keel myself. It was only a tiny area and went back to solid sealant. The top edge of the keel isn't a clean 90 degree edge and is quite rounded. So the "crack" was just sealant that hadn't bonded to the keel at the rounded front edge. It was still bonded to the fibreglass on the hull.

I was completely happy that it was a trivial defect and it still looks perfect after more than 2 years.


UPDATE: Managed to find a closeup of the crack I mentioned. It looks as if yours goes a lot further back but could still be the same basic reason.

Probably worth OP cleaning it back to see if it just looks like the same issue. i.e. Front edge of keel is slightly rounded and isn't a perfect match to the hull.

Rust will still need sorting out before applying sealant but i might not turn out to be a big problem.

 

[Hamma]

The initial pictures look very similar to the keel on my SO42DS though I didn't have rust streaks...

...Probably worth OP cleaning it back to see if it just looks like the same issue. i.e. Front edge of keel is slightly rounded and isn't a perfect match to the hull.

Rust will still need sorting out before applying sealant but i might not turn out to be a big problem.

Thanks for posting that picture - they do seem similar. I'm not too worried about her - she's only 6 years old and in otherwise excellent condition. There are no marks on the keel to indicate that she's been aground - though I guess it's possible so I will check all the keel bolts carefully as suggested.

Seems like a stupid question - but is it the keel bolts causing the rust, or some part of the keel, or is it a case of cleaning it out and having a look?

 

[vyv_cox]

Seems like a stupid question - but is it the keel bolts causing the rust, or some part of the keel, or is it a case of cleaning it out and having a look?

In the majority of cases the keel bolts will be stainless steel and the keel will be iron (NB not with Moodys, which have steel bolts) Any rusting you see on the external surface of the boat will be from the keel itself, almost certainly from the paint-free part between itself and the hull. The critical point is whether you see any rust inside the boat, in which case a loosening of bolts or sealant failure is indicated. I once had this situation, the rust only appearing during windward passages in a fresh breeze. The answer then is to rebed the keel.

 

[Hamma]

In the majority of cases the keel bolts will be stainless steel and the keel will be iron...

The critical point is whether you see any rust inside the boat, in which case a loosening of bolts or sealant failure is indicated

I'm going down to take some pictures of the bolts tomorrow - but I am sure there is no water ingress, rusting or any other adverse indication. I'm hopeful this is just either, six year-old sealant letting go, a slight shift in the keel due to the haul-out - or, worst case, that the front keel bold needs tightening.

I will report back - thanks to all contributors. I'm a lot less concerned than I was.

 

[Hamma]

Hi,

She's been inspected (Owen Catchpole) and scraped, and she is fine. It's just a filler issue. I'm doing the update as a thank you to everyone that offered help but also in case someone in future searches on:

Sun Odyssey 35 Keel Hull Joint

Person from the future this is for you - if your cracks look like ours - there's not much to worry about!


Thanks for the advice everyone.