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Keel Bolts and General Topics on Keel - Swan 44 Keel Crack
28 February 2010 - 13:15
#1
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David Fuller
Join Date: 14 May 2008
Posts: 5

Swan 44 Keel Crack
Greetings

I've just lifted my 1975 Swan 44 to be greeted by horizontal foreward and aft fine cracks about 15 cms long on the keel where it's married to the hull. Now I've searched the forum for 'keel cracks' in the hope this might be a common problem, but sadly I've seen no mention of this issue being raised before. I can appreciate the fixing of the keel to the hull is down to the keel bolts, but are these cracks I see normal as a result of flexing, or do they suggest something more sinister?
28 February 2010 - 15:31
#2
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CLA7003
Join Date: 16 May 2009
Posts: 252

If you are talking about the line that appears at the forward area of the keel/hull joint, also called 'shark's mouth' - my Swan manual says right in there not to worry about it (as long as it doesn't open up to a significant gap, just a line more or less).

The previous owner of my boat exposed the keel bolts, tightened them (or tried to, they would not go any tighter at proper torques) and then reglassed it all over - all evidently for naught, but I am glad he did that check so I don't have to.

Do you have any pictures?

Best Regards,

Geoff Corazon 411 #41
28 February 2010 - 22:46
#3
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john bailey
Join Date: 01 February 2007
Posts: 234

David don't worry seems to be normal. I used to get quite vexed every winter when we lifted and sat her down. The crack appeared after a few weeks and we filled and repeated the process for many years.

Recently I took of the cover, filled and faired then put some mastic in the gap. It looks and works a treat now.

 
28 February 2010 - 22:56
#4
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matteosalamon
Join Date: 29 January 2007
Posts: 1019

Dear David

just for my records, is your boat hull # 065?

Many thanks, and Fair Winds!

Matteo (38/067 Only You)
01 March 2010 - 19:23
#5
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David Fuller
Join Date: 14 May 2008
Posts: 5

Dear Geoff, John and Matteo.

Many, many thanks for your replies - I was having a bit of a crisis there for a moment. Great to hear it's in the manual and love the reference to shark's mouth, which I've used liberally since.

Here's a couple of pics of the damage. The Hairline cracks look slightly more severe than they are due to the scale. I hope they don't change your opinion.

I'll follow your advice and refill, hoping for the best.

Matteo, my hull is indeed 65. She was formaly Kratos in Rimini, but has since been re-named Solo and is now in Lymington UK.

Thanks again
01 March 2010 - 19:25
#6
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David Fuller
Join Date: 14 May 2008
Posts: 5

Dear Geoff, John and Matteo.

Many, many thanks for your replies - I was having a bit of a crisis there for a moment. Great to hear it's in the manual and love the reference to shark's mouth, which I've used liberally since.

Here's a couple of pics of the damage. The Hairline cracks look slightly more severe than they are due to the scale. I hope they don't change your opinion.

I'll follow your advice and refill, hoping for the best.

Matteo, my hull is indeed 65. She used to be called Kratos in Rimini, but has since been re-named Solo and is now in Lymington UK. Keep up the great work

Thanks again
01 March 2010 - 21:24
#7
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matteosalamon
Join Date: 29 January 2007
Posts: 1019

Dear David,

I endorse what has already been told by John and Geoff, that's no more than a minor cosmetic problem, anyway, are you able to see if there is any water coming inside from the keel (really unlikely...).

Fair winds!

Matteo (38/067 Only You)

p.s. you have a private message...
02 March 2010 - 01:44
#8
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CLA7003
Join Date: 16 May 2009
Posts: 252

David

I still think there's probably no need to worry - I would however point out the difference between what I observe in your latest pics, vs what I have seen on my boat and other previous boats - that being the line of the crack. On my boat, it is horizontal (parallel to the ground) - if you send me your email address I can send a picture (it's pdf and wont show if I upload with this reply). I am assuming that your boat was designed with a different joint geometry and the crack in your case still follows the joint.

The only difference between your pics and what I have seen is your pics seem to show the crack at an angle to the ground, with the front of the keel angled up as you work aft, and the aft angled up as you work forward. If you think about it, it makes a wedge design that should be tighter as you torque up the keel, but in the end, the same interface problems will show the joint. So, what does that all mean? I would (if I were you) send the pics to S&S office and ask them to confirm that the cracks are on the joint line - then you can really sleep easy.

Best, Geoff
02 March 2010 - 19:29
#9
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the professor
Join Date: 02 January 2008
Posts: 1547

Dear all

The cracks in the pictures occur in the joint between the lead keel and the GRP hull.

The sloping top-of-lead line can be seen for example on the S44 interior drawing presented on this web site.

The boat should not stand on her keel but be hanging in slings in order to evaluate the cracks. This condition corresponds to the boat floating in the water.

It is very important that water can not enter and reach the keel bolts in the cracks, and therefore they must be kept within limits. If the cracks open up with the boat hanging the recommendation is to dry them out, fill them with mastic, and stand the boat on her keel when tightening the bolts.

If the intention is to lay an expansion joint of mastic on the outside over the joint, a rectangular groove abt 10 mm high and 5 mm deep should be made for the mastic, and care taken that the mastic attaches only to the upper and lower edge, but not to the bottom of the groove.

This can be achieved by applying primer to the upper and lower edges, and putting in a strip of plastic covering the bottom of the groove.

Kind regards

Lars
02 March 2010 - 19:56
#10
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david fuller
Join Date: 14 May 2008
Posts: 5

Dear Lars. Very helpful advice, but can I seek clarification? You say the recommendation is to dry the crack out and fill with mastic, but you go on to suggest a method for laying an expansion joint. As this is the first time I've noticed the crack on the shark's mouth, and she's currently out of the water supported by her keel, it would seem to make sense to grind out the crack now and fill with mastic. Would this suffice, or do I need to lay an expansion joint?

Thanks again. David
03 March 2010 - 08:42
#11
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the professor
Join Date: 02 January 2008
Posts: 1547

David

If the cracks are filled now and they open up when the yacht is lifted the filling was a waste of time.

The recommendation is to lift the yacht and fill, and then let it down again, and torque the end bolts.

The bolts are M24, recommended torque 260 Nm, equals 190 lbsft

The bolt tension can be increased a bit by putting mastic in the threads, it works very well as thread grease.

If the cracks open after this treatment an expansion joint is recommended.

Does the yacht have a hydraulic backstay tensioner?

This increases mast compression and the global bending moment in the hull, and tends to induce cracks at the ends of the stiff ballast keel.

Kind regards

Lars
05 March 2010 - 18:08
#12
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David Fuller
Join Date: 14 May 2008
Posts: 5

Dear Lars

Many thanks and sorry for the confusion. No I don't have a hydraulic back stay tensioner, but I'll check the tension regardless.

Thanks again

David
12 March 2010 - 19:40
#13
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CLA7003
Join Date: 16 May 2009
Posts: 252

David don't worry seems to be normal. I used to get quite vexed every winter when we lifted and sat her down. The crack appeared after a few weeks and we filled and repeated the process for many years.

Recently I took of the cover, filled and faired then put some mastic in the gap. It looks and works a treat now.

 

John

You say you 'took off the cover' - was there a covering layer of glass on the joint?

Please advise -

Thanks,

Geoff
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