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Keel Bolts and General Topics on Keel - Keel Bolts for a 47. Dear Lars.
27 March 2009 - 07:57
Join Date: 01 February 2007
Posts: 35

Keel Bolts for a 47. Dear Lars.

Dear Lars,


What can you tell me about Keel Bolts on a 47?


What material are they made of?

Why are the Bolds/ Nuts imbedded in glass fibre?

At what tension/ moment are they tightened (Boat on land!)

What is the procedure if they have to be changed?



Looking very much forward to hearing from you.


Many regards



Cygnus Pea # 20.

27 March 2009 - 19:03
Join Date: 02 January 2008
Posts: 1547

Dear Carsten

There are 15 bolts M24, and 3 bolts M30, M means metric and the number is thread diameter in mm.

The bolts and nuts are stainless AISI 316. Be careful not to cause thread galling, this happens fairly easily if forcing the nut onto the bolt with this material.

The standard practice at the time of build was to cover the bolts with GRP. If you remove the GRP the nuts have to be locked in a reliable way.

Recommended torques are: M24 - 260 Nm, M30 - 510 Nm

The bolts are cast into the lead, and it is unlikely that they can be taken out. I can give some suggestions for how to attempt this if you want to try.

Guess your question is caused by concern about possible corrosion on the bolts. If you can not see any traces of rust weeping from the bolts neither inside nor from the keel/hull joint it is pretty sure that there is no bolt corrosion.

Best regards


30 March 2009 - 18:59
Join Date: 01 February 2007
Posts: 35

Thank you very much Lars!

You are a fantastic asset to this forum.



14 April 2009 - 06:28
Join Date: 26 March 2008
Posts: 69


Are there any keel bolts forward of the mast on the 47s? (see pic)

My lead keel is slightly separated from the fiberglass hull. It was much worse today in a sling when the boat was lifted, as compared to 2 years ago while the keel rested on a block and bore the weight of the boat.

I appreciate the lifting would make it gape. Some folk here seem to be not worried. Others suggest tightening the forward keel bolts.

What would you do Obi-Wan Kenobi? :)



14 April 2009 - 10:54
Join Date: 02 January 2008
Posts: 1547


I would recommend tightening the forward bolts, preferably with the boat weight resting on the keel.

The forwardmost bolt is found below the hole in the mast step top plate visible on the picture. There are two more bolts below similar holes under the mast shoe, accessing them means the mast has to be lifted out.

Your yacht has the CB keel, and there are 17 bolts M24, and none M30.

Kind regards


14 April 2009 - 21:28
Join Date: 26 March 2008
Posts: 69


In a perfect world, I would follow your instructions to the letter.  Unfortunately, my world is way less than perfect. Access to the forward bolt is extremely limited and I cannot clearly define it. I am guessing it is covered in fiberglass. I cannot see how to access this bolt, or any other, without stepping the mast.

What are the implications of NOT tightening the bolt and leaving the crack as it is? Is this something compromising significant and severe structual integrity or is it something that needs to be addressed, but not in the next 12 months? Or is it something else again?

As usual, any input will be deemed helpful and appreciated.


15 April 2009 - 09:10
Join Date: 02 January 2008
Posts: 1547


Suggest you take a look through the hole at the forward end of the mast step. The bolt is straight below it, and not matted over. If there are two nuts the upper one is a lock nut. Remove it, and tighten the lower nut. For this you need a M24 socket with an extension shaft.

Check on the outside if the crack closes, ideally you should be able to make it disappear. Closing the crack is more important than applying the recommended torque, and a torque wrench it not necessary. Finally put the lock nut back.

In the water the crack behaves in the same way as when the yacht is hanging in strops, and to prevent possible leakage and oxygen starvation in the crack it is recommended that you try tightening the forwardmost bolt as suggested above. The two other bolts can be attended later when the mast is out.


16 April 2009 - 14:47
Join Date: 05 February 2007
Posts: 102

Thank you Lars! timing is truly everything, and thank's to all in this thread for the precious questions and advise, am feeling a little better now. upon hauling out yesterday you can see what I found. was very worried, and a little skeptical about the boatyard's lightness to the issue, but also hesitant to want to touch the keel bolts if at all risky. as Milo, have always had a bit of a crack, but this time it is definitely more pronounced. will update as to results.
Aorangi 47/047

19 April 2009 - 03:03
Join Date: 26 March 2008
Posts: 69

Jayne/ Prof:

With more determination, I was able to find the nut to the forward bolt, which, not surprisingly, was exactly where the Prof said it would be...just under all sorts of dirt and crud. Anyhow, had a professional come in to tighten it and, after three hours and $200, he could neither tighten nor loosen the nut. It is staying right where it is for now!

I had the crack in the leading edge of the keel grinded out. Then filled with 5200. The rest of the treatment will occur this week and will update you in due time. I will be interested to see how the keel looks over the next couple of years.



s/v The Last of the Normal People


19 April 2009 - 10:48
Join Date: 02 January 2008
Posts: 1547


It sounds like the threads have galled. If soaking with CRC or similar does not help, one known remedy is to split the nut. This is usually done by drilling vertical holes in the nut, either on one or both sides, and then splitting it with a chisel.


21 October 2009 - 19:22
Join Date: 25 July 2008
Posts: 26

Dear All,

We have exactly the same problem and will try to tighten the bolts.  After some heavy cleaning the bolts apared OK.  We have taken the mast off and will be able to tight them also.  My question:

There is water stagnating at this level and we haven't seen any gelcoat/polyester over the bolts.  Should we fill this so that no more water can stagnate.  The yard tells me that there is no way they can garantee that the polyester will not crack leaving water coming below and this would be worse than nothing.

By the way we will also make a hole at the bottom of the mast shoe to avoid water stagnating inside the mast.

Ludovic of Rumtrader

26 February 2021 - 17:59
Join Date: 24 April 2020
Posts: 18

As the new owner of 47 048 and with the gap in the forward part of the keel still there - my turn to have a shot at getting the front keel bolts tightened.

Question - when doing this - should I just trying to tighten or should I back it off a little and then re-tighten? It has been soaking in CRC for the last 3 months so let's see if it will move!!!

27 February 2021 - 07:34
Join Date: 02 January 2008
Posts: 1547

Dear Adrian

If the bolts are soaked in CRC this means that their threads are lubricated, and you should use lower torques, for M24 172 Nm and for M30  343 Nm. 
Backing off not required, unless you want to check that the threads are undamaged.
The bolts have slacked off, and for closing the gap several turns may be needed.
Kind regards

27 February 2021 - 07:46
Join Date: 05 February 2007
Posts: 102

Dear Adrian, 

Congrads on your choice, and may you have many years of joy with your 47. 

I would be VERY interested in hearing how you fare with the tightening of the bolts to Lars specifications, as we are still drydocked and mastless, so would like to address this. 

Thanks in advance.

Jayne / Aorangi 47/047 


27 February 2021 - 07:52
Join Date: 29 January 2007
Posts: 947

Dear Jayne,

you have all answers you need in a dedicated document on our "Techincal papers" page:

Fair winds!

matteo (47/069 Vanessa)

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