B42 keel bolts

[tckearney]

Hi all I have  A 2000  B42.   Can anybody advise me should I routinely check the toque on the keel bolts.  There are no leaks and no problems.  The boat is 17 years old now and no groundings that I know of.   I did notice a very small gap at the  aft edge  between the keel and the hull while the boat was in the lifting slings but is disappeared when in the cradle.   If it needs checking any idea on the settings.   The Aft bolts are a different diameter than the foreward bolts.     

[Noelio Abrunhosa]

hi

On my boat because of the profile of the keel the bolts are quite forward from the edge. it left about a 5 mm gap at the end of the keel. our surveyor said that is normal on my type of keel. also we had no leaks from the keel area and the bolts are shining with no sign of rust. the keel was however reset and reseal as a precaution

regards

Abby

[tckearney]

Many thanks Noelio that's reassuring.      I will not be resealing i'll take the chance, and if any leaks appear it is easy for me to just lift out again. 

[Impavidus]

Tckearney. You should definitely not keep torquing the nuts. The stainless steel suds will stretch, even the M24 keel bolts. Every time you go back to them they will not have the original torque that you last set them to. This stretching is taken into account when the nuts are first torqued. If you keep tightening them they will eventually snap! Also, stainless steel nuts and bolts will gall (sometimes called friction welding or cold welding). You could very easily lock the nuts on the studs or lock them together. Then you or the next owner will have to cut them out when the keel joint needs re-bedding, which it will do at some point in the boats life. Good info here; https://www.bssa.org.uk/topics.php?article=12


Ant   

[tckearney]

Many thanks Ant I totally understand your reasoning.  30 years ago I had to inspect a steel tower that had special bolts thay should be torqued to a set limit.  They were not but on retightening six months later every one snapped

[Impavidus]

Quick story; A few years ago we had a "Expert" consultant come and inspect a job we were doing for the client. I left him with one of my project managers to do the inspection. We were using M12 A4/316 stainless bolts to secure some big structural brackets holding up some pretty heavy kit. We got a copy of his "so called" report and he sighted the nuts on the bolts as not being torqued to the correct setting.

I asked my manager what had happened and he told me the "Expert" had produced a calibrated torque wrench to check the nuts. He had told him they were all set and paint marked as part of our QA procedure.

The client insisted the "Expert's" findings should be acted on and we should re-torque the nuts. I insisted on a contractual instruction. A few weeks later the "Expert" came back ad reported they were still not right. We explained the properties of 316 but he knew better.

Needless to say, it was not long before the bolts started to fail. The heavy bit of kit was soon hanging on 75% of the designed fixings and these were in danger of failing too! Suffice to say we got paid to replace all the bolts on night work at a premium. I also charged them for the abortive time and the attendance at the inspections :-)

Some of the bolts that were 250 mm long when fitted were stretched by 10 mm.

Moral of the tail is "X is an unknown quantity" and "a spurt is a drip under pressure!"     Its good to trust experts but its better not to!

There is no substitute for experience!!! 

Ant.