keel bolts

[Motor_Sailor]

Could you give us an example of one of these boat manufacturers recommendations?

Bolts are sized to transfer their full load to the hull structure. Torquing is as per normal bolted joint as the static loads imposed by fully torqued nuts must by definition be less than the breaking strain of the bolt. The washers / backing plates / structural members are designed to handle those loads.

Every time you see examples of where keel failures have resulted in the bolts pulling through the hull structure, the verdict is always the same - inadequate load bearing structure, not over tightened keel bolts.

There's no conceivable reason to use power tools to tighten keel bolts as the threads should be clean and in good order before reassembly by hand. The reason I would actually forbid it in a job spec with stainless steel keel bolts is that you could completely miss any signs of the threads galling. The primary worry when assembling large keel structures is that a bolt will gall and a highly expensive keel assembly will be ruined.

 

[Bilgediver]

I thereby assumed the sheared bolt/stud queried above was due to it being seized upon disassembly, as you shouldn’t be impact torquing anything down anyway.

Never been to Kwik Fit. ¡!!!!!!!

 

[Zing]

Tightening or undoing?

Were you tightening or loosening them?

Loosening, or trying to. I have a small Makita impact driver for small screws/bolts, and after all other methods failed, so did it. So sorry fellas for not responding sooner, I got no automatic notification. YBW likes me less than you. These were small stainless bolts, 8mm dia which were seized due to corrosion. They ended up being drilled out after shearing. A frikin PITA.

 

[dankilb]

Never been to Kwik Fit. ¡!!!!!!!

Well, I'd confess an element of 'do as I say...' when it comes cars/vans - as I often bang down wheel nuts/bolts with an impact (after first threading by hand and stopping sharpish after a couple of impacts). I always aim to go back over them with the torque wrench...!

But assuming someone has gone to the all the effort involved in getting to the stage of re-installing keel bolts, you'd presume they'd opt to do it by hand?!

Could you give us an example of one of these boat manufacturers recommendations?

Interestingly, a quick search suggested no definitive number for our Jeanneau 22mm keel fasteners. Posts on the owners' forum ranged from 150nm (too little IMHO) to 350nm (more than the spec of my cordless impact claims - but easily exceeded by the big Milwaukees).

 

[Poignard]

Loosening, or trying to. I have a small Makita impact driver for small screws/bolts, and after all other methods failed, so did it. So sorry fellas for not responding sooner, I got no automatic notification. YBW likes me less than you. These were small stainless bolts, 8mm dia which were seized due to corrosion. They ended up being drilled out after shearing. A frikin PITA.

If these were so weakened that they sheared whilst you were trying to loosen them with an impact driver, they would have been just as likely to break using a spanner with an extension.

But, regardless of that, you have my sympathy for what started off as a simple job turning into a PITA. I guess most of us have experienced that.

(ps I can't imagine why you would think I don't like you. Goodwill to all is my motto.)

 

[vyv_cox]

Could you give us an example of one of these boat manufacturers recommendations?

Bolts are sized to transfer their full load to the hull structure. Torquing is as per normal bolted joint as the static loads imposed by fully torqued nuts must by definition be less than the breaking strain of the bolt. The washers / backing plates / structural members are designed to handle those loads.

Every time you see examples of where keel failures have resulted in the bolts pulling through the hull structure, the verdict is always the same - inadequate load bearing structure, not over tightened keel bolts.

There's no conceivable reason to use power tools to tighten keel bolts as the threads should be clean and in good order before reassembly by hand. The reason I would actually forbid it in a job spec with stainless steel keel bolts is that you could completely miss any signs of the threads galling. The primary worry when assembling large keel structures is that a bolt will gall and a highly expensive keel assembly will be ruined.

I agree. I put together an article on keel bolt torques a few years ago. The figures were all from boat builders, mostly Sadler but also Jeanneau and a couple of USA builders. The figures provided were very similar to standard torques for a variety of bolting materials. The only small rider is that they seemed to be at the low end of the standard range where one was available.

 

[vyv_cox]

I agree. I put together an article on keel bolt torques a few years ago. The figures were all from boat builders, mostly Sadler but also Jeanneau and a couple of USA builders. The figures provided were very similar to standard torques for a variety of bolting materials. The only small rider is that they seemed to be at the low end of the standard range where one was available.

Ha! Just discovered I put the article on my website. Keel bolt tightening torques

 

[fisherman]

Surely a cylinder head bolt is torqued with reference to the risk of stretching the stud and not that of crushing the component, while a wheel nut is about not damaging the wheel. The crushability of a GRP/backing pad structure is a little more fluid, I imagine, so many variables.

Having said that I fitted out a GRP FV in 1983, it had to meet Seafish specs, and I learned a lot off the guy in the workshop opposite who came from the Coventry motor industry and moulded car body parts. He was very meticulous about mixes and temperature, and had a chart on the wall for ambient temp, accelerator and catalyst; he also weighed every last gramme of resin/mat.

 

[Zing]

If these were so weakened that they sheared whilst you were trying to loosen them with an impact driver, they would have been just as likely to break using a spanner with an extension.

My point is that they put out max torque with no control, so really only should be used when you are sure the fixing will not break.

 

[PabloPicasso]

Could you give us an example of one of these boat manufacturers recommendations?

Bolts are sized to transfer their full load to the hull structure. Torquing is as per normal bolted joint as the static loads imposed by fully torqued nuts must by definition be less than the breaking strain of the bolt. The washers / backing plates / structural members are designed to handle those loads.

Every time you see examples of where keel failures have resulted in the bolts pulling through the hull structure, the verdict is always the same - inadequate load bearing structure, not over tightened keel bolts.

There's no conceivable reason to use power tools to tighten keel bolts as the threads should be clean and in good order before reassembly by hand. The reason I would actually forbid it in a job spec with stainless steel keel bolts is that you could completely miss any signs of the threads galling. The primary worry when assembling large keel structures is that a bolt will gall and a highly expensive keel assembly will be ruined.

My bolts WERE NOT stainless

 

[PabloPicasso]

Well, I'd confess an element of 'do as I say...' when it comes cars/vans - as I often bang down wheel nuts/bolts with an impact (after first threading by hand and stopping sharpish after a couple of impacts). I always aim to go back over them with the torque wrench...!

But assuming someone has gone to the all the effort involved in getting to the stage of re-installing keel bolts, you'd presume they'd opt to do it by hand?!


Interestingly, a quick search suggested no definitive number for our Jeanneau 22mm keel fasteners. Posts on the owners' forum ranged from 150nm (too little IMHO) to 350nm (more than the spec of my cordless impact claims - but easily exceeded by the big Milwaukees).

I can't imagine we torqued to 350nm. But we were over 110nm

 

[Fr J Hackett]

My point is that they put out max torque with no control, so really only should be used when you are sure the fixing will not break.

Not all of them you can set various levels on some I wouldn't expect it to be accurate but good enough to choose a level below specified torque.

 

[Poignard]

My point is that they put out max torque with no control, so really only should be used when you are sure the fixing will not break.

The torque at which a bolt shears is determined by its dimensions, the material from which it is made and the condition of that material.

 

[Beneteau381]

Typical surveyor making you do work to cover him against missing anything. Every survey I have read has so many exclusions on what they have checked like employ an engineer to check the engine, an electrician to check the electrics, a rigger to check the rigging, sailmaker to check the sails, etc. Unfortunately insurance companies insist on an independant opinion of the boat. When I bought Concerto I did not agree with a couple of recommendations the surveyor made and I conducted my own checks and the "problems" he wanted investigated were not a problem at all, just like the keel bolt.

My survey said i had an MD2030 engine, it was an MD22!He said the b&g instruments were shagged, they weren, he saidthe clutch plates in the gearbox were burned, my box diesnt have clutch plates. And so it went on!

 

[PabloPicasso]

It's an imperfect system. How much are you willing to pay for a survey that would accept full liability for everything. It'd probably cost more than my boats worth and, hence, prevent me from owning and sailing.

Did you query any of this with the surveyor? Did he get his qualification from a Christmas cracker?

 

[fisherman]

Bro found a buyer's surveyor had dug holes in the Cascover sheathing while he wasn't watching. The whole thing needs an overhaul, insurance and surveyors, they seem to feed off each other. Or, rather, off boat buyers and sellers.

 

[PabloPicasso]

Bro found a buyer's surveyor had dug holes in the Cascover sheathing while he wasn't watching. The whole thing needs an overhaul, insurance and surveyors, they seem to feed off each other. Or, rather, off boat buyers and sellers.

What is a "Cascover"?

 

[Tranona]

What is a "Cascover"?

Nylon sheathing set in Cascophen adhesive. Sort of predecessor to epoxy glass sheathing and popular with high class builders in 1960- mid 70s. I had a 1963 boat with original sheathing - excellent. Very expensive and went out of fashion when wood hulls were superseded by GRP.

 

[PabloPicasso]

Nylon sheathing set in Cascophen adhesive. Sort of predecessor to epoxy glass sheathing and popular with high class builders in 1960- mid 70s. I had a 1963 boat with original sheathing - excellent. Very expensive and went out of fashion when wood hulls were superseded by GRP.

Well, I learnt something new there.

 

[fisherman]

Well, I learnt something new there.

...as the Dalek said as he climbed off the dustbin.