hunter49 keel bolt torque

[Zencra]

hi there, we've crossed to Europe where we are currently hauled out in Portugal. After noticing a rust line at forward section of keel joint I made a 6ft long 1 1/2" socket to check keel bolts. I was shocked to find the rear nut was only hand tight, the forward 5 were only at around 100nm and remaining rear at 120nm.
hunter specs have torque at 440nm. Whilst they were incredibly and probably dangerously loose 440 nm seems very high. can anyone confirm these numbers?
thanks in advance
Craig

 

[sail sfbay]

Your torque specification will be based on the diameter of the bolt/stud and the alloy of the metal used to make it. Use a properly calibrated torque wrench. I would guess that a boat of your size might need in excess of 200 ft. lbs. of torque. Many times the bolts are of different diameters and will have different torque specs. Might refer to this Keel bolt tightening torques – Cox Engineering but check with your boatyard to be sure.

 

[Jake N Eggs]

A nut that is 1 1/2" AF suggests that the keel bolt is 1" diameter. Standard torque for a 1"- 8/12 grade 5 bolt is 645 - 710 Nm. I have a chart that shows Stainless fasteners(18-8 & 316), 1"- 8 dry 410 Nm - 1"- 12 dry 460 Nm. There are some charts that show the stainless torques at a slightly lower value. It would appear that 440 Nm is plausible.

 

[Hello Below]

This reference does show 440 nm (325 ft lbs) torque at least for the 1" studs. Certainly it depends on the stud material, diameter, thread count and if lubricated or not. Good on you to ask this question before you tackle the project.

Source Marlow Hunter

 

[Ralph Johnstone]

I received the same chart (as per @Hello Below ) from Hunter many years ago. I would go with their slightly lower values as they may have applied a small factor of safety to avoid crushing the FG. Published torques are for the maximum allowable torque without damage to the bolt.