Keel Bolt torque specs

[YACHT TARENTELA]

Does anyone have the actual torque specs for Hunter Passage 450 keel stud nuts? Keel weight is 960 lbs, keel has 7 studs which are 1" s/s and use nuts which take a 1.5" socket. I don't buy into the Armchair Admirals' adage that they should be "as tight as you can get them" and am looking for the actual torque value in ft lbs if possible. Thanks in advance.

[Sailmonkey]

http://www.imperialsupplies.com/pdf/...rqueCharts.pdf

According to the torque chart, somewhere between 3100-3500 in lbs.

[Kenomac]

Be very, very careful. When we first purchased our Hunter 450 passage, the keel came loose and we almost lost it. This was primarily due to poor keel design. If you have noticed some weeping at the keel joint during a haul out or loose keel bolts.... there's much more to the problem than just loose keel bolts. There's very little bedding surface area between the keel and the hull due to Hunter's terrible honeycomb keel design. The keel is filled with water absorbent foam that will obviously hold salt water within the keel and eventually corrode the bolts. The first sign of a problem was loose bolts.

I'd be happy to send you pictures of our Keel repair while underway at KKMI shipyard in Sausalito, CA. if you contact me directly. Or simply call KKMI yourself; they will remember the repair since the rig had to come off along with the keel. The internal foam needed to be removed and the deep interior voids filled with epoxy resin... a very big job. Good luck.

[perchance]

Generic torque charts for fasteners should be available online. Although they won't be specific to your application and are based on bolt size but should do.

[DeepFrz]

Kenomac, it could help forum members if you could post some of those pictures along with a short write up of the job.

[Kenomac]

I'd be happy to do a complete write up, but someone will first need to instruct me on how to insert/paste photos onto one of these threads. The photos I need to insert are in my pictures file and I already know how to copy and paste.... but not how to insert the images onto a post. Thanks Ken

[Nicholson58]

Originally Posted by perchance

Generic torque charts for fasteners should be available online. Although they won't be specific to your application and are based on bolt size but should do.

This was my first inclination too. We buiild machines and we know to torque bolts to chart values or at least to some tensions in excess of the expected maximum cyclic loads to avoid parting of the joints or fatigue. The problem in boat systems is that you are squeezing a composite structure instead of metal. I think that the charted tensions assume metal joints and may be too high. I suggest the best source is the builder if the data can be retrieved. Make sure the chart values you use are for the bolt material at hand. This can easily vary 2:1.

There are on-line sources to estimate tension from bolt torque and thread pitch. If you can't find any difinitive source for your boat, calculate the torque needed to equal the tension due to the keel weight. Add to this the additional tension applied to the bolts as the boat heels. You will need to estimate the center of mass of the keel and the heel angle and apply this force to calculate an bending moment. This moment must be resisted by the keel bolt spacing across the width of the keel. In short, calcuate the foot-# of overhung torque and divice by the spacing (ft) of the bolts. This is the bolt tension needed to keep the keel base in contact withthe hull. Add this to the above tension only number. Add a safety factor. I suggest about 150%. If it is a race boat or otherwise is subjected to a lot of impact you may want a greater factor. Compare this number to the charted maximums you might look up just for a sanity check. Don't exceed the chart numbers. Remember that the keel 'weighs less' in the water by the volume of water displaced by the keel.

[GordMay]

Here’s a lubricated Keel Bolt Torque Table (A7) from ISO/DIS 12215�]9.2
➥ http://xa.yimg.com/kq/groups/1881217...rque-Table.pdf

Here the specs for C&C keel bolts ➥ Keel Bolt Torques

1" Bolts (1 ½" Nuts) are listed at 165.2 (ISO) to 350 (C&C) Ft. Lbs
The large difference may be due to lubricated vs dry torque vales. I don't know.

[Nicholson58]

Thanks for finding that GordMay. Its always better to follow the directions. Just don't let my wife hear me say that.

[GordMay]

The ISO standard:
"Small craft — Hull construction - Scantlings — Part 9: Sailing boats -
Appendages and rig attachment"

ISO 12215-9
➥ http://www.nmma.org/assets/cabinets/...2004-03-02.pdf

See also ➥ http://www.j24class.org/news/keel-bo...ance-bulletin/

[avb3]

Old thread I know but relevant to me currently.

My boat is on the hard and boat yard suggested keel bolts be torqued before splashing it again. I obviously concur, however, when I asked how many foot pounds, he said 80.

I expressed surprise at it being that low. His comment was that one wouldn't want to make them to tight so not to pull them out of the lead keel.

Really? That doesn't ring right.

[jeanathon]

I found a recommendation somewhere. I cannot remember exactly, but I think I did mine between 100 and 110#s.

[Nicholson58]

The bolt tension will be a function of torque as we all know. Consider that you are not pre-loading steel plates but a lead-bedded bolt against fiberglass & calk. What will matter is that each bolt is pre-loaded to the level required to carry the weight of the keel, also allowing for the excess loads due to the catalever as the boat heals. Torque/tension will be a function of the bolt size and thread pitch. Here is a calcualtor and I am sure there are others if you search. Bolt Torque Calculator - Engineers Edge Engineering Calculators At least do a sanity check to see if you might strongly disagree with 80. There are probably also values you could search for by boat or maker.

[Jim Cate]

Is not C&N still in business? I would query them as first authorities. Second would be a random naval architect who deals in yacht design. Boat yard workers would be far down on my list of experts on such an important issue.

And FWIW, 80 ft lbs seems way low for such a large vessel... but I ain't an expert!

Jim

[model 10]

Originally Posted by Jim Cate

Is not C&N still in business? I would query them as first authorities. Second would be a random naval architect who deals in yacht design. Boat yard workers would be far down on my list of experts on such an important issue.

And FWIW, 80 ft lbs seems way low for such a large vessel... but I ain't an expert!

Jim

Well, often times, someone who has no clue hides behind that kind of statement. Sometimes boat yard workers do have a clue. I would put lots of them way above lots of owners.