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Keel Bolt Torques As Posted May Not Be Correct

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Fellow 99 owners,

I have been in the process of re-torquing Kingfisher's keel boats this season.  I contacted Tim Jackett and Chris Ranney at Tartan Legacy Yachts in Ohio.  Chris looked up the values recommended for the 99 from their data library when the 99 has 3/4" bolts as ours does (Hull #6, 2002 build).

For 3/4" diameter bolts that torque is supposed to be 140 ft/lbs. ...not 250 ft/lbs.

I then re-checked this forum and the "Resources" page and saw the chart prepared by Art Averell at C&C many years ago.  That chart indicates a torque of 250 ft/lbs.

So I called Chris Ranney back again and at his request sent the forum string as well as a screenshot of the table on the Resources page.  He then took that to the engineers, who helped design and build the 99s.  They indicated that I should go with the 140 ft/lb torque.  Chris was not sure where the previous numbers came from.

Now, the issue with over torquing, as I am sure many of you know, is not only over stressing the bolts, and the J-bends within the lead, but also possibly damaging the threads.  Worst still could be potential damage to the keel stub, which though very hefty, still is built with layers of e-glass.  If that should be over compressed it could still delaminate (according to my boatyard).

When I torqued the bolts this time, I used a 5 ft long torque wrench, starting with clean threads and from the middle-most bolts outward, alternating right/left and fore/aft as I went.  I turned on the wrench twice when I heard the wrench "click" indicating it was at the preset torque.

Now, feeling more confident in keel bolt tension, I will relaunch Kingfisher this Friday when tides are favorable.  But, before we get wet, we will push laterally on the keel to see if there is any flex.  Flex, particularly if it is not in the actual joint, may indicate other issues, such as in the stub.

Chris Ranney also advocated removing the keel about every 15 y to examine it and re-bed with 5200.  That's something to think about in all of our boats as they are likely sailed and raced hard and the actual keel fin is rather thin.

As I own an older hull, I am not aware whether C&C increased the keel bolt diameter in later models.  If they are 1" bolts, the recommended torque is 300 ft/lbs

Hopefully I can post an update Friday and let you all know how this turns out.  But I felt compelled to relay this information to you all as soon as possible.

Regards

 

Thanks Dixon,

 

We torqued ours two years ago and they all tighten a bit, not a lot,  and the most torque we could get was 235 foot pounds.  I was told the table came from Tartan so we will remove it.  When we checked  ours there is no way we were going to slack ours off.  We have had no issues with out keel bolts but we knew they hadn't been tightened since the boat was new in 2004 and the boat had been trucked a few thousand miles since it was built.  There is further discussion further down in this thread.

Sure thing.  I was of course a bit wary in posting my original email.  But given that I spoke directly to the people at Tartan (nee C&C) in Ohio, I felt I needed to speak up. I am fully planned to do the Down The Bay Race (Annapolis to Norfolk) at the end of May so as a safety issue, this is of major concern.

My yard manager has left it that if we put our boat in the slings Friday AM and we push on the keel and there is movement, we then pull the mast, loosen the bolts and remove the keel.

Not something I am looking forward to as you might understand.  But if necessary I will  do this.  I may pull the keel off next winter haul out in any event. (also not something I would look forward to).

Will do my best to keep you all posted.  I have too many years of sweat equity in this boat to give up!

I am glad that you wrote this.  In May 2019, I wrote of our experience filed under keel bolts and sump box

After much research,  my husband's "take on all the collected items that follow (in the original post) is that 250 ft-lbs is far too much for a 33’ sailboat: that it’s the stretch point for the bolt itself, the limiting torque value if the bolt were being used in an application that’s bolting together two pieces of solid steel, not a lead keel and a plastic, fiberglass, or epoxy boat together. For fear of pulverizing the keelson, he wouldn’t feel comfortable going beyond the 95 ft-lb range; and he not sure that from what he has learned that he would torque it even that far until the keel was no longer supporting the weight of the boat on land (because of any possible off-center pressures from perfectly square alignment). I’m thinking maybe 70-75 (some of them were only 40-50 when I checked the torque with the boat resting on keelblocks and jackstands after Fall haul-out).

The other item to note is that keel bolt specs are usually given for clean, dry bolts. No lubrication.  If lubrication is used, remember that each lubricant will have its own coefficient of friction.

Did Chris Ranney specify whether or not the torque is for clean and dry or lubricated. If lubricated, which lubricant?

Kathy,

Chris did not specify whether for clean and dry or lubricated.  I used a tiny bit of light silicone based grease on our threads mostly to help get the nuts started onto the bolt.  In as much as they were already wet from bilge water.  This is the same procedure I use on my Ti racing bicycle to avoid seizing and loosening and I do use a torque wrench on those bolts and screws.   I realize that a 140 ft/lb level would be higher torque than if the bolt was bone dry, but it still will not be anywhere near the 250 ft/lb level spec'd elsewhere.

I am glad you made the point about overstressed bolts compressing the stub.  In any event, it was clear to us that a 75 ft/lb value was way too low.  As I state above, if we lift the boat on Friday and find that there is still wobble we will then pull the keel totally off to assess other issues such as keel stub degradation.  However, on Chris' recommendation, I performed a very thorough inspection of the dried out bilge to look at the cross bracing in the bilge.  I was not able to see any cracking or any evidence of delimitation on the inside of the bilge.  That's a good sign.

Update on the launch of Kingfisher.

 

We lifted her in the slings last Friday.  When that happened the paint at the aft end of the keel did crack about 1.5 in.  On inspection it appeared that this was in the paint only and not in the G Flex covering the joint.  There was no flex at the keel joint when lateral pressure was applied.

We placed a dark paint mark where paint crack ended and will observe this over time as we sail the boat.  IMO this was a successful repair and re-torque with all the bolts set at 140 ft/lb.

I was thinking about the paint cracking and realized that the aft-most keel bolt is fairly far forward from the aft end of the keel itself.  That means there is no direct bolt support over that aft end.  Further, in the Std draft keel, the bulb extends a couple of feet aft of where the keel stub ends.  Given that, it may be understandable why the downward moment arm produced by that bulb might impart more stress on that aft-most keel bolt.  Plus, the 99 has a rather thin keel, tapering to a rather sharp training edge.  All these factors might contribute to my observations at launch.  Just a thought I felt I should pass along.

Thanks Dixon.  We have the deep keel and there is no evidence of cracking anywhere.  As I said we torqued to 235 foot pounds and we only moved the nuts very little to get to that and considering the boat was trucked several thousand miles by truck we expected them to be looser. I guess it all depends on what they had been tightened too previously.  I do know that the first few boats were underbuilt in the bow section and Tartan did come up with a fix and that fix is indicated on our resource tab.  I am not sure at what hull number the fix was incorporated into the new builds or if that fix may may have incorporated additional stiffening elsewhere.  I do see that 250 foot pounds on line for other boats with 3/4" keel bolts.  Hopefully we'll here from others as time goes on.

Actually, that transverse stringer you refer to was a result of my conversations with Tim Jackett when we had problems with twisting of the hull's forward section.  The transverse stringer we had built in seemed to solve that problem, stiffened the bot and eliminated the cracking we had observed down near the center line.  I sent up to this site the structural diagrams I received from Tim and am happy to share them again with anyone.  It is a worthy fix to the front end of the boat.

As to the keel bolt issues, I have to reiterate what i learned from our boatyard.  They adamantly reminded me that re-torquing keel bolts requires that the nuts be totally removed before re-torquing is done with a proper wrench.  They said you should not simply wrench on the nuts in place to get to the required torque values.  I too had simply wrenched on our keel bolt nuts in the past without removing them but this may not get you to the correct torque and could give a false value of torque since the threads may not be clean enough.  Just sayin'...

As to whether the 140 ft/lb value actually works...well I'll let you all know as the season progresses.  I will be watching it carefully.

Do you know approximately when Tartan built the fix into the design of the hull?

believe we have your drawings under the resource section, thanks for that.

Yes we'll see about the 140 ft/lb.  All I know is what ours showed so I assume it could be higher that what actually got transmitted to the bolt.

Thanks for the great feedback.

I do not know when Tartan/C&C started building the stringer into the hull.  We had our stringer installed in March of 2011. So I am guessing the C&C "fix" to new construction would have been some time after that (?).

 

Here are photos from the completed (nearly, sans Interprotect 2000 coating) stringer construction).  This is from March 2011.  At the time, the tabs holding int he blackwater tank were also reinforced with new e-glass cloth and resin.

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