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26-04-2018, 15:53
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#31
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Registered User
Join Date: Feb 2013
Location: Kingston Ont Canada
Boat: Looking for my next boat!
Posts: 3,101
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Re: Insufficient threads on keel bolt. Double nut?
Your issue, along with the recent increase in concern about failing keel bolts, brings up a design flaw with bolt on keels...the bolts cannot be inspected, and replacement is a major project, often exceeding the value of the boat.
Perhaps the manufacturers should be taking note of this. If they expect their product (boats) to be long lived and serviceable, perhaps they should take a different approach.
Keel bolts could be "through bolted" to the bottom of the keel. The lower nut could be recessed slightly within the keel and the space filled with epoxy and glassed over. It would still be a big project, but the lower nuts could be removed and the keel bolts pulled up from the bilge. One at a time, on the hard, so that the overall integrity of the boat and hull to keel joint is never compromised. Comments?
While we are discussing boat design, I'd also like to see bilges widened and deepened to accommodate a substantial number of FLA batteries. The move to electric motors has already begun, and designers need to catch up with the need for more electric storage. Down low, as part of the ballast would be ideal.
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26-04-2018, 16:15
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#32
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Registered User
Join Date: Apr 2008
Location: Oro Bay Puget Sound
Boat: Irwin sloop
Posts: 407
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Re: Insufficient threads on keel bolt. Double nut?
Post #18 is the real solution. Coupler nuts are commonly used to solve this problem and are readily available
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26-04-2018, 17:25
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#33
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Registered User
Join Date: May 2014
Location: USA
Boat: 41' yawl
Posts: 1,187
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Insufficient threads on keel bolt. Double nut?
Quote:
Originally Posted by hamburking
Keel bolts could be "through bolted" to the bottom of the keel. The lower nut could be recessed slightly within the keel and the space filled with epoxy and glassed over. It would still be a big project, but the lower nuts could be removed and the keel bolts pulled up from the bilge. One at a time, on the hard, so that the overall integrity of the boat and hull to keel joint is never compromised. Comments?
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Both bolt-on keel boats I’ve owned are through bolted. One cast iron with a flange (and the bolts were in miserable shape) the other lead with very long bronze bolts (which are immaculate, but I still replace a few every few years since they are over 50 yrs old)
I also had a boat with encapsulated lead ballast and a sistership apparently had the internal ballast break loose inside the fiberglass keel and was totaled. I personally prefer inspectable, repairable keel bolts over some invisible lump someone tossed in while laying up the keel.
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26-04-2018, 23:14
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#34
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Registered User
Join Date: Oct 2011
Location: ORYGUN
Boat: Jeanneau 52.2, Merit 25
Posts: 164
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Re: Insufficient threads on keel bolt. Double nut?
Quote:
Originally Posted by 01kiwijohn
Only one bolt? I see you're in Oregon so, freshwater boat? I think you'll be ok with that solution.
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Boat resides in Bellingham and takes jaunts outside of the sound into the pacific. That said, I think the solution still holds merit.
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26-04-2018, 23:25
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#35
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Registered User
Join Date: Oct 2011
Location: ORYGUN
Boat: Jeanneau 52.2, Merit 25
Posts: 164
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Re: Insufficient threads on keel bolt. Double nut?
Thanks for everybody's advice. Some variety but essentially people seem to basically be in agreement. My hunch is that if I randomly chose any of the many ideas I would likely be fine.
That said, I'm going to try and source a stainless coupler nut tomorrow for the fix (with anti-seize). If I can't source one off the shelf locally I'll just add another nut, using a deep socket to sleeve both nuts while torquing.
I'll make sure to update the thread if the fix doesn't work... unless of course my keel falls off resulting in my imminent death in which case I suppose I should have called Catalina, dropped the keel, and worn my belt and suspenders.
Quote:
Originally Posted by hamburking
I believe your plan to use a second nut as a spacer is a good solution. FWIW, I'm a mechanical engineer (and a sailor).
I would suggest you keep an eye on it in the future though. If there is some mystery stress causing the problem, then the second nut will fail too. My guess would be the threads were stripped during installation when the boat was built. It would take a massive force to strip those threads.
Obviously, dropping the keel to replace the bolt would be a ridiculous cost, and totally unnecessary.
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Sound advice from a mechanical engineer...Thank you! I find your theory of a factory stripping of the nut to be very plausible.
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27-04-2018, 03:00
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#36
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,087
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Re: Insufficient threads on keel bolt. Double nut?
Greetings and welcome aboard the CF, Taipe.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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27-04-2018, 10:05
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#37
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Registered User
Join Date: Oct 2011
Location: ORYGUN
Boat: Jeanneau 52.2, Merit 25
Posts: 164
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Re: Insufficient threads on keel bolt. Double nut?
Put the problem to bed with a stainless coupling nut and generous amounts of anti-seize.
Thanks for all of your generous and excellent advice!
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27-04-2018, 10:43
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#38
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Registered User
Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 10,208
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Re: Insufficient threads on keel bolt. Double nut?
Quote:
Originally Posted by Swift Drift
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Great! It would appear to be better than new. I would bet the problem had been there since installation?
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27-04-2018, 16:28
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#39
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Registered User
Join Date: Oct 2007
Location: Charleston, SC
Boat: Stevens 47
Posts: 199
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Re: Insufficient threads on keel bolt. Double nut?
Quote:
Originally Posted by chris95040
I think I see cracks, too. I'd want to really know what was going on there.
Hey, for folks with J-bolts, couldn't you just get off cheap by drilling and tapping new bolt holes from inside the bilge?
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Yes, you can double up the bolts. Of course, the issue with lead is that it is soft, so you can't tap it. You really have to drill all the way thru the keel so you can put a nut on the bottom. Recess the nut of course and fill the resulting void with epoxy fairing compound.
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27-04-2018, 23:49
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#40
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Registered User
Join Date: Apr 2015
Location: Stockholm, Sweden
Boat: Sun Odyssey 45.2
Posts: 149
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Re: Insufficient threads on keel bolt. Double nut?
How did you find out what torque to use?
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28-04-2018, 05:03
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#41
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Registered User
Join Date: May 2014
Location: USA
Boat: 41' yawl
Posts: 1,187
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Insufficient threads on keel bolt. Double nut?
Quote:
Originally Posted by Recy
How did you find out what torque to use?
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I think in the absence of data from the manufacturer, if you’ve got good washer plates distributing the load, you can go with recommended torques for your bolt diameter, thread, and material like the ones found here:
https://www.boltdepot.com/fastener-i...ed-Torque.aspx
I’m not a mechanical engineer but I believe bolt torquing is less about the particular assembly its a part of, more about the bolt itself and it’s role in the assembly. I think the reason you pre tension it is to decrease how much cyclic loading it sees? And those torque specs listed above probably just get you to some standard percentage of the overall strength of the bolt. Hopefully if thats wrong someone here will correct me...
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28-04-2018, 05:13
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#42
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Registered User
Join Date: May 2014
Location: USA
Boat: 41' yawl
Posts: 1,187
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Re: Insufficient threads on keel bolt. Double nut?
FYI I still see what looks like cracks in the bilge around that bolt. I’m not really sure what I’m looking at when I zoom in, but the washer? under your new bolt is pathetically undersized. A nice plate to distribute the load beyond those mystery cracks would probably be smart.
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28-04-2018, 07:52
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#43
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Registered User
Join Date: Oct 2011
Location: ORYGUN
Boat: Jeanneau 52.2, Merit 25
Posts: 164
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Re: Insufficient threads on keel bolt. Double nut?
Quote:
Originally Posted by Recy
How did you find out what torque to use?
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One of the advantages of owning a Catalina 34 is that there is a strong owners website with tons of info. Many other trustworthy Catalina 34 owners have documented the spec of 105 ft lbs.
On a side note, my understanding is that the there is a slight margin for error on torque specs so long as all bolts are torqued equally. Unequal torquing can cause more problems than being slightly off on the exact torque spec.
Can some "super sailor engineer" confirm this?
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28-04-2018, 07:54
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#44
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Moderator
Join Date: Feb 2010
Location: La Ciudad de la Misión Didacus de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 20,441
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Re: Insufficient threads on keel bolt. Double nut?
What’s the bolt diameter?
__________________
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For all of your celestial navigation questions: https://navlist.net/
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
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28-04-2018, 07:59
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#45
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Registered User
Join Date: Oct 2011
Location: ORYGUN
Boat: Jeanneau 52.2, Merit 25
Posts: 164
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Re: Insufficient threads on keel bolt. Double nut?
Quote:
Originally Posted by chris95040
FYI I still see what looks like cracks in the bilge around that bolt. I’m not really sure what I’m looking at when I zoom in, but the washer? under your new bolt is pathetically undersized. A nice plate to distribute the load beyond those mystery cracks would probably be smart.
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Fair observation however, I think the picture is deceptive as it shows a washer which is covered up by superficial resin/gel coat...the edges of which are superficially cracked.
I think you are seeing my lock washer (on top of fender washer) and assuming that's the only washer.
No doubt it would be "better" to throw in some backing plates that are more substantial than fender washer, but I'm not sure it's necessary.
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