To torque or not to torque - SailNet Community
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post #1 of 23 Old 11-11-2009 Thread Starter
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To torque or not to torque

Do to the spat of news about keels falling off I got to thinking that a torque test of the keel boats might wisely be part of a standard survey. So I sent the following question to Catalina.
I have the answer. Anyone want to weigh in befor I spill the beans?


Would it be Ok to torque the keel boats as part of a normal survey and/or normal maintenance? I am familiar with the plywood sump replacement and the lag bolt replacement process. My question is not how to affect a repair but rather how to prudently determine if a repair is necessary. What bothers me is that a simple visual inspection will not show me crevice corrosion of the bolts hidden below the washer. If every fall I could just put on the torque wrench and see that the bolts hold torque it would make me feel better about the integrity of the hull. But of course if there is some reason it is a bad idea I’m asking in advance. Assuming it is allowed I have the following questions? 1. What torque lbs is appropriate? 2. Is any movement allowable? 3. Is it a good idea to back the nut off a quarter turn before tightening? 4. This should only be done when the boat is blocked on land yes? 5. Any special blocking instructions? Sorry about all the questions but I would rather ask than do something stupid. Thanks
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post #2 of 23 Old 11-11-2009
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In my experience, most keels fall off because of broken bolts due to fatigue or broken hulls, not due to loose bolts. So I would guess that Catalina will say "Don't bother, just tighten them properly"

Just a guess.


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post #3 of 23 Old 11-11-2009 Thread Starter
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Quote:
Originally Posted by Omatako View Post
In my experience, most keels fall off because of broken bolts due to fatigue or broken hulls, not due to loose bolts. So I would guess that Catalina will say "Don't bother, just tighten them properly"

Just a guess.

Mainsail showed us lots of pictures of keel boats that look normal at the nut end maybe 1" but were only 1/8" about 4" below the nut.

My theory is that if the bolt is crevice corroded enough I may be able to twist it off. If there is something rotten in the keel stub I should not be able to get it to hold torque as it will just keep compressing until the floor of the sump is obviously distorted.
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post #4 of 23 Old 11-12-2009
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Unfortunately, to really, properly inspect keel bolts, you usually need to drop the keel. Crevice corrosion can be very insidious and the bolts may look fine and tension fine, but be close to giving way where you can't see them.

I'd also correct what Andre said, and point out that one of the biggest causes of laminate failure is flex, and that loose bolts allow the keel to move, and that is likely to cause the laminate to flex and fatigue, eventually leading to its failure.

I don't think that torquing the keelbolts is generally an accepted part of a survey, since a survey, like a medical doctor, should do no harm...and torquing weak keelbolts could snap them.

As for what torque they should be tightened to, that really depends on the boat. BTW, messing with keelbolts with the boat in the water is a really, really dumb thing to do. If you want to re-torque the bolts annually, then backing off a 1/4-1/2 turn and then torquing them back down to specification is a good idea.




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post #5 of 23 Old 11-12-2009
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Any mechanical engineer will tell you torque testing a bolt that has been in situe any length of time will tell you nothing worth knowing .to torque a bolt properly it must be removed ,cleaned and lubricated before replacement only then is it possible to torque acurately. K ( ex factory chief engineer)

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post #6 of 23 Old 11-12-2009
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Looking forward to the answer.

By the way, my BIG 45mm wrench came in the mail this week. I can't wait to take a keel bolt out and take alook at it.

Regards,
Brad

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"I can't wait to take a keel bolt out "
Only a Benetoy owner could say that. REAL keel bolts are more than three inches long, and permanently cast into the keel, unlike the terribly convenient bolts that Beneteau uses to attach their iron keels.
They're bolts, they're in the keel, all true, but they aren't "keel bolts" according to the general laws of this universe. There just has to be a better way to describe them.

Or perhaps real keel bolts should be called "keel studs" instead. Heck, I drink US-made domestic "sparkling wine" and still call it Champagne. :-)
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post #8 of 23 Old 11-12-2009
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It is true that the only way to know for sure is to drop the keel. If your keel bolts are loose, there is something wrong though. Something either stretched or compressed to allow it (a little settling is to be expected but not measurable). If the bolts are loose, the forces change greatly and everything is going to wear out a lot faster.

A note on checking torque. From some of the posts I have read on previous threads, I gather that a lot of people simply put a torque wrench on and see whether the nut spins before you reach the torque setting. This is not correct. At the very least, you should paint a line on the bolt/stud and nut so you know where the old lineup was then loosen the nut and retighten to torque. To do it right, you need to take the nut off, clean and check the threads and lubricate them then do the torque. If the paint line doesn't line up, it was loose.
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Quote:
Originally Posted by hellosailor View Post
"I can't wait to take a keel bolt out "
Only a Benetoy owner could say that. REAL keel bolts are more than three inches long, and permanently cast into the keel, unlike the terribly convenient bolts that Beneteau uses to attach their iron keels.
They're bolts, they're in the keel, all true, but they aren't "keel bolts" according to the general laws of this universe. There just has to be a better way to describe them.

Or perhaps real keel bolts should be called "keel studs" instead. Heck, I drink US-made domestic "sparkling wine" and still call it Champagne. :-)
You may pick on Benetoys all you want, our is simply an excellent boat to own - to me. I'm pretty sure I couldn't afford a similar boat if it wasn't a production boat. (I guess it's the same reason I drive a Honda - 13 years since I bought it new and it keeps running strong. Last one lasted me 225000 miles. You can't argue with that. And you get to keep going back to the place that guaranteed your muffler for as long as you own your car.) As the manufacturer who has made the most sailboats, and is still in business, it's easy to talk with them with questions and to buy parts and keep a Beneteau well maintained. And from what I can tell, they don't inflate the price either.

Usually, Beneteaus are made with galvanized keel bolts. Our boat has Stainless Steel bolts. Annual maintenance includes pulling one each year to look at it. If I can get ahold of a camera, I'll post pictures on the keel bolt thread that I started.

So yes I can't wait. I love "messing about in boats" as much as anyone else on these forums.

Regards,
Brad

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Last edited by Bene505; 11-12-2009 at 05:58 PM.
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post #10 of 23 Old 11-12-2009 Thread Starter
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Thank you gentleman. The following is the official answer:

David,
You should be able to torque the keel bolt nuts to 83 ft-lbs while the boat is on the hard and the keel is supported. If you can not get that reading then most likely the wood has rotted and is compressing. We usually do not back of the nuts off but you could to inspect the threads. We do sell 1/2" x 10" lag bolts that you can add to help reinforce the keel if you are questioning the integrity of the existing bolts. You can forward this to [email protected] to order them. I believe they sell for around $15.00. Usually 5 or 6 are added, evenly spaced between the existing bolts.
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