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diySailor
1st Mate

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USA
39 Posts

Response Posted - 06/30/2012 : 20:31:07

The rods were about 6.5 inches long with about 3.5 inches in the casting and sole of the bilge. From the corrosion evident on the upper part of the threads on the rod, it appears that the there are 2.5 inches of thread engagement in the casting. As I understand it, the corrosion resistance of stainless steel is effective when oxygen is present so if there is stagnant salt water intrusion in the threads (no oxygen) then the stainless steel will corrode (crevice corrosion). Search for examples on the net. I am using zinc plated carbon steel rods (not galvanized) with custom machined hex ends to be able to easily remove the rods if required. Since I am using anti-seize only on the threads that go into the casting the hex end will allow for holding the rod stationary while torqing the nut (no anti-seize). This eliminates any grinding between the threads on the casting and the rod. Torque ratings vary for plain, plated and lubricated threads. I am using a stainless steel flat washer with the epoxy as a barrier between it and the threaded rod as mentioned in my previous post. The nut is grade 5, zinc plated, with an aluminum hex nut for a jam nut that is to be a sacrifical part of the assembly. When and if I see corrosion on the aluminum nut, I'll replace it in order to prevent any galvanic potential between the casting and the zinc plated rod or the zinc plated nut and the stainless steel flat washer...that's the theory anyway. If you check the net for keel bolt replacement on bilge keel boats in Europe (England), it appears many were plain carbon steel and still corrosion free after 25 and 30 + years.

Edited by - on

diySailor
1st Mate

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USA
39 Posts

Response Posted - 07/05/2012 : 18:54:46

Keel bolt installation update - the reality!

One correction on my previous post. I bought grade 5 hex nuts to go with the grade 2 threaded rods thinking I would minimize thread deformation and strip-out due to the smaller number of threads in the nut. What I didn’t realize was that the first thread on the harder nut takes over 30% of the force exerted by the torque. The last thread takes approximately less than 10%. This scenario leads to thread fatigue and possible fastener loosening. Using a grade 2 nut with a grade 2 threaded rod allows deformation of the threads to essentially share the load induced by the torque more evenly. So it’s grade 2 for both the nuts and the threaded rods.
http://www.fastenal.com/web/en/78/screw-thread-design

It appears that my keel-bolt arrangement is original but I’m not sure. I reinstalled new 6 inch threaded rods in the existing holes since the threads looked OK after I inspected them with an optical scope. Something bothered me that I didn’t fully realize at first. The internal threads were in the sole of the bilge as well as in the casting. The threads in the sole of the bilge were embedded in some kind of rigid material. Who knows how much torque was lost on the threads in the casting by the threads in the sole of the bilge! I wonder if this is a leading reason for the Catalina smile. So after I epoxied the threaded rods in the existing holes to fill up the void left by routing out the damaged wood or other material, I removed them (glad for the anti-seize) and drilled down to the threads in the casting by the OD of the threaded rod (5/8”) and added a C’sink to contain flexible epoxy. Since there doesn’t seem to be any details on how far the casting is below the sole, I used a small magnet attached to a string to find the start of the casting. Worked like a charm. It appears that the threads in the casting range from 1.50 to 1.75 inches long as opposed to the 2.5 inches I mentioned in my previous post. This number may vary with each bolt so it’s important to check each one individually (the threaded rods also varied in overall length too). After drilling out the threaded hole and adding the C’sink, I inserted the rod in the casting and applied a flexible wicking epoxy around the C’sink to prevent any water in the bilge from following the threads to the casting. Catalina suggests using an O-ring coated with 3M 4200 but I used Permatex high temp RTV around the threads and coated the underside of the flat washer with 3M 4200 per Catalina’s instructions. When I applied the correct torque to the nut the force deformed the flat washer into a slight conical shape and noticeably indented the top of the fiberglass on the sole. In order to spread the load out further on the flat washer (the surface of the sole isn’t flat), I’m going to get a heavy hex nut or flanged hex nut and thicker washer if available. Apparently the threads in the sole took a good part of the load as I suspected. The flexible epoxy probably doesn’t do any good in this application if using a regular hex nut due to the high force concentrated around the drilled hole so an O-ring or some kind of elastomer sealer (like Permatex) will help seal the threads against water intrusion. Sealing the edges of the flat washer and the nut -washer/rod interface with 3M 4200 will definitely help prevent water intrusion as well.

I don’t know how long the hairline crack was evident between the hull and the casting before I got the boat, but it appears that Catalina must have used a very strong adhesive between the hull and casting or the crack should have been substantially bigger due to the above observations. Between the material selection and method of assembly, this is a much more complicated design and assembly procedure than it first appears. I may dig out the wood in the sole and re-glass later if the bolts can’t maintain the torque. I’m doing the four middle bolts this year and the front (bow) and rear (stern) bolts next year. One caveat for anyone wanting to re-tap or reinstall bolts or threaded rods in the existing holes; the long drills sold in the kit would not line up with the holes since and the lip of the floor overhangs the holes.

As bad as my rods looked rusted to less than half their diameter, I needed a 3 foot pipe to break them loose. The threads on the rods in the casting proper were in near original condition. I still can’t believe the stainless steel nut didn’t twist off the rod. The stainless steel nut threads were as new and the threads on the plain steel rod were very good…maybe locktite made the rod and nut inseparable. At least now I don’t have to guess about their condition.

Edited by - on

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 07/06/2012 : 07:01:07

Great post, thanks!

Just one question, you had the SS nuts? I suppose that's not original. My nuts are ordinary steel and rusted like the rod but not that much as yours.
If I understand you correctly, you were slacking the nuts but the rod comes with it?
From yours but your picture it seems that your bilge suffered from repeated flooding :-)

Edited by - on

Joe Diver
Master Marine Consultant

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USA
1218 Posts

Response Posted - 07/06/2012 : 09:12:20

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by diySailor

<hr height="1" noshade id="quote"></blockquote id="quote">

I think this picture is very telling....and echoes what my surveyor buddy told me about my keel bolts. Even though the upper part of the exposed bolt is corroded, internally the bolts are fine. In this picture you can see the exposed part of the all-thread is badly corroded...but under the nut, through the stub, and into the keel, the all-thread is just fine. As is the nut.

Just because your keel bolts may look like a pile of brown crud, it does not necessarily mean they're bad.

My surveyor buddy tapped around mine, cleaned and scraped the surface corrosion, and gave me a thumbs up. Mine aren't as bad as the pictured one above.

Edited by - on

diySailor
1st Mate

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USA
39 Posts

Response Posted - 07/07/2012 : 04:12:38

Tomas, the nuts were stainless steel. From just looking at the corrosion between the nut and rod I thought it was the rust that locked the two together so that when I turned the nut the rod turned with it. But after examining the threads in the nut and on the rod I'm sure that it was some type of locktite that held them together. As you suggest, I think there was standing water in the bildge for some time.

Sounding the bolts will indicate if the bolt is OK but in my case it wouldn't have predicted locktite in the nut (no torque adjustment) or whether the sole was tapped (loss of force on the threads in the casting). This design requires occasionally readjusting the torque (turning the nut since the threaded rod is bottomed out in the casting) especially if water penetrates the wood in the sole allowing the fastener to take a set. Any thread engagement in the sole will reduce the force transfered to the threads in the casting when applying the specified torque on the nut. Being able to pull and inspect at least one fastener at least provides some assurance in the integrity of the keel attachment.

I probably wouldn't have bothered with any of this if it wasn't for the Catalina smile

Edited by - on

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 07/10/2012 : 01:56:37

I've made some photos of my [url="http://www.kruska.cz/C25_High_Anxiety/listing.php?path=keel/"]keel stub[/url].

PO painted all he could, even bilge pump hoses so rods seems much better than yours but nuts are bad. I don't have keel smile or cracks in the keel joint but I think it needs to be replaced until its possible.

Edited by - on

Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 07/10/2012 : 09:05:52

Tomas,
Compared to the condition of my studs/nuts, when I sistered mine, yours appear to be in pretty good condition for 35 years old. Mine were essentially piles of rust with no threads detectable on the stud above the nut. Like you I had no smile or crack but the overall condition of the studs prompted me to act. Yours look ten times better than mine did. Hope that eases your mind somewhat.

Edited by - on

diySailor
1st Mate

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USA
39 Posts

Response Posted - 07/10/2012 : 18:59:52

Maybe the rust is mainly surface rust. Wire brush off the paint (with a drill) and remove a nut to evaluate the threads of the nut and rod. It might also be worthwhile to get a surveyor to inspect the keelbolts if you're not really wanting to replace them. Catalina suggested removing one or two layers of plywood (if installed) to get to solid core material if you have had decay from water intrusion and thread damage mainly on the top of the rod. Then after you glass over the exposed wood you can put new hardware on the the good portion of the threaded rod. Contact Catalina for their advice if the damage is more extensive. I replaced mine for the assurance that the keel was secure and for eliminating the keelbolt issue as a problem in a potential future sale. Let us know what course of action you decide on.

My final installation:
A 1.75" OD stainless steel flat washer, a 1.50" OD extra thick stainless steel flat washer and a flanged nut to spread the load as far outward as possible. This assembly made a significant difference in reaching and maintaining the torque rating as opposed to just the flat washer and regular hex nut.

Edited by - diySailor on 07/10/2012 19:02:10

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 09/05/2012 : 03:31:57

Just one last question. Is that UNC or Whitworth thread? They have the same 11 threads per inch but different thread angle. Thanks

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9081 Posts

Response Posted - 09/05/2012 : 06:08:54

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Tomas Kruska
 Just one question, you had the SS nuts? I suppose that's not original. My nuts are ordinary steel and rusted like the rod but not that much as yours.<hr height="1" noshade id="quote"></blockquote id="quote">When Catalina switched from the cast iron fin keel to encapsulated lead (1983?), they also switched from carbon steel nuts and bolts to stainless. I'm guessing they used carbon steel with the cast iron to minimize galvanic corrosion between them--don't know.

Edited by - Stinkpotter on 09/05/2012 06:09:28

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 09/05/2012 : 10:25:42

Yes thats right. I'm just not sure if you americans use whitworth threads for steel rods normaly or UNC?

Edited by - on

diySailor
1st Mate

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USA
39 Posts

Response Posted - 09/05/2012 : 14:36:20

Yes, the keel bolt threads are 5/8 - 11 UNC (course) for bolts and rods State side.

Edited by - on

JKBIXBY
1st Mate

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USA
38 Posts

Response Posted - 09/05/2012 : 16:58:40

The last time I did a bottom job we had it hauled at Hillmans just off the ship channel and did it there. The price for pulling it out was good and as best I remember it included three days out of the water. Then there was a per day charge after that.

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bigelowp
Master Marine Consultant

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USA
1778 Posts

Response Posted - 09/07/2012 : 18:29:39

Interesting thread. My 1980's bolts look horrible and have been a point of concern. The keel seems fine, minimal "Catalina smile" no "wobble" -- and the bilge is always dry unless there is a severe rain event. That said, I have thought from time to time that it might be prudent to sinter replacement or add new bolts. It has been my understanding that such a project is really for a professional AND very expensive -- especially for those of us who live near large, expensive cities like New York. I would be interested in anyone's experience with "machine shops" such as how you find one that understands marine issues. Or if anyone has used a cost effective yard (I know, oxymoron) in the northeast how it went. My guess is that for casual day sailing the bolts as pictured above will work fine. It's when the weather turns unexpectedly severe that the stress test would be experienced -- and while no one to date has reported a failure, I sure don't want to be the first!

Edited by - bigelowp on 09/07/2012 18:31:05

Stinkpotter
Master Marine Consultant

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Djibouti
9081 Posts

Response Posted - 09/09/2012 : 11:10:55

Peter: The fullest-service yard in your area probably is Norwalk Cove... You could probably get an estimate from them if you describe the job to sister in some studs in a cast iron keel in place. I suspect they've done that work before. Hathaway might be another option--they have a machine shop, riggers, etc., and do lots of work on large sailboats.

Edited by - Stinkpotter on 09/09/2012 11:11:55

bigelowp
Master Marine Consultant

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USA
1778 Posts

Response Posted - 09/11/2012 : 15:11:30

Dave:

Both have done great work for me and both are very $$$$$$$$$$$$$$$$$$$$$$$$$$$$. That said, living where I do I think you are right, when I am ready just take a deap breath and pay. I am intrigued, however, in the idea of finding a knowledgable machine shop that does industrial work and may be more cost effective . . . . OK, time to wake up!

Edited by - bigelowp on 09/11/2012 18:39:23

Jan Briede
Navigator

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USA
162 Posts

Response Posted - 09/11/2012 : 17:48:38

I sistered in 5 keel bolts and it was work! It took me a couple of weekends after which I needed to fix the smile etc. I'll haul the boat in March and will see how good the job was that I did.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 09/12/2012 : 06:04:27

Although it is on a C-22, here is an excellent step-by-step keel rehab blogged by another sailor at my club.

Start here and follow the posts... http://svstilltime.blogspot.ca/2011/11/dropping-keel-not.html

Starts with removal of a fin keel, and goes through to replacing studs, fairing, re-installing, and re-doing the bottom. And I can tell you one thing, if there is something Still Time is not, its still. He is a good (fast) sailor and I am regularly beat by him on race day. Which is tonight...

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9081 Posts

Response Posted - 09/12/2012 : 08:02:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Prospector
 Starts with removal of a fin keel...<hr height="1" noshade id="quote"></blockquote id="quote">...which is 1200 lbs. lighter...

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 09/13/2012 : 06:54:38

Yes Dave - to be sure there is a scale to be factored in, but it gives you a good feel for the magnitude of the task, and the effort involved.

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