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 Catalina/Capri 25/250 Sailor's Forums
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 swing keel pivot pin		  New Topic  Topic Locked
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cleffe
Deckhand

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USA
21 Posts
Initially Posted - 09/13/2007 :  20:20:12  Show Profile
question for anybody. i have a 87 c25 swing keel, i have removed the keel and had it sandblasted. i then took it to the machine shop to bore out the worn pivot pin hole and press a new sleeve into it. while at the shop i was talking to the guys there and showed them the brass pin i purchased from catalina direct. they were amazed that they would use brass for such a heavy keel. they strongly recomended a stainless steel pin and to replace the s.s. bushing with a brass one. they thought that the brass pin was to weak/soft. they gave me a s.s. pin so i have the hard part done, but my question is:
is there a reason for the brass pin, or do you think this is a good idea. it seems like a good idea to me, but i may not be aware of something? any suggestions thanks
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ClamBeach
Master Marine Consultant

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3072 Posts
Response Posted - 09/13/2007 :  20:40:45  Show Profile
AFAIK the keel pin isn't brass, it's bronze... which quite a bit harder and stronger than brass. also I believe bronze is slightly less reactive in saltwater than many common stainless alloys.

IMHO: Either bronze or SS should work as a pin.. The PO on my boat had replaced the keel pin with SS and epoxied it in place. No wobbles after many years of service though the bronze keel hinge is starting to wear just a little bit.
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jerlim
Master Marine Consultant

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USA
1484 Posts
Response Posted - 09/14/2007 :  18:45:01  Show Profile
AFAIK???
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ClamBeach
Master Marine Consultant

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3072 Posts
Response Posted - 09/14/2007 :  19:11:10  Show Profile
Standard Web abbreviation for 'As Far As I Know...'
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Leon Sisson
Master Marine Consultant

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USA
1893 Posts
Response Posted - 09/15/2007 :  19:09:53  Show Profile  Visit Leon Sisson's Homepage
IMHO (In My Humble Opinion ) most stainless steel alloys are poor choices for submersion in water, particularly warm stagnant seawater and under heavy load (as a percentage of ultimate tensile strength). I consider silicon bronze is a much better option for submerged use.

Stainless steel (stains less, really -- not stain proof) requires a supply of oxygen to avoid or reduce rust damage. (I realize that's counter intuitive -- hang on, it gets worse.)

Most of us are familiar with the symptoms and progress of rust in carbon steel -- surface oxidation, pitting, flaking, even to the point of 'plates' of rust popping off, orange near the surface, darkening through brown to black the deeper you dig. The fault lines/planes run more or less parallel to the surface (the source of oxygen). We've all seen steel boat trailer frames with rust falling off like tree bark, which still retain usable strength, and can even be salvaged with enough sandblasting, acid etching, and really good paint.

In stainless steel alloys, corrosion creates fault lines perpendicular to the surface. What can appear as a surface scratch or hairline crack can be the edge-on view of a shear plane extending nearly the entire thickness of the fastener. (Remember the lower pintle failure photo I posted a while back?)

Silicon bronze and similar marine alloys are not only more resistant to corrosion, but the progress of any corrosion is much easier to evaluate with the naked eye.

So what was Catalina thinking when they used stainless steel fasteners to attach the 1,500 pound swing keel? Beats the heck out of me, but it might have included the phrases "stored on a trailer and day sailed on a fresh water lake" and "marine grade bronze sure is expensive."

My 1979 C-25 swing keel has spent all but a couple years of its entire life floating in tropical saltwater without a keel failure that I'm aware of. I replace the submerged stainless steel parts every couple of years. Being a belt&suspenders kinda guy, I also added a thru-bolted bronze support at the pivot, I'll be the first to agree such a level of overkill borders on nutty paranoia. On the other hand, I've put my swing keel through abuse which might make the original designer cringe, and I haven't had any problems with things breaking.

-- Leon S.
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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.