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Swing Keel Pivot Hardware Notes

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Initially Posted - 11/21/2004 : 22:22:03

<center>Swing Keel Pivot Hardware Notes</center>

From time to time a few of you have asked me for more info on the modifications I made to my swing keel pivot. Here are a few a low-res images of the modifications.

In the first photo, we see the stock pivot parts on top of the external portion of the added hardware. The two long bars were made by splitting an 14" section of 1-3/4" bronze prop shaft lengthwise in a bandsaw. Then four 1/2" holes were drilled and counterbored for silicon bronze bolts (shown). Also cluttering up this photo are the new pivot hanger bolts, a new teardrop zinc, an old pancake zinc from the cable area of the keel, and its new replacement zinc.

There's a sacrificial zinc at each end of each bar. These are made by sawing 5" teardrop zincs in half. In the next tow photos, we see the modifications from inside the boat. The square backing plates were made from the same 1-3/4" bronze half-round. The hull was reinforced with several layers of 14oz roving and epoxy in the areas of the bolt holes. There are of course lift out covers for the holes in the cabin sole.

The bolts for the bars and zincs are electrically bonded in the bilges by 10awg marine grade wire with tinned and soldered copper ring terminals. All the bronze hardware will be thoroughly cleaned for good electrical contact before being reinstalled. Polysulfide bedding compound is used.

There is a very heavy gauge wire from the mast step to one of the 1/2" bolts which allows the swing keel system to provide lightning protection. This feature has passed the real-world test with flying colors.

Let me know of you'd like more details, higher resolution images, etc.

-- Leon Sisson

� Leon Sisson

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ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 11/22/2004 : 09:47:32

Leon, what did you do on the outside of the hull to accomodate the extended fittings? Do they just bolt flush to the hull? (Reckoning so)

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 11/22/2004 : 21:31:46

ClamBeach,<blockquote id="quote">quote:<hr height="1" noshade id="quote">what did you do on the outside of the hull to accomodate the extended fittings?<hr height="1" noshade id="quote"></blockquote id="quote">The parts I added stick down from the hull maybe 3/4" or so at the swing keel pivot. If I were a world class one design racer, I might obsess about the added drag.

Being the cruising oriented slob that I am, I just added the cut up teardrop zincs to give it a semi-streamlined head and tail.

-- Leon Sisson

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ronrryan
Admiral

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USA
561 Posts

Response Posted - 11/23/2004 : 21:25:15

Leon, many thanks for your post. Two questions, possibly of interest to others as well: (1) Does your keel have the epoxied-on discs in the "crescent" designed to reduce slap in the trunk and further stabilize the keel in place? (2) Have you made any modification to the tail end of the keel, a/la the "keel-up bang fix" mods shown on the tech tips site? All these modifications might make the keel a bit more able to "take the ground" as our English cousins say...Thanks for more info, ron srsk Orion #2343 SW FL

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Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 11/23/2004 : 22:20:51

<blockquote id="quote">quote:<hr height="1" noshade id="quote">originally posted by ron:
(1) Does your keel have the epoxied-on discs in the "crescent" designed to reduce slap in the trunk and further stabilize the keel in place?<hr height="1" noshade id="quote"></blockquote id="quote">I think you're talking about a pair of Plexiglass or Lexan disks, maybe 4" to 6" diameter, one glued to each side of the head of the swing keel, and intended to bear on the head of the keel trunk to reduce "swing keel clunk." Nope, I didn't go that route.

When I first got my 1979 C-25, the pivot hole in the swing keel was worn hourglass shaped, maybe 1-1/2" at the waist, 2" at the outside, very oval and uneven. I had the keel removed, sandblasted, and the p[ivot hole bore cleaned up to clear a 1-1/2" O.D. bronze bushing. I had a machinist set the radial pivot clearance to about 0.025" by boring the bushing, and the axial clearance to maybe 1/16" to 1/8" by milling the pillow blocks or carrier bearings. I then bedded the bushing in WEST epoxy reinforced with powedered metal and maybe milled fiberglass. That cured the keel clunk for sure.

This pivot repair has withstood the test of several years of use and abuse. I happen to have the pivot apart right now for regular preventative maintenance. The epoxy around the bushing shows no signs of chipping or cracking. The moving parts still fit tight, and were still coated with the waterproof grease I put on them 2 years, and about a thousand saltwater miles ago.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">originally posted by ron:
(2) Have you made any modification to the tail end of the keel, a/la the "keel-up bang fix" mods shown on the tech tips site?<hr height="1" noshade id="quote"></blockquote id="quote">When I did a refit on the boat soon after getting it, I removed several bad repairs to the hull below the waterline, including a thick peeling patch inside the aft end of the keel trunk. After grinding back to solid fiberglass, I built up lots of new glass cloth with epoxy resin to restore or exceed the original exterior shape. I then faired the entire wetted surface with epoxy putty and a longboard before applying several layers of epoxy barrier coat.

I also got a copy of the modified factory layup schedule for the later year C-25 swing keel trunks. I then added much of the additional roving laminations to the trunk from inside the cabin, including cutting away some of the liner and tabbing for better access. I was especially careful to pile on the epoxy and roving around that vulnerable aft end of the trunk where the keel cable to-hull is.

-- Leon Sisson

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ronrryan
Admiral

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USA
561 Posts

Response Posted - 11/24/2004 : 17:56:23

Leon, thanks. Sure hope there is a way to have your photos and description end up on the tech tips list...??? Ron srsk Orion Fla

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ronrryan
Admiral

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USA
561 Posts

Response Posted - 11/24/2004 : 17:56:25

Leon, thanks. Sure hope there is a way to have your photos and description end up on the tech tips list...??? Ron srsk Orion Fla

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Jay Schkloven
1st Mate

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USA
84 Posts

Response Posted - 11/27/2004 : 13:43:45

I have sanded and cleaned the keel where rust has come through. The keel was then coated with a 2 part epoxy mix that has held up well. There are a few rust stains on the keel but no problems. I use the boat in the Chesapeake Bay. The boat sits in Frog Mortor Creek at a slip. I have not seen a zinc on anyother swing keel in the marina, but I will look this winter. I have not seen any problems with the keel or cable. Is the zinc necessary? I have a zinc on the motor, but do not keep it in the water most of the time.

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