Cracks around strut caused by using cutlass bearing tool

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Mon, 12/29/2014 - 08:12

Chachere

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Joined: 10/27/10

Posts: 826

Cracks around strut caused by using cutlass bearing tool

The issue of cracks in the "skeg" around the prop strut has been the subject of several threads I found, but I've got a new wrinkle here.
    This weekend I began replacing the cutlass bearing using the Association's tool, and the old bearing was about halfway pressed out when there was suddenly a "bang" and a crack developed in the area of the skeg aft of the strut (see photos). I could actually see light through to the other side. I was totally surprised, as I had replaced the bearing once before with no problems whatsoever.
    I immediately backed off the tool and the crack closed up. I also unbolted the coupling flange to give the prop shaft a little more play (I'm also in the midst of trying to slowly press off the coupling flange so I can replace the shaft log hose, but that's another headache), and resumed the bearing removal with no further problems.
   I can't figure out why using the tool would have produced some sort of pressure that distorted the hull around the strut in this manner, since the tool is exerting force only on the bottom of the strut. But be that as it may, I need to figure out how to repair this crack, and whether there is other damage I need to look for.
From reading the other threads on strut repair and viewing the drawings of the strut installation, it does not appear that the "skeg" area aft of the strut is structural, so I'm thinking that maybe I just need to grind out the crack and inject epoxy? Or is something more extensive involved? Should I pull the water tank and inspect the inside area as well?
   Thoughts/suggestions/comments on the repair (and theorizing as to why this happened) welcome.

—

Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY

Tue, 12/30/2014 - 09:06

TomSoko

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Joined: 2/15/07

Posts: 978

Matt,
If you've done research on this site, you most likely have seen the picture of Gerry Douglas, Tom Senator, Bill Harvey, and myself looking at the strut of a C36 during production (Catalina Factory photo gallery). The crack you see on your boat is simply the filler around the strut separating from the hull. The filler is not structural. I have absolutely no idea why that would happen when changing your cutless bearing. I can only guess that some part of the cutless bearing tool was not cleanly and squarely on the strut, and it was pulling/pushing the shaft and strut out of alignment??? It's a royal pain the take the aft water tank out, but I would do so just to check the nuts/bolts under the tank holding the strut in place. Once you verify that nothing is loose, I would enlarge the crack, fill it with thickened epoxy, and forget about it. Hope this helps.

—

Tom Sokoloski
C36/375IA Past Commodore
Noank, CT

Tue, 12/30/2014 - 13:34

(Reply to #2) #3

Chachere

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Joined: 10/27/10

Posts: 826

   Thanks so much for the reassurance, Tom, to my surmise that the skeg material is not structural.
I'll probably go ahead and remove the water tank just to check things out, but I'm not feeling any movement at all in the strut --- probably why it was able to crack the skeg.
   As to the cause, I should add that when I got the bearing out, the brass shell at the end was pretty chewed up. My best theory is that the collets that the tool uses to push the bearing out weren't precisely lining up with the edge of the brass bearing shell, and partially slipped between the bearing and the shaft (displacing the rubber material) and thus caused some lateral force on the shaft. Hard to imagine it could be so much force as to do this, but its the best theory I can come up with. I'll try to post a picture next time I'm at the boat of the old hearing, just so other members can avoid this problem.
    As I said, I've used the tool before without this problem, but it was the Association's other tool (I understand we have 2 now), so perhaps the collets don't line up as well on this one.

—

Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY

Tue, 12/30/2014 - 12:23

(Reply to #3) #4

newguy

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Joined: 8/1/11

Posts: 408

See if this helps: https://www.catalina36.org/members/technical/maintenance/replacing-prop-...

Specifically this image:
https://www.catalina36.org/sites/default/files/styles/large/public/legac...

Looks like the crack follows where the fairing compound meets the hull structure. Fairing compounds are typically brittle as they don't contain any cross-linked material. I don't think that anything happening "inside" of the strut tube would do this, but rather a side load on the entire strut, perhaps simply by the torque imposed by tightening the bolts on the tool.

—

Nick Caballero
Retired C36/375IA Mk II Technical Editor

Tue, 12/30/2014 - 13:31

(Reply to #4) #5

Chachere

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Joined: 10/27/10

Posts: 826

Thanks, Nick.
Yes, that was one of the threads I looked at.
I should note that our Encylopedias section of the site has a page titled "Strut Repair Info & Drawing"
( https://www.catalina36.org/members/encyclopedias/strut-repair-info-drawi... ) but the links in it are all dead.
But the search tool came up with quite a few alternative articles and threads, which I'll catalog below for members' future reference:

—

Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY

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Cracks around strut caused by using cutlass bearing tool