Catalina 27 crack at rear of keel. Not a “smile” issue...

Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
Hi, my boat is on the hard in its cradle, and I noticed a small crack just aft of the keel. I’ve sanded down to look and find a crack in the hull that, judging by the added mat and different colors of fairing I find, has been an issue before. The crack is a V shape, following the keel shape, about 3” long each side, and is showing moisture as I sanded it. I did not notice any significant leak last season, but my guess is it goes all the way through. I want to make a good repair as I’ve already fixed the keel stub, and want to keep the boat for long time.
My current thinking is to cut up the cabin floor above this point ( inside the boat it is halfway between the bilge opening and the engine hatch ), clean/sand the hull and the apply a significant amount of 1708 and epoxy (10 layers - 0.5”, feathered in size, starting 24”*12” ). Then go outside, grind out 1/4” or so over 12” area and then glass it back with more 1708.
Do you kind folks have any better suggestions ? I did find a post where an owner had a yard grind out the cracked area and replace it, but with the complex shape (hard to get cloth to form with good strength ) and high loading I don’t like that idea.
Also, any insight as to how the cabin floor interfaces to the hull ? I can feel that the cabin floor has ply bonded to its underside, but it is tabbed or stuck to the hull some point ? I don’t want to cut out my access hatch shape and then find I can’t remove the piece I cut..
 

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RoyS

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Jun 3, 2012
1,276
Hunter 33 Steamboat Wharf, Hull, MA
Not an expert in this area, just some thoughts; If it were me I would not remove flooring at this time. Check that cradle rear supports are not too tight. Boat should be resting on keel. Tighten all keel support nuts. Add a few layers of cloth and epoxy on the outside and fair. Check it again after this season on next haul-out. If it cracks again then re-assess.
 

Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
Thanks for input Roy. My boat sits in the standard cradle, in which the four support posts are not adjustable. It has been a concern for me, as obviously where it sits fore/aft in the cradle affects keel/post load so there is a fair chance in has been mispositioned a time or two over its 36 years. I do also suspect it is the time on the hard that is causing the crack issue rather than the time in the water, where the loads are much more evenly distributed. However, the prospect of a leak or possible keel loss under way are significant concerns.
Are there any further opinions out there ?
 
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Jul 6, 2013
174
Catalina 30TR, Atomic 4 2480 Milwaukee
I agree with Roy.
I’ll add that if the material in the crack is soft, I would dig it out and backfill with epoxy.
 

Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
Thanks for the input. I am now considering plan 2 which has some advantage. I will address the crack externally as Bob/Jim suggest and splash. Assuming that goes well and no leaks - go sailing.
However, I will continue with the interior repair over the summer. I like the advantage this provides as I can now build the interior glass in the hulls "natural" position, vs the clearly stressed state it has on the hard. As I'm not having to grind down inside ( I will clean up then just build extra thickness ) the work poses no risk. Only small change is I'll need to catch any drips from the prop shaft while I'm working, and keep the area dry.
Anyone see any issues glassing while afloat ? I won't be laying glass until the water is above 50F - that's June around here..
 

Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
I decided to proceed and took a look at the hull from the inside. Good news, all looks sound, so the outside crack is probably nothing to worry about as previous guidance had suggested. I’m still going to beef it up to prevent re-occcurance.
In case someone has a similar issue, here’s how I made the inspection hole.
First I layed out the hole, staying on flat area so I knew I was still over the plywood and not close to the hull.
I made the corners a 3 inch radius, so marked the hole centers with the inner lines of tape.
At each center I placed wooden pins hot glued to the sole which interface with an attachment I made for the rotary tool. I took three passes at increasing depth, having measured plywood depth by breaking through where I knew there would be a space below the plywood.
Then I hot glued a wooden guide between the radii, and made the straight cuts through the glass with a vibratory tool. I made an aluminum “spacer” to fit onto the vibrating tool so it didn’t attack the guide.
Then finished off with wood cutting vibratory tool to cut the plywood.
All, went very well. The part removed will be a able to be put back as a removeable access hatch. Did find that the plywood had delaminated, so I can fix that before it goes back.
 

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Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
Well, I was out at the boat today and took a closer look at the inside area, and what I though was a black mark where the bilge hose had rubbed is actually the crack. I was able to scratch off pieces of delaminated glass down about 1/4”.
So I have a bigger problem. I’m planning to sand it out from the inside with 12\1 slope, for about 1\2 inch and then glass back with 1708\1808 before doing similar on the exterior. My only concern is if the crack might grow as I sand it back... does anyone know how thick the hull is in this area ?
 

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Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
I have also lowered the rear cradle supports, removing loading on the cracked area. The crack should now be neutral to slight compression loading.
 

RoyS

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Jun 3, 2012
1,276
Hunter 33 Steamboat Wharf, Hull, MA
Just a thought: Thinking of forces that could stretch the connection between the hull and the keel. Hard groundings are obvious. You already adjusted your cradle. What about your shrouds? If your shrouds are tightened excessively you would effectively be pulling your hull away from your keel since your mast or compression post is set on top of the keel. Just a thought.
 

Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
Thanks for the thought Roy. I don’t slacken the shrouds for storage, the assumption being it will happen naturally as the aluminum mast contracts more at low temp than the shrouds. I know the backstay in particularly loses tension as I can feel that when I climb aboard. I was hoping to get the work done this week as I’m furloughed, but the weather let me down.
 

Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
Quick update : I drilled through the hull where the crack is. It is only about 5/8 thick. What surprised me when I started grinding was that it was not solid glass, as there is a very thin (1/8inch) layer of foam in the middle. Luckily it is closed cell foam and the through crack hadn’t caused the foam to get saturated.
What I’ve done is to grind ( 36 grit on my angle grinder made for quick work, finishing off with 60 grit on my vibratory tool ) from the inside sbout half way through and feather the groove, and then glassed back with 1708 and epoxy, plus several extra layers.
Then, I repeated similar process from the outside, taking the grinding all the way until I reached the glass I put in from the inside. I also took the chance to add some extra glass at the rear of the keel stub, as while grinding I found a decent sized bubble in the existing glass (2” by 1/2”).
Now just need to fair the outside, barrier, and bottom paint. ( and put back the stuff I tore up inside...).
 
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Kopite

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Mar 11, 2015
107
Catalina 27 Monroe MI
Back in the water, and everything good. Have decided to modify my cradle to add screw jacks to each leg so I can adjust load - the cradle is nice but very dependent on exact boat position, and I don’t know what position it was designed for...
 
Aug 1, 2011
3,959
Catalina 270 255 Wabamun. Welcome to the marina
You should have jack screws, and 4 may not be sufficient. Also, just in case, do not focus on the boat sitting "flat" in the cradle. You should be able to drop one pad at a time with little to no chance that the boat would fall over, but if you had a pad 1/2 way along each side, there is a significantly reduced chance of "oil canning", and a much better opportunity to paint, or maintain.
The attached picture does show a trailer, but, you get the point, there is still load on each pad, but the position of the boat is entirely dependant on where it "wants" to sit, and in the case of my keel, that's not flat.
DSC00437 copy.JPG