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Old 24-09-2017, 04:24   #1
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Split down skeg centerline

Hi all,
I have an old contest 40, which I've been working on for the past year. I'm about to tackle a job, and I wanted to get a few opinions.

The skeg has a crack on its leading edge starting from about halfway down, all the way to the bottom, with some spots that look they haven't split(or were filled from PO). On the trailing edge, the cracking is much more wide, and goes from top to bottom.


Here is the whole crack after removing antifouling
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You can see here that it is fairly deep. I did hit the bottom though
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It's hard to see in the picture, but as opposed to the leading edge, this crack is a little more ragged
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The split pretty clearly looks like the seem between the two moulded halves of the hull.

Originally I was going to scrape a v out of the crack, and apply a few layers of fiber then fair the leading edge out.

Is there something else I need to look out for?
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Old 24-09-2017, 04:45   #2
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Re: Split down skeg centerline

Quote:
Originally Posted by teddythetwig View Post
The split pretty clearly looks like the seem between the two moulded halves of the hull.

Originally I was going to scrape a v out of the crack, and apply a few layers of fiber then fair the leading edge out.

Is there something else I need to look out for?
You need to determine what may be going on inside of the skeg. Including water ingress, & if there's any wood in there, rot. Ditto regarding any internal metal bits, as well as the rudder attachment hardware, & any rust that may be eating things from the inside.

Realistically, you need more structural material holding the 2 halves together than any adhesive shoved into the crack can provide. Even if there is none of the above listed type of internal damage. Meaning that you'll likely want to use multiple layers of glass & resin to bond the 2 halves together. And this will likely entail some grinding down, & rebuilding of the leading & trailing edges to allow for this thickness of glass, while still maintaining the skeg's foil shape.

But the 1st step is to better ascertain what's going on inside, if anything.
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Old 24-09-2017, 07:50   #3
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Re: Split down skeg centerline

From the last photo it appears that a steel armature may be rusting and blowing apart the two halves. Get it surveyed by a pro.
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Old 25-09-2017, 01:00   #4
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Re: Split down skeg centerline

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Originally Posted by Terra Nova View Post
From the last photo it appears that a steel armature may be rusting and blowing apart the two halves. Get it surveyed by a pro.
Hmm, I went back to the yard today, and this makes sense. There is a metal bracket at the heel of the skeg for hanging the rudder, and all the cracks get wider as they move down and aft.
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Old 25-09-2017, 04:22   #5
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Re: Split down skeg centerline

When you have splits like that, it's either an interior metal armature issue as noted or marine growth inside that is forcing it open, with the strong likelihood that it is the former.

The only real option is to open it up and investigate. You can cut some "ports" on one side and start digging but it's pretty clear to me that the whole thing should come apart and be reconstructed.
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Old 25-09-2017, 06:16   #6
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Re: Split down skeg centerline

Skegs don't have armatures, there is usually only some plates to tap the gudgeon bolts into. That looks quite typical to me. The two hull halves would have been put together and then they glassed the hell out of the inside of the skeg and poured it full of something (this is the usual method). That crack probably has an inch of glass on the inside of it. You were on the right track, fill it and fair it and move on. They rarely glass the exterior of these major structural seams, which can lead to a cosmetic issue, but the reason is because they put so much glass on the interior that it isn't structurally necessary. Usually, YMMV, etc etc.


Fire a drill bit into the crack in a couple of places and see what you hit. If it's a bunch of solid glass, you're golden.
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Old 25-09-2017, 12:29   #7
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Re: Split down skeg centerline

An abnormal internal pressure is causing your cracks: not an unusual problem in both rudders and skegs. Glassing over the cracks is a temporary fix, at best. The worst that can happen is a catastrophic failure ... which won't occour at the dock ...

Internally, fibreglass rudders, and many skegs, have a metal mandrel with welded on tabs, normally all stainless. Without oxygen, and underwater, stainless corrodes and expands as it corrodes - exactly what will eventually occour, if water gets into the rudder/skeg. The vertical cracks suggest a mandrel corrosion problem, caused by water ingress. Drill multiple holes to drain the water.

You need to find the cause, and extent, of the corrosion. If it were my boat, I'd also grind down the fore and aft edges of the rudder, and inspect for cracks.

Now is the time to call in a surveyor and/or x-ray the assembly(s). I'd also want to physically examine as much of the stainless as possible, before rebuilding the fiberglass.
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Old 25-09-2017, 12:35   #8
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Re: Split down skeg centerline

If the boat has been on the hard during a freeze the water can freeze and expand, causing clamshell components to split.
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Old 25-09-2017, 13:11   #9
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Re: Split down skeg centerline

Yes, I agree that water will expand when frozen and can cause cracks in both rudder and skeg. However, water should not be there in the first place. It needs to be drained and the cause of water ingress be determined, and rectified, so surveyor and/or x-ray still advised.
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Old 25-09-2017, 13:51   #10
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Re: Split down skeg centerline

It is easy to test for water ingres by drilling a small hole towards the bottom of the skeg.

I have seen similar cracks and none of them this far was structural. The skeg is built in two parts and, as it works, some fairing from the joint goes.

A more serious issue is always an option, but unless the gap drips for a day out on dry (first day out or so), there is no proof of such an issue.

Check, test and investigate, but do not loose your sleep.

Cheers,
b.
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