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Old 25-04-2022, 10:11   #1
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Rudder Crack Repairs

There are a variety of thin cracks in my rudder; some at the toe, one long one at the middle, and some around the stem post.

Right now I am planning on grinding out shallow V's in the cracks and applying epoxy.

For those in the middle and up to the stem post I'm planning to grind out shallow V's and applying G-Flex.

Alternatively I can apply glass fabric on the "cheeks" on each side of the stem and address the cracks on the top as described with G-Flex.

Thoughts?

BTW, its been in fresh water all its life. I did drill holes in the bottom to drain it and only a small bit of water came out.
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Old 25-04-2022, 10:59   #2
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Re: Rudder Crack Repairs

Would be interesting to see how deep the cracks are when you V them out.
If they are deeper than the surface gel coat, then there still may be more water in the rudder/foam than you think.

How did you initially notice the cracks? Where there wet spots in those areas?
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Old 25-04-2022, 11:49   #3
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Re: Rudder Crack Repairs

Guess what I've been doing the past three weekends.

I'm short on time, so have to be brief:

The cracks are likely from water freezing and expanding.

Drilling holes in the bottom doesn't do much, since there's no intake. On the previous boat I'd anually drill two holes at the bottom, two on the sides near the top (same places every year) and by spring it would be dry.

New-to-us boat rudder, not so much. It was still weeping in spring, likely because water was retained in voids in the foam. I drilled a couple more holes top and bottom, and couldn't blow out the water I knew was there. So I drilled a dozen holes, and blew out water with a compressor for three weekends; it was horribly inconsistent- blowing in hole 2 would drive water out hole 7, but blowing into hole 10 would drive water out holes 2 and 6. Weird, but that's voids. Eventually got it pretty well dried out, blew in Great Stuff Window, which is closed cell, low expansion foam. Then filled holes.

I suspect you still have water in there. At least put a hole in the rudder side near the top and try to blow out water. If you have water retained in the rudder and patch the cracks, you'll simply get new cracks next Spring.
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Old 26-04-2022, 06:32   #4
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Re: Rudder Crack Repairs

Quote:
Originally Posted by Bill O View Post
How did you initially notice the cracks? Where there wet spots in those areas?
This is the first year I owned the boat. The cracks showed up through the paint. The paint is VC 17 so its quite thin. No water showed through them.

Tetepare's point is a good one and I hadn't thought of using a compressor to get more of the water out.

As a side note the Surveyor recommended wrapping the rudder in something white (Tyvek) to reduce differential warming as the sun passed over. This helps prevent cracking as the rudder warps.
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Old 26-04-2022, 07:24   #5
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Re: Rudder Crack Repairs

Quote:
Originally Posted by Tmacmi View Post
This is the first year I owned the boat. The cracks showed up through the paint. The paint is VC 17 so its quite thin. No water showed through them.

Tetepare's point is a good one and I hadn't thought of using a compressor to get more of the water out.

As a side note the Surveyor recommended wrapping the rudder in something white (Tyvek) to reduce differential warming as the sun passed over. This helps prevent cracking as the rudder warps.
Tetepare's idea of adding more holes is a good idea, but think more needs to be done to get the water out of the foam core than just the compressor. If you could bag and continually pull a vacuum on the rudder with some slight warming, you could get more water out. This would take more time, but a better process.

Once the water is in a confined space and freezes/expands, it will cause enough pressure to form cracks/rupture the outer skin. Not sure which would be worse for structural integrity, a solid freeze/expansion or freeze thaw cycles.

Having lived in MI for a long time, I know the winters are very cold and ice can cause major damage if not attended to properly.
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Old 26-04-2022, 15:11   #6
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Re: Rudder Crack Repairs

I assume since it's a spade rudder that the post is solid, correct?
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Old 26-04-2022, 15:22   #7
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Re: Rudder Crack Repairs

They look like just gel coat cracks, but hard to say.
You can drill and drain the water but I can tell you from experience, it will still be wet inside.
I cut a window on one side of a rudder and scraped out all the wet foam and let it dry. Filled with light weight epoxy filler from the top after glassing the side back in.
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Old 27-04-2022, 09:01   #8
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Re: Rudder Crack Repairs

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I assume since it's a spade rudder that the post is solid, correct?
Yes, solid and recently surveyed.
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Old 28-04-2022, 06:01   #9
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Re: Rudder Crack Repairs

Quote:
Originally Posted by Bill O View Post
... Once the water is in a confined space and freezes/expands, it will cause enough pressure to form cracks/rupture the outer skin. Not sure which would be worse for structural integrity, a solid freeze/expansion or freeze thaw cycles.

Having lived in MI for a long time, I know the winters are very cold and ice can cause major damage if not attended to properly.
Ice jacking/heaving occurs when water permeates a confined space within a structural support, ultimately causing structural fracture, when the water freezes and expands. Water expands its volume, by up to 9%, when it turns to ice.

Freeze-thaw cycles are a severe problem in civil construction [one of my late father's specialties], but often require the addition of more water during the thaw cycle - not likely with a boat, stored on the hard.
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