Repairing a Rudder with Polyethylene Glycol

[Catch the Sun]

I am looking to repair a rudder for my C&C 32. This rudder has a wood core that has become saturated with water. I understand that water infiltration in a rudder via the post is common but as the wood core freezes each winter the fibreglass shell has begun cracking like old porcelain and the moisture seeps out , and presumably in, through these cracks.
This fall after I hauled out I drilled a ¾ hole from the bottom of the rudder up into the wood core. There was no flush of water when I did this but I did drill out some damp saw dust and the occasional drip of water.
I can see that if I don’t deal with this the rudder will continue to degrade over time and could become a serious issue of seaworthiness. Granted, where I sail seaworthiness is not a major concern still I’d like keep my boat solid so that she can keep me safe.
Somewhere I read about infusing Polyethylene Glycol into the core to displace the water and stabilize the wood preventing it from absorbing water in the future. Has anyone done this? How does one infuse a liquid into the wood core when it’s encased in fibreglass? I’m envisioning a series of holes drilled through the fibreglass into the wood through which I would inject the PEG somehow. Once I’ve confident the wood is full of PEG I will rout out and repair the cracks and maybe go over the whole thing with a fresh layer of glass for rigidity and then Interprotect.
C&C does sell a replacement rudder but at $3,120.00 I’m thinking I can do a repair myself and save some funds for something else.
https://www.c-cparts.com/product/product_view.aspx?UID=5a4e550a-65be-46cc-a9fb-a6ca0b45b010
If anyone has any experience with this type of repair please let me know.
Mark

 

[RichH]

A mixture of PG + borax + tin compounds have been touted over the years as a chemotherapy for wood rot. The PG 'may' help against freezing .... but you will have no way of knowing if the PG penetrates into the affected area of rotted wood core, even if you vacuum 'bag' the rudder, apply a high vacuum and then fill the rudder with PG. Even then you can never be 'confident' that the wood is saturated with sufficient PG ... AND any rot that has weakened the interior structure still cannot be ascertained.

If you suspect that rot is interior to a rudder the only way to be sure is to 'fix it' or replace it ... not a 'halfway' measure. Although a 'core' in such a (box beam) structure bears comparatively little load, its important job is to the keep the 'skin' at a defined geometric shape, once that 'holding power' (now rotted) is compromised you have a much weaker structure overall because that 'skin' of thick fiberglass 'may' now be able to 'flex'.

 

[Don S/V ILLusion]

Sounds like someone with a vivid imagination contrived this scheme. For one reason, I can't buy the concept of glycol displacing water already there - maybe mixing with it but not displacing it physically. Mixing might lower the freeze point some undetermined amount but how would you know?

Secondly and more important, if water has infiltrated the rudder, the chances are great that the welds throughout the steel webbing holding the rudder in place have rusted and therefore been compromised. Even if the above trick could displace the water, the damage is already done.

The only way to understand what, if any damage has been done and fix it is to strip down the rudder and inspect and repair both the frame and structure.

 

[Catch the Sun]

PEG is commonly used to stabilize compromised wood or to prevent green wood from cracking as it dries.
http://owic.oregonstate.edu/pubs/peg.pdf

 

[Don S/V ILLusion]

PEG is commonly used to stabilize compromised wood or to prevent green wood from cracking as it dries.
http://owic.oregonstate.edu/pubs/peg.pdf

We know but not when the wood is encapsulated and water has potentially rusted the steel holding the rudder on the post or has already saturated the wood. Your boat, your choice...

 

[Catch the Sun]

I was expecting to wait weeks or months for replies and here we are just hours after my original post and you have provided two thoughtful and helpful replies. Thank you for that.
Firstly, I’d love to know what the interior of this rudder looks like so I’ll contact C&C Yachts and see if they can help me with that. I don’t know if the structure is hollow in places or if the core is completely encased in resin. If it’s hollow I could simply fill it with PEG and drain it after a few weeks before fixing the surface cracks.
I don’t believe the interior is rotten just damp and I don’t think the rudder has structural issues yet. I believe the steel is stainless and should be solid. The freezing and expanding of the core and cracking of the surface is what I am concerned with.
Don, you’ve given me an idea if the rudder is solid on the inside. I could introduce PEG into the top of the rudder and draw it out at the bottom with a vacuum pump. This would take time and I would have to apply heat the whole time. OK admittedly, that idea needs some work.
The surveyor I hired suggested drilling into the wood from the bottom with a long bit and trying to make Swiss cheese out of the core to help it drain. Clearly he wasn’t concerned about the structural integrity of the core. He also suggested that I install a drain plug at the bottom and drain it each fall. As I stated before I have drilled into the wood from the bottom but not quite Swiss cheese yet.

 

[Don S/V ILLusion]

I understand your desire to deal with the problem externally which isn't necessarily wrong but you'll never know how well it works without opening it up. The rudder is packed with closed cell foam which itself will not absorb water. The sole concern is the steel webbing.

As you said, it may be stainless but probably not. REGARDLESS, the welds are not stainless and will rust quickly especially in the absence of oxygen which is what you have inside a rudder filled with foam.

No amount of water displacement therapy will obviate the above.

I know RichH and his advice is authoritative but you don't know either of us so by all means find someone you trust and who has some understanding of the issues here. Just keep in mind the builder, who did not make the rudder, might not be the best source of info on the rudder and specifically it's composition. Also, they have no real experience in fixing it once problems arise. My strong suggestion to you is to find someone who does.

 

[Merlin Clark]

I'd take my handy 4" side grinder with a cut off disc and cut all around the edge then split it open. The FG skin should be plenty thick enough to handle some prying.
Dig out the core and inspect the welds between the tangs and the post (better yet have a professional welder inspect), repair what needed it and then using very low density filler and epoxy to fill the void and then high density/epoxy to glue the shell halves back together. Lay a good bead of something really sticky and nasty like 5200 around the post where it enters the rudder as this is where the leaks I've seen happen.
Rudders have been known to fail when the SS tangs break away from the SS post after corrosion has weakened the welds and surrounding metal.
Take a day or 2 and I'd KNOW it was right.
Just my 2c.

 

[Catch the Sun]

More great advice.

Don, Until now I had not been concerned about the steel inside but I know you are right.

I had thought about splitting it open I would not have though that would be possible without destroying it.

Now I’m thinking I should bite the bullet and buy the new rudder because

1. It’s available
2. I could fix the old one and have a spare.
3. Money is only paper right?

 

[Gunni]

You have got a wet, wood-core rudder with a cracking skin. Don't know the condition of the stock and web. Before spending lots of time taking it apart and repairing it I would look at a new one. That factory price looks to be high. Did this last year and my B411 rudder was $1,500. The factory is not your only source, there is a whole industry building sailboat rudders. FinCo and Foss Rudder build C&C rudders. Google them up.

 

[Catch the Sun]

Decided to route out the cracks and repair with epoxy. I think it was too cold when I did this and the epoxy sagged down the cracks. Lesson learned.

 

[Squidd]

Did you Bondo the cracks before you put the epoxy on...?

 

[Catch the Sun]

I used West Systems Microlight filler. Maybe not enough. It was thick like peanut butter when I put it on but it still sagged. It was probably too cool out when I did this.

 

[Catch the Sun]

This job is now done. The cracks repaired and the whole rudder freshly painted with Interprotect 2000 and VC17. It looks like new. Before I launch I will attempt to seal the rudder/stock joint and I was going to use sicaflex. Is there a better choice?

 

[py26129]

For future reference, you have a composites shop right in Ottawa. http://www.fastcomposites.ca/site/marine/

Matt

 

[kenn]

The surveyor I hired suggested drilling into the wood from the bottom with a long bit and trying to make Swiss cheese out of the core to help it drain. Clearly he wasn’t concerned about the structural integrity of the core. He also suggested that I install a drain plug at the bottom and drain it each fall. As I stated before I have drilled into the wood from the bottom but not quite Swiss cheese yet.

This is a reasonable first approach, if the core actually isn't structural. Also you can possibly make use of our long, dry Canadian winters by letting the rudder sit in a shed or barn over the winter, to help draw more of the water out. Drilling and draining, followed by hole-patching, a drain plug, and stopping water ingress into the top of the rudder, might be sufficient to keep the rudder going.

I'd take my handy 4" side grinder with a cut off disc and cut all around the edge then split it open. The FG skin should be plenty thick enough to handle some prying.

Dig out the core and inspect the welds between the tangs and the post (better yet have a professional welder inspect), repair what needed it and then using very low density filler and epoxy to fill the void and then high density/epoxy to glue the shell halves back together. Lay a good bead of something really sticky and nasty like 5200 around the post where it enters the rudder as this is where the leaks I've seen happen.

I agree this is the ultimate fix (short of a brand-new rudder). Now that I've done some fiberglass structural work, I don't think the splitting and re-assembly would be too daunting and you could end up with a rudder that's better than original. Again, not a bad winter project.

 

[Robert M.]

Couple of points:

1. I agree with the comments that corrosion of the SS web and its welds are the most important concern.

2. I don't agree with the comment about splitting the rudder into two shells. First, it can be very difficult to do. Second, assembling the rudder stock and the repaired shells is extremely difficult to do well. Without a jig, proper alignment of the shells around the shaft and web would be a nightmare.

3. The method I've used is to open windows through the skin on one side of the rudder. (Use the other side to serve as a form to help restore the original shape of the repaired side.) Then remove the failed core material and replace it with blocks, either balsa or a synthetic core material, buttered with resin putty.

4. Then restore and fair the skin of the repaired side with new fiberglass laminate. Then remove the failed fiberglass of the other skin and repair and fair it to the original shape.

5. The area at the top of a typical spade rudder is often the biggest part of the problem regarding water penetration and should receive special attention. A thin fiberglass shell is often bonded to the stock with resin putty that has separated from the stock, allowing water penetration. After taking measurements, remove all of the original material. Then mold new fiberglass laminate completely around the stock with resin and CSM. Mold and fair it to the original shape.

6. One trick others have used is to create a shallow groove in the top surface of the fiberglass shell around the shaft. Then fill the groove with 3M's 5200, providing a flexible seam between the shell and shaft. This trick isn't necessary if the repair has been done as outlined in 5. above.

 

[Steve Dion]

I am with Don. You may know that you have a SS interior structure, but you will have no idea on the welds (which is normally the problem).

From a safety issue, I would "assume" that the rudder is damaged and needs an inspection. Maybe you can get one of those cameras that allow you to drill holes and look inside your rudder.

http://www.harborfreight.com/digital-inspection-camera-67979.html

Some models will allow you to store the photo for further examination (I don't know if this one does this or not).

 

[Bob McL]

Quote: Some models will allow you to store the photo for further examination (I don't know if this one does this or not).

It says it "captures" jpeg images, so it should

 

[JVB]

One way to dry out a core, rudder or hull, is to duct tape a shop vacuum cleaner to an opening to the core. The reduced air pressure will hasten water evaporation. It might take two or three days to get to the point where no more water is coming out.