What's inside my rudder?

[Dean Abramson]

Can someone tell me how my 31's rudder is constructed? In other words, what all is inside, and how it's put together?

I had a tiny crack and was using the corner of a flat file to open it up to do a repair with epoxy. It was disconcerting to find that in that location (who knows where else?) the digging was easier than I would have liked. As I opened up the crack I got into an area that was somewhat crumbly. Not sure what to make of that. Maybe an earlier repair that was not done well? ??

I decided to quit digging, before I found out more than I wanted to know! I wetted the area with West System epoxy, let that dry for about 10 mins, then filled the cavity with epoxy thickened with colloidal silica. I feel okay about the rudder for this season. But going forward, I'll need to know more about the rudder construction if I'm going to diagnose and repair any issues.

The little crater I filled has a rim of about 1/4". I fixed three other cracks, and in those cases found nothing to alarm me.

[Paul D.]

CD Rudders are constructed with two preformed fiberglass half shells filled with reinforced polyester compound. This compound surrounds a pre formed rudder shaft. Two layers of glass tape are added to reinforce the shell joints. The shaft is 304 stainless probably 1" or 1 1/2" diameter bent to fit inside the rudder. There is a bronze gudgeon in the bottom of the rudder to accept the bronze pintle embedded in the bottom of the keel. They are pretty well built as rudders go but not without issues.

When you are poking and finding soft mush you are probably going through the fibreglass shell and into the filler which may or may not be wet. If it is wet it may weaken the rudder and under a heavy torsional loads it could split and go to Davy Jones Locker leaving you with a bent stainless shaft trying to the turn the boat. A moisture meter will be able to tell a significant level. Often rudder readings are higher than a hull would be. If it is the original rudder it may well be wet and mushy in there. I think all our original rudders have some degree of moisture. May not be a problem if you are not out on the big seas or dries out on the hard each year but if you have some of the below signs and plan an offshore passage you may want to consider rebuilding or getting a new one made. $3000 at Foss Foam. They may have a template for it already. They have one for the 33.

Signs of a wet rudder

• Drill a 1/8 inch hole in the bottom and water drains out
  High moisture readings
  Tapping it with a plastic hammer and it doesn't sound light and hollow inside
  You can press in areas of the fiberglass, oil canning
  The whole thing flexes like a Morgan or Irwin hull (Sorry Morgan or Irwin owners, bad taste! But ask me how I know.)

Others may have more experience with this issue and can chime in here. When I got my boat, I drilled holes in my rudder in the fall after haul out and seen a little water, then I have let sit all winter and fill and glass over with epoxy in spring fitting out. Been fine for 20 years but...

[Dean Abramson]

Thanks so much, Paul. A lot of good information there. Much appreciated.

In case I decide to drill some holes in the rudder ...
All the hole-filling I've ever done (related to removing or moving hardware) has been in the deck, where a) I could access the place where the bit came out, and b) I had gravity working for me when I poured stuff into the hole. I that scenario, I just taped a barrier below, and filled the holes with thickened epoxy.

How would you go about filling a hole from below? (I really ought to know this by now.)

[Carl Thunberg]

You mean something like this? Totally different boat, but this may show you what you're up against. Freeze thaw is the enemy of rudders. Mine came completely de-laminated under way. By the staining, mine had clearly been leaking at the seam for a while.

[Paul D.]

For filling a hole from below I have used blue tape or epoxy mixed with colloidal silica to a peanut butter consistency. Just be sure to check it as the epoxy kicks so you can scrape any excess off and save some sanding time.

[Dean Abramson]

You mean something like this? Totally different boat, but this may show you what you're up against. Freeze thaw is the enemy of rudders. Mine came completely de-laminated under way. By the staining, mine had clearly been leaking at the seam for a while.

Just to be clear, is that your boat?

On our rudder, you couldn't even see the cracks unless your eyes were about 8 inches away. 4 very tiny cracks, now filled.

[sanderling]

I've searched this board vigorously, and have never found anything conclusive that suggests every rudder is the same. Some describe 3/8 inch horizontal fingers coming off the rudder stock (shaft), some say their shaft is not continuous through the rudder (two parts). The only description that seems to apply to all is they are constructed in two pre-formed halves, include some kind of polyester core material, and the seam was then glassed. I was surprised that Far Reach's web page on rudder repair didn't include a forensic x-ray or ultrasound. No mention of horizontal "fingers" there. If anyone has any further info (pics of any actual framework inside the rudder) I would be very interested to see them (especially for a CD 33).

[Frenchy]

Though I'm sure not all rudders are constructed this way, the below set of pictures give a pretty typical
idea of how they're put together. As a side note, Foss Foam recommends covering a dark-painted rudder
with some kind of a white shield during layup to reduce heat from the sun. Perhaps this might be one of the causes
of gelcoat cracks.



https://www.newrudders.com/rudder-construction/

[Jim Walsh]

I've searched this board vigorously, and have never found anything conclusive that suggests every rudder is the same. Some describe 3/8 inch horizontal fingers coming off the rudder stock (shaft), some say their shaft is not continuous through the rudder (two parts). The only description that seems to apply to all is they are constructed in two pre-formed halves, include some kind of polyester core material, and the seam was then glassed. I was surprised that Far Reach's web page on rudder repair didn't include a forensic x-ray or ultrasound. No mention of horizontal "fingers" there. If anyone has any further info (pics of any actual framework inside the rudder) I would be very interested to see them (especially for a CD 33).

Perhaps if you PM John he could share some details which never made it to his website or an entry in this forum. Then again, the processes and standard work varied greatly between product lines at CD generally and from one hull to the next during production of the same models.

[mgphl52]

I was surprised that Far Reach's web page on rudder repair didn't include a forensic x-ray or ultrasound.

I suspect he skipped the ultrasound because he was quite sure the rudder wasn't pregnant...

[Dean Abramson]

Though I'm sure not all rudders are constructed this way, the below set of pictures give a pretty typical
idea of how they're put together. As a side note, Foss Foam recommends covering a dark-painted rudder
with some kind of a white shield during layup to reduce heat from the sun. Perhaps this might be one of the causes
of gelcoat cracks.



https://www.newrudders.com/rudder-construction/

Those pix are enlightening. And I've seen similar ones before. But this is what I don't get. I assume the foam, after it's been sprayed in, is somewhat liquid until it sets up. So how do you flip one of the halves upside down (to place on the other half) without all the foam running out?

I occurred to me that maybe they let the foam dry first in each half. But then there would be no chemical bond between the two foam sections. Maybe they spray an adhesive on each (now dry and set-up) foam section before clamping the halves together; but I've never seen mention of that in articles like this.

What am I missing?

[Keith]

I believe that the two mold halves are put together and then the foam is injected into them. I have seen similar processes done this way but not sure on the rudders since I have never witnessed it.

Keith

[sanderling]

Perhaps if you PM John he could share some details which never made it to his website

It never occurred to me that could be possible.

[sanderling]

I occurred to me that maybe they let the foam dry first in each half. But then there would be no chemical bond between the two foam sections. Maybe they spray an adhesive on each (now dry and set-up) foam section before clamping the halves together; but I've never seen mention of that in articles like this.

What am I missing?

Dean,

Either way those pics show a specific type of lightweight "fin" being made with fast fabrication methods. It doesn't look like they even bond the SS framework to the outer shell in any way, which is the part I'm interested in for any rudder. So for these fins the foam is the only thing keeping the outer shell from shifting vertically it seems. There's a good description of rudder repair with pics for a Leopard Cat rudder(s) showing the tangs and the core problems: http://svmaple.blogspot.com/2016/03/thi ... night.html

I haven't done any intrusive investigation on mine since it's in good shape, but I do note that there is almost an inch of buildup on the leading edge of my rudder forward of the stock (shaft) , as compared to a very thin amount on the smaller CDs which tends to fail and let the rudder slide off the tanks in the "glove-like" fashion described by others.

[John Stone]

CD Rudders are constructed with two preformed fiberglass half shells filled with reinforced polyester compound. This compound surrounds a pre formed rudder shaft. Two layers of glass tape are added to reinforce the shell joints. The shaft is 304 stainless probably 1" or 1 1/2" diameter bent to fit inside the rudder. There is a bronze gudgeon in the bottom of the rudder to accept the bronze pintle embedded in the bottom of the keel. They are pretty well built as rudders go but not without issues.

When you are poking and finding soft mush you are probably going through the fibreglass shell and into the filler which may or may not be wet. If it is wet it may weaken the rudder and under a heavy torsional loads it could split and go to Davy Jones Locker leaving you with a bent stainless shaft trying to the turn the boat. A moisture meter will be able to tell a significant level. Often rudder readings are higher than a hull would be. If it is the original rudder it may well be wet and mushy in there. I think all our original rudders have some degree of moisture. May not be a problem if you are not out on the big seas or dries out on the hard each year but if you have some of the below signs and plan an offshore passage you may want to consider rebuilding or getting a new one made. $3000 at Foss Foam. They may have a template for it already. They have one for the 33.

Signs of a wet rudder

• Drill a 1/8 inch hole in the bottom and water drains out
  High moisture readings
  Tapping it with a plastic hammer and it doesn't sound light and hollow inside
  You can press in areas of the fiberglass, oil canning
  The whole thing flexes like a Morgan or Irwin hull (Sorry Morgan or Irwin owners, bad taste! But ask me how I know.)

Others may have more experience with this issue and can chime in here. When I got my boat, I drilled holes in my rudder in the fall after haul out and seen a little water, then I have let sit all winter and fill and glass over with epoxy in spring fitting out. Been fine for 20 years but...

Concur with Paul’s assessment. Mirrors my own experience. I don’t know how all the CD rudders were built. Rudder failure seems rare. I have not personally heard of one though I know owners have replaced them. My rudder was pretty beat up. It had a substantial crack that ran the full length (cord) of the rudder along the bottom due to water ingress and seasonal freeze-thaw under previous ownership. It was ghastly looking.

On the 36 I think rudder construction is very stout. Many rudders are built in two parts with a gap in the rudder post where the aperture is located. Then fingers welded onto the stock above and below the aperture (at least on full keel boats) span out into the rudder to provide leverage for turning. The fiberglass shell holds the thing together. But as Paul describes, on the 36 the 1.5” rudder stock is one piece and bent all the way around the aperture and that provides rudder rigidity as well as the lever arm as the rudder is turned back and forth. Maybe the 31’ rudder is built the same way? Enormously strong. I would think the rudder post would have to snap for rudder failure to occur. And while you can certainly have corrosion of the shaft inside the shell in an oxygen starved saltwater immersion scenario, in my case I thought it unlikely.

I made an educated “guess” mine was still pretty robust especially after I reinforced it. In almost 10,000 offshore miles I have not thought about it for a second.

I can’t really offer much else. I bet you’re good to go though Dean....