The Offshore Voyaging Reference Site

Planning a Refit—The Problem With Rudders

Colin has shone the bright light of reality on fibreglass boat rudders, but here’s a quick summary:


  • It is near impossible for the joint between a metal rudder shaft and a fibreglass shell to remain waterproof for 20 to 40 years, the typical age of the boats we are looking at refitting.
  • Therefore, pretty much every rudder on every fiberglass boat we are dealing with in this series has, or has had, water in it.
  • If the boat has been stored in a winter climate, it’s likely water will have frozen inside the rudder and done further damage.

Worse Than We Thought

That was all bad enough, but then I had a chat with Al Walker at Foss Foam Products in Florida. Al and his team have probably looked inside more old production boat rudders than anyone on the planet. Here’s what I learned:

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Patrick Ryan

Great article. Thank you very much for writing it. Have you ever considered starting these very technical articles with a glossary of terms? Not everyone subscribing to the site because of the same level of expertise. For example, what is mild steel?

Ole Otto

I myself was not aware of what mild steel was. A quick Google search brought me up to speed. 🙂

Andrew Craig-Bennett

Thank you for going into this issue. Looking forward to Part 2 – and perhaps Part 3 might look at steering gear issues?

Ernest E Vogelsinger

John, it is clear that you are focusing on “plastic” rudders as they are the sheer majority. But if one intends to look for a steel boat, or Aluminum, there must be something different to look out with rudders made out of metal?

Daniel Kerns

Still, I’d like to hear about Aluminum and Steel someday.

Denis Foster


Is using titanium in stead of SS or mild steel the solution , Obviously much more expensive ?



Alex Borodin

There are also super duplex steel grades, which are supposed to stand up much better to the abuse than 316 stainless and are not much more expensive. I don’t know why no one is using them. Maybe one of engineers here can enlighten me.

Marc Dacey

One of the more promising metal boat materials was, evidently, cupro-nickel, as seen in the 1967 full-keel sailboat Asperida (see Asperida was, as of 2018, still sailing and still looking good in her 50s:

So I’m not sure why these type of alloys weren’t pursued, to my knowledge.

Marc Dacey

Sorry, John! That vessel is stuck in my memory.

Deborah Lloyd

My rudder is presently at the very top of my “to do” list even though it is still functioning for the light duty sailing I’m currently doing. But I don’t trust it. My 36’ sailboat is a 1973 Morgan Out Island, and the rudder has been weeping a small amount of rusty water for about 15 years every time it is hauled. It was likely built by Foss Foam in Florida under contract to the old Morgan Yachts. Actually, it’s a positive testament to Foss for a job well done so many years ago since this rudder is now nearing 50 years old!
Just because of the age of this rudder I do not plan to inspect it as outlined in this article. I am going to have a new one built and have already been in contact with Foss. I really should have done this years ago, but life intervened. I’ve been lucky it’s lasted. When you think about failures and how you’ll cope, a rudder is at least as vital as a reliable engine. And not as expensive to preemptively replace. Relying on luck is not a good plan. I’ve known for a while how these rudder are made with mild steel. It’s amazing to me that it could seep rust for so long and still hold together, albeit in gentle use compared to what most readers of this web site are interested in.

Eric Klem

Hi John,

Thank you for taking this on, definitely a worthwhile but also tricky subject.  For whatever reason, things like keel attachment get much more discussion in my experience than rudders despite rudders also presenting a single fault system for a mission critical functionality.

One thought is that prior to the survey, it can be useful to try to learn what the rudder design is and if there are known issues.  This is likely not possible on some low volume designs but ones like ours, rudders are a common discussion point on the owners list and a potential buyer could easily learn the construction type and see pictures of ones that people have split apart.

Did Al Walker give any idea of what percentage of rudders he condemns at say 30 years of age?  


Eric Klem

Hi John,

Good point on the results being skewed.  What got me thinking about it is whether all rudders of this construction and of a certain age would be condemned by definition making it unnecessary to even drill pre-purchase.  Of course, if you feel you could negotiate price on it, it may be harder without the evidence for that specific unit.  Since drilling is easy enough, it seems like the logical choice.


Marc Dacey

My old boat was sold to a fellow who had the rudder (which I knew was on its way out at age 44) replicated in stainless reusing the old, but fine, stainless post. He’s happy with the results, and the boat’s in fresh water on a mooring away from dock power.

Mathieu Fortin

How about two fiberglass half rudders bolted together through the plates? Each half is really water-tight, you can leave open channels to inspect the plates with a scope. Hell, splitting it open only means redoing a little filler on the edges and over the bolts.

Mathieu Fortin

You sound like my agile coach! “This is not the time for solution mode”

Fine, I’ll wait 🙂

Drew Frye

Oh dear. Mild steel. I’ve seen a few rudders pealed open, but the armature was always stainless. They were catamaran rudders, and because there are two of them, they are smaller.

Re. fiberglass cloth and epoxy, the usual problem is mat, cloth with mat attached (1708), or other products that include a resin bonded scrim. The resin that holds the mat together dissolves in polyester resin but not in epoxy resin. So ask about the suitability if you are not certain. As a general rule, avoid mat with epoxy. Jamestown Distributors is a good source for many cloth and core materials.

Terence Thatcher

After your first articles, I drilled holes in my Morgan’s rudder, as suggested, (There was some small amount of rusty water seepage around the post.) Morgan made the 382 rudders and used a resin slurry, not foam (which made them heavy and very sturdy). Foss made the 383, 384 rudders, which fit on the 382. I found a lightly rusted mild steel plate, welded to a stainless post. The welds I could see looked quite good. But there are, by my estimate, perhaps 8 to 10 spot welds along the post and I saw parts of three. I was going to seal it up when some chisel work revealed a spot where the mild steel had rusted sufficiently that there was a 1/16″ gap between the weld and the mild steel plate. I think the rudder would probably have been ok for many more years, especially since I routed out the glass near the post to fill with 5200. (Foss does that on all its rudders now.) Nonetheless, the rudder is 40 years old. My boatyard received my new rudder from Foss two weeks ago. Foss still had the original molds used when they built Morgan’s rudders. And the old rudder will go in the trash. The work to free the stainless and mild steel for recycling would take days.

Steve D

A number of years ago, pre-recession, I toured the Hunter factory, and having rebuilt a few Hunter rudders I was not entirely surprised to see stainless stocks and mild steel blades. They didn’t seem very concerned, which concerned me, I memorialized the “union” with a number of photos.

I’ve used Foss FL on many occasions, a first class outfit.

Notable in the photos of the rusty plates you’ve shared is the lack of any gusseting what so ever. Again, having cut open and rebuilt a number of rudders that’s not surprising, just disappointing.

Paul Padyk

John, this is excellent buyer beware information, likely otherwise available only through bitter experience. Once again you have proved the return on an AAC investment is worth at least $1000x the cost of a subscription, not to mention preservation of all of the way more important intangibles of life that might be lost due to a rudder failure.

Lawrence Lare

Your comments about steering vanes probably not capable of lasting long as an emergency rudder neglected to include the Hydrovane. After all it is ALWAYS steering the boat when in use.
Also, on a boat with a Hydrovane it seems likely that with any forward motion a skeg mounted rudder that has become disconnected from it’s shaft will align itself behind the skeg in the slip stream, rather than beating the boat up.

I have no connection with the Hydrovane company, but keen to get one.

Otherwise, a good article on rudders, and getting Foss Rudders Florida involved to comment was great.

Could you do a similar article on 40+ year old lead keels joined by stainless bolts, with someone like Mars Keels of Canada involved?

I am a new subscriber but already seeing value in your blog.

– Eddie