Calling a Spade, a Spade

If you have read our book you will know how we feel about spade (unsupported) rudders. We don’t like them and consider them a pretty bad idea for a voyaging boat. For those that haven’t read the book, a properly supported rudder is an essential facet of a voyaging boat. A spade rudder simply hangs down from the hull on a stainless steel shaft. This make them fantastically vulnerable to damage from collision with sea debris (floating logs, half submerged containers, dozing mermaids, etc.) and we go to great pains in our book to discourage all potential sea gypsies from buying this type of boat. (See picture).

A typical spade rudder

A typical spade rudder

Something we did not go into (and probably will in the next edition) is the added risk of “work hardening” on spade rudder shafts. We have all experienced work hardening in other areas of our lives. This is the process that allows us to break certain materials by repeated bending. Take a paper clip and straighten it out. Now bend it backwards and forwards. Pretty soon the paper clip will break at the point where you have been bending it. This is not because it has got softer, but because the point where all the “work” was being done actually got harder, and therefore more brittle and no longer able to bend as efficiently.

As is often the case in so many areas of life – that which cannot bend, breaks.

All rudders have to absorb large forces from the sea. That is a given. The problem the spade rudder has (being unsupported at the bottom) is that each time a wave rolls across it, the shaft flexes from one side to the other – just like the paper clip in the experiment – with the point doing the most work being where the shaft of the rudder exits the hull. Can you guess what happens?

You got it – work hardening at that point. Then failure.

Funnily enough, I was just explaining this very process to a potential sea gypsy who contacted us after reading our book, when we heard that a boat had been towed into the local yard with rudder problems (we are currently in Fiji).

Being fantastically nosey about this kind of thing, I dashed over (all of 500 meters) to find out what had happened. I think the pictures tell the story (see below).

Spade Rudder sheared off.

Spade Rudder sheared off.

As you can see in the first picture, the rudder has gone. The whole thing is now resting in the silt 5 kilometres under the surface of the Pacific Ocean and will cost several thousand dollars to replace.

DSC02273

The shaft has sheared off

In the next picture, you can see that the shaft has snapped at precisely the place the principal of work hardening would predict.

This poor sailor is also facing a bill of $7000 for the tow into Fiji, and a couple of thousand for the boatyard. Had he been further offshore, the tow could have cost several times that. If he had been offshore in bad weather, the cost may not have been calculable in dollars.

Spade rudders are cheap to produce and fit. Manufacturers tell us that they are also a good idea and produce all kinds of spurious figures and twisted logic to convince us that what they want to sell us is what we want to buy.

Regardless of what the salesmen and racing crowd say, there is no possible way a spade rudder is stronger than a supported rudder. The numbers simply don’t add up any better than the numbers for building a house without foundations. Find me a qualified engineer that will say any different in writing and I will show you someone who is working for the yachting industry.

But while uninformed sailors continue to buy spade-ruddered boats for their marble counter tops and en-suite bathrooms, this is what the manufacturers will continue to produce.   And who can blame them? They have to sell boats in a very competitive environment and new sailors don’t give a hoot about the rudder.

It is up to us to demand sea-worthiness in yacht design by rejecting unsound practices – no matter how nice the cockpit cushions are or how large the aft cabin is.

Rejecting spade rudders is a good place to start.

Fair Winds,

Rick and Jasna

PS Has anyone else got any spade rudder horror stories? We would like  to hear them -especially if you have photos.

 

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12 Responses to Calling a Spade, a Spade

  1. Phil Ryan says:

    After reading your book I don’t like spade rudders. It had to be said….

  2. Good man Phil! Glad to know even the land-lubbers are getting the message.

  3. Gary says:

    If it was not for your book and advice, me and my wife could have been in the same situation as the above boat.

    Thanks.

  4. Jonathan Brown says:

    Just finished reading your book which I simply could not force myself to put down.
    My wife has actually been getting angry at me for reading which is most unusual.

    Well written and so impelling.

    I’m now dead-set on becoming a sea gypsy.. Only slight bit I can’t quite fathom: how to do it with a 2yr old boy and a 5month baby boy in tow??!

    • rick says:

      Hi Jonathon,

      Sorry for the tardy reply – been away from the online world for a while! Thanks a lot for your positive feedback on the book, it is greatly appreciated even if it gets you into marital difficulties.

      Don’t let a couple of ankle biters put you off the sea gypsy life! There are hundreds of couples with young families bringing up glowing neurosis free kids on board. Have a look at this and get yourselves out here!

      Thanks again and let us know if you need any help or kicking towards taking the plunge

      Cheers,

      Rick and Jasna

  5. Endurance, fault tolerance, and redundancy are key elements for a voyaging yacht. Spade rudders offer none of these. They are superior for racing yachts. We have a racing yacht with one and have no complaints… for the purposes of coastal racing. We also don’t cross oceans in it. (Aphrodite 101, Averisera)

  6. rick says:

    No argument from me there Norman! The problem is that many manufacturers are marketing their fin keel/spade rudder boats as “bluewater” cruisers….

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