Technical Information / FAQ / Tuning

Dotan Rudders

Dotan Rudders on a Unicorn Catamaran   15th August 2006

I saw Dotan rudders for the first time in the summer of 2005 on one of our Shearwater Catamarans at  Stone Sailing Club and I was so impressed that I immediately decided to investigate the possibility of fitting a pair to my Unicorn 1073 for the 2006 season. My boat is a 1988 built GRP Unicorn which still had the original rudder stocks and blades in use. I had become thoroughly fed up with these rudders, as they were a rather cruder system of the Hobbie / Dart arrangement where the tiller arm is lifted and pulled forward to raise the blades. Also the blades were held down by a loop of shock cord which had always been a far from satisfactory arrangement.

I looked up the Dotan web site (, and after an exchange of E mails and drawings I decided on a set of their Rudder 20 stocks and Blade 1 blades, which turned out to be the same as the Shearwater was using.

Dotan’s stockist in the UK is Rooster Sailing at Emsworth, Hants, whom I contacted and found that they had exactly what I wanted in stock, and so within four days of placing my order the package was on my doorstep.

Each rudder set comes with a 1 metre long straight tiller tube which needed to be bent in two directions, upwards to enable the tiller connecting bar and extension to clear the rear beam, and inwards to give a suitable ‘tow in’ angle to the tillers, although this latter requirement can be done, as the Shearwater has, by fixing suitable side extension plates to the ends of the tillers to give the appropriate ‘tow in’ angle.

Attaching the stocks to the transoms of my boat required virtually no changes, just the addition of a pintle attached to the top gudgeon on the transom, because the top gudgeon fitting on the stock is adjustable to suit a wide range of transom fitting positions.  

At this point I must explain how these rudders work, which is the reason that I decided to purchase them. You attach them to your boat and they are in the up position with the blades clear of the water at an angle of approximately 15 to 20 degrees. You push off, and as soon as you are in water of sufficient depth you just raise the tiller arm to approximately 30 degrees, bring it immediately back down again and the blade goes from the fully up position to fully down. Carry out exactly the same movement with the tiller and the blade immediately comes back to the fully up position. So very simple and so very effective. There is also the bonus that you can lift the tiller arm and not bring it back down and the blade will trail in the water giving you an adequate amount of steerage for manoeuvring in shallow water when launching and landing.

My first trip afloat with them was made with a certain amount of trepidation, but I pushed off, reached deep enough water, made the appropriate tiller movement and ‘hey presto’, the first blade went straight down. With the same movement on the other tiller the second one did likewise. How often does that happen with a new piece of equipment ?

I sailed around for fifteen or twenty minutes and it was just as though they had been on the boat forever. The boat still had perfect steering balance, there was absolutely no noise, and the water turbulence was probably half of what the old rudders produced. They have now been in use for four to five weeks and they have continued to work perfectly. During that time I have sailed some very ‘hairy’ reaches and not once have the blades cavitated , which had often been a problem on the old rudders, and twice while tapezeing on a fast reach I have sailed too close to our sandbanks and the windward blade has touched bottom and kicked up with no problem (as it is designed to do). I just continued the reach on one rudder with the boat having virtually the same degree of control as with two. At the end of the reach I just flicked the tiller arm and we were back to two rudders again.

It is not often in any sphere of endeavour that we obtain something that gives complete satisfaction from day one. I realise that I have not been using these rudders for very long, but their design is clever and it works perfectly, and only time will tell if their construction will withstand the rigors that most catamarans put onto their equipment. If the construction matches their design they should be in for a very long life.

Bob Dorks. (Unicorn 1073)

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