transom rudder or spade rudder?

Wheel, tiller and autopilots

transom rudder or spade rudder?

Post by Taniwha » Fri Nov 28, 2008 7:11 am

Hi dialan

Funny you say that. The very same thought went through my mind. Isn't this the same sort of thing with some wind vanes, where the trim tab acts to move the whole rudder? Does this sort of thing work on a cat, and do you know if its been done? A very interesting idea.

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transom rudder or spade rudder?

Post by puremajek » Fri Nov 28, 2008 7:51 am

I'm not sure I understand this bit. Are you saying the boats have hydraulic steering because of their weight, or they weigh what they weigh because of the hydraulic steering, or they are that weight because of the cost of something?
What my choice was based on are the statistics I got my hands on witn regards EASY catamarans. The analysis shows clearly that of the total number of vessels mentioned in my previous thread, few had chosen to use hydraulic systems (not inferring that one is better than the other – just stating a fact from the statistics of installations of this vessel type).

My next question was, why?
these vessels are around the 3500 - 5000kg AUW mark
- being light vessel weight may be a factor of hydraulic verse mechanical - , is it? who knows
or the actual steering cost
- being the cost of the components and associated installation, may be a factor of hydraulic verse mechanical steerings , is it? who knows

Why they chose their various directions - your guesses are as good as mine, there must be a reason or reasons that it is weighted one way.

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transom rudder or spade rudder?

Post by 44c » Fri Nov 28, 2008 6:28 pm

I'd say it would be cost. Hydraulics are a bit of a spend up front.

With the Easy and probably the Waller it's much simpler to have a link bar than it is with my boat - the rudders are a long way , about 8 feet aft of the rear beam, so to have a link bar across the boat would require some extra linkages and bellcranks, making it all get very complicated and introducing areas where more play could happen over time. Add to that the fact that the rudders can lift... most 44C's have hydraulics. (Actually I think all of them to date)

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transom rudder or spade rudder?

Post by dialdan » Tue Dec 02, 2008 8:28 pm


The system I described works very well, Chris White who wrote the Cruising Multihull has a pic of such a system in his book .I tried to send a link to an excellent site about homebuilt systems but evidently I haven,t posted enough.

Pm me if you like




transom rudder or spade rudder?

Post by CC40 » Tue Dec 09, 2008 1:12 am


I will add some more fuel to the fire in your head!

Have received plans for spade rudders. Look good still designed with a connecting rod. Rod is doglegged under Transom deck.

Info from Hydraulic steering guys are suggesting just one Ram attached to the connecting rod. No prices as yet.

If in the event of damage to one rudder I will simply diconnect the from the connecting rod.

Not sure yet what sort of back up rudder system I will make.

The third rudder option sounds good or maybe just a bloody big oar like from Surf boats but that may not mean much to you.

Considering I have already made my Transom rudders it is making me indecisive.

Epoxy/glass rudder post and tubes sound like the way to go. Mike did suggest Stainless but that is discussion is already done.



transom rudder or spade rudder?

Post by Taniwha » Tue Dec 16, 2008 1:51 am

Hi Iain

Nice to see you on here. The fire in my head has gone out! Mike sent me the spade plans too. I had a chat to a ex Wharram man who thought I was crazy to go with anything but transom rudders (interestingly he even successfully used wind vanes on his boat!). Anyway, before I go off on a tangent...I have settled for transom rudders for simplicity and strength. Though people have considered damage from grounding, no-ones mentioned damage from big seas. I can't help thinking I'd rather have transom rudders as they will be strong and more fixable. Apart from that I already have one rudder post in place. Using a servo tab is also a very appealing idea. The only downside about the transom rudders on the CC40 is that they aren't NACA foils - hopefully they won't hum. Hopefully they won't cavitate either. Considering the CC40 doesn't have transom steps I don't see a big advantage of spades.

Sorted...until I change my mind again. If you don't want your rudders feel free to post them to me!


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