Transom hung rudder options - 50 ft catamaran

Would like to get some insight and thoughts on transom hung rudder options for a 50 ft catamaran. I am considering the following options:

Daggerboard rudder system (farrier style) with longer cassette such as this



Permanent mount (balanced transom hung rudders) such as this


Retractable (balanced style rudders) such as this


I understand that thru hull rudders would be best so no need to explain why.. Looking more for opinions on transom hung rudder options with focus on ease of build and strength and practical use.

Thanks

 

I hate to say it, but I think a standard, through hull rudder that does not kick up would be the easiest to build. I think that's why most production boats have them.

As your project moves along, you will notice this - the most common things on commercial boats (though not superior) are always the fastest way to do something.

 

I think the balanced rudder would be best as long as the "balance" area didn't exceed about 19% of total area BUT the balanced board is not retractable-unless you opt for a beachcat like kick up rudder where you can have balance and retractability(as shown above). Depends on how important retractability is and if you view balance as important. A guy here locally has a 30' tri that has a "daggerboard" cassette system like the Farrier except the thing is designed to break free w/o damage if the rudder hits hard. 99% of the time it is a retractable daggerboard like blade.

 

The idea behind the retractability is more for being able to pull the foils up out of the water when the boat is not being used in addition to the hull daggerboards or when you want to anchor her in shallower waters. In that case the steerability of the retracted foils is not super important and they are not under tremendous load as you will be more likely under power anyhow. During normal sailing Would the cassette daggerboard rudder create a lot more load on the tiller of a big cat vs the more balanced rudder shown above?
Appreciate the thoughts...

 

the Farrier rudder is balanced, it is raked under the boat.
You can make them kick up too.

 

Farrier type as pictured, then. It will retract to any depth for use in the shallows and you can take it right out and fix it while underway if there ever was a problem.

The load on the tiller would be largely irrelevant, as it's all a matter of leverage and quality of the linkage. You can have the biggest load in the world, but if you are at the far end of a very long tiller, you can move it with your pinky.

 

The other advantage of the Farrier is it has very solid rudder stops. If you wind up going backwards things are less likely to break.

 

i would recommend Permanent mount (balanced transom hung rudders)

Its what I have on my 8.5m tri

very strong and light

very balanced to steer and small

they are antifouled but grow bugger all slime so far

 

Remember an underhung rudder is more efficient than a transom setup (which has no end plate effect from the hull, plus also aeration because of surface piercing) and the cassette setup therefore can be smaller in area and depth. If you're worrying about smashing into reefs, your deeper dagger or centreboard is going to hit first anyway.

 

It totally makes sense to have retractable rudders on a cat for obvious reasons, while underhung rudders may be easier to build for a production cat, easier is not why you build a custom boat. You can certainly have a retractable daggerboard style rudder such as in the 1st picture that has balance by simply angling the top of the cassette aft a little at the top so that the blade angles foreward at the bottom under the transom, not as easy to retract but doable.
Steve.

 

Would a souped up version of the system in the pictures work?
It is of the Newick 8.5

 

It is more usual to see a kick up stern section with a spade rudder. The one area that needs consideration is the force needed to pull the flat stern section through the water if the boat still has speed on when you try to reset.

 

Cav, although I haven't yet been able to test the setup sailing the boat, it worked pleasant surprisingly well when I tried to cut some corners on a lake (It was getting dark and the water liturally froze behind me) while transferring the boat with the outboards doing 8 knots.
The stern is easily retrieved with 2 lines with a handle and secured by adjustable snap locks.
When kicked up, the rudder following the shoals, I still could easily steer the boat into deeper water.

 

No one has mentioned the fact that transom hung rudders stuff up a perfectly good set of swim steps.
Personally, this style of thing is the go if you must have them


In reality, I would prefer a bog standard balanced spade and keep the boards down a touch for rudder protection.

 

Hello HASYB, nice to hear some real time experience...a bigger transom would take more effort I think, maybe a lever or tackle.

I've seen this adaption Sabahcat and like how the aft edge supports the stern. The kick up section needs to be wide enough to allow steering and retraction with the rudder turned though. If you ran aground while hard over to avoid a shoal not enough clearance could get expensive.