Catamaran: Retractable Rudders

[spiv]

Originally Posted by beiland

The First-Ever Lifting, Underhung Rudder System in a Cruising Catamaran
..........
I'll have to find a photo/dwg to post
Brian

Brian,
Have ever found pics of this system?

[valhalla360]

Originally Posted by spiv

Brian,
Have ever found pics of this system?

https://valhalla433.wordpress.com/about-valhalla-ii/

Try this page.

We have found them to be a great option with negligible issues (broke a downhaul line once in 10yrs and it took more time clearing the lazzertte out to get at it than actually replacing it).

18" draft has let us sneak into places no other boat would consider and we've even gotten deals on slips a few times when the slip was too shallow to rent otherwise.

[unbusted67]

Originally Posted by mikereed100

I used a dagger and cassette system set in a rotating drum on my boat. Pros and cons are as stated above plus it eliminates the stainless shaft.

Hey Mike, Can you explain this a little bit more? I don't understand how this works.

[thinwater]

Originally Posted by Karletto

my opinion is that you don't need rudders that can be pulled out of the water entirely. your hull will scratch the bottom anyway. in other words: your hull doesn't end on the waterline, there's underwater part too....

Not true.


I've bent rudders twice after striking a submerged log or dredge pipe that was pressed down under a fixed keel, and then floated back up and smacked the rudder.

[44'cruisingcat]

Originally Posted by thinwater

Not true.


I've bent rudders twice after striking a submerged log or dredge pipe that was pressed down under a fixed keel, and then floated back up and smacked the rudder.

Yep, floating or semi submerged objects can bounce back up and get you.

[Mr B]

Gemini 105MC, rudder arrangement,
Its very solidly built into the boat,

They are lowered and lifted by two ropes that are attached to bungy cords,
When they hit some thing they flick up and ride over what ever is in the water,
You can pull them up out of the way when parked on the sand,
Then pull the ropes to put them fully down again,

Nothing breaks on them when they are down and hit something,
Up out of the water, You still have full steering from the sillette drive leg which is also lowered and raised by a Hydraulic pump,

Cheers, Brian,

[spiv]

Originally Posted by Mr B

Gemini 105MC, rudder arrangement,
Its very solidly built into the boat,
Cheers, Brian,

Hi Brian,
do you have more pictures (or drawings) showing how it all fit together and works?

[thinwater]

Also the corsair F-24.


Basically, the rudder tube is housed in the trapezoidal block which hinges up with a hing on the cockpit floor. A rope and 2:1 tackle hold it down

[mikereed100]

Originally Posted by unbusted67

Hey Mike, Can you explain this a little bit more? I don't understand how this works.

Looking at the second photo in post #23, the drum on the left fits into one of the drums on the right and is free to rotate. If you zoom in you can see the black UHMWPE bearings in the top of the outer drum. There are identical bearings at the bottom. The rudder slides up and down in the slot at the center of the inner drum.

Advantages:
- Very robust, the boat can be pushed backwards by a wave without risk of damage. No shaft to break.
- Rudders can be retracted partially for moving about in particularly skinny water. They can be retracted completely for maintenance or to clear fouling.
- Great way to meet the curious in boatyards.

Disadvantages:
- Increased friction, especially under load. I plan to experiment with PTFE bearings someday.
- If the drum is not quite high above the waterline, water can be forced out of the tops in rough seas, creating a wet lazarette. This is not an issue on my boat as there is nothing else in the lazarette, but still.
- While the rudders are fully retractable they are not "kick-up"

[Mr B]

It all hangs on the tube going sideways and its a push pull cable that goes thru the inside of the tube with the large nuts on it,

Its a box that is built into the Hull, The rudder slides up into it,
It pivots on the steering tube,
Steering cable and Pivot pin is one fixing, Or unit,
The rudder is pulled up and down by ropes on the rudder itself,

Its a two piece rudder, The top piece only pivots up and down, it has a stainless bar thru it that the rudder turns on,
The bar and the rudder are one solid piece,

The bar is turned by the steering cable inside the rudder box, Push pull outer cable is fixed, Inner cable slides inside the outer cable,
The tube with the thread on it is hollow and the inner cable slides thru it.

The Blue piece is the rudder with the pivot point, Allowing the rudder to flick up if its hit by any thing under the boat,
The silver flat bar turns the rudder inside the top of the rudder,
Only the rudder turns under the boat.

I had to repair both rudders when they snapped off during the salvage work, They dropped the boat off the stands,

Cheers, Brian,

[Dan GB]

Originally Posted by beiland

That old link for the Shuttleworth rudder doesn't work any longer. Does someone have some better illustrations, photos of his rudders that they might post here?

This is a good video about Shuttleworth rudder:
https://youtu.be/IBoMJFrZj4w

I don't know if this was his only solution, but it's pretty much what was on my 1988 boat. Buried in a transom extension by previous owner and causing all sorts of issues for me, so I killed it at great expense.

[spiv]

Originally Posted by Mr B

It all hangs on the tube going sideways and its a push pull cable that goes thru the inside of the tube with the large nuts on it,
....
Cheers, Brian,

Thank you for taking the time to compile this thorough explanation!

[44'cruisingcat]

A photo from when I was building mine:



The wide cassette allows the rudder to be steered while partly lifted or floating, also allows it to kick up when not in the straight ahead position.

[unbusted67]

Originally Posted by Mr B

It all hangs on the tube going sideways and its a push pull cable that goes thru the inside of the tube with the large nuts on it,

Its a box that is built into the Hull, The rudder slides up into it,
It pivots on the steering tube,
Steering cable and Pivot pin is one fixing, Or unit,
The rudder is pulled up and down by ropes on the rudder itself,

Its a two piece rudder, The top piece only pivots up and down, it has a stainless bar thru it that the rudder turns on,
The bar and the rudder are one solid piece,

The bar is turned by the steering cable inside the rudder box, Push pull outer cable is fixed, Inner cable slides inside the outer cable,
The tube with the thread on it is hollow and the inner cable slides thru it.

The Blue piece is the rudder with the pivot point, Allowing the rudder to flick up if its hit by any thing under the boat,
The silver flat bar turns the rudder inside the top of the rudder,
Only the rudder turns under the boat.

I had to repair both rudders when they snapped off during the salvage work, They dropped the boat off the stands,

Cheers, Brian,

Oh boy, I think I am more confused than before. How does the steering cable rotate the rudder post? How is it fastened to the rudder?

[Mr B]

Originally Posted by unbusted67

Oh boy, I think I am more confused than before. How does the steering cable rotate the rudder post? How is it fastened to the rudder?

Look at the pictures, The lever is what moves the rudder,
It goes thru the Threaded tube and push and pulls on the one side of the tube,
Its a two piece rudder,
Top and bottom,
The top piece dont move except for pivoting up and down,
The post goes thru the top piece and turns the rudder under it,
The flat bar is what moves the rudder from side to side,