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unbusted67 · 20-06-2019, 15:56

A lot of cats use a cassette type kick up rudder in order to keep the sugar scoop transom. To me this design is cumbersome and seems like it has too many failure points. I am not a big fan of hacking large chunks out of the stern of any boat either.

I’ve been working on a couple of design ideas for a kick up/removable rudder that sets into a gear housing which is recessed into the very aft end of a sugar scoop. The rudder post is kept in place with a simple snap ring on top of the bearing and can be removed by pulling the snap ring and dropping it out of the bottom of the boat.

Another design is an actual kick up rudder on some kind of carbon tube frame that can be lifted up and down off of the sugar scoop (think the safety bar on a roller coaster) and then clicks into a pintle and gudgeon on the end of the sugar scoop. This idea isn’t that fleshed out.

Anyone have any other design ideas? They can be more or less hair brained than mine!

Chotu · 20-06-2019, 16:29

Can you upload some sketches? Even just hand drawings? So we could discuss this in detail? This has always been a weak point to me as well. Especially when you start to integrate the steering system, since that has to kick up too.

44'cruisingcat · 20-06-2019, 17:34

Can you list the "too many failure points?"

As for "hacking large chunks out of the stern", that might be how you build, but not everyone.

44'cruisingcat · 20-06-2019, 18:17

The advantages of the cassette type as per my boat:

It's automatic. If the rudder hits something it kicks up.

The rudders can be partially or fully raised.

The steering still works with rudders partially raised.

Fully down, the rudders have the advantages of spade hung rudders, the efficiency, the hull as an endplate etc, but with virtually none of the disadvantages.

In swelly anchorages, the shallow flat run aft can lift out the water then slap down again. Over and over. Being able to "hack out a large chunk" (or simply lift part) of that flat run can make a huge difference to the noise.

The only downside I'm aware of is that the rudders won't automatically kick up if we hit something while reversing. I can live with that.

owly · 21-06-2019, 09:47

Build it so that the bottom step is cut off angling down as the cut goes forward. This is attached to a central piece that fills what would be a vertical slot if it were all removed. The works hinges upward from the upper rear corner. The rudder shaft goes down through this piece. Rods with ball type connections join the tiller to whatever cross linkage is used so that nothing is damaged if the rudder kicks back and up.

One of the neatest designs I've seen is where the steps form a hull section that is entirely separate, behind the actual hull transom. The rudder is entirely contained in this, and it all can hinge up in a strike.... Ordinary cable ties could hold it in place and would break in a strike and be easily replaced. This has the advantage of the rudder bearing tube does not go through the hull and cannot leak into it.

H.W.

Chotu · 21-06-2019, 09:56

I feel mentally deficient. All parts of a boat are easily pictured in my mind... Except kick up rudder mechanisms.

thinwater · 21-06-2019, 11:11

I'm with 44. A cassette can be very simple and reliable. Mine are 25 years old. I just gave mine an overhaul, first one, and it is probably better than new (added anti-ventilation plate). A tackle to haul it down, and a simple pivot axle up on deck.

Really, what new failure points, other than the axle? Because it kicks up, impact damamge is less likely.

Bean Counter · 23-06-2019, 13:46

With the cassette, what happens if you hit the bottom with rudders turned. It would seem to me that the top of the blade would hit the underside of the boat and possibly damage the hull and the rudder and tiller arm if done at speed.

44'cruisingcat · 23-06-2019, 15:31

Quote:

Originally Posted by Bean Counter

With the cassette, what happens if you hit the bottom with rudders turned. It would seem to me that the top of the blade would hit the underside of the boat and possibly damage the hull and the rudder and tiller arm if done at speed.

This is true if the cassette is narrow.

A wider cassette allows the rudder to lift while turned or turn while lifted.

Ours is wide enough for about 20'.

But remember, with fixed rudders hitting something solid at speed = damage, every time, and could completely disable the steering.

owly · 23-06-2019, 17:55

Quote:

Originally Posted by 44'cruisingcat

This is true if the cassette is narrow.

A wider cassette allows the rudder to lift while turned or turn while lifted.

Ours is wide enough for about 20'.

But remember, with fixed rudders hitting something solid at speed = damage, every time, and could completely disable the steering.

This is one of the reasons I like the hinged transom.... the whole assembly kicks up....to me that's both simpler and more rugged. Hinged at the top edge, the hinges can be spaced wide

Simi 60 · 23-06-2019, 18:05

Pretty sure I have seen truncated wedge shaped cassettes that allow more than 20degrees not that there's probably much reason for more.

Simi 60 · 23-06-2019, 18:06

Quote:

Originally Posted by owly

This is one of the reasons I like the hinged transom.... the whole assembly kicks up....to me that's both simpler and more rugged. Hinged at the top edge, the hinges can be spaced wide

No good if you have a boat over about 12 ft long
Imagine the whole back step near a meter wide kicking up on a 40 fter?

unbusted67 · 23-06-2019, 19:36

Quote:

Originally Posted by thinwater

I'm with 44. A cassette can be very simple and reliable. Mine are 25 years old. I just gave mine an overhaul, first one, and it is probably better than new (added anti-ventilation plate). A tackle to haul it down, and a simple pivot axle up on deck.

Really, what new failure points, other than the axle? Because it kicks up, impact damamge is less likely.

What is the thing at the top of this picture? Is that cork insulation?