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Old 23-06-2019, 20:52   #16
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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Originally Posted by Bean Counter View Post
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.

Has this actually happened to anyone, or is it a purely hypothetical risk? Remember that the rudder would have to be turned rather significantly since the cassette has some width. That means it cannot be done at great speed.


I think this is a lightning strike kind of scenario, except rarer.


In fact, most of the bent rudders I'm aware of on cats involved going backwards, which nothing helps.
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Old 23-06-2019, 23:37   #17
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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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
Simpler? That would depend on the design of the boat. It certainly wouldn't be simple on ours.

Also, it would make access from the beach a bit difficult when dried out wouldn't it?
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Old 24-06-2019, 04:30   #18
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

The firebirds cat (about 26ft long if I recall it right) from England had the complete sugars co-op with rudder hinge up. In front was a bulkhead/false transom...
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Old 24-06-2019, 06:13   #19
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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The firebirds cat (about 26ft long if I recall it right) from England had the complete sugars co-op with rudder hinge up. In front was a bulkhead/false transom...

That is what I remember too, but I couldn't find an image on-line. I know I saw one 25 years ago.
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Old 25-06-2019, 05:02   #20
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

I am with 44 - this is an engineering idea for a non-problem. The cassettes work really well. On our 38ft er we have hit crab pots and found out afterwards when the rudder pops up. Then I slow down a bit, go down aft, push it down again and insert new dowel hold down. I couldn't see how you could do that with a whole stern assembly. The buoyancy of the thing would possibly exceed my weight and would need winching - let alone the huge drag to pull it back under at speed. I only slow down a tad with cassettes.

In the trailer sailer I don't have cassettes because rudder boxes are easier. The transom idea is in the Chris White book but would be hard to use when on the hard for a week or so at Percy Island. In this case I unbolt the cassette and rudder (takes 5 minutes) and pop it on the net. I only do it for the side we use most often.

We don't go hard over much with steering and I can't remember anytime the cassettes didn't pop when needed - ours are thinner than 44s. Most of the time the rudders are pretty straight. So go cassettes and save your think time for something else.

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Old 25-06-2019, 05:30   #21
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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I am with 44 - this is an engineering idea for a non-problem. The cassettes work really well. On our 38ft er we have hit crab pots and found out afterwards when the rudder pops up. Then I slow down a bit, go down aft, push it down again and insert new dowel hold down. I couldn't see how you could do that with a whole stern assembly. The buoyancy of the thing would possibly exceed my weight and would need winching - let alone the huge drag to pull it back under at speed. I only slow down a tad with cassettes.

In the trailer sailer I don't have cassettes because rudder boxes are easier. The transom idea is in the Chris White book but would be hard to use when on the hard for a week or so at Percy Island. In this case I unbolt the cassette and rudder (takes 5 minutes) and pop it on the net. I only do it for the side we use most often.

We don't go hard over much with steering and I can't remember anytime the cassettes didn't pop when needed - ours are thinner than 44s. Most of the time the rudders are pretty straight. So go cassettes and save your think time for something else.

cheers

Phil
Point taken Phil. Thanks for the input.
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Old 25-06-2019, 05:36   #22
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

I'd say this is not a non problem. Try putting a hydraulic steering ram for each rudder, or pull/pull cabling into the mix and let me know what happens when it kicks up.

(Don't cheat with a crossbar)
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Old 25-06-2019, 14:06   #23
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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I'd say this is not a non problem. Try putting a hydraulic steering ram for each rudder, or pull/pull cabling into the mix and let me know what happens when it kicks up.

(Don't cheat with a crossbar)
I have hydraulic steering rams for each rudder. I've installed the rams inside the cassettes. There are flexible hydraulic lines running to the cassettes. The system works well.

A boat I know has pull-pull steering and kick up cassettes. AFAIK it works ok. The amount of steering lock that can be applied when the cassettes are raised is more limited than mine is though, because the tiller is mounted to the rudder shaft by a single axis pivot. A universal joint would allow greater steering movement.

On a boat I converted from fixed rudders to kick up cassettes I installed universal joints. Works well.
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Old 25-06-2019, 15:22   #24
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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I have hydraulic steering rams for each rudder. I've installed the rams inside the cassettes. There are flexible hydraulic lines running to the cassettes. The system works well.

A boat I know has pull-pull steering and kick up cassettes. AFAIK it works ok. The amount of steering lock that can be applied when the cassettes are raised is more limited than mine is though, because the tiller is mounted to the rudder shaft by a single axis pivot. A universal joint would allow greater steering movement.

On a boat I converted from fixed rudders to kick up cassettes I installed universal joints. Works well.
Is there any way you can attach a drawing of this? how does the hydraulic ram inside of the cassette have enough room to rotate the rudder?
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Old 25-06-2019, 15:32   #25
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

44CC:. That's because you're a genius!

For the rest of us, we struggle a bit.

I followed plans for my kickups and they are too narrow for hydraulics or anything other than a crossbar. It's unfortunate I didn't understand this better before building but it was a hard thing to picture in relation to the rest of building a Catamaran. About as hard as trying to figure out doors, frames, latches.

On mine, I need to rebuild the kickups so a platform to the side of them on a step kicks up with the cassette, enabling a hydraulic ram to kick up with it.
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Old 25-06-2019, 16:19   #26
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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Is there any way you can attach a drawing of this? how does the hydraulic ram inside of the cassette have enough room to rotate the rudder?
I've made the cassettes tapered, wider at the top than the bottom. This allows enough room for a tiller inside the cassette, up near the top of it.

There's a photo here:

http://www.cruisersforum.com/gallery...00&userid=3477

The black item on the deck next to the cassette is the composite tiller, (Still under construction at the time) which fits and clamps onto the rudder shaft inside the cassette.
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Old 25-06-2019, 16:28   #27
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Re: Sugar Scoop Kick Up Rudder Thought Experiment

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44CC:. That's because you're a genius!

For the rest of us, we struggle a bit.

I followed plans for my kickups and they are too narrow for hydraulics or anything other than a crossbar. It's unfortunate I didn't understand this better before building but it was a hard thing to picture in relation to the rest of building a Catamaran. About as hard as trying to figure out doors, frames, latches.

On mine, I need to rebuild the kickups so a platform to the side of them on a step kicks up with the cassette, enabling a hydraulic ram to kick up with it.
Don't know about genius, I spent an awful lot of time thinking about ways of doing stuff.

I didn't exactly follow the plans for my cassettes. Made them a bit wider overall, and wedge shaped, wider again at the top to accomodate the tiller and hydraulic ram.

Bob actually asked me to do a drawing of them, which he included in the plans as an option for later builders.
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