Beaching Catamarans

[GRIT]

Yes. We'll be leaving Friday, weather permitting.

[GRIT]

A pic showing what I'm calling a strut. The shaft goes through it, and the prop is mounted just behind. The zinc is mounted within the cutout.

Cheers.
Paul.

[Matt Johnson]

Originally Posted by GRIT

A pic showing what I'm calling a strut. The shaft goes through it, and the prop is mounted just behind. The zinc is mounted within the cutout.

Cheers.
Paul.

Great photo GRIT. We're building something similar, but it's only planned to extend to just below the prop hub to protect from direct impact. After seeing yours, I may extend it further.

Matt

[GRIT]

That's pretty much what we have. The end of the blade is about 2 inches or so higher than the "strut". I plan on putting a small horizontal wing on the bottom of the strut, to help support the boat better in softer bottoms.

I couldn't find a photo with the props installed for my earlier post, then found this one, which shows a little better how the strut is fairly close to the same height as the prop blades. The photo is taken at a downward angle, so they look nearly even, but the strut is lower than the prop in real life. We always ensure the props are folded before beaching the boat.

That beautiful young lass is my wife; the guy with the fashionable headwear, is me.

Cheers.
Paul.

[smj]

Love all the pics of your cat Paul, absolutely beautiful.

[GRIT]

Thanks SMJ.

That's kind of you to say. We're very happy with her; and as we finish the interior, and add our own personal touches, we enjoy her even more. She's exactly what we'd hoped she'd be.

Cheers.
Paul.

[Matt Johnson]

She is beautifully finished. Our original design had daggerboard rudders in cassettes, but we've since switched it to kick-up the same as you have to better protect them. Always nice to see another similar design.

We're 8 degree for our engines and prop shaft. So in the end it will probably be similar.

[GRIT]

Thanks Matt. That's always nice to hear.

What do your rudder hinges look like? We have two 8 inch by 3/4" pins in gudgeons, for each rudder; and the gudgeons (Delrin) got sloppy within a year, just due to the rudders constantly moving.

It's not a functional problem, but we can hear the sloppyness, a light clunking, while we're trying to sleep, at anchor. We now lift them at each anchorage, and are designing a more robust hinge, which should allow us to leave the rudders down all the time, without slop.

Just an fyi, in case your hinges are similar. If I were staying with the 19mm pins, I'd use Bronze, in lieu of Delrin.

Our shafts are also tilted at 8 degrees, the engines are horizontal. We have ZF25A transmissions.

You'll be happy with your skegs. They lend a little peace of mind for beaching, and for running over fishing buoys.

Cheers.
Paul.

[Matt Johnson]

The gudgeons, pintle/pin are stainless and mounted at the mid point of the chord on the side of the rudder well - not at the forward part of the rudder as typical. The bushing inside is acetal/delrin. Neither have been built yet, so still open to suggestions like this.

Unfortunately our Yanmar 3ym30ae only come with parallel transmissions, so the engine is mounted at the max of 8 degrees.

[GRIT]

Your designed hinges, mounted near the midpoint is similar to one of our designs. Which is based on what I saw on the Catamaran Fujian.

He had wear issues too.

Our newest idea is to use 6 inch drums, with roller bearings, possibly made by Antal. I've also considered repurposing they're 100mm tulip blocks for hinge duty.

These would be mounted back 20% of the chord from the front of the rudder. We're still in the preliminary phase of the design process. Our present rudders work fine, so we're not in a hurry to change things. Yet.

Cheers.
Paul.

[catsketcher]

Re rattling hinges,

It is not really a hinge problem - more a cassette issue. I really like the cassettes on my cat. They have a slight taper to them, both vertically and fore and aft. This makes them snug when full down and easy to lift as soon as you lift them. Also I made the cassettes by moulding them off the cutout. Again this makes them a snug fit when down. I would always urge people to make cassettes this way - slightly tapered and moulded from the cutout.

I would suggest putting little wedges on your cassette at the top and bottom, to take out the slop. It is fine to be sloppy when lufted, just not when full down.

[Matt Johnson]

Originally Posted by catsketcher

Re rattling hinges,

It is not really a hinge problem - more a cassette issue. I really like the cassettes on my cat. They have a slight taper to them, both vertically and fore and aft. This makes them snug when full down and easy to lift as soon as you lift them. Also I made the cassettes by moulding them off the cutout. Again this makes them a snug fit when down. I would always urge people to make cassettes this way - slightly tapered and moulded from the cutout.

I would suggest putting little wedges on your cassette at the top and bottom, to take out the slop. It is fine to be sloppy when lufted, just not when full down.

Are the tops of your rudders foil shape or flat sided like GRIT? Our have a rectangular trunk that goes in the saddle cassette and below that is the normal foil rudder shape. The original design's daggerboard style were to be foil shaped for the whole length with a molded cassette to allow them to be wedged at any depth. Maybe this is closer to yours?

[JustMurph]

Another big fan of kick up rudders and dagger boards. This was a week ago.
Probs on the Mumby sit just above the sand when folded. We touch bottom in about 600mm, much like grit. My mates Oram only draws about 400!

[catsketcher]

Originally Posted by Matt Johnson

Are the tops of your rudders foil shape or flat sided like GRIT? Our have a rectangular trunk that goes in the saddle cassette and below that is the normal foil rudder shape. The original design's daggerboard style were to be foil shaped for the whole length with a molded cassette to allow them to be wedged at any depth. Maybe this is closer to yours?

I have normal rudders and normal looking cassettes. There is just a 5mm taper in the cassette sides - tapering inwards at the bottom and tapering 5 mm inwards at the front. As soon as the cassette slides back a bit she has some play but she is absolutely tight when in place.

I don't think parallel sided cassette sides are as good an idea as a slight taper. This fits well with making the cassettes moulded from the slot (IMHO). My first cassettes made joggly noises at night so I made new ones that were moulded from the slots with the un-noticeable taper I built into the boat. Been silent and working well for 2 decades now.

Cheers

Phil

[fxykty]

You don’t have to have kick up or cassette rudders to be able to ground your boat as long as you have robust skegs (with a foot plate to prevent sinking into the sand/mid). Although we do sit bow down as our skegs are 1.1m and the deepest point of the hulls 0.8m.



Works well nose in to a beach with a slope, but the one time we dried out on a sand flat (Indian Head) it wasn’t that comfortable to sleep. And all the Australian critters that can come on board!