Catamaran Steering

[ausnp84]

Hey gang,

Part way through the refit of my catamaran and need to address this little issue.

That there is the steering linkage rod for the rudders - only the port starboard rudder has cables directly linked to it.

I want to remove the bar as it’s vulnerable to damage and frankly - ugly. I could run cables to the other rudder (have alreay got two bronze Edson pulleys for this) but how are other cats setup? Is the linkage rod essential?

Appreciate any help... it’s doing my head in!

N

[44'cruisingcat]

That's definitely an unusual setup!

You could move the crossbar to the front of the tillers, but then it would run across the duckboard.

A longer crossbar with bends in it could run mostly next to the back beam, which would be a bit tidier, but you still have to allow room for fore and aft movement.

Can you access the rudder shaft below deck level?

There are some good cable steering setups, I think Edson does a pull-pull setup, but not cheap.

[bluenomads]

Don't move the crossbar without considering Ackermann. Boat with multi-rudders, especially if further apart, need to consider the Ackermann geometry. If you remove the crossbar then the cables/hydraulics should take care of the problem.

[Pottasch]

If you go with cables then an emergency system becomes difficult. If the cable or any sheaves fail you would need to be able to operate both rudders at the same time to effect a turn. I have cables on my cat and am trying to figure out how to manage such a situation.

[blubaju]

Old cat: hydraulic, "new" since 10 years pull-pull Dyneema ropes. This was the designers suggestion (Schionning, Australia) and performs great, easy to repair on bord and if one rudder has a problem, disconnect.

[ausnp84]

When you say pull-pull, do you mean this type of setup?

[blubaju]

Originally Posted by ausnp84

When you say pull-pull, do you mean this type of setup?

No, each quadrant is directly and independently controlled from the steering wheel. Quadrants are not directly connected to each other. In your drawing you give away the security of 2 independent rudders

[atoll]

what a silly impractical design.
firstly the lever arms connecting the rod does not need to be so long as it is not used for any mechanical advantage.,they only need to be about 10" long.

reversing and shortening the arms would be a good solution to at least get the assembly inboard.

if the system is set up for pull-pull cables i would leave it that way,new cables and fittings are available from lewmar uk and marinesuperstore.com
and would cost roughly £350 to replace for your size system.

[ausnp84]

Originally Posted by atoll

what a silly impractical design.
firstly the lever arms connecting the rod does not need to be so long as it is not used for any mechanical advantage.,they only need to be about 10" long.

reversing and shortening the arms would be a good solution to at least get the assembly inboard.

if the system is set up for pull-pull cables i would leave it that way,new cables and fittings are available from lewmar uk and marinesuperstore.com
and would cost roughly £350 to replace for your size system.

My thoughts exactly. The builder has invested thousands in custom teak woodwork, then installed this ridiculous tie bar on the back.

I’d thought about shortening and reversing, but then it’ll foul the rib on the platform. I could always raise the platform 8” to negate this of course.

There’s no pulleys in place currently for the port rudder cabling to run through but I’ve bought two Edson ones. Only prob is fitting them... if I was to mirror the pulley placement on the starboard rudder, it puts them at the back corner of the port diesel tank. It looks like the starboard pulleys are bolted to a piece of hardwood that’s just been glassed to the inside of the hull... would this be strong enough? Or do I ideally need to bolt it through something first?

N

[atoll]

Originally Posted by ausnp84

My thoughts exactly. The builder has invested thousands in custom teak woodwork, then installed this ridiculous tie bar on the back.

I’d thought about shortening and reversing, but then it’ll foul the rib on the platform. I could always raise the platform 8” to negate this of course.

There’s no pulleys in place currently for the port rudder cabling to run through but I’ve bought two Edson ones. Only prob is fitting them... if I was to mirror the pulley placement on the starboard rudder, it puts them at the back corner of the port diesel tank. It looks like the starboard pulleys are bolted to a piece of hardwood that’s just been glassed to the inside of the hull... would this be strong enough? Or do I ideally need to bolt it through something first?

N

bolted through the hull to a stainless plate on the outside is going to be the strongest option and easiest as a retro fit.

blind bolts through a hard wood block laminated to the hull might be strong enough if done properly with epoxy,glass,no humidity and ground out sufficiently.
but you have no way of checking the bolts have not corroded,or changing them or if the wood has rotted.

i would be inclined to heavily glass in with epoxy a stainless plate with threaded studs welded into it if going down that route

my outboard steering pulleys are through bolted into the toerail.
the 6mm plate outside was drilled and counter sunk and recessed into the toerail then through bolted with m10 counter sunk bolts so as to have a smooth surface outside with no projections to avoid damage if going alongside a dock or another boat.

marinesuperstore.com can supply all the components for the wire pull-pull "constellation" steering systems,much cheaper than lewmar.
link to the lewmar site below FYI

https://www.lewmar.com/node/11841

[Fore and Aft]

Atoll it reminds me of the learner bar on my mates ski boat. I think it’s very practical. Since most cats sail at double digit speeds what better opportunity to get some bare foot practice in.
Cheers

[atoll]

Originally Posted by Fore and Aft

Atoll it reminds me of the learner bar on my mates ski boat. I think it’s very practical. Since most cats sail at double digit speeds what better opportunity to get some bare foot practice in.
Cheers

catamarans will also surf just as fast backwards as forwards if they lose their steering in heavy weather

[ausnp84]

Originally Posted by atoll

bolted through the hull to a stainless plate on the outside is going to be the strongest option and easiest as a retro fit.

blind bolts through a hard wood block laminated to the hull might be strong enough if done properly with epoxy,glass,no humidity and ground out sufficiently.
but you have no way of checking the bolts have not corroded,or changing them or if the wood has rotted.

i would be inclined to heavily glass in with epoxy a stainless plate with threaded studs welded into it if going down that route

my outboard steering pulleys are through bolted into the toerail.
the 6mm plate outside was drilled and counter sunk and recessed into the toerail then through bolted with m10 counter sunk bolts so as to have a smooth surface outside with no projections to avoid damage if going alongside a dock or another boat.

marinesuperstore.com can supply all the components for the wire pull-pull "constellation" steering systems,much cheaper than lewmar.
link to the lewmar site below FYI

https://www.lewmar.com/node/11841

Ok cool, thanks. The plate will actually go into the back of the diesel tank which is a bit of a PITA, but strength is key and I’d rather the setup work correctly than be worrying about it down the track.

N

[atoll]

Originally Posted by ausnp84

Ok cool, thanks. The plate will actually go into the back of the diesel tank which is a bit of a PITA, but strength is key and I’d rather the setup work correctly than be worrying about it down the track.

N

yes the tensile loads can be quite high from the short lever arms on the rudder shafts to the cables.

also, with only about 10 inches (25cm) of travel it is important that there is no slack in the system ,so there must be adequate provision to adjust the tension and alignment to each lever arm from the helm.

expect about 5cm of adjustment on each cable initialy,then about a further 1-2 cm of stretch as the cables bed themselves in.

[ausnp84]

Yep no worries.

If I go the cable route and disconnect the tie bar, everything can go below decks and I’ll be running the cabling to the rudder quadrant. That way I can ditch the above decks lever arms (other than a small tab to connect the emergency rudder to) and adjust the cables for stretch over the coming weeks.

N