440: Back-up Auto Pilot for Lagoon 440

[beauris]

hello people,

first message in the forum which i started reading extremely recently..as i m looking into buying myself a cat ( probably a L440)...on the subject of AP here in France even though raymarine it probably the most distributed brand we tend to use for more "extreme" sailing ( ie solo transat and races) a french Brand called "NKE" which has proven itself for reliability...i'm using one on my current sailing boat and i'm pretty happy with it..even though its probably NOT as user friendly as the Raymarine unit that seem to be fitted to most Lagoon..

probably not as price friendly as raymarine as well which would explain why it's not fitted on most sailing boat
anyway for those who do not know the brand you can check it out there HomeÂ*-Â*nke marine electronics

[dougdaniel]

Originally Posted by a64pilot

Still wonder why these Cats don't use hydraulic steering? From an integration standpoint I can see real advantages with it.

Full disclosure: Never sailed a Lagoon cat but would love to!

Lagoon literature says they do use hydraulic steering on the 440.

This is a TO WHOM IT MAY CONCERN post. I have been following the big boat vs small boat debate that has been going on in this thread. Perhaps a resolution could help decide a good back up autopilot issue.

IMHO bigger boats do have greater forces on them and on their rudders than smaller boat. But I cannot fathom how this larger force necessarily translates into greater force at the helm. Wouldn't the designer simply use leverage to reduce the force to something manageable at the helm?

I was sailing a First 47-7 when a steel cable in the steering mechanism snapped. That cable must have had a tensile strength of several tons. Clearly those tons were reduced to something manageable at the circumference of the wheel.

It seems to me that a wheel-mounted autopilot would enjoy the same mechanical advantage of a human steering the boat.

Please help me to understand how the size of a boat would necessarily increase the force that the helmsman or autopilot must exert on the wheel.

[colemj]

You will notice that the larger the boat is, the larger the diameter of the wheel for mechanical steering - doesn't matter with hydraulic. That increased wheel diameter is providing the helm leverage for the increased steering forces needed.

Typically, a wheel pilot has a single drum size, so it does see increased forces with increased boat size. Some pilots may have a choice of drum size to accommodate, but at some point, they all become over-powered.

The increased force itself comes from increased rudder size, increased waterline, increased submerged volume, increased sail plan, etc. All of these contribute to the effort required to direct the boat through the wind and water.

Mark

[dougdaniel]

Originally Posted by colemj

You will notice that the larger the boat is, the larger the diameter of the wheel for mechanical steering - doesn't matter with hydraulic. That increased wheel diameter is providing the helm leverage for the increased steering forces needed.

Typically, a wheel pilot has a single drum size, so it does see increased forces with increased boat size. Some pilots may have a choice of drum size to accommodate, but at some point, they all become over-powered.

The increased force itself comes from increased rudder size, increased waterline, increased submerged volume, increased sail plan, etc. All of these contribute to the effort required to direct the boat through the wind and water.

Mark

Thanks Mark,

So would I be correct in saying that the ONLY way that sail boats get mechanical advantage is by increasing the wheel size and that, without exception, the greater a sailboat's displacement, the larger the wheel?

Thanks in advance for your response.

[colemj]

The diameter of the quadrant also increases with increased ship size (usually in only a few steps - small, medium, large). Like the wheel diameter, it also increases mechanical advantage.

Other than those two leverage arms on each end, the cables, sheaves and sprocket don't really give any advantage, although they may be sized larger to carry the larger loads.

Mark

[antoha]

Some of the older designs (pre-hydraulic, like the old ships) would use worm gear for mechanical advantage/reduction.


Sent from my iPhone using Cruisers Sailing Forum

[cll2]

It's my understanding that all L440s have cable steering systems from the factory and that L450s can be ordered with either cable or hydraulic. Is that not correct?

[atoll]

Originally Posted by cll2

It's my understanding that all L440s have cable steering systems from the factory and that L450s can be ordered with either cable or hydraulic. Is that not correct?

L440's have cable steering,the auto pilot has a hydraulic ram attached to the crossbar on the port side

[cll2]

Thanks Atoll. That's what I understood and that's what I have on my boat. Someone earlier mentioned that L440s have hydraulic steering but I'd never seen one.

[colemj]

The earlier references to hydraulics was in reference to hydraulic ram autopilot drives, not hydraulic steering.

Mark

[Emerald Sea]

Originally Posted by cll2

It's my understanding that all L440s have cable steering systems from the factory and that L450s can be ordered with either cable or hydraulic. Is that not correct?

L450s are all cable steering based systems. Hydraulic steering is not an option. Also, on L450's the AP smarts are Raymarine (SPX30 or the new Evo up to Q1 2015) and the hydraulics are from Lacombe&Schmitt. I viewed a 440 a few weeks ago and it was also installed with Lacombe&Schmitt hydraulics though an earlier generation. This first owner hadn't had any issues with his AP however I don't know what he carries as spares.

Which spare to carry for ocean crossing journeys, such as what we do, is a questionable debate. What can go wrong: the smarts of the system, the hydraulics, etc. Its quite expensive to keep a full redundant system available. Lightening can wipe out the smart electronics in a flash including a backup; the hydraulics seem quite robust. How much do you want to spend? Try to find out from owners and/or an honest RM tech where the anomalies exist?

We have a spare set of hyd hoses, thats all. Knocking on wood!




Steve
L450
SV Emerald Sea

[dougdaniel]

Originally Posted by cll2

Thanks Atoll. That's what I understood and that's what I have on my boat. Someone earlier mentioned that L440s have hydraulic steering but I'd never seen one.

I was the one that said that Lagoon's literature mentioned hydraulic steering. I was certain that I had seen that said. So, me being lazy and computers being hard working, I told my computer to search all of the PDFs for 'hydraulic.'

So to set the record straight, here is what the Lagoon 52 spec says:
• Fully hydraulicsteering mechanism:
- 1 hydraulic jack per rudder blade
- hydraulic system in starboard engine

I can find no evidence on my computer of any other Lagoon model with hydraulic steering.

Sorry for the confusion.
Doug

[cll2]

No worries Doug, just wanted to make sure I wasn't confused.

[meirriba]

Originally Posted by a64pilot

Still wonder why these Cats don't use hydraulic steering? From an integration standpoint I can see real advantages with it.

I believe the answer to that is that an hydraulic steering looses all feeling at the helm and people like to feel response when helming.
The hydraulics are there when the AP is deployed.

[meirriba]

Originally Posted by dougdaniel

I was the one that said that Lagoon's literature mentioned hydraulic steering. I was certain that I had seen that said. So, me being lazy and computers being hard working, I told my computer to search all of the PDFs for 'hydraulic.'

So to set the record straight, here is what the Lagoon 52 spec says:
• Fully hydraulicsteering mechanism:
- 1 hydraulic jack per rudder blade
- hydraulic system in starboard engine

I can find no evidence on my computer of any other Lagoon model with hydraulic steering.

Sorry for the confusion.
Doug

Further to my previous post, when the rudders get to large and hand steering (even mechanically assisted) boats do get hydraulic steering at the cost of feeling response.
I have surveyed recently an Lagoon 620 that had original hydraulic steering (and I mean at the wheels, not the AP that was hydraulic as well of course).