Autopilot Experts - we need your advise

[Stumble]

The most secure option is a completely seperate identacle system. Not only do you get a complete backup, but in the event of a failure of both systems you can likely scavenge parts from both of them and build one working system.

If starting from scratch I would probably install NKE gear, but since you already have a system installed, I would just duplicate what you already have.

[Paul L]

Originally Posted by Stumble

The most secure option is a completely seperate identacle system. Not only do you get a complete backup, but in the event of a failure of both systems you can likely scavenge parts from both of them and build one working system.

If starting from scratch I would probably install NKE gear, but since you already have a system installed, I would just duplicate what you already have.

I understand the logic of having a matching secondary system in theory. In practice most people are adding the second system many years after the original was installed, so the models are often many versions back from the current. Also in my case the original system was Raymarine. I really don't like Ray APs after going through way too many controllers and experiencing the AP driving onto flyers too many times. So I installed the AP I wanted and relegated the Ray to backup.

[bruce v]

Originally Posted by Revelations

Yes, I had a look at a wind vane system which can be fitted to a catamaran. Maybe it's all in my mind, but it does not look right. For now, I am more interested looking at a plugged in system.

You are right. It's all in your head. Find out how it works (if you take a few pics and post your questions here, some will certainly be able to instruct you on how to set it up and use it. You might also look for detail on type, quality and capacity. Not too hard and if you already have it, why not. Worst case scenario, it doesn't pass muster and then it becomes excess bagge you can get rid of.

[Paul L]

Originally Posted by Revelations

Yes, I had a look at a wind vane system which can be fitted to a catamaran. Maybe it's all in my mind, but it does not look right. For now, I am more interested looking at a plugged in system.

I really doubt that you will find a windvane that functions well on a 50 foot cat. Where would you mount it that the vane saw clear air?

[Moontide]

Had the hydraulic ram go out on a 18 year old B&G autopilot. It was the single piece unit. Replaced it with the HS 40 Plus unit from the link. Was a rush job as we didn't want to head from Isla Mujeres to the US without a functioning AP since there were only two onboard. Paid $1,800 (the link earlier in this thread was $1,095 lbs). Good news is I ordered it at 1030 PM on a Thursday and it was delivered from England to Florida Monday morning for $80.

After ordering did more digging and could have bought the equivalent individual parts for less than 1/2 the cost. To a great extent rams are rams and pumps are pumps.

Regarding backup systems. Any part can fail so for a completely failsafe system need all off them for a totally redundant system. On the other hand, certain parts are more likely to fail so you can improve your odds by picking only certain parts.

A friend has two identical AP's installed. Instead of valves, etc. to switch over, he just pulled the bolt connecting the ram to the steering linkage. To switch just removes the bolt from from bad unit and puts in the one for the good unit. About a 3 minute job.

[briblack]

we've done something similar, for similar reasons.
the boat (hylas 46) came with an old raymarine 300 ball-screw linear autopilot. certainly not state of the art, and arguably undersized, but they do work. I also had awccess to a slightly newer raymarine smartpilot-vintage linear hydraulic. so we put it in, too.
wasn't really too easy, it needs to be a very strong mount. we set it up so one rotary switch could put the power to either, but never both. one ram or the other could drop onto the rudder actuator. etc.
put in a fully redundant system. duplicate fluxgates, rudder position sensors, and control heads, in the cockpit. one of the hardest parts was getting the fluxgate information to the chartplotter for boat symbol and radar overlay alignment. switching the seatalk from one autopilot to the other, so the active went to the chartplotter.
but now it's working great, we were going to have to carry all this as spares anyway, so we'll just carry 'em installed. except now we're carrying another spare course computer, rudder sensor, fluxgate, and control head. just to be ready. this older generation equipment can turn up at pretty reasonable prices.
a wind vane wasn't an option for us, because of the access hatch to the locker in the swimstep.

[foufou]

With respect to storing equipment in aluminum foil with hope that this might prevent lightning strike damage, I do not believe that foil qualifies as a "Faraday" box. My understanding is that the enclosure must be steel. Others please chime in.

[Paul L]

Originally Posted by foufou

With respect to storing equipment in aluminum foil with hope that this might prevent lightning strike damage, I do not believe that foil qualifies as a "Faraday" box. My understanding is that the enclosure must be steel. Others please chime in.

A Faraday cage or Faraday shield is an enclosure formed by conductive material or by a mesh of such material, used to block electric fields

from Wikipedia
What happens after a lightening strike is always a gamble. Wrapping in foil and placing below is more likely to preserve the devices than having them mounted with wires running out. Anecdotal evidence does support this, but it is only anecdotal.

[Canuck Sailor]

I have been using the same autopilot unit for 20 years and crossed the Pacific with it. The motor failed south of Tonga and we had to hand steer for 9 hours.(Miinerva Reef) That was enough for me. I can appreciate your hand steering for two weeks, wow.

I repaired the motor by replacing the brushes stolen from a mascerator pump with modifications and finished the voyage plus some 4,000 extra nautical miles.

I now have two hydraulic motor/pumps of different capacities that switch over with a double pole double throw DPDT switch for instant under way changes. One is great for sailing, lower power draw, the other for very heavy seas.
Now I use Octopus pumps of 1.2 & 2.0 litres capacity and they have been working well. They are reversing pumps. No tank no problem and maintains a course much better than I.

One time a lightning proximity strike took out the sailing instruments but I was able to separate the autopilot and continued on without a problem, just a slight delay. I have a second server, very recent technology, that I can put in but prefer the 20+ year box that has more features.

[barnakiel]

I would go with two identical units, one per each hull. One with the ram suspended while the other drives. Swap the rams now and then.

Expensive and bullet proof.

I have been on monos with such a set-up.

b.

[Mainstay]

[QUOTE=Blue Stocking;2147960]

Originally Posted by Mainstay

I have basically the same requirements for my Venezia 42. Currently I am looking at installing something like this:

Linear Drive for Raymarine Simrad Autopilots | eBay[/QUOT

That looks like a good price. Pump capacity is capable of delivering the " hard over-to-hard over" times you will need ?

I have not run the numbers yet - I still have to convince myself that it is the way to go. I would much rather have a windvane system, though, as I think it is the only system that will give me true redundancy for my auto pilot. In my mind I want to be ready for a catastrophic event, like a direct lightning strike that takes out ALL electronics - and I mean ALL electronics, even spare parts stored in boxes or installed but not online. (a friend once relayed to me how his boat was struck and even the spare alternator that was stored away in a wooden box in some cupboard somewhere, got fried!!) So, in a situation like this I would like to pull out the windvane, install it most probably on the upwind rudder quadrant, pull out my sextant and keep going in the right direction.
I will be doing some serious research into catamarans and windvanes in the foreseeable future - I'm not in a hurry as we plan to cruise the Bahamas for the next few years and spares can easily be flown in over night.
I would love to hear from fellow catamaran owners and their experience - or ideas - regarding windvanes.

[seandepagnier]

Originally Posted by Revelations

... had to hand steer for almost 2 weeks continuously.

I have heard similar stories and I really don't understand it, because there are so many alternatives.

About 20 minutes after I lost my wine vane oar, I was continuing on with sheet steering using an elastic cord, after 48 hours I reached the next port.

I know a larger catamaran than yours that entirely relies on sheet to tiller steering for all conditions.

I think you need roughly 6 inches of cord per ton of boat using standard head sails, but you can use a smaller head sail for control requiring much less bungee, and less chafe.

If you have a stay sail, you can also back wind it spoiling it's overall small amount of power but gaining superior sheet steering.

In stronger winds, in my boat for example, I can run dead downwind in 30-40 knots doing hull speed by locking the rudder exactly midway, and setting a small head sail which is sheeted tight on _both_ sheets.

I think it makes sense to consider designing a rig specifically optimized for self balance on all courses rather than upwind performance.

[knockabout]

motors can be rewound or rebuilt/compare with new price/a tiller pilot will steer a cat if the helm is geared well /a small L bracket clamped to the wheel on the inside at the bottom when the wheel is centred a solid bracket on the steering bulkhead to take the tp pivot /hook up wiring extend rod 1/2 travel /then fit the above solid bracket /trim sails set up on course drop the tiller pilot ram end on the wheel pivot press the steer to course button /not much helm travel but safe
back up system// for ohpoo chinese jibe etc lift the weel end off, spin the weel some have the strong bracket built so as to hold the tp up and close to the weel wen not conacted /works on any wheel, stink boat etc

[Neptune's Gear]

Originally Posted by Revelations

Thank you - I will certainly check if it's perhaps the bearings or brushes.

Regarding your Triton suggestion;
I have spoken to two B&G retailers but suspect that they are trying to make more money out of me than necessary. They are hell bent on selling me a complete B&G system with all the trimmings - radar, chart plotter, instruments and many other items. Which basic essential components/equipment would we need for a secondary autopilot system.

It is not necessary to replace your whole electronics package. Although you may be tempted when you see what a new one can do .

There is likely also no reason to replace the ram - carry a spare set of seals for it, and learn how to replace them. Hydraulics are incredibly robust and reliable, provided they are treated with a bit of respect.

The pumps can, and do, fail quite a bit more often, So, if I were you, and were not about to re-do all the electronics, I'd get a set of Hydraulic seals, a spare pump, a spare set of brushes and bearings, solenoid, a spare AP computer, controller, rudder sensor and heading sensor. Total cost for this gear for a B&G triton system would be somewhere around $4500 USD. It can interface to your existing gear via NMEA0183 or NMEA2000, whatever is easier for your install.

Of course you can continue to add spares list and still not have something you end up needing. Not really practical to carry a spare boat! This is where lateral thinking and ingenuity can get you home. IMO part of the attraction of the cruising life.

All that being said, I once hand steered for about 1000 NM due to a failed AP computer :-( (well, sheets and bungies, but you still had to watch it all the time)

Send me a PM if you'd like me to do a real quote, rather than an estimate. I ship stuff everywhere.

Cheers
Matt

[svrevelations]

Originally Posted by boat_alexandra

I have heard similar stories and I really don't understand it, because there are so many alternatives.

About 20 minutes after I lost my wine vane oar, I was continuing on with sheet steering using an elastic cord, after 48 hours I reached the next port.

I know a larger catamaran than yours that entirely relies on sheet to tiller steering for all conditions.

I think you need roughly 6 inches of cord per ton of boat using standard head sails, but you can use a smaller head sail for control requiring much less bungee, and less chafe.

If you have a stay sail, you can also back wind it spoiling it's overall small amount of power but gaining superior sheet steering.

In stronger winds, in my boat for example, I can run dead downwind in 30-40 knots doing hull speed by locking the rudder exactly midway, and setting a small head sail which is sheeted tight on _both_ sheets.

I think it makes sense to consider designing a rig specifically optimized for self balance on all courses rather than upwind performance.

No doubt experience and knowledge counts - man is limited to what he knows. I will be great to meet up with you one day so that we may learn new ways of doing things.