Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 29-11-2007, 22:19   #1
Registered User

Join Date: Nov 2007
Posts: 12
Autopilot advice?

So if you're buying an autopilot, do you throw down the extra US $600 for the rate gyro (how useful are they really?), or do you throw down $600 for a unit rated for 8,000 pounds more than your displacement, or do not throw down the extra $600 at all and just get the basic (and still expensive), non-rate gyro unit rated for 4,000 pounds more than your displacement???
__________________

__________________
KodiakMike is offline   Reply With Quote
Old 29-11-2007, 22:39   #2
Registered User

Join Date: Oct 2007
Location: Southern California
Boat: Was - Passport 45 Ketch
Posts: 837
Quote:
Originally Posted by KodiakMike View Post
So if you're buying an autopilot, do you throw down the extra US $600 for the rate gyro (how useful are they really?), or do you throw down $600 for a unit rated for 8,000 pounds more than your displacement, or do not throw down the extra $600 at all and just get the basic (and still expensive), non-rate gyro unit rated for 4,000 pounds more than your displacement???
Big question....too little info.

What kind of boat?

Center or aft cockpit?

What kind of steering? (wheel, tiller, hydraulic, cable)

What kind of cruising?

Do you have a wind-vane?
__________________

__________________
Kanani is offline   Reply With Quote
Old 29-11-2007, 22:53   #3
Registered User

Join Date: Nov 2007
Posts: 12
good questions. answers: crealock 37 (balances well)aft cockpitwheel/cable steeringyes we have a windvane (monitor) which typically works great, so autopilot is for motoring (just had a very light air summer in the Gulf of Alaska) and redundancy for the windvanewe're about to leave U.S. for a winter in Mexico, then across the Pacific to Australia...
__________________
KodiakMike is offline   Reply With Quote
Old 29-11-2007, 23:07   #4
Registered User

Join Date: Oct 2007
Location: Southern California
Boat: Was - Passport 45 Ketch
Posts: 837
Quote:
Originally Posted by KodiakMike View Post
good questions. answers: crealock 37 (balances well)aft cockpitwheel/cable steeringyes we have a windvane (monitor) which typically works great, so autopilot is for motoring (just had a very light air summer in the Gulf of Alaska) and redundancy for the windvanewe're about to leave U.S. for a winter in Mexico, then across the Pacific to Australia...
I think that the answer to your question is obvious. Your autopilot should see minimal work because of your wind-vane. However, if you go to the smaller unit, be sure to carry plenty of spares. You may find yourself motoring for days on end, at times.

Your concern should be more about wear & tear then about stress. Forget about the autopilot as a back-up for the wind-vane. If the wind is blowing hard enough for the wind-vane, use it (it won't fail you). If it is too light for the wind-vane, the autopilot doesn't need to work very hard. If it's blowing hard and the wind vane fails (which it probably won't), hardly any (wheel steering) autopilot will do the job.

If you have a steering quadrant and the room and you want a serious autopilot, go to a quadrant mounted electric/hydraulic pilot. That way, you iliminate the stress on your steering cables and can steer the boat with the pilot in the event of a cable (or other) failure.

If you have the extra $, it sure wouldn't hurt to go bigger. However, if you are like most of us, the $ could probably be better used elsewhere.
__________________
Kanani is offline   Reply With Quote
Old 29-11-2007, 23:38   #5
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,863
Images: 4
I have a Pacific Seacraft 44 (Crealock), with a Monitor windvane, and a B&G belowdeck electric/hydraulic AP. The AP fluxgate compass is the non-rate gyro version.

The AP works well in most conditions. The only time I really wish I had the gyro is in moderate swells and wind, downwind under spinnaker. The AP just doesn't react quickly enough in these conditions. I think the gyro unit would help, but that's just a theory. In these conditions, I either hand-steer (racing), or switch to a more reasonable sail configuration (cruising).

I do have a "gyro" compass for the chartplotter/radar, and this makes a huge difference in the radar/MARPA performance. Unfortunately, my older B&G AP isn't compatible with this gyro.

The Crealock can be balanced quite well, but the rudder is not really a balanced design, so when actively steering (as in swells), there is still a lot of loading that the AP has to handle.

If you have to choose, your first priority is to make sure the AP is beefy enough. An under-powered AP just won't last. If you *only* use it while motoring, then a smaller AP drive unit is probably OK, but I've found that in some conditions the AP just works better than the Monitor. I do like having the redundancy. A stronger AP drive unit may also have a quicker response (a good thing), but this is going to depend on the unit.
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 30-11-2007, 09:42   #6
Registered User

Join Date: Oct 2007
Location: Southern California
Boat: Was - Passport 45 Ketch
Posts: 837
The "rate gyro" compass may be handy if you are racing or flying an airplane. Even a Gyro compass has questionable value while motoring in light airs or sailing in light airs under spinakker on a cruising yacht.

When you are under wind-vane you may well experience a 30 degree variance in course, if you stare at your compass. However, once you establish the best course possible, you will find that your plot will be fairly straight.

Even if you could steer a perfectly straight course over a passage of 1000 miles, as apposed to the erratic course of a wind-vane or non-gyro compass, I doubt that you would see more than a few hours difference in your total passage.

Cruising is not racing and it is an opportunity to take your time and spare your gear. On the other hand, it is important to limit your "At sea" weather exposure as much as possible. However, you will get far more positive results from personal experience than from expensive gear that will (most likely) eventually fail.

I am a big proponant to the below deck electric/hydralic pilot. Especially when it is attached directly to the rudder quadrant. One of my worst, at sea, experiences was from a steering cable failing on a delivery vessel. Long story, I will spare you .

On my boat, I even ran my wind-vane lines directly to my emergency tiller (attached directly to the rudder post) as apposed to running lines all over the boat and deal with the indirectness of wheel/cable steering. Windvanes work far better on tiller steering than they do on wheel steering, especially in light airs. I often ran down-wind, in light airs under spinakker. The wind-vane worked just fine as long as it had he slightest amount of apparent wind. Kanani is a center cockpit though. The tiller is harder to rig on an aft-cockpit boat.
__________________
Kanani is offline   Reply With Quote
Old 30-11-2007, 12:18   #7
Registered User

Join Date: Jul 2006
Location: Airlie beach (for the moment)
Boat: newport30, Blues Traveler
Posts: 141
Have you considerd hooking your auto pilot to your windane. i just saw a story in "cruising helmsmen" were it was done and it seemed like good idea as it uses the mechanics of the windvane for an easy life and not much stress. They just made up a bracket and i worked basisally as a tiller pilot. and then just slip out a pin to make it back to the windvane. it is in december issue but i can not find it at the moment for more information
__________________
viking69 is offline   Reply With Quote
Old 30-11-2007, 13:39   #8
Moderator Emeritus
 
Pblais's Avatar

Join Date: Mar 2003
Location: Hayes, VA
Boat: Gozzard 36
Posts: 8,700
Images: 15
Send a message via Skype™ to Pblais
Quote:
I am a big proponant to the below deck electric/hydralic pilot. Especially when it is attached directly to the rudder quadrant.
So am I. with a boat as big as a 37 you'll need it to to be able to do real autopilot stuff. A wheel pilot is only really suitable for those times you really don't need one. A windvane is great on long legs and saves a lot of power. When you get into closer quarters and choppy connditions your wheel pilot will be worthless. A below deck hydralic system can handle the wheel and the computer control can handle cross winds and heavvier conditions a wheel pilot lack the power to handle.

We have a rdundant quadrant so the autopilot is also a spare. We also have a Monitor Windvane as well. Both is better. I would just forget an autopilot if you can't do it below decks. It will be a constant problem and require at least two identical units to have one that is working.
__________________
Paul Blais
s/v Bright Eyes Gozzard 36
37 15.7 N 76 28.9 W
Pblais is offline   Reply With Quote
Old 30-11-2007, 13:54   #9
Registered User

Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,076
Images: 6
On track with a rate gyro

When at sea, especially in heavy following seas, the three main factors regarding the autopilot are:
Power; You need horsepower to move the rudder in fast moving water quickly enough to not broach.
Electrohydraulics; The most reliable when directly connected to the rudder post via a tiller arm or quadrant (if and only if the quadrant is designed for single point torque loading from the ram)
Rate gyro input; You will not believe how quick a rate gyro can respond to the beginning of a yaw and correct for it before a broach can occur.

A good autopilot meeting the above criteria will outperform any windvane. I realize that this statement will probably raise a few cries. A good autopilot can save your boat when even a good helmsman might not be able to. Even excellent helmsmen get tired. There is no way that a windvane can correct against yaw when the wind gives an immediate shift as the boat gets blanketed by a huge following sea overtaking the craft.
__________________
"I don't think there'll be a return journey Mr. Frodo". Samwise Gamgee
Rick is offline   Reply With Quote
Old 30-11-2007, 14:03   #10
Registered User

Join Date: Oct 2007
Location: Southern California
Boat: Was - Passport 45 Ketch
Posts: 837
Quote:
Originally Posted by Pblais View Post
So am I. with a boat as big as a 37 you'll need it to to be able to do real autopilot stuff. A wheel pilot is only really suitable for those times you really don't need one. A windvane is great on long legs and saves a lot of power. When you get into closer quarters and choppy connditions your wheel pilot will be worthless. A below deck hydralic system can handle the wheel and the computer control can handle cross winds and heavvier conditions a wheel pilot lack the power to handle.

We have a rdundant quadrant so the autopilot is also a spare. We also have a Monitor Windvane as well. Both is better. I would just forget an autopilot if you can't do it below decks. It will be a constant problem and require at least two identical units to have one that is working.
AHHHH!! I finally found something to disagree with you on .

The OP is talking about sailing from Mexico to the South Pacific. Crossing the Equator without some sort of an autopilot (and plenty of fuel) can be challenging without some sort of autopilot. It is a long slow sail to the Marquesas Islands.

I do agree with the need for plenty of spares. Maybe even a 2nd complete unit and additional high-wear items. There aren't any marine stores on that route.
__________________
Kanani is offline   Reply With Quote
Old 30-11-2007, 14:23   #11
Registered User

Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,076
Images: 6
Below deck electrohylraulic autopilot

I agree with Paul. Above deck autopilots (all that I've seen) could be classified as "toy autopilots". To do a skookum job it should be mounted belowdecks. Keep in mind that the toy autopilots all lack the horsepower necessary to move the rudder as fast as necessary in rough conditions, no matter how many spares you carry. Every toy autopilot that you purchase adds to the overall total losses you will incur when cruising.

Get a REAL autopilot. You can easily buy spare ubiquitous seals for the ram to use as a rebuild kit. A rebuild ram kit is usually less than $25, especially if you inspect the seal numbers to buy generically available ones from any bearing supply house in the world.

The electronics can be easier to protect both from the sea as well as lightning discharges with below deck autopilots.
__________________
"I don't think there'll be a return journey Mr. Frodo". Samwise Gamgee
Rick is offline   Reply With Quote
Old 30-11-2007, 15:18   #12
Registered User

Join Date: Oct 2007
Location: Southern California
Boat: Was - Passport 45 Ketch
Posts: 837
Quote:
Originally Posted by Rick View Post
When at sea, especially in heavy following seas, the three main factors regarding the autopilot are:
Power; You need horsepower to move the rudder in fast moving water quickly enough to not broach.
Electrohydraulics; The most reliable when directly connected to the rudder post via a tiller arm or quadrant (if and only if the quadrant is designed for single point torque loading from the ram)
Rate gyro input; You will not believe how quick a rate gyro can respond to the beginning of a yaw and correct for it before a broach can occur.

A good autopilot meeting the above criteria will outperform any windvane. I realize that this statement will probably raise a few cries. A good autopilot can save your boat when even a good helmsman might not be able to. Even excellent helmsmen get tired. There is no way that a windvane can correct against yaw when the wind gives an immediate shift as the boat gets blanketed by a huge following sea overtaking the craft.
All I can say is...."WRONG"...."Been there.....done that" (hundreds of times) and my windvane has NEVER failed to perform flawlessly in big following seas, even in the Southern Ocean. Even in a hurricane in the Tasman Sea.

The wind-vane paddle is not the only thing that effects the movement of the pendulem rudder. Before the vessel begins to yaw, the first thing hit by the on-coming sea is the pendulem rudder. It will be slammed to one side and immediately throw the helm over. It will correct your heading even before the vane feels the air or your vessel starts to yaw. The harder the wind and bigger the seas, the more acurate the wind-vane will steer your boat.

As for power, there is no person or auto-pilot that has the power of a wid-vane on a vessel that is moving at any decent speed. There is NO WAY, that a person can over-power a windvane on a boat moving at hull speed.

I consider myself to be a pretty good helmsman but there is NO WAY that I would attempt to steer in conditions that my wind-vane has held me in total awe and admiration. I have video tape of that thing steering in conditions that would make most people puke watching it on the screen.

I would never select an electronic device in life threatening situations.
__________________
Kanani is offline   Reply With Quote
Old 30-11-2007, 17:43   #13
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,863
Images: 4
I'm not claiming any particular expertise here, but in my experience the performance of the windvane (such as the Monitor) systems depends much on the conditions and the boat configuration. Servo-pendulum types (Monitor) are more powerful and have more control range than the aux-rudder types. The aux-rudder units do require much more careful sail balancing, and they are more easily overwhelmed should (for example) your boat develops weather-helm in a gust, or a swell pushes the stern over.

In the spinnaker example I posted, this is a particularly *unstable* sail configuration. Once it gets out of balance, the boat will start a "death-roll" oscillation, then ultimately round up or round down. Once this starts, the only way to correct is through very careful, anticipatory, steering. I found that neither the Monitor, or the AP (with non-gyro fluxgate, or steering to masthead apparent wind), were up to the task. I have heard that the gyro units are better at correcting for the boat motion that otherwise confuses the fluxgate.

My boat is a heavy displacement vessel, and I understand that the lightweight racers are even more sensitive in this area.

Where safety or comfort is an issue, I would *not* be flying the spinnaker under such conditions where things can so quickly get out of control. Twin jibs, or a single jib, are much more stable in these conditions, and I agree, the Monitor performs admirably in high winds with an appropriate sail configuration.

I really like having a sturdy belowdeck AP, and a Monitor. With the Monitor, sometimes a line chafes, or the breakaway safety tube snaps, and then having the backup AP is a big plus.

On the other hand, the AP sucks Amps big-time. The Monitor is much kinder to my power budget. I do have a tillerpilot that I can hook to the Monitor, for a low-power option, but I have not actually used this setup.

Quote:
Originally Posted by Kanani View Post
I would never select an electronic device in life threatening situations.
Perhaps. Mechanical stuff breaks too. My belowdeck hydraulic AP has fewer parts under high load then does the Monitor. I like and use them both, and I try to be prepared for any failure. Well, most any failure...
__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Old 30-11-2007, 18:03   #14
Registered User

Join Date: Oct 2007
Location: Southern California
Boat: Was - Passport 45 Ketch
Posts: 837
I agree with all you said.

As I stated before, I too have a below deck hydraulic/electric AP, bolted to my rudder quadrant and an Aries wind-vane. IMO (as yours) it is the "Best" way to go.

All I am saying is that the OP would be better off having a wheel pilot then no AP at all. Plenty of people have used them succesfully. If used sparingly in light weather, they can do a good job. Don't get me wrong, it's NOT my prefference by any means. It's just an option that shouldn't be disgarded IMO.
__________________
Kanani is offline   Reply With Quote
Old 30-11-2007, 18:23   #15
Moderator
 
Paul Elliott's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 3,863
Images: 4
Quote:
Originally Posted by Kanani View Post
All I am saying is that the OP would be better off having a wheel pilot then no AP at all.
Absolutely correct. You want two ways to avoid having to hand-steer. Best if they are both bulletproof, but even a fragile backup is way better than none. Do keep the wheel (or tiller) pilot protected, so it will work when you need it.

Hey, I'm itching for a good fight, and there you go being all reasonable!
__________________

__________________
Paul Elliott, S/V VALIS - Pacific Seacraft 44 #16 - Friday Harbor, WA
www.sailvalis.com
Paul Elliott is offline   Reply With Quote
Reply

Tags
autopilot

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
CPT Autopilot? Gallivanters Marine Electronics 3 03-11-2008 10:35
Which Autopilot?????????????? avazquez Marine Electronics 21 30-09-2007 22:35
Raymarine autopilot irwinsailor Construction, Maintenance & Refit 3 14-09-2005 20:48
Autopilot salty Marine Electronics 3 25-03-2004 17:48
Looking at B&G autopilot kd7lmq Marine Electronics 0 14-05-2003 17:03



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 22:27.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.