Reply
 
Thread Tools Display Modes
 
Old 02-15-2016, 11:18 AM   #1
Guru
 
CaptTom's Avatar
 
City: Southern Maine
Country: USA
Vessel Name: Cygnus
Vessel Model: Prairie 36 Coastal Cruiser
Join Date: Dec 2012
Posts: 1,375
Minimum Autopilot

I'm just not seeing the justification for the $4K+ price tag for an autopilot.

I get that a hydraulic pump costs $500+. I'm questioning the need for some of the other parts.

I've never installed one, but I have used them. In it's purest form, the autopilot runs the pump to turn the rudder one way or the other as needed.

I just don't see why you need a $2,000 computer to do that.

I already have two multifunction displays that talk NMEA 0183 and NMEA 2000.

They already spit out my current speed, heading, desired course and cross-track error. I can set them to them display a "highway" graphic and tell even the dullest helmsman to "just keep the boat in the middle of the road".

That's all I want my autopilot to do.

Why not just have a simple device that reads the NMEA XTE and tells the pump to go right or left? How much could that cost? I'm betting a Raspberry PI could handle it easily.

I don't even see the need for a fluxgate compass. If I'm not moving, my autopilot it useless anyway. If I am moving, my GPS heading is good enough to steer by.

Even the rudder position indicator is of questionable value, although I can see maybe wanting to know when it's hard over one way or the other, and can't be moved any further.

Adding it up; $500 for the pump, $50 for the Raspberry PI and associated hardware, $200 for a rudder indicator and $150 for a fancy control panel.

Total price, $900.

Am I missing something? Why do I need to spend another $3,100+?
__________________
Advertisement

CaptTom is online now   Reply With Quote
Old 02-15-2016, 11:45 AM   #2
Enigma
 
RT Firefly's Avatar
 
City: Slicker?
Country: Bumpkin?
Join Date: Oct 2007
Posts: 9,996
Greetings,
Profit.
__________________

__________________
RTF
RT Firefly is online now   Reply With Quote
Old 02-15-2016, 11:45 AM   #3
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,712
I had the need for an AP when I was single but now Chris and I trade off and we really don't miss it. Had it on the previous boat. I'm not even having small thoughts about getting one now. We have a boat that doesn't take much helm tending. Hydraulic steering helps too because when you let go the helm it stays put and doesn't wander.

I would like a rudder position indicator though.
__________________
Eric

North Western Washington State USA
Nomad Willy is online now   Reply With Quote
Old 02-15-2016, 11:53 AM   #4
Guru
 
River Cruiser's Avatar
 
City: UMR MM283
Country: US
Vessel Name: Northern Lights II
Vessel Model: Bayliner 3870
Join Date: Jan 2013
Posts: 1,228
If all you want is a AP that will hold a course there are ones on the market that will do that for a lot less than what you quoted. Look at the ComNav or ones rebranded as Si-Tex units. Raymarine has a complete system for $1300.00 if you do some shopping, it'll work on a 38' boat. I found mine a ComNav 1420 with pump on eBay for $620.00 shipped, I bought a new 2nd station control for $230.00 shipped from a dealer in California. How big is your boat?


Sent from my iPad using Trawler Forum
__________________
Ron on Northern Lights II
I don't like making plans for the day because the word "premeditated" gets thrown around in the courtroom.
River Cruiser is offline   Reply With Quote
Old 02-15-2016, 12:25 PM   #5
Veteran Member
 
WD40's Avatar
 
City: Mount Vernon, WA / La Conner, WA
Country: USA
Vessel Name: Otter
Vessel Model: 1985 President Sundeck 41
Join Date: Dec 2015
Posts: 78
Quote:
Originally Posted by manyboats View Post
I would like a rudder position indicator though.
I'll second that! But I suppose we're talking a whole new thread in that case.

After reading CaptTom's description, I think I'll pull out the manual for our AP and see what type of system we have, and how many components there really are.
WD40 is offline   Reply With Quote
Old 02-15-2016, 12:58 PM   #6
Guru
 
caltexflanc's Avatar
 
City: North Carolina for now
Country: USA
Vessel Name: Small Incentive
Vessel Model: Boston Whaler 130 Sport
Join Date: Aug 2011
Posts: 3,798
River Cruiser's got it. We chartered boats with the simplest ComNav unit and I really liked. Also one with a basic Raymarine, ditto. The fancy ones have all sorts of cool features many cruisers may never use... like the ability to follow figure 8 or other prescribed courses for trolling, or follow a depth line on the chart, not to mention auto adjusting for sea state and boat steering characteristics.... and many many other goodies.

When we were cruising, in open water I found myself just setting to the direction I wanted to go and using the hand held remotes (which I LOVE) to tweak the course, and a lot of the time in more confined waters just using it as a power steering wheel while reclining back in the helm seat. For some real long legs out on the ocean, I would use the Nav function to steer to a GPS way point, but I liked to be still actively manning the helm.
__________________
George

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
caltexflanc is offline   Reply With Quote
Old 02-15-2016, 02:00 PM   #7
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,153
Quote:
Originally Posted by CaptTom View Post

Am I missing something? Why do I need to spend another $3,100+?
To have it work properly. To have adjustments for different conditions. To have the ability to go quickly out of it. To have the ability to set courses, not just straight paths. To have the ability to react to currents and wind shifts.
BandB is offline   Reply With Quote
Old 02-15-2016, 02:30 PM   #8
Guru
 
CaptTom's Avatar
 
City: Southern Maine
Country: USA
Vessel Name: Cygnus
Vessel Model: Prairie 36 Coastal Cruiser
Join Date: Dec 2012
Posts: 1,375
Thanks for the quick responses. Definitely going to look up ComNav!
Quote:
Originally Posted by BandB View Post
To have it work properly. To have adjustments for different conditions. To have the ability to go quickly out of it. To have the ability to set courses, not just straight paths. To have the ability to react to currents and wind shifts.
Work properly - Yeah, I agree that's important. What's the failure mode with what I suggested in the OP?

Adjustments for different conditions - Such as? Slower or faster turns in different sea states? Couldn't just a +/- control on the panel do that?

Quickly shut it off - That seems pretty achievable in any configuration.

Set courses - My MFDs do that, and put the course to the next waypoint out on the NMEA networks, along with XTE along the way. No need for a $2K computer for that!

Current and Wind shift - likewise, my MFDs don't care about set or drift. They just figure out which direction I traveled over the past second or so, and spit out the correction to get back on course. They deal with what's really going on, no vector arithmetic required.

Sorry if I sound like I'm nit-picking, but I'm really trying to figure out what all those extra $$$ will buy me that I don't already have. I don't really need the figure-8 thing.
CaptTom is online now   Reply With Quote
Old 02-15-2016, 03:07 PM   #9
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,371
Most will say a properly working AP steers better than a seasoned helms person. For serious cruisers an AP is near the top of the list needs. My wife really likes the AP in snotty, foggy, rainy and windy weather. For many, APs, stabilizers, good anchors and thrusters are unnecessary expenditures.

So CaptTom, I know nothing about your cruising style, wallet, gizmo interest or if you have a wife who really likes an AP. So no advice, just a recite of what we deem our needs. My guess though is you don't need one and are New England frugal. Smart of you to ask.
sunchaser is offline   Reply With Quote
Old 02-15-2016, 03:20 PM   #10
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
Autopilot and rudder indicator are "must haves."

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 02-15-2016, 04:15 PM   #11
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,153
Quote:
Originally Posted by CaptTom View Post
Thanks for the quick responses. Definitely going to look up ComNav!

Work properly - Yeah, I agree that's important. What's the failure mode with what I suggested in the OP?

Adjustments for different conditions - Such as? Slower or faster turns in different sea states? Couldn't just a +/- control on the panel do that?

Quickly shut it off - That seems pretty achievable in any configuration.

Set courses - My MFDs do that, and put the course to the next waypoint out on the NMEA networks, along with XTE along the way. No need for a $2K computer for that!

Current and Wind shift - likewise, my MFDs don't care about set or drift. They just figure out which direction I traveled over the past second or so, and spit out the correction to get back on course. They deal with what's really going on, no vector arithmetic required.

Sorry if I sound like I'm nit-picking, but I'm really trying to figure out what all those extra $$$ will buy me that I don't already have. I don't really need the figure-8 thing.
Not saying you can't do it and have it working and functioning fully. Just saying that's a big challenge. Basically that's what the manufacturers do. They take $1500 parts, add $500 labor and sell for $4000.

The adjustments I was referring to were sensitivity.
BandB is offline   Reply With Quote
Old 02-15-2016, 04:38 PM   #12
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,888
For AP algorithm to work, it does need a heading sensor such as a fluxgate or gyro or gps heading sensor. Course made good numbers from std gps take too long show a change. AP would be very sloppy in that case.

Try steering your boat while looking only at gps display and you will see what I mean!!
Ski in NC is offline   Reply With Quote
Old 02-15-2016, 05:15 PM   #13
Guru
 
caltexflanc's Avatar
 
City: North Carolina for now
Country: USA
Vessel Name: Small Incentive
Vessel Model: Boston Whaler 130 Sport
Join Date: Aug 2011
Posts: 3,798
Quote:
If I am moving, my GPS heading is good enough to steer by.
Ski got it right, your GPS does not tell you your heading, it tells you your track. I do think the OP should go ahead and do a DIY and let us know how it works. Especially interested in how it does in a steepish quartering sea. I note labor and R&D expense isn't built into his cost calculation; if you value your time at zero, then you'll always save cash. So go ahead and give it a shot!
__________________
George

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
caltexflanc is offline   Reply With Quote
Old 02-15-2016, 05:24 PM   #14
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 4,817
My first AP was a Raytheon system that was belt driven off the helm wheel. Consisted of the drive motor and a display box that housed the electronics with the built in compass. Think I gave under $500 for it new. It worked fine for my charter boat and held a decent course in the ocean in many conditions. Wasn't good in following or quarter following seas.

Would I own it again, no. Part of what you pay for is the more refined electronics that require a rudder sensor and a fluxgate compass. These do a much better job and allow you to have a reliable pilot in almost any conditions.

IMO, this is like an anchor. If you anchor miles from anything, maybe you don't care how often your hook drags. To me, I want it to work as closed to perfectly as much of the time as possible. Use my AP 90+% of the time...because my AP is that good!

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 02-15-2016, 05:36 PM   #15
Senior Member
 
waddenkruiser's Avatar
 
City: Southern Baltic
Country: Europe
Vessel Name: Sømarken
Vessel Model: AMS 40'
Join Date: Jul 2012
Posts: 183
Minimum Autopilot

I'm not at all an instruments and control engineer, but at least an engineer. What I remember from the i&c lectures at university is that course control of a vessel needs a so called PID controller: the controller has to adjust the rudder
P- proportional to the offset (or deviation) of set course and actual course = the higher the offset the higher the change of rudder angle, plus
I- integral to this offset = the higher the offset added over a given time the higher the change of rudder angle, plus
D- differential to this offset = the faster this offset increases the higher the change of rudder angle.
An AP needs an actual course signal which is to be compared to the desired or set value. A normal GPS signal is to slow. please try to steer your boat looking only at your GPS display (I'm not talking about sophisticated GPS compasses, they might be fast enough), as it was already suggested above.
And the algorithm needs a rudder signal, i.e. a rudder position.

And: While hand steering we are intuitively doing all that without giving any thought to it!


best regards / med venlig hilsen
wadden
__________________
best regards / med venlig hilsen
Wadden
waddenkruiser is offline   Reply With Quote
Old 02-15-2016, 07:22 PM   #16
Guru
 
CaptTom's Avatar
 
City: Southern Maine
Country: USA
Vessel Name: Cygnus
Vessel Model: Prairie 36 Coastal Cruiser
Join Date: Dec 2012
Posts: 1,375
Good discussion, thanks! And no, I wasn't going to try to build this myself. Just trying to make sense of the high cost.

A ComNav 1420 at a cost of 1.6 Boating Units certainly brings it down into the straight-face realm. I'd prefer if it had a wireless remote option like just about every other piece of consumer electronics that costs more than $50 nowadays. But it's far from a necessity, and the wired console has a pretty long wire.

And I agree that the normal chartplotter GPS updates wouldn't be fast enough in following or rough seas. That's why I asked "what am I missing?". That was one thing I hadn't considered. I was thinking in terms of the monotony of long passages on calm days.
CaptTom is online now   Reply With Quote
Old 02-15-2016, 07:37 PM   #17
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,153
Quote:
Originally Posted by CaptTom View Post
Good discussion, thanks! And no, I wasn't going to try to build this myself. Just trying to make sense of the high cost.

A ComNav 1420 at a cost of 1.6 Boating Units certainly brings it down into the straight-face realm. I'd prefer if it had a wireless remote option like just about every other piece of consumer electronics that costs more than $50 nowadays. But it's far from a necessity, and the wired console has a pretty long wire.

And I agree that the normal chartplotter GPS updates wouldn't be fast enough in following or rough seas. That's why I asked "what am I missing?". That was one thing I hadn't considered. I was thinking in terms of the monotony of long passages on calm days.
Technology
Research and Development
Labor
Profit

That's the sense of the cost.
BandB is offline   Reply With Quote
Old 02-15-2016, 07:55 PM   #18
TF Site Team
 
FlyWright's Avatar
 
City: California Delta and SF Bay
Country: Sacramento, CA, USA (boat in Vallejo)
Vessel Name: FlyWright
Vessel Model: Marshall Californian 34 LRC
Join Date: Apr 2008
Posts: 10,179
Here's a basic system for $1300 that will steer your boat. Simple and basic...but one like it works on mine.

Raymarine EV-100 Wheel Evolution Autopilot - T70152 | Anchor Express

__________________
Al

Custom Google Trawler Forum Search
FlyWright is offline   Reply With Quote
Old 02-15-2016, 09:32 PM   #19
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,888
Dang it Al, how much more cr@p are you gonna hang between you and the windscreen??
Ski in NC is offline   Reply With Quote
Old 02-15-2016, 09:36 PM   #20
Guru
 
No Mast's Avatar
 
City: Atlantic Highlands, NJ
Country: US
Vessel Name: Moana Huaka'i
Vessel Model: Selene 53
Join Date: Dec 2014
Posts: 816
Quote:
Originally Posted by Ski in NC View Post
Dang it Al, how much more cr@p are you gonna hang between you and the windscreen??

He can still see out the window, there's room for a few more instruments. Besides the hula bobble is still missing
__________________

No Mast is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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





All times are GMT -5. The time now is 09:22 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012