DIY autopilot OpenCPN

[NorthernMac]

Hey guys,

I was looking at that PyPilot (https://pypilot.org) for OpenCPN.

I want to swap my raymarine wheel mounted heading only autopilot AP for something that’ll play better with the opencpn system, allow me to take advantage of all the autopilot control modes of opencpn and also be more trust worthy to help me take a better single handed nap

What hardware am I looking at to get something installed under deck, any tips or suggestions would be very welcomed




Thanks!

[NorthernMac]

So basically something like this layout from my Edison




Using maybe a raymarine like this



https://rm.factoryoutletstore.com/de...ogitemid=37849


Or one of these



https://www.pyiinc.com/jefa-autopilo...ketdrives.html



And using the PyPilot controllers and OpenCPN?

[smac999]

Can’t you just feed nmea 183 data from pc to existing ray pilot?

[Singularity]

Agreed why not just drive the Ray pilot? I have an old functional Comnav AP with the chain drive under the deck. If/when that motor goes sour it's $1550 for a new motor (plus bracket work) vs $1900 for a complete CPT system on the wheel (I'll choose the latter). It's my understanding that with a little head scratching either can work with PyPilot...

Perhaps you want to de-clutter the cockpit or improve aesthetics, but I'd at least offer moral support for keeping everything on the wheel.

[NorthernMac]

Originally Posted by Singularity

Agreed why not just drive the Ray pilot? I have an old functional Comnav AP with the chain drive under the deck. If/when that motor goes sour it's $1550 for a new motor (plus bracket work) vs $1900 for a complete CPT system on the wheel (I'll choose the latter). It's my understanding that with a little head scratching either can work with PyPilot...

Perhaps you want to de-clutter the cockpit or improve aesthetics, but I'd at least offer moral support for keeping everything on the wheel.

Is the wheel system anywhere near as robust or precise though?

Just thinking if I’m single handing it for a few days, would I get much more reliability with wheel vs below deck?

[Singularity]

Originally Posted by NorthernMac

Is the wheel system anywhere near as robust or precise though?

Just thinking if I’m single handing it for a few days, would I get much more reliability with wheel vs below deck?

I only have user experience with my own autopilot. I've tried to keep tabs on newer autopilot systems given the antiquity of my own (either to buy a backup or replacement).

Several threads on the CPT, here's one thread discussing pros/cons that seems to be proportionately representative of deeper investigation on the CPT:
http://www.cruisersforum.com/forums/...ot-210760.html

[thomm225]

So in this video of the Pypilot with wheel steering, he (Sean) is saying the Pypilot makes a better course than CPT.

https://www.youtube.com/watch?v=KQuBwLSMSxI

[kenbo]

If your looking for increased reliability and redundancy, put a hydraulic or electric ram on the quadrant.

Either can be driven by the Pypilot with the appropriate motor controller.

[Bill O]

Originally Posted by kenbo

If your looking for increased reliability and redundancy, put a hydraulic or electric ram on the quadrant.

Either can be driven by the Pypilot with the appropriate motor controller.

Pypilot has a separate heavy duty controller for below deck installations as you describe. We have one and works well w/our fairly large hydraulic pump. While we don't have any direct comparison for an electric drive on our boat, the hydraulic pump is very quiet and seems to be energy efficient as compared to other boats we have helped deliver w/large electric drive motors (below deck).


Bill O.

[tljohnsn]

What did you use to control the hydraulic pump? I would like to try this with a simrad rpu 160.

[Bill O]

Originally Posted by tljohnsn

What did you use to control the hydraulic pump? I would like to try this with a simrad rpu 160.

We are using a pypilot controller. The hydraulic controllers were previously up in the pypilot store, but recently they haven't been up. You should contact Sean to see if he can make one for you or when they may be back in stock.

Will say ours works very well to control our larger Kobelt pump.

[hpeer]

I have been fooling with the Pypilot for a while. I have no criticism of it as a control head. I am having some problems I don’t t understand but they are related to my steel boat and not the Pypilot.

The way to think of this is to consider the autopilot as 3 pieces.

Mechanical
Sensing/Control
Computer

Mechanical is the wheel drive or tiller ram.

CPT has a Sensing/Control Unit (SCU) that drives a proprietary wheel mechanical unit. No computer tie.
Pelagic has a SCU that drives an over the counter ram, but would also drive a different mfg. ram or some wheel drive mechanism. No computer tie.
Pypilot is a SCU only, it can drive the same ram as Pelagic uses, or another ram, or a wheel drive unit.

I have made some simple modifications to an CPT wheel drive unit and drive it with a Pypilot. The unit works just fine. I am sure I could use the Pelagic ram as well, or use a Pelagic SCU to drive a modified older CPT mechanical drive.

My problem is with the compass interference from the steel. CPT, Pelagic and Pypilot all use compass sensors. At first glance the Pypilot has a GPS option but according to Sean even that relies upon some underlying stable compass.

Pypilot is the only one of the 3 that allows a computer connection, but I haven't fooled with that yet. I got stumped somewhere along the line of downloading the plugin and then Covid and then 5 months of yard time.

I am hoping to find a way to use OpenCPN to drive the Pypilot to drive the CPT wheel motor. I have all the pieces. I need the time and some help.

Alternatively I would like to find a SCU that will steer to a GPS input.

[Frankly]

I have posted this before but maybe worth repeating:

If your steering system configuration will allow, attaching the drive to the wheel end of things is better than the rudder post from an energy consumption point of view. In a modern autopilot (ie rate sensor model) a large part of the energy consumed is just overcoming the polar inertia of the steering components (ever notice when grabbing the rudder and trying to move it, it starts hard and then get easier). Polar moments of inertia are reflected across gear/ mechanical reductions as the square of the ratio. When driving from the wheel shaft, the wheel inertia is what it is and the rudder inertia is decreased by the square of the mechanical ratio. When driving from the rudder shaft the rudder inertia is what it is and the wheel inertia is increased by the square of the mechanical ratio.

I have a chain drive on the opposite end of my wheel shaft (std IP rack and pinion). Jimmy Buffet uses more electricity than my AP in moderate sailing conditions.


Frankly

[tljohnsn]

Thanks Bill - Sean said he is waiting for second round of prototypes for high power controllers and to check back in January.

Originally Posted by Bill O

We are using a pypilot controller. The hydraulic controllers were previously up in the pypilot store, but recently they haven't been up. You should contact Sean to see if he can make one for you or when they may be back in stock.

Will say ours works very well to control our larger Kobelt pump.

[kenbo]

Having sailed for many years using a windvane before AP's were readily available, what I learned was the key to self steering is balancing the boat. Now this usually is not the fastest way to sail but it's essential to making any self steerer, wind or AP, work efficiently. That translates into less power used and less need to correct yawing.