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**hpeer** · 04-12-2019, 06:54

A64,
Have you tried the CPT auto belt tensioner?

**a64pilot** · 04-12-2019, 08:23

Quote:

Originally Posted by hpeer

A64,
Have you tried the CPT auto belt tensioner?

No. My run is so short there is no need. To explain the belt jump is normal if the device is bound up and can’t move. It’s not a defect as I see it. The CPT is easily strong enough so that if the belt slips, somethings wrong, you need to investigate it.
I have a Spade rudder and a very small wheel. Since I have a small wheel the CPT is way more powerful than needed, since the CPT drive wheel is a fixed size, it’s apparent advantage is greater on a smaller wheel, and of course a Spade is easier to turn, that’s its greatest point.
I called CPT when I did the install and asked about the tensioner and was told not to, it’s only for unusually long belt runs. It’s a Kevlar belt and doesn’t stretch of course and I can easily tighten it up so there is no looseness, but I keep it so there is a small amount.

The tensioner works by taking up the slack on the loose side of course and I just don’t have any slack.

Exile · 04-12-2019, 10:46

Quote:

Originally Posted by a64pilot

I’m leaning towards getting a B&G autopilot next year and using it to drive the CPT drive, then having a second CPT in a box down below as backup.

I'd like to read how that goes, should you care to post about it. In my usual pedantic effort to explore as many options as possible, I've been pricing out a second, redundant B&G myself (brains only) based on their website pricing (may be able to do better elsewhere).

NAC-2 Computer - $849 ($1499 for NAC-3)

Triton Controller & Display - $799

Not needing the compass will save you $645, and not needing the rudder sensor $310. (Not sure if will be needed or not). So $1648 total (potentially). More $$$ if you need to install a N2K backbone for it, although some of the wiring & peripherals are included with the Triton.

The PelagicAP (brains only) for your application would be $849 ($895 for the heavier duty one). It can be integrated with NMEA data for wind steering but not course.

The PyPilot, of course, is much less expensive as we know and appears to be as fully functional as the name brands. (many thanks to Bill & Martin for the info and links)

I've also looked at a couple of more commercial-type brands that claim to be popular on fishing boats (ComNav, TMQ) but not much savings there as far as I can tell. Pricing similar to the B&G and other name brands but it may be worth looking into further given your more limited application.

**a64pilot** · 04-12-2019, 13:30

I won’t need a compass as I have an AHARS already.
I assume a rudder indicator is needed, and thought that my Zeus plotter will function as the display.

Exile · 04-12-2019, 13:47

Quote:

Originally Posted by a64pilot

I won’t need a compass as I have an AHARS already.
I assume a rudder indicator is needed, and thought that my Zeus plotter will function as the display.

I didn't realize you already had a Zeus plotter. That can serve as your control head display which would probably eliminate the need for a Triton. The small, push-button controller they offer could be nice to have within reach at the helm or maybe down below. Unless you have two Zeus plotters -- above & below. They offer a wireless remote as well. At that point you'd be in good shape to install a below decks ram down the road, if you ever wanted to. But of course all the other AP "brain" products being discussed would work as well. As would leaving well enough alone given the performance you've enjoyed from the CPT. But how many of us are able to leave well enough alone when it comes to our boats?

**a64pilot** · 04-12-2019, 15:59

I’ve been reticent to do a below decks install for a few reasons, first the only logical install is a chain drive to a sprocket on the end of my pinion shaft, as that keeps rotary motion rotary, and I don’t think that’s common, and custom if you don’t do it yourself can be difficult and expensive.
A linear actuator or especially a hydraulic system would be much more inefficient and unnecessarily complex, then there is the obvious fact that its below decks and may be a real PIA to try to affect repairs in a sea way.

As the CPT maintains rotary actions and drives through my rack and pinion steering it’s exceedingly miserly, CPT claims .4 amps average, but I believe mine is much less, a normal sailboat’s wheel is likely at least twice mines diameter, but as the CPT drive is the same regardless of wheel size, I believe the forces to steer my boat are about half of normal, cause I’ve honestly tried to measure the amp draw unsuccessfully, I think it’s down there about .2 amps or so, and even then only intermittently.

I hear as how others use much more power underway and figure it must be their autopilot, but I think my CPT draws about 10 AH or so in a full 24 hr day. It’s nothing, or next to nothing anyway. I’m the opposite of most, I use more power at anchor than underway.

I have not done the below decks Zeus, instead I mirror the plotter on my IPad Pro, which allows me full control, except the autopilot. But I don’t see the need to control the autopilot from down below I don’t think.

Exile · 04-12-2019, 16:32

You may wind up talking me into a CPT after all. My biggest power draw underway is definitely my below decks AP. But then for better or worse (mostly worse), I don't have 12v refrigeration (110v & engine drive). Your CPT's low power consumption is extraordinary.

I probably use the steer-to-wind setting on my AP more than any other. Very effective when trying to get upwind. It also allows me to run deeper downwind than I ordinarily would for fear of gybing. In rough conditions I trust my AP's ability to keep a heading more than I do myself. Although I use it less often, the ability to follow a route I've created on the plotter can also come in handy. In other words, if you can successfully mate up your CPT with your NMEA data I would think you'd have the best of all worlds.

My boat came with AP control heads above & below, but now that I think about it I don't think I've ever used the one at the nav station. The ability to mirror your Zeus onto a tablet (or phone) is one of the better features of the new plotters. Btw, can you mirror onto more than one device?

**a64pilot** · 04-12-2019, 17:37

Quote:

Originally Posted by Exile

Btw, can you mirror onto more than one device?

Never tried, and I rarely do the mirror thing now, really only did when I had the kids on watch and I was down below, I liked being able to do a Radar scan and watch our track and AIS targets.
But look here where CPT says .4 amp is average. I wondered why I was having a tough time measuring it’s draw.
http://www.cptautopilot.com/features.php

Frankly has installed a sprocket on the end of his pinion shaft and added a motor drive as an autopilot. Island Packet must have intended that as there is a key way and a key already in the pinion shaft. I believe his is as efficient as a CPT.
Now this is not a hit on a CPT, but it’s my understanding that the drive motor on a CPT is nothing more or less than a Bosch 24V windshield motor for an OTR truck

Exile · 04-12-2019, 18:01

Quote:

Originally Posted by a64pilot

Never tried, and I rarely do the mirror thing now, really only did when I had the kids on watch and I was down below, I liked being able to do a Radar scan and watch our track and AIS targets.
But look here where CPT says .4 amp is average. I wondered why I was having a tough time measuring it’s draw.
Features of the CPT Autopilot - CPT Autopilot Inc.

Frankly has installed a sprocket on the end of his pinion shaft and added a motor drive as an autopilot. Island Packet must have intended that as there is a key way and a key already in the pinion shaft. I believe his is as efficient as a CPT.
Now this is not a hit on a CPT, but it’s my understanding that the drive motor on a CPT is nothing more or less than a Bosch 24V windshield motor for an OTR truck

Yup. 0.4 amps. Remarkable. Of course, unlike a typical below decks ram, it's using the significant leverage of your wheel steering system as you've pointed out. But it also must mean you're adept at balancing your sails. Yes, I recall reading about the windshield motor. I also read from one of the links related to the PyPilot that its creator Sean favors using windshield wiper motors from auto salvage yards. Come to think of it, I've owned from new some very high mileage vehicles and don't ever recall having a wiper motor go out on me. They must have exceptionally durable electric motors.

**a64pilot** · 04-12-2019, 19:20

What’s unusual to me is that CPT uses a 24V motor and drives it with 12V.
Now why would they do that?

**a64pilot** · 04-12-2019, 19:21

Quote:

Originally Posted by MartinR

Yes, in principle it is only two wires. In reality you want to be able to switch between the pypilot controller and the CPT controller and this means 4 wires. It is a very simple thing to do.

I drilled a hole in the bottom of the CPT drive unit and installed another watertight cable gland.

A 4*1.5mm cable is connected to A) the drive motor B) the CPT motor controller output. The other endof the cable is connected to two DPDT switches, that lets you choose controller and supplies it with power. A single 4 pole DPDT switch would be better, but I took what I had. You can either have this switch in the CPT drive unit, or like me outside somewhere in the cockpit.

The rest is just installation of the tinypilot unit and motor controller. Pretty straightforward. My tiny pilot is situated next to the Nav screen.

The whole process took me about 2 hours, most of the time spent pulling a data cable from the Nav station to the motor controller.

Here look at the second pic of Martin’s post, look on the motor, it says 24V

Exile · 04-12-2019, 19:27

Beats me. I have enough trouble with 12v to 12v! Wouldn't it have to have some sort of transformer to step the voltage down?

**a64pilot** · 05-12-2019, 00:56

I don’t think so, I believe it’s just run on 12V, maybe to slow it down, I don’t know why

MartinR · 05-12-2019, 05:22

Quote:

Originally Posted by a64pilot

I called CPT when I did the install and asked about the tensioner and was told not to, it’s only for unusually long belt runs.

That is a little funny. They told me I needed the belt tensioner as I had a very short run meaning the angle was to big and there are not enough cogs engaged with the belt on the drive wheel. So I do use one, and the belt never slips. The photo down below is from the CPT home page. In my installation the drive unit is actually inside the wheel diameter.