New Autopilot for Catamaran.

[Tupaia]

Originally Posted by Joh.Ghurt

Just compass mode steering, no NMEA, no GPS, no Tetris-game included.

This is not a good way to go with a light catamaran. Compass tracking does not react fast enough in the conditions that are causing issues.


Far better to have GPS tracking under these circumstances, control is then based purely on XT error. Setting a WP some considerable distance away will make tracking in difficult conditions less challenging.

[sv_pelagia]

Originally Posted by Tupaia

This is not a good way to go with a light catamaran. Compass tracking does not react fast enough in the conditions that are causing issues.


Far better to have GPS tracking under these circumstances, control is then based purely on XT error. Setting a WP some considerable distance away will make tracking in difficult conditions less challenging.

How is GPS tracking faster than compass?

(And likely it makes a difference on type of "compass": a tri-axis gyro would be faster than a traditional analog magnetic compass.)

No expert here... in process of replacing our autopilot.

[Frankly]

I have never sailed on a cataraman (other than non AP Hobie Cats). One thing some may not realize on modern autopilots the rate sensor is the primary input. On my old RM X-5 if I rotate the fluxgate without turning the rate sensor (mounted on the power unit circuit card) the heading will not reach a new steady state value for nearly 60 seconds. Rotate the power unit and the heading will change immediately.

If you stop and think about passive rudder watercraft control, the rudder does not control the craft heading it controls the rate of change of heading. Design an AP with this the primary focus and you have a entirely new animal. The heading sensor is there simply to correct the long term integration drift error that will creep into a rate system.

As an aside on my RM Evo system, in the vane mode that AP seems to anticipate the wind shifts (put that in your artificial intelligence pipe and smoke it for a while).

Frankly

[fxykty]

On our cat we have a Raymarine EV-400 autopilot with the EV-1 9-axis instrument module from 2014 controlling the two rudders via their hydraulic rams. No problems at all in any of the conditions we’ve experienced so far, including intermittent high speed surfs and big waves, upwind, reaching and running.

Other than for gust response in squalls and light air upwind, the autopilot steers better than we can.

[Chotu]

Originally Posted by fxykty

On our cat we have a Raymarine EV-400 autopilot with the EV-1 9-axis instrument module from 2014 controlling the two rudders via their hydraulic rams. No problems at all in any of the conditions we’ve experienced so far, including intermittent high speed surfs and big waves, upwind, reaching and running.

Other than for gust response in squalls and light air upwind, the autopilot steers better than we can.

I have the same electronics but a push/pull cable system (telestar). The cable system has had slop in it since day 1. Nearly 1/8 turn before rudders start to do anything.

This causes the wheel pilot to just keep goin port or starboard.

It just incrementally turns to one direction harder and harder until I have to cut it out.

I’m going to try to get the slop out of the cable system and keep this AP to save some $$$. Otherwise I’m going to have to replace the whole steering system with hydraulic and a hydraulic AP pump.

Also thinking of getting a rudder position indicator to feed back to the AP brain.

Anyone successfully running this AP with a push/pull cable system?

[smj]

Originally Posted by Tupaia

This is not a good way to go with a light catamaran. Compass tracking does not react fast enough in the conditions that are causing issues.


Far better to have GPS tracking under these circumstances, control is then based purely on XT error. Setting a WP some considerable distance away will make tracking in difficult conditions less challenging.

There have been CPT autopilots installed on a few lightweight performance catamarans including ours. One circumnavigated with a CPT and at times was surfing at over 18 kts.

[seaskip]

Thankyou all. I have much to learn about the ways pilots work.

[django37]

My boat came with Raymarine pilot and L&S hydraulic ram. 7 years later all Raymarine was changed to B&G. Especially the Autopilot was much better. Steered us round the world, also wellmannered surfing at 18-19 knots boatspeed.

[44'cruisingcat]

Originally Posted by chasfgr

I doubt ANY autopilot, whether on windvane mode or steering to compass, can cope with a boat which surfs intermittently - this has to do with both drive and sensor.
It's comparatively easy when the sufrfing become continuous rather than intemmittent. Henmce, under such conditions, I tend to head more downwind than if I'm on hand-steering.

Our Simrad handles it fine. I've found we need to be sailing to true wind angles when running under working sails, (ie goosewinged) but apparent wind angle when flying the spinnaker.