[TG] [TG11] Autohelm T300 computer & Raymarine Smart Heading Sensor via NMEA

[Sailing_Sergio]

Hi,

Would a Autohelm T300 course computer (165P16 software) work without its flux-gate compass if Raymarine Smart Heading Sensor is connected to it via NMEA ?

If it does, will it take into consideration the Turn Rate (yaw) info on all Response Level setting (1, 2, 3) or will it only for setting 3 ?

Would a firmware update be required ?

Regards,

[Tom - Raymarine - Moderator]

Hello Sergio,

The T300 will steer to NMEA0183 heading data, but not terribly well. 10Hz NMEA heading is ok for radar overlay, chart navigation etc. but isn't really fast enough for decent autopilot performance, even on a product of the vintage of the T300.

The Smart Heading Sensor doesn't output ROT data, only HDM.

Unless there's a good reason that's not immediately obvious to me, I'd stick with the fluxgate on the T300. It only becomes worth using an SHS with T150/T400/S1/S2/S3-generation pilots because they can take in and use raw rate-gyro signal in addition to their own fluxgate, giving much better steering performance than fluxgate alone. (For anyone else reading this, connect raw rate gyro only from the SHS, don't output digital NMEA/Seatalk heading from the SHS to T150/400/S1/S2/S3; the fluxgate stays connected to the pilot, not the SHS.)

Regards,
Tom

[Sailing_Sergio]

Thanks Tom... your reply is very clear and helpful. May I have been using this "vintage" pilot quite successfully in the last 9 yrs while sailing around the world. However I find that on rolly seas, it is difficult to adjust Response Level / Gain combination to keep the pilot from over-steering. I suspect it comes from the fluxgate hence my question about SHS. Adding a gyro help keeps a tight course but that is not my issue. And let me add that my fluxgate is located on the pitch/yaw pivoting point of my sailboat and slightly above water level.

That being said:
a) Any suggestions to help quiets down my busy pilot on a rolly seas ?
b) On the continuum of pilots generations (T150/T400/S1/S2/S3)...is there a point where there was a significant evolution in the brain on these pilot that made them better in rolly conditions and in the affirmative, why and what was added (software or better fluxgate) ?

Regards,

[Tom - Raymarine - Moderator]

Hello Sergio,

Even with your fluxgate low and central, I suspect it's moving a fair bit in its gimble and that this is the cause of the problem. Fluxgates only work accurately when they're horizontal. If the problem is inaccurate heading data then about all you can do to reduce the activity is to turn down the Response level to 1, on that generation of pilot.

There's a fairly steady improvement in pilot performance from T100/300 > T150/400/S1/S2/S3 > T150G/400G/S1G>S2G/S3G > SPX range, which all used fluxgates (the latter two groups with rate gyros added), and then a big leap in performance with the latest Evolution pilot range (the name was chosen appropriately) introduced in around 2013. The EV pilots no longer use 2-axis fluxgate heading sensors, they use a solid-state, high-speed, 3-axis AHRS sensors including 3-axis accelerometer and 3-axis rate gyro. This means that they're no longer affected by boat movement and can give rapid and accurate heading and movement data in all sea states. This allowed us to completely re-write the steering algorithm and drop almost all of the previous static calibration values and have the pilot steer 'by feel' instead. I wouldn't worry about changing to any of the intervening ranges, but you will really see the benefit if you change to an EV pilot.

Regards,
Tom

[Sailing_Sergio]

Thanks Tom... again, your reply is very clear and helpful. As an retired electronics & software developer, I can appreciate the effort made to integrate the new sensor to the autopilot course computer. Sound exiting... it would be very nice to upgrade to the the new EV sensor and software if only to compare and report back to you on its performances while sailing back to Montreal Canada from here in the next few years. However, our old T300 and Linear drive will have to do for now because of our limited budget.

p.s.:Leaving Tasmania sometime next month for New Zealand sailing across the Tasman Sea in the Roaring 40's !

Regards,

Sergio

[Tom - Raymarine - Moderator]

Good luck with the crossing, Sergio, and the rest of your cruise. If you need anything when you get to NZ that we can't solve online, we have a good distributor there, Lusty & Blundell who I'm sure will be able to help.

If you're sailing short-handed and this is the only pilot aboard it certainly might be worth at least talking to them about a pilot, because the Pacific's a long way to hand-steer if the T300 were to reach the end of its lfe part way. Obviously we don't expect or want it to, but it is around 20 years old.

Tom

[Sailing_Sergio]

Tom,
You got me interested in the new Evolution Autopilot. Looking at the available model, I am wondering if I could get away with EV-200/Type 1 Linear Drive Evolution (T70158) ? The boat displacement is 20 000lbs but over all weight more 22000lbs with all of our cruising gear. However, we sail very conservatively keeping a the helm balance at all point of sail. On the other hand, we are sailing on long ocean passages under autopilot for weeks at the time 24/7. The cost for the next size up might not be worth it if the difference between the two model is that one is more powerful ?
I value your technical opinion on this Tom.
Best Regards,

[Tom - Raymarine - Moderator]

Hello Sergio,

The T1 Linear / EV200 would be right at the upper limit of its specification. So that you can make an informed decision, here are the potential problems you might encounter when using a pilot that's right on its upper specified displacement limit, for blue-water cruising.

1. Greatly accelerated drive wear and likelihood of early failure. If you use a small car to tow a large boat a short distance to the boat ramp occasionally, no problem. If you use the same car to tow the boat across the country, it probably won't get to the end of the journey.
2. Higher likelihood of failure of the drive FETs in the Actuator Controller (ACU). The FETs in the ACU200 are lower-rated than those in the ACU400 and if they're running at close to the specified maximum current for long periods then they'll get very hot and be much more likely to fail. This would leave you with no drive output (no functional pilot.)
3. The drive may stall when you need it most, e.g. when the pilot's trying to prevent a gybe in a following sea. Keeping the sails well balanced helps keep the pilot's load down much of the time, but makes little or no difference when it's a sea that's pushing the stern round and the pilot is trying to force the rudder back the other way. You might not feel all that load at the helm but you have a large mechanical advantage there compared to the drive (its stroke is 300mm whereas your wheel's movement is say 3 turns of perhaps 3.5m circumference to achieve the same rudder movement.) Several decades of experience of building pilots has taught us that vessel displacement is the best guide to the maximum loads that the pilot's likely to have to cope with under such circumstances.
4. The Actuator Controller (ACU) may reach its peak current and raise a Current Limit alarm, causing the pilot to drop to Standby. Again, this is most likely at times when you least want it to happen.
   
   

The key differences between harbour usage and ocean passage-making are the very high duty-cycle, the fact that you're out in all weathers, and the consequences if the pilot can't cope. I don't like taking support calls from people who've had to hand-steer watch-and-watch for 2 weeks, so I always recommend over-specifying the pilot, and if two-up or solo, having a complete second pilot installed with an On-Off-On changeover switch (not just sitting in a box ready to be fitted at sea.) In your case, I'd keep the T300 as the backup and install an Evo as the new primary.

We don't expect a well-specified/installed pilot to fail, but it's possible - what happens if it does, is the question I ask people.

Regards,
Tom

[Sailing_Sergio]

Tom,

That makes lots of sense...thank you.

Humm... I would then need the EV-400, EV-1, P70 kit plus a Type 2 Linear Drive, Seatalk1 to NG interface for my ST60 instrument and C80 Plotter, a new Raymarine GPS since my RS120 failed some time ago and it has been replace by a third party NMEA0183 hooked to the T300 while AIS's use the C80 NMEA port. Lastly a Seatalk1 (or NG) to NMEA converter to feed everything back to my computer running a back up electronics chart system.

I may need to upgrade my C80 Plotter since its radar does not work more than 15 to 20min and can't be services while a new one would not be compatible.

I may talk to the guys in NZ but unless they put an order to Santa Clause for next Xmas, I fear we will have to keep hand steering on cold & wet night in heavy seas. Living on a shoe string budget while sailing the great oceans slowly around the world does has its challenges...but its way better than watching TV !

Thank you again for your wise advice and for your time.

Kind Regards,

Sergio
Canadian Yacht Spirare...soon to sail from Hobart to NZ.

[Tom - Raymarine - Moderator]

Sorry for the delay replying Sergio - good luck with the cruise.

Regards,
Tom