We’ve been unhappy with the performance of our old ST6002 autopilot and S3 course computer for several years. It was particularly bad about overshooting course corrections in anything but the calmest conditions. It could deviate up to 15-20 degrees from the desired course heading, particularly when sailing deep apparent wind angles. This made it dangerous to use in situations where an accidental jibe could occur or in dense boat traffic.
The new Raymarine EV1 system had a good reputation. Its marketing materials say that it is a 9-axis sensor. Well there are only three physical dimensions, so how could it have a 9-axis sensor? After some research, we determined that it senses three factors in each of the three dimensions:
- direction/orientation of the boat in X, Y, and Z - think of this as heading and attitude
- speed of rotation around each axis (roll (X), pitch (Y), and yaw (Z)) - measures how fast the orientation is changing
- acceleration around each axis - measures how quickly the speed of orientation is changing
This combination allows the system to quickly adapt to the boat’s interaction with the wind and waves. Like a good helms-person, it can anticipate changes in orientation. For example, if a wave knocked the boat's heading 5 degrees off, the autopilot adjusts the helm. Acceleration sensing tells it how fast the heading change is occurring and to begin correcting the helm before it overshoots.
Staying with Raymarine meant that we could re-use some existing equipment: the HD Color radome, the rotary drive unit, and the masthead wind instrument. We had previously upgraded the chart plotter to the Raymarine a75, but decided that we wanted the larger 12-inch display for the new installation. We also wanted the hybrid version that has the knob and a few buttons (particularly MOB) and SD card slot on the front. This required changing the helm layout because there wasn’t enough room between the engine gauges.
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| Prior installation with a75 display |
We bought the Axiom Pro 12S, depth transducer, EV1 sensor module, ACU-400 course computer, p70s autopilot control head, three i70s instrument displays, and the iTC-5 analog interface for the wind and depth sounder. Total outlay was about $8000. We produced a schematic of the installation before we started, so we knew that we had everything.
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| Raymarine Upgrade Schematic |
Removing the old instruments was easy. We pulled out a fair amount of old SeaTalk cabling. The only catch we encountered was the depth sounder cable ran to the ST40 depth readout mounted below the VHF radio at the Nav Station. We extended it back to the iTC-5 that we mounted under the galley sink, next to the ACU-400 that controls the rotary drive.
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| ACU-400 drive and iTC-5 analog instrument interface |
The SeaTalk-NG buss cabling is sweet and makes for a very clean installation. The EV1 sensor core was installed near the centerline and above the headliner inside the salon sliding door to keep it away from sources of magnetic interference
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| EV1 sensor core above ceiling |
The 12-inch display required moving the two engine ammeters.
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| Cutting and drilling the new layout |
The final installation looks very nice and we’re delighted with it.
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| New installation |
The third i70s instrument replaced the old ST40 depth display at the nav station. We really like the flexibility of the new i70s instruments.
What about operational results? The EV1 and ACU-400 combination is great. It holds course reliably when going downwind and we’ve held the bow into the wind to set the main by using the wind heading hold feature. It seems to be better than we can manually steer.
The one thing we're missing is a speed-through-the-water sensor. I dislike the paddlewheel sensors that require constant cleaning and a doppler sensor is $2000, which doesn't seem to be worth it for the benefit of slightly better wind instrumentation.
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| New instrumentation under way |
-Terry
