Raymarine Autopilot, Giro or Not?

[mikesyam]

Hi
Would love an autopilot for my Sealine F33 and I can get a non/giro version for around £900, the giro version is around £450 dearer so question is if I fitted the non-giro version what would it be like compared to the giro version?
Thanks Mike

 

[jfm]

I dont know, as have not tried the with/without on the same boat

We specced the gyro version for the extra £450 on a new boat 2yrs ago. We did it becuase they say you absolutely need gyro for radar/chart overlay. On reflection, we never use overlay. I hate it and consider it to be a useless gimmick. I prefer radar and chart on side by side screens with overlay only of cursors and Marpa targets and their 5-minute vectors. So we probably would have been fine without gyro and if I were speccing a boat again and wanted to keep cost down I'd choose the non gyro

 

[powerskipper]

I believe it would make it slower to react when correcting, as the auto requires I high speed feed which is what the Giro gives it

 

[tome]

Oooh, careful

The so called 'gyro' is actually a rate gyro which works in conjunction with the fluxgate compass. The fluxgate only provides an output once per sec which is far too slow to maintain MARPA target lock. The rate gyro provides an additional 10 heading outputs per sec

Try disconnecting it and see the effect on MARPA. Worth the extra dosh, though I would chose a Honeywell sensor which combines the 2...

 

[Oldhand]

The rate sensor output is input to an algorith with the fluxgate heading output to provide more accurate heading output corrected for pitch and roll effects on the fluxgate. It is because the total heading output has much greater short-term accuracy that the design is to supply heading output at a higher rate. The "rate gyros" supply output internally continuously as does the fluxgate compass, its just that the accuracy of the fluxgate in unsteady short term conditions isn't good enough for high speed data output.

 

[[2068]]

As above, if you don't need MARPA or radar overlay or any kind of low speed or in-the-chop accuracy, you can probably get away without the gyro. MARPA simply doesn't work sensibly without a stabilised and high-refresh rate heading input. You end up with targets doing 20kts, then 40kts, then back to 20kts again on a different heading, just because you rocked around a little...

dv.

 

[tome]

Well, I'd take some issue with your description as we use a fluxgate which has been calibrated against a spinning gyro and provides a 20Hz output, reasonably stabilised for pitch and roll up to 40 degrees. If you stated that the rate gyro has drift then I'd agree

But no matter - Raymarine use a less sophisticated model and when coupled with the rate gyro it does the trick nicely

 

[SpiderDiver]

To sum up the G version of the computers i.e. S2G are required for MARPA and also I believe provide better steering control over the non-G versions.

The main point I wanted to add is that you can upgrade a non-G type with an external kit or as I eventually found from a very helpful Raymarine dealer there is also an internal module that can be retro-fitted in the computer itself. Costs around £ 190 I think - if you want part numbers PM me (just had fitted to my boat),

 

[oceanfroggie]

It's a completely difference auto pilot with the rate gyro.

1) it will steer much straigher especially in a following sea
2) it is essential if you want to use MARPA

Important though to have a professional set it up and calibrate it on the water. The gyro is worth every penny.

 

[rob1699]

My S1 computer went wrong on my T34, and under warranty had a new course computer fitted but decided to upgrade to G version for an extra £400ish.

I found that I was forever fine tuning the settings on my non g, couldn't seem to ever find the perfect setup.

In total agreement with the above post plus I would add that the initial seatrial set up is so much simpler on the G version. Deviation is setup the same way (turning a couple of circles), but then the Autolearn feature does the rest all for you - a 5 minute job max. Brilliant.

 

[spannerman]

A customer of ours had an F33 and it wandered all over the place with the AP on despite calibrating it several times, spoke to Raymarine and they insisted that it needed to have a gyro as a fast planing boat pitches and rolls more than a displacement boat and the ordinary compass gets upset and can't keep up. So we swapped it for a gyro and it was fine, its reccommended for most planing craft.

 

[jfm]

Ah, thanks Tom. I forgot about Marpa. Yes, my post above is complete bollox. Radar/Chart overlay might be a gimmick (imho) but Marpa is essential for serious passagemaking/night work and I see your point that Marpa will work loads better with gyro. So yes, get a gyro everytime, well worth the £450.

 

[amf]

JFM:Interested in your comment about overlay mode.

We're about to move up to a boat with Raymarine kit/radar. Without having ever used radar before my first thought was that overlay mode seemed to make it much easier to distinguish actual targets - or am I missing something?

- Andrew

 

[[2068]]

One of the problems with overlay mode is that the screen gets quite messy in crowded waters. Any land with elevation gets covered in huge purple blobs, and having lots more smaller purple blobs (boats) peppering the chart can make it hard to decipher what's going on.

I tend to use split screen mode if I really need the radar. At least it separates what I'm going to run aground on from what I'm going to hit...

dv.

 

[jfm]

You will find the screen very cluttered with overlay, and as the boat heading changes the machine is constantly re-drawing etc. I think items on the chartplotter can actually obscure radar targets. In contrast, the radar alone shows targets as yellow blobs on black background, very clear. But that's all just my opinion, others might like overlay

I'm not sure there is any need to "distinguish actual targets". Everything ahead of you that is a yellow blob on the radar is a target and you need to sit up and deal with it. It might take you a few moments to compare with the chart to figure out what it is, but it is always gonna be something you dont want to hit! (use linked cursor, put radar cursor on the target on the radr screen, and see the replica of the cursor on the chartplotter screen. You then know if it is a buoy or a headland or whatever). Exceptions will be seagulls and (if you boat near Nice, for example) aeroplanes

Also, many folk (me included) like radar course up, and chart plotter north up. You cant do that with overlay

 

[mikesyam]

Looks like it has to be the Gyro version then.
Many thanks for all the views and posts.

Mike

 

[tome]

John

Must look up linked cursors, thanx for the tip - makes a lot of sense and handn't realised you could do that on split screens

Cheers
Tom