Gyroscopic Autopilot - Is it worth the extra?

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Bloater

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I was wondering if anybody could comment using their real experience of a gyroscopic upgrade to an autopilot.

I am thinking of specifying the Ramarine Smartpilot but I noticed for another £500 there is a gyroscopic option. That's a lot of money if it doesn't make much of a difference. I plan to have Radar fitted as well.

Can anyone comment?
 
Not an expert but having installed a new a/p I was surprised to realise the "gyro" is not actually a gyro compass but is described as a "gyro rate". In laymans language it was described to me a just a faster response time. It was suggested you couldn't tell the difference if you had to trial!!! Repeat not an expert but I don't think it's worth the price difference.
 
I beleive you need it for Radar MARPA to be of any use at all. If you try and track targets without it, their aparent speed and closest approach is all over the shop, and pretty useless. (AIS may be a better solution anyway)

It gives more accurate/responsive helming as well, but not worth buying just for that.
 
This is really useful if you are downwind sailing. Coming down the face of a large roller the gyro helps the A/P keep on course otherwise the gybe risk is greatly increased. I have seen this in action and it is very impressive but it was on a very large yacht. If you don't do much of this type of sailing then it is probably a waste of cash.

cheers,
 
We have the lowest spec raymarine that comes with autogyro, sorry I dont know which model it is, on our yacht and I would really recomend it. It means the Autopilot can cope with much bigger seas especially down wind, No radar or other stuff as yacht is only 25 ft.
 
Thanks for all the comments - it's still not a clear choice but I have to say that sticking with the standard version is slightly ahead at the moment.
 
According to the Raymarine site it is but a rate gyro, not a steering gyro compass. As these are now available as very low cost solid state devices £500 seems a tad pricey even if it does give better performance.

As the collision avoidance problem is fundametally a relative motion problem heading of any kind is not essential thus heading is not needed for MARPA as such though there are niceties that can be achieved on a radar display with heading and speed input, though in some respects SOG and HOG inputs from GPS are just as valid.
 
Correct! It's not a gyrocompass at all. It is a rate stabilised fluxgate that will improve the performance of the autopilot marginally. It is however essential if you are going to use your radar in MARPA mode and IMHO necessary if you use radar in anything but head up mode. AIS is not a substitute for MARPA it's an adjunct to it, but it all depends on what sailing you want to do. If you are on a budget and don't intend to cross shipping lanes etc. it's not strictly necessary. If you want the best out of radar either now or in future it's essential.
 
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Correct! It's not a gyrocompass at all. It is a rate stabilised fluxgate that will improve the performance of the autopilot marginally. It is however essential if you are going to use your radar in MARPA mode and IMHO necessary if you use radar in anything but head up mode. AIS is not a substitute for MARPA it's an adjunct to it, but it all depends on what sailing you want to do. If you are on a budget and don't intend to cross shipping lanes etc. it's not strictly necessary. If you want the best out of radar either now or in future it's essential.

[/ QUOTE ]

Why, as I stated above collision avoidance is a relaive motion problem, yes some heading input will give a better own ship vector, but the primary indicator of the collision risk is the target ship relative vector relative to own ship. The target ship relative vector will give you both the CPA and the time to CPA, thats is how we did it in the days of grease pencil and rulerand that is the fundamental info the radar has. As for only being able to use a rate gyro stabilised heading source, I don't really see that either, as I don't see why you can't just use a kalman filtered raw fluxgate output. Of course we can roll over into other esoteric arguments as to whether you should go for a ground or water stabilised picture on the ARPA. Some one once explained that one to me but the mind dims.
 
The rate gyro that is fitted by Raymarine is a standard unit used in such things as automotive GPS systems, it is not a proprietary Raymarine part.
If you keep an eye on Ebay the gyro unit comes up for sale fairly often at around £150 - £200. I have also looked at electronic wholesalers etc and the wholesale price is about £100 - £120 if you buy 5+.

I bought one about 12 months ago from Ebay and it came with fitting instructions etc for the Raymarine Course Computer. My unit is a 2003 Type 400 Course Computer and the gyro simply screws on the back of the PCB and plugs in to an existing connector. The software to cope with the upgrade is already in the computer and it automatically recognises the gyro and gives access to the settings etc related to the gyro.

It is a fairly simple upgrade for a competent DIY type - basically unscrew the computer lid, take out the backboard, fit gyro and reassemble everything - takes about 20 mins, make sure you use an anti-static wrist strap. Obviously this is not really applicable to a new unit because it will void the warranty, but perfectly feasible after that.

The autopilot does keep better course and the MARPA function on the radar is much improved. Overall good value if bought of Ebay but a bit pricey from Raymarine.
 
I raced 2 handed recently with a Raymarine gyro pilot.

My god it's good! The first pilot I've ever trusted to helm downwind in breeze with the kite up. If I hadn't seen it I wouldn't have believed it.
Now if they just made something to hoist and drop the kite.....
 
Thank you llamedos... It is starting to make sense now - I had noticed on the Raymarine web site that the standard unit was 'upgradeable'.

Does this mean that if I was to retro fit at a later date then the AST (Advanced Steering Technology) and the self learning bit would appear by magic by virtue of being preprogrammed as you say?
 
Hi Quo,
Yes that is exactly what happens, all the auto learn etc is already in the black box it just needs the gyro plugging in to enable it all. Then simply consult the manual for the AutoPilot control head to get at all the extra settings etc.

Just in case anyone is unsure if they have a gyro fitted to their autopilot or not - the easiest way to check is to try adjusting the "response" function with the control head - gyro type computers will give 1-9 levels for response, non gyro computers will only give 3 levels.
 
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[Why, as I stated above collision avoidance is a relaive motion problem etc etc..

[/ QUOTE ]

I agree it should be possible without the rate gyro, but it doesn't do it. I guess the MARPA system does not average over a long enough time to get the relative courses and speeds. Perhaps because it is designed to work where both objects are high speed and so the averaging times are relatively short.
 
I believe gyro is basically an accelerometer input - acceleration more easily measured from a gyro than from a fluxgate - that is why it is so good at dealing with following/quartering seas because it measures/calculates the acceleration - fluxgate compasses could do that with appropriate software, but changes are quicker to detect and differentiate with inertial (ie Gyro) than with fluxgate (magnetic) gear.
 
An accelerometer is a totally differnet device used for measuring changes in velocity in a straight line. Now there are a few patents around for using accelerometer clusters for measuring rotational accelerations the new generation of low cost rate gyros really makes such systems overcomplicated and for this type of application almost certainly too costly.
 
Definitely go for the rate gyro model. It's worth every penny.

It's a totally different auto helm with a rate gyro - 400% better steering and almost eleminates snaking especially at low speed and in following seas. It's a no brainer.
 
I thank you all for your comments...

In this thread we have had arguements for and against, and even some technical details on the system.

It doesn't make any decision clear cut.

Does anyone on the forum have direct experience of both systems, either on the same boat or very similar boats? The arguement that 'I've tried it and it's great' is nice to hear but if you had the standard version would it still have been 'great'?

Is there anyone who has tried both who could share some of their experiences?
 
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