Nav n Compass

[RoyP]

my compass needs setting, which can be altered using the internal mags.
Do i stay on a straght course and adjust to the nav course or use a seperate compass to set.

As i will be using the nav, i assume this would be the best case. I appreciate neither will be 'spot on'........ just looking for some feedback.

Hope you are all ok

[Sutty]

Much more difficult/technical than that. To be done accurately you need a deviation card as the deviation will be different on different headings. Buy a cheap chart plotter, much more accurate.

[RoyP]

I have a simrad plotter which gives me a course that I am taking via the GPS. do I set the onboard compass to that course.

[GuyC]

Is it miles out? I only tend to use mine as a rough guide as within 10 degrees represents straight steering.

You could try heading N,S, E and W on your chart plotter and seeing what the error is in each direction. If it is consistent you could correct it but there is every possibility it will be out by different amounts which is where the deviation card comes in.

[GuyC]

Originally Posted by RoyP

I have a simrad plotter which gives me a course that I am taking via the GPS. do I set the onboard compass to that course.

Yes, normally. GPS's tend to be configured to give magnetic bearings.

The only other thing to throw in the mix is if you have leeway due to tide or wind, your course will be different from your heading and it is the latter that your compass wants to replicate. Do it without wind and tide effects i.e. up / down wind / tide.

Unless it is being affected by something close by on the boat, compasses tend to work out of the box, certainly enough for RIB work.

[Pikey Dave]

Originally Posted by RoyP

my compass needs setting, which can be altered using the internal mags.

Do i stay on a straght course and adjust to the nav course or use a seperate compass to set.



As i will be using the nav, i assume this would be the best case. I appreciate neither will be 'spot on'........ just looking for some feedback.



Hope you are all ok

As Guy says, unless it’s miles out, you’re over thinking it. You’re not going to steer an accurate course on a RIB using a compass. A few degrees here & there will make no difference whatsoever.

[Maximus]

Originally Posted by RoyP

my compass needs setting, which can be altered using the internal mags.
Do i stay on a straght course and adjust to the nav course or use a seperate compass to set.

As i will be using the nav, i assume this would be the best case. I appreciate neither will be 'spot on'........ just looking for some feedback.

Hope you are all ok

A few degrees won't matter much as said previously ...
If you're doing some out of sight of land passages (especially in poor conditions)....like a Channel crossing or distance Island Hop it's always a a good idea to take a (precise as possible) bearing from the Compass whilst on the pre determined Plotter course before the start...take a note ...and trust that Compass!....
That way if the plotter goes down (or you can't read it properly for any reason) you'll have a choice....either continue and arrive roughly at you're destination on the Compass ...it's also easy to work out a reciprocal bearing to re-trace you're course back.

[RoyP]

Points taken and many thanks to all for getting back to me. I appreciate the external issues regarding a course and know it will not be spot on. The compass could be about 15d out, so I am going to set it roughly to the navigator course. it just a guide rather than look at the looking at the nav

[Poly]

Originally Posted by Maximus

A few degrees won't matter much as said previously ...
If you're doing some out of sight of land passages (especially in poor conditions)....like a Channel crossing or distance Island Hop it's always a a good idea to take a (precise as possible) bearing from the Compass whilst on the pre determined Plotter course before the start...take a note ...and trust that Compass!....
That way if the plotter goes down (or you can't read it properly for any reason) you'll have a choice....either continue and arrive roughly at you're destination on the Compass ...it's also easy to work out a reciprocal bearing to re-trace you're course back.

I’d suggest (because I’m still a bit old school, and quite like pouring over a paper chart for planning) that having your entire passage plan as some scribbled bearings and distances would be better than just noting the current leg. A reasonably correct compass: means you can translate the numbers on the chart to the compass; that the numbers on the gps are the same as the compass (assuming gps set to M), means you have a sense check against a mistyped coordinate in your GPS. Steering to a good compass (mine is not) provides better real time feedback than the gps so is actually easier to maintain in rough conditions.

Whilst intended for WAFIs this link may be useful:
https://www.pbo.co.uk/expert-advice/...-compass-17845

With smartphones as a backup (preinstalled and full charged) and modern electronics there is definitely much less chance you’ll end up with no navigation systems at all - but the simplicity of a compass as a robust tool is hard to pass by. Paper charts are hard to use in small open boats, especially at speed, so IMHO it’s well worth having the plan roughly sketched out before the instruments fail!

[Pikey Dave]

Originally Posted by Poly

I’d suggest (because I’m still a bit old school, and quite like pouring over a paper chart for planning) that having your entire passage plan as some scribbled bearings and distances would be better than just noting the current leg. A reasonably correct compass: means you can translate the numbers on the chart to the compass; that the numbers on the gps are the same as the compass (assuming gps set to M), means you have a sense check against a mistyped coordinate in your GPS. Steering to a good compass (mine is not) provides better real time feedback than the gps so is actually easier to maintain in rough conditions.

Whilst intended for WAFIs this link may be useful:
https://www.pbo.co.uk/expert-advice/...-compass-17845

With smartphones as a backup (preinstalled and full charged) and modern electronics there is definitely much less chance you’ll end up with no navigation systems at all - but the simplicity of a compass as a robust tool is hard to pass by. Paper charts are hard to use in small open boats, especially at speed, so IMHO it’s well worth having the plan roughly sketched out before the instruments fail!

I’ve just ordered a (decent) compass for Piglet. Not that I’m going to be doing any major offshore trips in her, but after our trip out last week, I just missed having a compass onboard. It felt odd, even thought I have a plotter.

[RoyP]

I am not going to do any off shore trips, though you never know. We are starting to venture further afield, again and I was just looking for all your experiences. I started off with a Philips Decca unit and continued from there. I know the compass will be out at various points, so I am going to set it close to the Nav unit course. Its purely for visual reference. I do carry a hand held too.
Its a learning curve with a big radius.

[jeffstevens763@g]

Plus one for a paper chart sit in the evenings with a beer and get a mental picture of the area that's how we did it years ago when a chartplotter was only a dream

[Maximus]

Originally Posted by jeffstevens763@g

Plus one for a paper chart sit in the evenings with a beer and get a mental picture of the area that's how we did it years ago when a chartplotter was only a dream

Always time well spent planning!....and the best place and time to study it.....sheltered at home and before you get on you're on passage at Sea
A Good idea to record Any pertinent info...best transcribed to water small proof pad....British Army surpluss ones are cheap and good quality.

[Bucksribster]

I was bought up with paper charts, and still use them when sailing, but they are tricky on a rib. I have the built in chart plotter plus Navionics on iPhone and iPad. Unlikely all three will go down.