Locating compass on 16' cruiser

zuunami · Posted: Tue Aug 09, 2022 9:25 pm Post subject: Locating compass on 16' cruiser

Getting ready to replace our chartplotter with a 9" Garmin, and a new SH VHF with ais receive. The existing icom radio has never worked well since we got the boat, now I'm reading that maybe it's compass interference (although the radio's pretty old, so maybe it's just the radio).

Anyway, why in the heck would someone mount a 4 inch compass on the dash of a 16' - although there are few other options. It's going to be (and already is) about 9" away from the chartplotter, and about 14" from the radio, as the crow flies. I like having a compass, but can't figure out any other place to put one. And it's going to leave a big 3 inch hole in the top of the helm (we can find a way to deal with that Smile

Am I maybe being too paranoid about how the compass will affect the electronics? Thanks! - Karen

zuunami · Posted: Tue Aug 09, 2022 9:32 pm Post subject:

oops, forgot the photo Smile

hardee · Posted: Wed Aug 10, 2022 1:20 am Post subject:

Well, maybe the compass will have an affect on the radio, but I would bet my bottom dollar, that the radio, that close to the compass, does have an adverse effect on the compass. You could do like the early Ranger tugs, (an maybe they still do this), get the proper distance by mounting the compass out on the fore deck. Shocked

Harvey
SleepyC Moon

thataway · Posted: Wed Aug 10, 2022 10:37 am Post subject:

Swing the compass and make a compensation table. You want to do this MFD on and off. Also with lights on and off. Anything within 3' can affect the compass.

I happen to like the Sun Compass to use in swinging--and when it is easy one will do it more often.

zuunami · Posted: Wed Aug 10, 2022 1:21 pm Post subject:

Thanks! The only reason I can imagine relying on the compass is if we were to lose power during sudden fog, unlikely Smile

Maybe we'll take it out, install the radio and chartplotter, see how they work, then put it back in to see if it affects either. If it does, maybe I can find a place to put it on a slider, like underneath one of the seat boxes. Really don't want to put it on the fore deck, if only because we would have to drill holes in the boat Smile

thataway · Posted: Wed Aug 10, 2022 5:22 pm Post subject:

As Harvey noted. The compass will not affect the radio or chart plotter. It is visa versa. Any ferrous metal will affect the compass as well as electrical circuits and DC electricity in parallel wires. There is most likely part of the push pull steering system which may also affect it.

Yes there are a few times you want a compass. I always like to have one, as a further safety measure.

All of this reminds me when about 10 miles off the S. Calif. Coast in fairly dense fog, we come upon an open runabout. He hails us and asks which way to King Harbor (Redondo Beach). I get my chart out, and give him a compass bearing. Response; "Oh no we don't have a compass, just point the way". You must understand that I boated for over 40 years before GPS was available....

zuunami · Posted: Wed Aug 10, 2022 5:38 pm Post subject:

lol On our first test run just a few months ago, we didn't even know how the chartplotter worked (shame on us), but we noted we were going NW on the compass. Of course, a big fog descended suddenly. We probably could have figured out the chartplotter, or navigated by phone, but we were in a bit of a tizzy Smile

We were only a mile out, so we just slowly went SE and voila, there were the buoys in the mouth of the port. So, I like having a compass Smile

thataway · Posted: Wed Aug 10, 2022 6:06 pm Post subject:

I would strongly advise taking the US Power Squadron series of courses. However looking up Fort Bragg, CA. there are none within 100 miles..! US Power Squadron does offer on line courses. I can check with one of my neighbors who is a local instructor about availability nearest your area or if there are a full weekend type of seminar/courses.

U S Power Squadron "America's Boating Club".

There are also multiple videos on using chart plotters, navigation. etc.

Being lost or disoriented off Fort Bragg, Ca would not be a good place to be. Your chart plotter can be set to leave a "trail" on the plotter as you go out--and you can follow that back. I have gone into Noyo River entrance using Radar in fog with my Cal 46, and it can be a hazardous entrance!

You might also consider contacting your Local US Coast Guard Auxiliary..

There are also multiple on line courses which are designed both for the boater and for persons who wish to obtain a Coast Guard license to carry passengers.

Be safe and you have already used the compass!!

thataway · Posted: Wed Aug 10, 2022 6:08 pm Post subject:

I would strongly advise taking the US Power Squadron series of courses. However looking up Fort Bragg, CA. there are none within 100 miles..! US Power Squadron does offer on line courses. I can check with one of my neighbors who is a local instructor about availability nearest your area or if there are a full weekend type of seminar/courses.

U S Power Squadron "America's Boating Club".

There are also multiple videos on using chart plotters, navigation. etc.

Being lost or disoriented off Fort Bragg, Ca would not be a good place to be. Your chart plotter can be set to leave a "trail" on the plotter as you go out--and you can follow that back. I have gone into Noyo River entrance using Radar in fog with my Cal 46, and it can be a hazardous entrance!

You might also consider contacting your Local US Coast Guard Auxiliary..

There are also multiple on line courses which are designed both for the boater and for persons who wish to obtain a Coast Guard license to carry passengers.

Be safe and you have already used the compass!!

zuunami · Posted: Wed Aug 10, 2022 7:24 pm Post subject:

We've since both taken courses, and know significantly more about chartplotters than we did Smile

Excited to be putting in a Garmin.

Word to the wise (which we were not), do both first! Smile

Thanks again, Bob, for all of your advice!

Marco Flamingo · Posted: Tue Aug 16, 2022 12:45 pm Post subject:

On my 16, my compass/MFD are mounted in the opposite configuration. The compass is forward of the MFD and tucked in under the window. That gives me another 2-3" of separation!! Probably makes no difference. Also, on a compass the size used in a 16, the compass lines are in 5 degree increments. Accuracy is relative. If your compass is within 10 degrees, that may be as accurate as you will ever see. Just the nature of the beast. When on plane, most little compass cards dance around. Navigating by sunlight or the direction of the seagulls may be about as accurate.

Look at the compass and turn on the MDF. Any movement? But activating the radio and the MDF isn't the only interference. They may interfere even when off. My Garmin MDF has a slot for a SD card. The cover of the slot is held shut with a magnet!! Opening the card door moves the compass, meaning that the magnet probably interferes whether open or not. Maybe Garmin thinks that magnetic compasses are obsolete and, thanks to Garmin, they may be.

zuunami · Posted: Tue Aug 16, 2022 8:09 pm Post subject:

Yeah, I think we're going to live with any deviation - the compass is almost 6" diameter, with a huge hole in the helm dash that I don't want to deal with right now. I think it'll be close enough for our purposes Smile

hardee · Posted: Tue Aug 16, 2022 11:34 pm Post subject:

With 5 degree increments, you may want to try what I have done in the past. Even with a plotter, There are times (Crossing Juan de Fuca, 25 miles in heavy fog), that I will intentionally aim for a spot that is a half mile or so in a known direction from my intended pass entry, so that when I do get close enough to shore to see/hear it, I know which direction to turn to get into the intended entrance point.

Granted, my chart plotter is way more accurate with my position that that, but it is, for me, compass practice. AND, your not lost, just navigating.

Harvey
SleepyC Moon