deviation card..Moody Eclipse 33

[golfclub]

Hi...need such a card....without attempting to be completely naive,is it not ' /forums/images/graemlins/blush.gifreasonably' accurate to assume that deviation card 'results' would be fairly accurately consistent for all Moody Eclipse 33's.???..has anyone done one..I would love to hear/see your results. Many thanks.

 

[Anonymous]

No, that is absolutely not the case unless there is no deviation at all. Deviation cased by iron objects depends upon the magnitude and direction of the magnetism of that item - not only will these vary from unit to unit but the same boat will change over time. If you have significant deviation you should swing your boat regularly. The deviation caused by electrical circuits (you should always swing with all the nav instuments swithched on) would be identical for identical boats but in practice there are usually significant differences in production wiring between boats of the same type. Boats aren't wired with pre-formed looms, unlike cars.

 

[Piers]

When measuring deviation, have two cards drawn up. One with all your electronics running, and the other without - just in case you lose elctronics and need to use the compass in earnest.

Depending upon installation and distance from the compass, you might be surprised at how much kit and cabling can effect the compass.

 

[Birdseye]

The various lumps of metal in your boat aquire their magnetism (which causes deviation) at different times and in different ways. So you definitely cannot use the curve from another boat.

But to be provocative, do you really need a deviation curve anyway? If you use a GPS, certainly on shorter trips, you arguably dont need a steering compass. Navigate in True and operate by comparing track with waypoint bearing.

On my last boat I checked the deviation using the hand bearing, and since the compass was more accurate than I can actually steer anyway (ie the deviation was up to 5 degrees max), I never bothered with a curve. If your compass is way out, you need to do something about the compass never mind a curve.

Incidentally, DC current through a wire generates a magnetic field so if you do check deviation check the effect of various bits of electicery.

 

[Ships_Cat]

I agree. Deviation should be correctable by adjustment of the compass so that it is much less than ones steering accuracy or the graduations on the compass card on a small vessel (most are graduated in 5 degree increments on pleasure boats).

A deviation card should not be necessary on a small vessel. In fact I personally am not familiar with any small pleasure vessel that has one (although I do see references on these forums to forumites having them /forums/images/graemlins/crazy.gif).

John

 

[Piers]

When the compass is swung to correct for deviation, a deviation card is drawn up showing the residual deviation, even if none exists - but I've never seen a dev card which shows nil!

 

[golfclub]

Hi folks..thanks for all your comments....the reason for asking is that I am coding the boat/SCV2 certification,and am led to believe at the moment that this is a necessity..any comments?? many thanks again.

 

[Anonymous]

An unswung magnetic compass is about as much use as a chocolate teapot.

 

[Ships_Cat]

Couldn't comment specifically for the MCA's requirements for small vessels, but most jurisdictions require most coded boats to carry a deviation card, whether it is useful or not. On most small coded boats it lives in a drawer somewhere, or in some other forgotten place. In most jurisdictions the requirement will depend upon both the size of the boat and its limits so probably best you actually check with the actual requirements by reading the rules that apply to your vessels intended service.

John