[Rhodes22-list] Compasses

[Alex Bell]

Here's a bit of information to keep things in prospective. We had our 
compass "swung" by the guy who does the US Coast Guard boats in 
Wilmington, NC. He said that if you got your compass within (2),  two 
degrees, it was considered perfect. You might also consider that nobody 
can keep a sailboat under sail set on a course better than =/- 5 
degrees, and that's doing good. My autopilot doesn't keep the boat on 
the exact heading when under sail. It's constantly making corrections, 
sometimes 8 to 10 degrees if there's a sea and or puff hits us.

So it's a moot point as to a compass being off a few degrees on the 
Rhodes. You shouldn't be out so far as to be out of sight of land 
anyway. The boat's not made for that kind of sailing.

Alex Bell

Bob Weber wrote:

> Slim, now do the same on the boat and you got it SWUNG.  Bob
>
>> From: Steve Alm <salm at mn.rr.com>
>> Reply-To: The Rhodes 22 mail list <rhodes22-list at rhodes22.org>
>> To: Rhodes <rhodes22-list at rhodes22.org>
>> Subject: Re: [Rhodes22-list] Compasses
>> Date: Fri, 08 Apr 2005 15:44:10 -0500
>>
>> Step one checks out.  I took a full sheet of newspaper and creased it in
>> half both ways and diagonally and drew lines with a straight edge.  
>> Since my
>> compass is still mounted on the splash board, it's an easy and sure 
>> way to
>> line the board up on the lines on the paper.  I laid the newspaper 
>> out on my
>> wooden dining room table and went to work on the adjustments. After 
>> about 35
>> minutes of fiddling, I got it to be consistent on all lines (8 
>> positions) to
>> within a half of a degree.  Then I repeated the test in other rooms 
>> of the
>> house and basement and out on the front walk.  Results were 
>> consistent, so
>> my compass is working.  However, I always thought my house and the 
>> street in
>> front ran exactly north and south but the compass is saying it's a few
>> degrees off.  And maybe the street isn't exactly north and south but 
>> I don't
>> have a second compass to cross reference.  I have a couple small 
>> hand-helds
>> on the boat but not here at home.
>>
>> Slim
>>
>> On 4/8/05 11:32 AM, "Bill Effros" <bill at effros.com> wrote:
>>
>> > Slim,
>> >
>> > From comments sent previously, you can infer the problems manifest in
>> > all compasses: they will all kick out numbers, but there is no fixed
>> > relationship between any two numbers until you discover what that
>> > relationship is.
>> >
>> > Let's start with your compass.  First rotate it 360°, slowly.  Is it
>> > capable of stopping at any number?  If the magnet has been badly
>> > damaged, it will jump over some numbers, no matter which way you point
>> > it.  If that's the case, you will not be able to use this compass
>> > because you will never be able to find another compass that makes the
>> > same mistakes in exactly the same way.  Consistency is the critical
>> > function of any compass.
>> >
>> > Assuming that your compass is capable of pointing in 72 different
>> > directions (5° intervals) you must next determine if it is consistent.
>> > Point the compass so it reads 0°.  Make a line in the sand.  Turn the
>> > compass 180°, and write down what number the compass points to.  
>> Turn it
>> > back to 0° using your line in the sand.  Does it say 0°?
>> >
>> > Please note, if the compass is working properly, the compass card 
>> should
>> > not move at all -- only the housing and the board you may have mounted
>> > it on should move.  It may not be pointing in a predetermined 
>> direction,
>> > but it should be pointing in the same direction all the time.  That's
>> > the way properly functioning compasses work.
>> >
>> > Using a protractor, draw a line in the sand at a 90° angle 
>> intersecting
>> > your first line.  Put your compass on this new line, first one way, 
>> then
>> > the other.  It should read 90° and 270°.  If it doesn't, you've got a
>> > problem.  Make more lines at 45° angles.  The compass card should not
>> > move.  Your computed angles should equal what you see on your compass.
>> >
>> > If they do not, someone may have "corrected" your compass.  The
>> > adjusting magnets, built into the housing of your compass, must be
>> > pulling your compass card in different directions as you rotate the
>> > housing around your compass magnet. Try to twiddle with them, so that
>> > they don't change the orientation of your compass card when you rotate
>> > them around.  If you can't make this happen, it's time for a new 
>> compass.
>> >
>> > If your compass is consistent, it's time to mount it on your boat, and
>> > figure out what direction it's actually pointing.
>> >
>> > Timid Virgins Make Dull Companions.  Lesson II.
>> >
>> > Bill Effros
>> >
>> >
>> >
>> > __________________________________________________
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>>
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