[Rhodes22-list] Compasses

[Steve Alm]

Thanks Alex.  Your message made me realize I made a mistake on my earlier
post.  I said I adjusted my compass to within a half of a degree.  What I
meant was to within half way to the next mark on the compass.  Each mark is
5 degrees, so I'm within 2 and a half degrees -- not one half.

Slim

On 4/10/05 7:58 PM, "Alex Bell" <alexbell at lpmonline.net> wrote:

> 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
>>>> 
>>>> 
>>>> 
>>>> __________________________________________________
>>>> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>>> 
>>> __________________________________________________
>>> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>> 
>> 
>> 
>> __________________________________________________
>> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list
>> 
>> 
> 
> 
> __________________________________________________
> Use Rhodes22-list at rhodes22.org, Help? www.rhodes22.org/list