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#277993 - 12/15/15 03:24 PM Re: A new compass thread [Re: Tom_L]
Mark_F Offline
Old Hand

Registered: 06/24/09
Posts: 714
Loc: Kentucky
with all the talk on how fragile some compasses are wouldn't it be prudent to find a way to protect it? At least while it's not in regular use. I must admit I've had concerns about my own compass, it's a cheapie clear base plate map compass and rides in a nylon compass pouch clipped to my pack. I'm wondering if it wouldn't be a good idea to see about finding a slim case (like the type for cell phones) it will fit in to help protect it.
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#277999 - 12/15/15 10:12 PM Re: A new compass thread [Re: Mark_F]
hikermor Offline
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 5994
Loc: southern Cal
This fragile compass talk puzzles me - my Suunto is more than twenty years old and still looks and works just fine. No bubbles at all. I generally stow it in an interior pocket in my pack next to the map when not in active use. When I am using the map and compass, it is tucked inside a shirt pocket and secured from loss by a neck lanyard. It does have a protective cover which houses the mirror - that may help its longevity. I also have a deck mounted kayak compass which is more than fifteen years old. It is doing just fine, although it hasn't been used quite as intensively in the last few years.

It would be truly bad news if compass quality has actually declined. When you really need to use a compass you more or less have to trust it completely.
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#278005 - 12/15/15 11:18 PM Re: A new compass thread [Re: Mark_F]
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 1970
Loc: NE Illinois
I think SOME compass models have a well-tracked history of bubbles. I have two of Brunton's high-end "eclipse-style" mirrored compasses and have had bubbles in both ... and the manufacturer replaced them both for free.

Then again, I have something like eight Brunton base style compasses (used to teach map & compass skills), they are now about 10 years old, have been used a lot by young Boy Scouts, and NONE of them have bubbles.

I KNOW that liquid-filled compasses can withstand time and abuse. My base Silva Polaris compass purchased in 1970 - my first compass - has been used so much that its surface is almost translucent with scratches ... and yet it is fully functional and still has no bubbles.

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#278011 - 12/16/15 08:11 AM Re: A new compass thread [Re: Mark_F]
Tom_L Offline
Addict

Registered: 03/19/07
Posts: 690
Originally Posted By: hikermor
This fragile compass talk puzzles me - my Suunto is more than twenty years old and still looks and works just fine.


Originally Posted By: KenK
I KNOW that liquid-filled compasses can withstand time and abuse. My base Silva Polaris compass purchased in 1970 - my first compass - has been used so much that its surface is almost translucent with scratches ... and yet it is fully functional and still has no bubbles.


I think there's a prevailing theme there. It seems that back in the day most compass manufacturers took quality control more seriously. Their products cost more relatively speaking but were made to higher standards.

To second Ken's experience, I have had my eye on a pretty old Silva, possibly from the late 70's, in near perfect condition (apart from the cosmetic nicks and scratches). Understandably enough, its owner would not part with it under any circumstances. Also, I have an Eastern European military issue liquid-filled compass in my collection, made ca. 1980 and with a lot of mileage. The capsule is still perfectly free of bubbles or defects.

Compare that to the current market offerings. Despite its excellent design, my ca. 2006 vintage MC-2G Suunto had some flaws even before the fatal capsule leak. The bezel developed slight play from use, nothing catastrophic but enough to affect the accuracy of readings up to maybe one degree. Not nice, or at least not what one would expect from a top-of-the line model made by a leading brand. I can attest from personal observation that the currently produced MC-2G is made to even lower standards.

I don't know, maybe I'm a little harsh on Suunto but I'm not the only person who's had serious issues with their products. A little while ago I came across this thread - clearly another unfortunate customer with a nice bubble in his almost new MC-2:
http://tasmania.bushwalk.com/forum/viewtopic.php?f=15&t=18780
Well, could be worse - the bubble in mine grows even bigger at some altitude. 4000' seems enough to do the trick already.

Just the other day I inspected the latest compasses at a local store (mostly Suunto, Recta and a few Silva models). Some of the less expensive (~$20) baseplate compasses - still in their original, unopened packaging - already had bubbles! The salesman retorted immediately that a bubble has no effect on the compass accuracy, therefore is not considered a manufacturing defect covered by warranty. Which is admittedly in line with Suunto's official warranty policy, so I suppose that's the end of that.

It's a shame really, but maybe now in the era of GPS the demand for quality compasses is decreasing so much that the manufacturers can get away with inferior products. Worse yet, a lot of people have started to treat compasses as disposable items. I know a local scout leader (and a great guy he is) who buys Silva and Suunto baseplate compasses by the dozen for his troop. Most compasses don't last longer than a few years due to "rough" handling and bubbles so they are replaced without much thought (not that it's a big investment in the first place). Curiously enough, a few of those inexpensive baseplate compasses soldier on for many years while the rest fall apart fairly quickly.

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#278013 - 12/16/15 02:27 PM Re: A new compass thread [Re: Tom_L]
hikermor Offline
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 5994
Loc: southern Cal
OK,here's a question - How MUCH does a bubble affect the accuracy of a compass and is there anything one can do in the field to reduce the inaccuracy? Deviations of one or two degrees are usually insignificant in most situations....
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#278017 - 12/16/15 04:37 PM Re: A new compass thread [Re: hikermor]
Mark_F Offline
Old Hand

Registered: 06/24/09
Posts: 714
Loc: Kentucky
by my calculations, being off by just one degree, and traveling just one mile, you'll be off course by about 92 feet (roughly 8.7 feet off per every 500 feet traveled)
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#278022 - 12/17/15 02:55 AM Re: A new compass thread [Re: Mark_F]
hikermor Offline
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 5994
Loc: southern Cal
That would be true if the error is not random;even if that were the case one could rather easily observe the objective and arrive at the correct spot. Usually you are dealing with a swinging needle that goes on either side of the true azimuth. In practice, one does pretty well to be within two degrees.


Edited by hikermor (12/17/15 03:18 AM)
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#278024 - 12/17/15 04:45 AM Re: A new compass thread [Re: Mark_F]
Teslinhiker Offline
Veteran

Registered: 12/14/09
Posts: 1314
Originally Posted By: Mark_F
by my calculations, being off by just one degree, and traveling just one mile, you'll be off course by about 92 feet (roughly 8.7 feet off per every 500 feet traveled)


Originally Posted By: hikermor
That would be true if the error is not random;even if that were the case one could rather easily observe the objective and arrive at the correct spot. Usually you are dealing with a swinging needle that goes on either side of the true azimuth. In practice, one does pretty well to be within two degrees.


As Hikermor mentioned. There is some deviation in a compass needle - especially when taking a bearing while on the move.

Unless someone is out in extreme weather such as fog or blinding snow where you cannot see your surroundings at all, there is no need to "dead stick" (our old school slang for needing a 100% accurate compass reading.) So being out 1-4 degrees over a mile with decent sight visibility of your surroundings is well within acceptable limits for 99% of hikers, hunters, boaters. And most times, you find the trail, road or boat dock you were navigating to.
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#278026 - 12/17/15 07:50 AM Re: A new compass thread [Re: Mark_F]
Tom_L Offline
Addict

Registered: 03/19/07
Posts: 690
IME a small bubble should not affect the accuracy at all. However, a bubble larger than 1/4" or so could already prevent the needle from swinging freely, introducing a completely random error that might be 5 or 180 degrees depending on how exactly you hold the compass and how the bubble moves inside the capsule.

A bubble this size is pretty bad. That compass needs to be repaired or replaced, either way it cannot be expected to give accurate, consistent bearings:
http://tasmania.bushwalk.com/forum/downl...4&mode=view

While a small bubble does not necessarily mean the end of a compass it's still a cause for concern. A small bubble is likely to grow bigger in cold temperatures and high altitudes.

Is it possible to repair a copass with this sort of defect in the field? I'm not sure. If there is really no other way you could poke a small hole and drain the liquid from the capsule. Unfortunately, that does not seem to work well in my admittedly limited experience.

Generally speaking, an accuracy of 2 degrees would be considered excellent, 3 degrees still acceptable from what I've been taught about land navigation. Keep in mind that even a compass in perfect working condition isn't really capable of perfect readings. IIRC, a top-notch prismatic compass has an ideal accuracy of +/- 0.5 degree. A good mirror or lensatic compass somewhere between 1 and 2 degrees. A baseplate 3 degrees or so.

This is the inherent accuracy of the compass and its sighting system (or lack thereof). It does NOT take into account user error or slight mechanical defects (loose bezel, slightly offset sighting mirror/sight line etc.).

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#278031 - 12/17/15 03:03 PM Re: A new compass thread [Re: Mark_F]
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 1970
Loc: NE Illinois
At one point I had tried to remove a bubble by placing the compass near an incandescent light bulb for a while - to heat it up. I'd read somewhere online that worked. Well, it melted the capsule. Too close I guess.

I sent the melted mess to the manufacturer with the story telling them that if they chose to ignore me due to my own damage I'd understand it ... and they replaced it anyway. I'm thinking it must have been the first of the two mirrored Brunton Eclipse compasses.

By the way, feature-wise and for ease of use I really REALLY like the Brunton mirrored Eclipse compasses. It looks like they are called the "Brunton TRUARC 20" now. They added a global needle and it looks like they dumped the info cards. They says its improved now - I hope they fixed the bubble issue.

That compass has a smaller width mirror that lifts up which is not quite so good for signaling, but I would bring Doug's survival pak anyway so not a big deal for me. Still, you'd better check them for bubbles before heading out.

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