Compass

[Megwyn 2]

A deviation chart is a list of the measured deviation of your particular compass in its normal installation for all the different directions. For instance, your compass in its normal mounting spot may be out by 3 deg E when the boat is heading NW and it may be out by 2 deg E when the boat is heading W, etc.

 

To develop a deviation card you "swing the compass". You go out and run the boat along known headings (transits that give you particular headings) and read off the compass value. You build up a list of deviations for all the major headings and apply those errors to any compass readings you calculate or read off the compass.

 

Oh Wow - thanks Grinna - See, you can learn something new every day.

 

M

[rigger 47]

attached is an excel spreadsheet that can be used to generate deviation card - it uses a method that was taught to candidates for an unlimited masters licence.

 

Just enter the observed deviations where there is blue text.

[Megwyn 2]

Thanks Rigger

 

As soon as I can get the compass working again, I will do that.

[PaulR 3]

Dave is the man!!

 

Previously he supplied me some oil for DIY.

 

Different compasses, common in small yachts, use different types of oils, so getting the right BRAND and MODEL for Dave is important.

 

Dave also advised me to rinse the bowl out twice, then put both the new oil and compass in the FREEZER for a day before finally filling up and sealing. This means the oil and compass plastic and metal is all at the same low temperature, which then allows the expansion bellows to work better in warm climates / summer, if we get a decent one next year!.

 

Using a seringe with a needle, allows easier filling through the small screw hole, especially for getting rid of the final few bubbles by bursting them and/or inserting small drips into the remaining bubble.

 

Then some gentle action to release any bubbles that were clinging to the bellows or hiding under the card, then back in the freezer for another day, then check for bubbles / topup or if all OK, refit.

 

 

WARNING: The oil makes the plastic and perspex bowl very, VERY slippery and often, if then dropped on concrete, the little spindle that supports the card snaps un-repairably, but the new compass then looks flasher anyway and the inclination scale is easier to read

 

Good Luck.

[Megwyn 2]

Spoke to David this morning. Have sent him some pics of the compass and he will let me know if it can be repaired.

 

It is a Suunto, and apparently they went out of business 14 months ago.

 

May be looking for a new one yet.

M

[Megwyn 2]

Dave cannot fix the Suunto.

 

So now we are looking for a new one.

 

Any one had any experience with the Plastimo Contest 101? They have a 5 year warranty, and are a sealed unit so are not repairable. Seeing as our last one was repairable , but no parts available to repair it, we are not sure whether buying a repairable compass is such a good deal or not.

Looked at the Silva 102B/H Challenger, but it uses a red light, which I would guess would light up the white figures in red at night. Awesome for night vision, but no good for me as I cannot read red on a black background.

 

Your wisdom is appreciated.

M

[Guest]

RO Had a compass? Well dam me, where did they hide that. I put in a perfectly good GPS what the heck do you want to go back in time for Megwyn?

[Guest]

The boat was faulty, send it back.

[Megwyn 2]

RO Had a compass? Well dam me, where did they hide that. I put in a perfectly good GPS what the heck do you want to go back in time for Megwyn?

 

Well, you see Offender, when the Aliens come and wipe out all the Global Positioning Satellites, I won't know where I am if I don't have a compass!

 

The boat was faulty, send it back.

 

Na - that won't work - we are now past the 30 days that the consumers guarantee act covers - so I am tough out of luck there. I am stuck with it now.

 

But seriously folks, does no one here have a comment to make on the Plastimos?

 

M

[Grinna 2]

I only know that the Plastimos are a decent compass. We have one (a Plastimo Offshore 135) on our boat and its clear and easy to read. I'm assuming (big assumption) its original fitment on the boat (24 years old) but has been protected from sun and UV damage and seems to work well. It needs to go to Dave Schafer for a service prior to a swinging so once we get around to doing that I'll be able to give you more info.

[Fogg 427]

All the boats I've owned have had plastimos. I think they must have been OK cos I never really noticed them i.e. they worked fine, never needed any maintance, kind of just quietly sat there all the time. Only other comment is that I remember one being a bit too brightly lit such that on a dark night I need to cover it to avoid too much glare.

[Bill 0]

Interesting, I did just the replacement you're considering -- the Plastimo 101 for the Suunto B -- for the same reason. In our case, the globe was cracked, probably from one too many knees over the years. The Suunto lasted 25 years, so I can't complain. I chose the Plastimo because it includes a clinometer, probably not a consideration for a tri, but I own a leaner, and it fit the existing hole with the least fuss.