Compass replacement?

[xeitosaphil]

Hi all need some advice on my old bulkhead compass replacement please if poss.

Has anybody personally had to replace an old Contest Class B- No 346 SN ? And found that there is a direct replacement for the hole size in the bulkhead. I don't want to have to get into filling holes because new compasses are smaller, but haven't removed old compass to find installation hole size.
Compass has now drained the fluid to the card level and reading posts, it suggested with the age, repair is not possible.

Any info gratefully accepted.

 

[johnalison]

I can't help with the specific model but I had to replace my compass a couple of years ago. I just scrolled through what was listed and chose just about the only one that would fit, which happened to be a Plastimo. Other makes are available.

 

[Refueler]

I can't help with the specific model but I had to replace my compass a couple of years ago. I just scrolled through what was listed and chose just about the only one that would fit, which happened to be a Plastimo. Other makes are available.

I had similar exercise about 6 - 7yrs ago ... my old had suffered from the sun and perspex was brown ... fluid had leaked ..... it was an old Plastimo ...

I looked at all sorts of onlines and I found what I thought was same Plastimo ... but updated version.

When I went to mount - it was similar diameter - but the screw holes were just a mm or so different position.

Spent a while with hand round file .... finally she went in ....

As I see it - like so many things in life - when we go for replacement - manufacturer has altered something .. why ? Who knows ... but seems they all do it.

If I ever have to do it again ... I will search online for the Mounting Template before committing to buy !!

 

[johnalison]

I was lucky. The new one was too different to be a problem. It just needed the hole cutting out a bit.

 

[Daydream believer]

I know that this is a bit off topic but i cannot helpwondering why people use those compasses with numbers on cards that roll in front of their eyes. I had one years ago but often when tired I had a job steering anything like the course needed & sometimes found myself steering the wrong course as I forgot the number.
I have had a grid steering compass since 1968 & still use the same one. I actually found a newer model from a MOBO that was set in a bench top 4 years ago so I made a set of gimbals for it
One just sets the course & lines the lubber line between the 2 grid lines & it is Sooo much easier to steer a course. Both of mine sit on a bulkhead bracket beneath the tiller where it is dead easy to see.
Here is the later one, with the gimbals I made, as a spare.

 

[srm]

I know that this is a bit off topic but i cannot helpwondering why people use those compasses with numbers on cards that roll in front of their eyes. I had one years ago but often when tired I had a job steering anything like the course needed & sometimes found myself steering the wrong course as I forgot the number.
I have had a grid steering compass since 1968 & still use the same one. I actually found a newer model from a MOBO that was set in a bench top 4 years ago so I made a set of gimbals for it
One just sets the course & lines the lubber line between the 2 grid lines & it is Sooo much easier to steer a course. Both of mine sit on a bulkhead bracket beneath the tiller where it is dead easy to see.
Here is the later one, with the gimbals I made, as a spare.
View attachment 159125

Very nice.
I liked steering with a grid compass, as you said once set no worries about forgetting the heading. They are almost essential with tiller steering as they can easily be read from the side. Interestingly, I remember seeing an ex wartime RAF magnetic grid steering compass with luminous markings. Apparently they were used on Hurricanes and Spitfires.
Also. one compass on the centreline is a bit cheaper than the usual pair on the forward bulkhead.

 

[johnalison]

Very nice.
I liked steering with a grid compass, as you said once set no worries about forgetting the heading. They are almost essential with tiller steering as they can easily be read from the side. Interestingly, I remember seeing an ex wartime RAF magnetic grid steering compass with luminous markings. Apparently they were used on Hurricanes and Spitfires.
Also. one compass on the centreline is a bit cheaper than the usual pair on the forward bulkhead.

I remember being taken aback when I saw one in the RAF museum Hendon. They also had an automatic RDF unit much the same as was available for sailors in the ‘70s.
I’ve nothing against a grid compass, but where would I put it? It’s not overly hard to steer to a conventional edge-on version.

 

[William_H]

johnalison said "They also had an automatic RDF unit much the same as was available for sailors in the ‘70s."
Ah. just to fill you in Auromatic direction (ADF) finders have been around since ww2 or just after on almost every aircraft, being the first navigation instrument beyond a compass. They tune the low frequency band from 200 to 400 khz and 500 to 1400 khz. They use a loop antenna being a block of antenna at right angles (often on ferrite) and a sense antenna being a long wire. The authorities built a network of Non directional beacons around Australia and I am sure the rest of the world operating in 200 to 400khz band. Each identified by a repeated slow morse code 3 letter ID. (but broadcast stations could also be used) In old or simple set ups the result was a direction indicator giving relative heading to the received station but more sophisticated systems used a Radio Magnetic Indicator where a flux valve compass presented heading on a rotating card upon which the relative direction of the radio beacon was presnted. Thus at a glance you could read off your position as magnetic heading from the station (beacon). The RMI could at a switch also give somewhat similar data from a VHF navigation receiver (VOR beacon).
All this now I think being superceded by GPS but as of 20 years ago when I got out of aviation radio all aircraft of any size would carry 2 ADF systems. All airports of any size at all would have procedures for instrument let down using ADF. So not so much taken up by amateur sailors but very much by aviation. ol'will

 

[Refueler]

Very nice.
I liked steering with a grid compass, as you said once set no worries about forgetting the heading. They are almost essential with tiller steering as they can easily be read from the side. Interestingly, I remember seeing an ex wartime RAF magnetic grid steering compass with luminous markings. Apparently they were used on Hurricanes and Spitfires.
Also. one compass on the centreline is a bit cheaper than the usual pair on the forward bulkhead.

Pair ?? I have one in the port fwd cockpit bulkhead .....

I also have a Suunto grid - but its non-gimballed designed to be screwed to a dinghy thwart .... useless !! As soon as boat heals - it stops moving. I have wondered about creating a gimbal for it and then a simple clip mount near tiller ..... but my bulkhead compass does well. The only disadvantage is that I need to remember not to put anything ferrous near it on other side of bulkhead !

Years ago in Solent .... guy sailing with me placed a metal mug of his tea on cabin top under the sprayhood ... yep - compass took a dim view of that and swung way off ... luckily being Solent - we could see destination !!!

 

[srm]

Years ago in Solent .... guy sailing with me placed a metal mug of his tea on cabin top under the sprayhood ... yep - compass took a dim view of that and swung way off ... luckily being Solent - we could see destination !!!

During my YMI exam I was on the helm at night. Steering a compass course but using a shore light as reference. The examiner came into the cockpit. I quietly asked him to remove the magnet from his pocket. He was most offended so I pointed out that the compass was now pointing north directly at him. He eventually found that the problem was the light meter for his camera (remember them?) that was in his pocket.

 

[johnalison]

During my YMI exam I was on the helm at night. Steering a compass course but using a shore light as reference. The examiner came into the cockpit. I quietly asked him to remove the magnet from his pocket. He was most offended so I pointed out that the compass was now pointing north directly at him. He eventually found that the problem was the light meter for his camera (remember them?) that was in his pocket.

I still have my Weston Master III. In my case it was fixing a fire extinguisher bracket on the other side of the bulkhead that gave 14 degrees of deviation.

 

[PabloPicasso]

If I ever have to do it again ... I will search online for the Mounting Template before committing to buy !!

Good plan

 

[xeitosaphil]

Some interesting reading on compass topic. Will have to see if I can get a template then prior to order? Or take the old one out and measure hole diameter and fixing centres.

Thanks for all the contributions.
Philip

 

[Poignard]

I know that this is a bit off topic but i cannot helpwondering why people use those compasses with numbers on cards that roll in front of their eyes. I had one years ago but often when tired I had a job steering anything like the course needed & sometimes found myself steering the wrong course as I forgot the number.
I have had a grid steering compass since 1968 & still use the same one. I actually found a newer model from a MOBO that was set in a bench top 4 years ago so I made a set of gimbals for it
One just sets the course & lines the lubber line between the 2 grid lines & it is Sooo much easier to steer a course. Both of mine sit on a bulkhead bracket beneath the tiller where it is dead easy to see.
Here is the later one, with the gimbals I made, as a spare.
View attachment 159125

I have one of those, also mounted under the tiller. I also have a Plastimo Contest but much prefer using the Sestrel.