compass query

[jneale]

I've got a really odd bulkhead compass. Top scale is normal 0 - 360 degrees, but edge scale is 0 to 20, with 0 on side corresponding to 90 magnetic
I knew the French wanted a 100 degree compass in the 1800s but this is rediculous.

Any ideas ???

 

[[70521]]

Picture please.

 

[Mistroma]

Only thing that comes to mind is that you are talking about a 0-20 range offset from North (i.e. Not marked all around the compass edge). I suppose that would allow you to correct for declination to find true North.

Just a stab in the dark. It will be interesting to see a picture and if it shows 0-20 starting at 90 deg. then I'm stumped. That was how I interpreted your description initially before thinking about it a little more.

 

[pvb]

The 0-20 scale is a tactical scale, used by racing crew to make things easier. Silva have for years used a tactical scale that divides the conventional scale into 20 units, marked 0 to 19, each corresponding to 18 degrees. 5 units is 90 degrees - nice number. The viewing lubber lines give the sailor an easy pair of numbers to remember. Suppose the helmsman reads 0 on the tactical scale on the starboard lubber line and given a tacking angle of 80 degrees the viewer will see 10 in the port lubber line. For every starboard number the port number is ten difference. So 1 on starboard is 11 on port. Easier to remember than actual compass courses.

 

[Salty John]

I think it might be what's known as a tactical compass - for racing. The edge reading is usually divided into four 5 'degree' sections, each a different colour.

 

[2Tizwoz]

Do you mean the heeling angle?

or is it a tactical scale?

 

[chrishelen]

so you can line up your course with one of these lines if sitting on the sides of the cockpit when heeling? thats what i use mine for.