Portland Plotter

[Torontotonto]

Can anyone please navigate me in the direction of a comprehensible 'how to use' set of instrutions for this plotter. Can't seem to find anything on the Net. Have plotter - no instructions. merci. /forums/images/graemlins/smile.gif

 

[Kawasaki]

Welcome tonto,chuck the plotter in the bin ,sorry "trash" get an electronic device or a" Bretton" Just taking the p*ss! Anyway your only buggering around on a lake! Sailed on your lake in a Fisher 37 in 82 "Nice"Nice City too. Somebody on this forum will give you the proper answer!

 

[alant]

Easy. just point the arrow at one end from your start point to destination (or fixed point for bearing to)(you point from the fixed point to you, for a bearing from), spin the centre disc so that its arrows point true north on the chart (just align the grid with the lat/long lines) & then read off the bearing (degrees true). It can adjust for variation etc, but you may just want to do that separately.
If you have just taken a bearing with a HB compass, adjust to degrees true, dial this up on the plotter disc, place the straight edge of the plotter on your chart against the object you have taken a bearing from, move the plotter around so that the disc arrows point north & then draw a position line on the chart along the straight edge, making sure the centre disc has not moved.
With practice, it can be quicker than using electronics as long as you have a 'paper' chart or chartlet.
Using a manual plotter, also has the benefit that it makes you actually read & use a chart, hopefully drawing your attention to anything overlooked.
You can also use the edge scale to quickly work out a speed vector triangle ( for course to steer or EP). Unless you have an older version, these scales are now marked in knots.
All of this can be v. difficult if you are doing this in a fast moving boat with lots of vibration.

 

[Torontotonto]

Merci bien! /forums/images/graemlins/smile.gif

 

[peterb]

A tip for plotting a compass bearing is to put your pencil point on to the object whose bearing is being plotted, then use this as a fulcrum round which the plotter can be turned until the lines on the cursor line up with parallels or meridians. Saves trying to line up two things at the same time.

 

[Kawasaki]

Nice and plain answer alant. Portland and Bretton are the same I think. At 0130 hours this am+ a wine glass or two I couldn,t even begin to explain how to get one out the box never mind use one! Toronto as mentioned there quicker to use than you would imagine and combined with just a simple GPS system I agree its the way to go (no pun intended) Plus I think its more fun to plot everything on a chart first than just relying on electronics. Probably safer too, for obvious reasons. Anyway more info on your boat , where do you keep Her and where will you intend to get to in The Geat Lakes. No. one brother has recentley left Toronto to Winter in the Bahamas B****TD! Nice enough to go boating today here,but in the middle of sticking my engine back in.Good boating, Rich

 

[peterb]

Breton and Portland are the same in principle, but differ in detail.

Worth noting that Blundell and Harling (B & H), who make the Portland, used to make very good slide rules in the days before electronic calculators, and are thus used to precision engraving. One check that you can make on any of these types of plotter is to compare the bearing with its reciprocal. I have one in front of me at the moment (not Portland or Breton) that claims the reciprocal of 30 to be 213!

 

[whisper]

For "very difficult" insert "bloody impossible" /forums/images/graemlins/wink.gif