navigation

I use a Portland plotter. I find no problem with it. There's *always* something on it you can line up with the grid. I've got a waterproof notepad for pilotage/nav notes when I know I'm gonna be stuck in the cockpit and not get to the nav table.
 
LadyInBed said:
forget parallel ruler!
Get two pairs of dividers.
For plotting a position on a chart, I use two pairs of dividers (bow type). One to transpose Lat and one to transpose Long. It saves a lot of faffing around altering it for Lat and Long.
Plotters - as you say, it just down to personal choice.
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Thats all very fine but with which do you draw course lines, tidal drift and such like.

My personal preference are Captain fields paralell rules, I have them in different lengths, I have both types of dividers but prefer my 8" brass and stainless compasses. I use a 24" straight edge for extended lines, and I also have a large chrome plated Brass roller Rule, but I tend not to use it at sea, only for planning.

Try the different options and use what ever you feel most content with.
 
kitcrazy said:
hi, been reading up on basic navigation and i've got myself some charts to pratice on, but i need to get a parallel ruler and dividers. I've noticed there's diffent types, does it matter which ones or is it just down to personal choice?
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As previously stated, its personal preference.
However, parallel rules are definitely for the bridge of a merchant vessel, particularly those with rollers.

Most important thing to remember, is that anything transferred from or onto a chart, MUST be in degrees TRUE! So learn how to apply variation/deviation correctly.

PS, another 'obvious tip' often forgotten - mention has been made regarding divider points becoming blunted, but how many times has the 2B pencil been blunted by putting them point downward in the chart table holder? They should always be put away point upward to preserve the point.
 
orbister said:
Which exam, as a matter of interest?
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Not Dayskipper or YM Theory, that's for sure. I, and everyone else who sat it with me, used a Portland plotter. I used to teach DS classes and most people used Portlands - I don't recall any rules on what you can and can't use.
 
You're all wrong, wrong, wrong. Just admit it!

Michael Green (the Art of Coarse Sailing) did it with two nails in the foredeck.

Leslie Phillips took "Troutbridge" (Navy Lark) to New york on a street map of Brighton!

Simple navigation, tiller in one hand, cuppa in the other, no faffing about with dividers and parallel rulers, just a couple of nails to blearily sight along!

Failing that, follow someone else!
 
mollyoxford said:
Not Dayskipper or YM Theory, that's for sure. I, and everyone else who sat it with me, used a Portland plotter. I used to teach DS classes and most people used Portlands - I don't recall any rules on what you can and can't use.
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Perhaps I put that a bit strongly. I think you should be able to show that you can do Variation calculations rather than just dial it in on the plotter.
 
peterb said:
In principle, nothing at all. That type of plotter was originally made in France, and called the 'Breton' plotter. When made in the UK by a different firm they had to use a different name.

A word of warning on dividers. As others have said, you want brass dividers with stainless points. I have seen brass dividers where the ends of the legs have been chrome plated; they look very similar, but the points rapidly bend or blunt. Look for a definite discontinuity between the brass and the stainless bits.
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Variation is so small now in this neck of the woods, that it can be virtually ignored (tell it not in Gath).
 
Navigation Aids

I swear by Weems and Plath dividers. The advantage of this type is that you can, with a wheel, adjust them to an exact distance and this will be held, whatever the motion of the boat. £9.75 from RYA shop.

Regarding navigation notebooks which are water proof. I open up old tomato/orange juice cartons, wash them and then write my pilotage plans in indelible pen on them. Write with a medium thickness nib and you can read them at night without using a torch, using the compass light.
 
Trad Nav

I am interested to know why some people think roller Parallel rules are unsuitable in a yacht. They are so much more convenient, especially for passage planning and they more easily transfer over a large chart. For detailed work when doing chart corrections, I use a large Douglas. I also use a Douglas in conjunction with a set square for plotting star-sights.
Stainless steel points on dividers? I have missed out. Mine have tool steel and I keep them shoved into a cork, preferably one from a Grand Cru Classe. They have never rusted thanks to Ducru Beaucaillou.
If you should want to make your own plotting sheet, then adjustable set-squares are good.
How much of that is true and how much a leg pull?
 
Really?

sticky said:
I swear by Weems and Plath dividers. The advantage of this type is that you can, with a wheel, adjust them to an exact distance and this will be held, whatever the motion of the boat. £9.75 from RYA shop.
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What happens when you simply want to quickly measure a distance on the chart between two fixed points? Do you hold on to them with one hand, while cranking the wheel with the other?

If so, seems like hard work and more suited to school geometry or a draughtsman's table.

Just curious to know!
 
Dividers

In reply to Jaybee of 0923 this am. You do not need to "crank" the dividers using the wheel, but can open and close them easily with one hand. Work well at sea with one hand for yourself and one for the dividers!

Sticky
 
More Dividers

Bow-type dividers have proved popular at sea since medieval times. In the classroom, however, for those ploughing through RYA or MCA shore-based courses, a draftman's type of compass with lead changed for a second "needle" would help achieve the degree of accuracy that keeps the examiner happy.
 
The great divide (cont.)

I like straight navigational dividers - brass, with stainless steel points, about 7 or 8 inches long and with a screw at the hinge keeping them together and allowing some frictional adjustment.

This could be a "personal" and possibly irrational prejudice, but I don't think so.

Unlike the "bow" type, they don't require the user to shift grip, alternately squeezing bow and legs when making small adjustments to the span. (Thinks: perhaps a YouTube video is required here.)

"Straight" dividers are to be found in their tens of thousands on the chart tables of merchant ships of all nationalities, whilst the sexy looking (medieval) "bow" types are almost never in evidence. As both versions cost about the same amount of money, I conclude that the overwhelming majority of professional navigators find the "straight" type easier and more convenient to use.

QED
 
Used the bow type dividers for years and got really fed up with having to open them 'the wrong way' because they never seemed to open wide enough the right way. Anyway, last time I sold the boat I let the bow dividers go with it and bought a new set of straight ones. Much easier and less hassle.

And Portland plotter, does anyone plot in 'true' on a coastal chart?
 
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