Portland STD Calculator

[Tideway]

Does anyone use one of these? If so can you post an idiots guide to this? As I've got one, been shown how to use it once, thought blimey that's good, bought it, and cannot now figure it out..!

I'm unfortunately of the calculator generation of maths students and I'm struggling with this slide rule business

cheers,

t

[Scotty]

A calculator for Sexually Transmitted Diseases........... you guys think of everything.

So herpes X clap = ????

[Tideway]

Originally Posted by Scotty

A calculator for Sexually Transmitted Diseases........... you guys think of everything.

So herpes X clap = ????

I KNEW that would happen as soon as I saw it posted...

Speed-Time-Distance was the hoped for interpretation. Although, I can see a market for the 'other', sailors being sailors...

I'll get me coat...

t

[Richard B]

The instructions are printed on the back of it

[Tideway]

I know, I've now worked it out . It was actually pretty easy, so much so that I kept thinking that I'd got it wrong! Initial post was after beers and it all seemed too hard...

Do people use these much or rely on electronics?

t

[donutsina911]

if i'm thinking of the same device (yellow ruler type thingy with slidy white bit), used to use one all the time in the RN watchkeeping / navigating, really simple to use and save the brain cells...ideal for a rib for quick s/t/d calcs

[tim griffin]

Originally Posted by Tideway

Do people use these much or rely on electronics?

t

distance multiply by 60 divide by boat speed
example 25 Miles x 60 = 1500 divide by your boat speed 20 knots = 75 mins
or you can use the 6 minute rule
example 27 knots boat speed (SOG) means in theory I will travel 27 miles in 60 mins move the decimal place once and every 6 mins you will travel 2.7 miles you can then use this in multiples of 6 , 12 , 18, 24 and so on.

[Tideway]

thank you chaps.

Although, Tim you generously underestimate the level of numeracy that I have completely failed to achieve... That was the reason this appealed to me, as I really struggle with all things involving numbers. It takes me half an hour to work out the reciporical of a course unless I can see the compass and look at the opposite number!

It is something that really bugs me whilst boating as there is a small amount of simple maths stuff that takes me ages eg. rule of 12ths, secondary ports etc... I get there eventually, but boy is it a painful process.

ho humm, practice makes it slightly less bad

cheers

t

[tim griffin]

Use a calculator easy option I do

Recipricol bearings +2 -2 rule or -2 +2
example

220 -2= 020 + 2 = 040 and go the other way 040 +2 =240 - 2 = 220
only time you have to think is 190 as = 370 =010
I always use a calculator for STD I always check on the Plotter as well when drawing bearings and getting the recipricol (Portland type).

Secondary ports www.easytide.ukho.gov.uk the more tools in your box the better equiped we are. Secondary Ports can be achieved by using Sharks tooth method or admiralty method practice using easy tide to check your answers.Same as plotting LAT AND LONG practice finding tidal diamonds on your chart then plot waypoints and find them. Practice is the key and so long as you have a method of checking your answers confidence will grow until it becomes second nature.Have fun