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[Brian60]

I came across this list of calculators over the weekend. I don't think there is any calculator left out of this list! Arcs, triangles, tangents, areas circumference, they are all here.......

http://www.handymath.com/calculators.html

[roycv]

Hi, at my slightly advanced age I have done most of the maths I need to do.  I use simultaneous equations just once a year now.  The rest I do in my head, I find it easier to use fractions than decimals.
Do you have a calculator to suit?
regards Roy

[Brian60]

So with equally tongue in cheek reply, here's your fractional calculator....

https://www.calculatorsoup.com/calculators/math/fractions.php

[roycv]

Hi Brian that's the bit I do in my head, its this one I have trouble with, I usually fall asleep before the end!

  I seem to remember writing a programme to sum the squares from 1 to 100, and I also remember doing one to calculate the displacement of a model hull against the prismatic co-efficient, but that was when I was trying to find something useful to do with a computer, not mine of course but a big blue box (not IBM) sitting in an air conditioned room. 
The outcome was that the air conditioning helped me give up smoking.
But now everything is smaller I am very content with the efforts of Sir Tim Berners-Lee, emails and the Internet.

Fascinating prog on BBC2 last night on how D.T. got elected.  Now there is calculation for you!

regards Roy

[Brian60]

 

https://www.symbolab.com/solver/equation-calculator

[roycv]

Hello Brian, you are indefatigable! when I said I usually fall asleep, that was good as I would be in bed and it would be around midnight and the lights would be out.  And Yes, I do not have a mobile phone to access the non sleeping world.
Good try though.
regards Roy

[Umi_Ryuzuki]

My absolute favorite for fractional inches and decimel to feet/inch and English to metric is
The Pocket Handyman II.

Very straight forward and allows you to crack on without any dithering about.

 

[malcolmfrary]

When calculating sail areas, which are usually not right angled, you often just have the three sides.  I had to wind the calendar back a lot of years and blow a big pile of dust off my old maths textbook to find the formula then get it into a spread sheet.  Couldn't see it in the list.


I wound up with - =SQRT(((A3+B3+C3)/2)*(((A3+B3+C3)/2)-A3)*(((A3+B3+C3)/2)-B3)*(((A3+B3+C3)/2)-C3))
Where a3, b3 and c3 are the 3 sides.  Originally done in Exel97, still works in libreoffics calc.

[roycv]

Hi Malcolm, I have made several sets of sails and started from scratch on a new yacht and also converted a yacht to 2 masts. 
I always used drawing and geometry.  I used the fact that all triangles convert to 2 right angles.  I have a method for calculating centre of effort as well, using a drawing, what do you do?
However I am impressed with the formula, a lot less than that would send me off to sleep quite easily.
regards Roy

[Martin (Admin)]

Speaking of difficult math problems.... YouTube - The Napkin Ring Problem - https://youtu.be/J51ncHP_BrY

[malcolmfrary]

Hi Malcolm, I have made several sets of sails and started from scratch on a new yacht and also converted a yacht to 2 masts. 
I always used drawing and geometry.  I used the fact that all triangles convert to 2 right angles.  I have a method for calculating centre of effort as well, using a drawing, what do you do?
However I am impressed with the formula, a lot less than that would send me off to sleep quite easily.
regards Roy

The problem with doing the two right angle triangles was determining the right angle "side" length without drawing it out.  The formula allowed playing with numbers until the right area was stumbled on.  There was a lot of dust on top of that old "Mathematics for Telecommunications", but it had a worked example, which bypassed a lot of thinking.
Once I had a suitable set of numbers that gave the area wanted, it was drawing to scale and geometry. And, using a scale card cut out of the sail plan, finding the balance point.  But it only needed doing once.  The balance point of the sails was very near to the drawn center found using the school compass and halving angles, the average of the pair coincided with that for the whole plan.  With more thinking, it might work with any number of sails.  I did something similar with a cut out of the underwater profile to guess at the center of lateral resistance.  I don't know if the idea was valid, but the yacht worked just fine. 
There was that story of Edison getting prospective employees to figure the volume of a light bulb.  Most used reams of paper doing calculations - the guy who got the job was the one who filled the bulb with water and measured that.  Theory is fine, sometime you just need to look.