VicS
Well-Known Member
I have
Secondary port crocodiles - what's the point?
- Thread starter BlueSkyNick
- Start date
Hydrozoan
Well-Known Member
Well an Otis King trumps my Pickett and Eckel for accuracy (30ft scale was it?) - but the P&E does have a fancy leather scabbard. 
Facit calculator, anyone?
Facit calculator, anyone?
DJE
Well-Known Member
Yes, still got it. I dug it out when I was doing yachtmaster theory - easiest thing there is for doing time/speed/distance calculations. It's on the boat now ostensibly for the same reason. But mainly to produce at the end of passage races to baffle anybody who doesn't understand the new NHC system.
Mariner69
Well-Known Member
Oughtred/UK Slide Rule Circle?
Last edited:
VicS
Well-Known Member
Well an Otis King trumps my Pickett and Eckel for accuracy (30ft scale was it?) - but the P&E does have a fancy leather scabbard.
Facit calculator, anyone?
Otis King has a 66" scale length
I was offered a Fuller but did not accept it. (41 ft scale length)
I could have had a Facit too.
7 figure log tables anyone ??
Poignard
Well-Known Member
Thats what I do. I reckon I'm better off in the cockpit, not down below pursuing spurious accuracy by drawing drawing graphs and crocodiles.
BlueSkyNick
Well-Known Member
Maybe you haven't met DJE - he still uses an abacus to convert the price of a pint to shillings and pence, before he pays for it!
Hydrozoan
Well-Known Member
If you're used to interpolation in other walks of life it's no big deal, but the graphs and crocodiles were presumably introduced for those who aren't.
DJE
Well-Known Member
Pays for it????
Babylon
Well-Known Member
Use the same principle to space out dovetails on a drawer-side. It doesn't matter how wide the side is, just cant a ruler with any scale on a diagonal from one edge (*) to the other. If you want say four divisions, then line up 0 unit at the bottom and 4 unit at the top (it can be any scale, mm or inches or any other scale as long as its consistent) then mark them off and square the diagonal marks along to the drawer end. Try to work it out by arithmetic and you'll take ten times as long and introduce errors.
(* NB: purists will recognise that in fact you don't go to exactly the top/bottom edges, but to allow for half-pins you first gauge lines a few mm down/up from the edges, then cant your dividing scale between these two inset lines.)
You can of course use your iPhone instead, but I'd suggest you tippex a scale on the back first!
(* NB: purists will recognise that in fact you don't go to exactly the top/bottom edges, but to allow for half-pins you first gauge lines a few mm down/up from the edges, then cant your dividing scale between these two inset lines.)
You can of course use your iPhone instead, but I'd suggest you tippex a scale on the back first!
nigelmercier
RIP
- Joined
- 20 Jun 2007
- Messages
- 16,234
- Location
- Live in Kent, boat in Canary Islands
I've never seen the need for this calculation other than in my YM SB exam, I just use my plotter. However it occurs to me that we are very familiar with a scale divided into 6 (actually 60) on a clock face.
lw395
Well-Known Member
Ever since I've started watching real time tide gauges, I've realised the precision is a bit of a joke.
But I value having a fair idea of the concepts.
But I value having a fair idea of the concepts.
snowleopard
Well-Known Member
Ah but in the exam would you fail because your not following "the method"
Some RYA examiners insist on the 'approved' method, others are happy with any method provided you understand it and it works. A friend and I sailed with a lady from this forum when she was preparing for her YM practical. She had a problem with MOB under sail so I confidently breezed in and said 'this is how you do it' - and failed miserably. Below a certain speed the keel stalled and the bow blew off resulting in missing the casualty by half a length. My friend, a YM instructor, couldn't do it either. We then tried her method of a crash tack to hove to. It worked every time but the examiner had seen that and said 'now let's see you do it the correct way' which of course she couldn't.
Then there was the argument I had on here about how to calculate a tidal stream. I do it using tidal stream diagrams while he insisted there was only one correct way - via the diamonds on an Admiralty chart. It went a bit quiet when I demonstrated that could result in the stream flowing across a river.
My tip - use your own method but be able to show you know the 'official' way.
p.s. In my school days I carried one of these:
Look closely - it's a 10" scale on a 5" body. Slightly more cumbersome to use as you sometimes have to use the cursor to get to the other side of the slide but it had the great virtue of being pocket size without loss of accuracy.
Last edited:
Neil
Well-Known Member
I have
The bottom one looks like my British Thornton. I pulled it out the other day (the slide rule, that is) and still remembered how to use it, at least the basics. If I ever get time, I'll try using it in anger........
Fantasie 19
Well-Known Member
onesea
Well-Known Member
Does not give one much confidence going for the exam, given an exam like that you have to know "the method" or you may fail...
Myself dad and mum bored waiting for the tide one day decided to have ago at some basic MOB procedures on thier motorsailer, all 3 of us did different ways but got back to the target. We then discussed which was best and quickest we could not agree, we all got the casualty to where we had pre-decided windward midships...
Second time round we did it again with a timer running. Result we all got back to the casualty within 10 seconds of each other, it was decided it was draw!
My thought is there is so rarely one right answer that any single method is going to be wrong at some point..
+1 The last time I calculated a tide in anger was when I just passed my YM, going into Conway. I had calculated my tides for the bar and we where waiting for the tide, then a local boat with about the same draft steamed straight in at 6 knots.
We followed cautiously and where never under a couple of feet :encouragement:. We promptly spend the night aground in a marina which they said was dredged to 2 meters (they said its just the sediment playing havoc with our depth gauge)... Where in-fact there was about 3 foot of water and 1 meter of soft mud. Luckily we always shut the engine seacock on that boat so no harm done.
Now I just take the view is it worth waving my keel in that harbor....
Skylark
Well-Known Member
I have
Very nice!
I still have the Thornton's slide rule and a Boots pocket one, too.
How about Murdock & Barnes Statistical Tables?
First year end of year degree exams was slide rule and tables but by the following year, 1976 IIRC, the Dean had capitulated and we all bought Commodore scientific calculators. Still have mine in its box somewhere.
Neil
Well-Known Member
The one time I needed to do it, I calculated there should have been 2m at LW and I went into Malahide at about 1.5 - 2 hr before LW and promptly ran aground just inside the safe water mark.......
Skylark
Well-Known Member
Sounds like your calculations were pretty much correct? There are 0.2m soundings very close to the SWM. Dublin MLWS is 0.7m with 3.4m range. MLWN is 1.5m with 1.9m range. Malahide is -0.2m and-0.4m respectively. Brave to enter that early
Neil
Well-Known Member
I did mean to get there earlier, and I knew I was pushing it, but saw a boat my size charging out......on the other hand, the bottom around the entrance does shift quite a bit, apparently.
Other threads that may be of interest
