GPS COMPUTER VS SEXTANT/ASTROLABE/Old ways/manual

[SmithDoor]

40 years ago when we were sailing in the windward islands with a skipper on a 44 footer we went to go scuba diving on a sunken British (wooden) gunboat. We were at least 3/4 mile out from the nearest island and in 6ft swells. Our skipper told my brother to get ready to drop anchor when he said. We bobbed along with him him at the wheel looking (sighting) here on this island, there on that island then eventually he said "DROP ANCHOR". He said "the boat should be somewhere in the area down there". We donned our scuba suits, went in and followed the anchor line down. The damn line was wrapped around the bow of the boat. I was blown away by his "Dead Reckoning".

Later that trip walking on the north side beach of Pitite St Vincent I had the crap scared out of me so bad I hit the deck when suddenly, and with no advance warning, over the mountain an American Apache attack helicopter came screaming down 20ft over my head and headed out 6ft over the water off the beach weaving from boat to boat - they were on patrols looking for Cuban gun running since the Grenada Invasion was on.

Do you remember what he use for calculating the dead reckoning?

Dave

 

[Daryl_bee]

He was just triangulating, by sight, points on different islands. He'd been piloting boats in that area since he was a kid. It was very smart of us to have him. He was a tremendously fun guy but brought a huge wealth of knowledge, not only of sailing but intimate knowledge of the entire area - from the sea bottom to the best bars. I remember being below decks eating breakfast one morning and a call came on the radio from another vessel "CSY - CSY...blah blah blah We've struck a reef". A coast guard ship had to be sent out to pull them off (at the time $5000min). They had gone bare boat (no skipper) and ours said smiling "I don't think they'll get their deposit back". Apparently not everything was marked on the nautical charts.

He also set us up for one of the most exciting things I've ever done in my life (and I've done a lot). We went from Admiralty Bay in Bequia to Mustique (where Mick Jagger's place is) but through two old whaling islands. The Islands form a funnel shape facing the open Atlantic and full size ocean waves enter but have no place to go but swell up into ginormous waves. He warned us to get ready. You enter the narrows calmly but within minutes the waves get inexorably bigger and bigger with the wind picking up even stronger until this 45 footer was angling up and down at +/-30°, every time coming down with a thundering crash and shudder that you thought surely the boat might break apart. Everybody was holding on for dear life to whatever they could find at hand. Then, as gradually as it built up, it eventually calmed back down but all of us were then talking at 90 mph about it as we were all so hyped up on adrenaline.

 

[SmithDoor]

He was just triangulating, by sight, points on different islands. He'd been piloting boats in that area since he was a kid. It was very smart of us to have him. He was a tremendously fun guy but brought a huge wealth of knowledge, not only of sailing but intimate knowledge of the entire area - from the sea bottom to the best bars. I remember being below decks eating breakfast one morning and a call came on the radio from another vessel "CSY - CSY...blah blah blah We've struck a reef". A coast guard ship had to be sent out to pull them off (at the time $5000min). They had gone bare boat (no skipper) and ours said smiling "I don't think they'll get their deposit back". Apparently not everything was marked on the nautical charts.

He also set us up for one of the most exciting things I've ever done in my life (and I've done a lot). We went from Admiralty Bay in Bequia to Mustique (where Mick Jagger's place is) but through two old whaling islands. The Islands form a funnel shape facing the open Atlantic and full size ocean waves enter but have no place to go but swell up into ginormous waves. He warned us to get ready. You enter the narrows calmly but within minutes the waves get inexorably bigger and bigger with the wind picking up even stronger until this 45 footer was angling up and down at +/-30°, every time coming down with a thundering crash and shudder that you thought surely the boat might break apart. Everybody was holding on for dear life to whatever they could find at hand. Then, as gradually as it built up, it eventually calmed back down but all of us were then talking at 90 mph about it as we were all so hyped up on adrenaline.

---

Bad. Hight lite between brackets for answer { Sounds like a %&*%% }

Dave

Sorry I am just joking.and that is a bad one
I have had a lot flights that was worrst. Just fun of flying NOT.

 

[SmithDoor]

Here is a 1919 Bubble Sextant/Octant used on aircraft and ground.

With manual too.

Dave

 

[around]

Thank for information

What is the high speed of currents on ocean?

From 10,000 feet [3,000M] or more look flat like a bath tub and very still water.

Dave

FYI
I like paper chart/maps and have Google map for printing maps. I still like old fashion maps and charts are better. Most even 50 years ago did not like the learning how to read maps or just did not bother. A lot of lost people back then . Still today try saying TURN NORTH ON.

Dave,

Currents can vary from 1 to 5 knots in the open ocean. For a large ship travelling at 22 kts this is a small impact compared to say a 150 kt Jet Steam on an aircraft travelling at 450 kts.

The Gulf Steam is normally viewed as the fastest ocean current at 5 kts but is confined to a very narrow band. The Antarctic Circumpolar Current is viewed as the most “powerful” at 2 kts but covering a very wide area, Near shore tidal currents can be much higher but fluctuate widely with time.

Cheers,

Adrian

 

[SmithDoor]

Dave,

Currents can vary from 1 to 5 knots in the open ocean. For a large ship travelling at 22 kts this is a small impact compared to say a 150 kt Jet Steam on an aircraft travelling at 450 kts.

The Gulf Steam is normally viewed as the fastest ocean current at 5 kts but is confined to a very narrow band. The Antarctic Circumpolar Current is viewed as the most “powerful” at 2 kts but covering a very wide area, Near shore tidal currents can be much higher but fluctuate widely with time.

Cheers,

Adrian

Thank
Ship speeds to slow for E6B

Do you know what ships/Navy used ?

Dave

 

[SmithDoor]

History on E6B computer a 1930's miracle.

⸻⸻⸻⸻⸻⸻

The device's original name is E-6B, but is often abbreviated as E6B, or hyphenated as E6-B for commercial purposes.

The E-6B was developed in the United States by Naval Lt. Philip Dalton (1903–1941) in the late 1930s. The name comes from its original part number for the U.S Army Air Corps, before its reorganization in June 1941.

Philip Dalton was a Cornell University graduate who joined the United States Army as an artillery officer, but soon resigned and became a Naval Reserve pilot from 1931 until he died in a plane crash with a student practicing spins. He, with P. V. H. Weems, invented, patented and marketed a series of flight computers.

Dalton's first popular computer was his 1933 Model B, the circular slide rule with true airspeed (TAS) and altitude corrections pilots know so well. In 1936 he put a double-drift diagram on its reverse to create what the U.S. Army Air Corps (USAAC) designated as the E-1, E-1A and E-1B.

A couple of years later he invented the Mark VII, again using his Model B slide rule as a focal point. It was hugely popular with both the military and the airlines. Fred Noonan, Amelia Earhart's navigator on her attempted circling of the globe, used one on their last flight. Dalton felt that it was a rushed design, and wanted to create something more accurate, easier to use, and able to handle higher flight speeds.

Closeup photo of a cardboard E6B
So he came up with his now famous wind arc slide, but printed on an endless cloth belt moved inside a square box by a knob. He applied for a patent in 1936 (granted in 1937 as 2,097,116). This was for the Model C, D and G computers widely used in World War II by the British Commonwealth (as the "Dalton Dead Reckoning Computer"), the U.S. Navy, copied by the Japanese, and improved on by the Germans, through Siegfried Knemeyer's invention of the disc-type Dreieckrechner device, somewhat similar to the eventual E6-B's backside compass rose dial in general appearance, but having the compass rose on the front instead for real-time calculations of the wind triangle at any time while in flight. These are commonly available on collectible auction web sites.

The U.S. Army Air Corps decided the endless belt computer cost too much to manufacture, so later in 1937 Dalton morphed it to a simple, rigid, flat wind slide, with his old Model B circular slide rule included on the reverse. He called this prototype his Model H; the Army called it the E-6A.

In 1938 the Army wrote formal specifications, and had him make a few changes, which Weems called the Model J. The changes included moving the "10" mark to the top instead of the original "60". This "E-6B" was introduced to the Army in 1940, but it took Pearl Harbor for the Army Air Forces (as the former "Army Air Corps" was renamed on June 20, 1941) to place a large order. Over 400,000 E-6Bs were manufactured during World War II, mostly of a plastic that glows under black light (cockpits were illuminated this way at night).

The base name "E-6" was fairly arbitrary, as there were no standards for stock numbering at the time. For example, other USAAC computers of that time were the C-2, D-2, D-4, E-1 and G-1, and flight pants became E-1s as well. Most likely they chose "E" because Dalton's previously combined time and wind computer had been the E-1. The "B" simply meant it was the production model.

The designation "E-6B" was officially marked on the device only for a couple of years. By 1943 the Army and Navy changed the marking to their joint standard, the AN-C-74 (Army/Navy Computer 74). A year or so later it was changed to AN-5835, and then to AN-5834 (1948). The USAF called later updates the MB-4 (1953) and the CPU-26 (1958), but navigators and most instruction manuals continued using the original E-6B name. Many just called it the "Dalton Dead Reckoning Computer", one of its original markings.

Frontside of the military 6B/345 Backside of the military 6B/345


For
more on this visit
https://en.m.wikipedia.org/w/index.php?title=E6B&wprov=rarw1

Dave

 

[around]

Thank
Ship speeds to slow for E6B

Do you know what ships/Navy used ?

Dave

Dave,

This was my last at-sea command:

https://en.wikipedia.org/wiki/HMCS_Algonquin_(DDG_283)

Now the primary major surface combatant in the Canadian navy is the Canadian Patrol Frigate:

https://en.wikipedia.org/wiki/Halifax-class_frigate

Cheers,

Adrian

 

[SmithDoor]

Dave,

This was my last at-sea command:

https://en.wikipedia.org/wiki/HMCS_Algonquin_(DDG_283)

Now the primary major surface combatant in the Canadian navy is the Canadian Patrol Frigate:

https://en.wikipedia.org/wiki/Halifax-class_frigate

Cheers,

Adrian

Nice looking ship
Look like it was fun

Dave

 

[ShopShoe]

SmithDoor and Friends,

I was reading an account of the pre-WWII submarines, and came across a description of a device that was also a paper "computer" referred to as an "Is-Was" that was used to project location from known historical sub position data. I think that was replaced by the torpedo-setting mechanical computers and plotters used in WWII. Do you know anything about that?

--ShopShoe

 

[SmithDoor]

SmithDoor and Friends,

I was reading an account of the pre-WWII submarines, and came across a description of a device that was also a paper "computer" referred to as an "Is-Was" that was used to project location from known historical sub position data. I think that was replaced by the torpedo-setting mechanical computers and plotters used in WWII. Do you know anything about that?

--ShopShoe

What little I know is they take submarines to Panama Canal
Cut a hole in the sub and place inside the submarines.
It used cams and gears and did good job of hitting the other sides ships.

The Airforce on the B29 had tub type for bombing. Used 37 tubes. I do not any else.

{The tubes at time could have multiple grids in side. This is like having 3 or 4 transistors in a tube and is analog.
To convert from analog to digital takes a lot of transistors.
Today it takes a IC chip to do same job. }.
It is amazing what did back in ww2.

Dave

 

[SmithDoor]

Here is a working sliderule on the internet.
This my drafting sliderule. Note leather case at top

Closeup in Black & White⁰ for better view

https://sliderulemuseum.com/VirtualSR2/react/hemmi_versalog_ii.html

 

[SmithDoor]

Dave,

Currents can vary from 1 to 5 knots in the open ocean. For a large ship travelling at 22 kts this is a small impact compared to say a 150 kt Jet Steam on an aircraft travelling at 450 kts.

The Gulf Steam is normally viewed as the fastest ocean current at 5 kts but is confined to a very narrow band. The Antarctic Circumpolar Current is viewed as the most “powerful” at 2 kts but covering a very wide area, Near shore tidal currents can be mu

ch higher but fluctuate widely with time.

Cheers,

Adrian

Here a online similar for E6B that goes to the Navy speeds too.

Works great you see what current will do to a ship.

Remember current speed directions use wind speed and direction

https://e6bx.com/e6b-simulator/

 

[SmithDoor]

Fun Facts ​

St. Elmo's fire (also called witchfire or witch's fire)[1] is a weather phenomenon in which luminous plasma is created by a corona discharge from a rod-like object such as a mast, spire, chimney, or animal horn[2] in an atmospheric electric field.

It has also been observed on the leading edges of aircraft,
as in the case of British Airways Flight 009, and by US Air Force pilots.[3]

Illustration of St. Elmo's fire
on a ship at sea

Electrostatic discharge flashes across the windscreen of a KC-10 cockpit.

The intensity of the effect, a blue or violet glow around the object, often accompanied by a hissing or buzzing sound, is proportional to the strength of the electric field and therefore noticeable primarily during thunderstorms or volcanic eruptions.

St. Elmo's fire is named after St. Erasmus of Formia (also known as St. Elmo), the patron saint of sailors. The phenomenon, which can warn of an imminent lightning strike,[4] was regarded by sailors with awe and sometimes considered to be a good omen.[5]
⸻⸻⸻⸻⸻⸻
Cause

St. Elmo's fire is a reproducible and demonstrable fo

rm of plasma. The electric field around the affected object causes ionization of the air molecules, producing a faint glow easily visible in low-light conditions.

Conditions that can generate St. Elmo's fire are present during thunderstorms, when high-voltage differentials are present between clouds and the ground underneath. A local electric field of about 100 kV/m is required to begin a discharge in moist air. The magnitude of the electric field depends greatly on the geometry (shape and size) of the object. Sharp points lower the necessary voltage because electric fields are more concentrated in areas of high curvature, so discharges preferentially occur and are more intense at the ends of pointed objects.

The nitrogen and oxygen in the Earth's atmosphere cause St. Elmo's fire to fluoresce with blue or violet light; this is similar to the mechanism that causes neon lights to glow, albeit at a different colour due to the different gas involved.[7]

In 1751, Benjamin Franklin hypothesized that a pointed iron rod would light up at the tip during a lightning storm, similar in appearance to St. Elmo's fire.[8][9]

In an August 2020 paper, researchers in MIT's Department of Aeronautics and Astronautics demonstrated that St. Elmo's fire behaves differently in airborne objects versus grounded structures. They show that electrically isolated structures accumulate charge more effectively in high wind, in contrast to the corona discharge observed in grounded structures.[10][11]

⸻⸻⸻⸻⸻⸻

 

[SmithDoor]

Fun fact on
Japanese Torpedoes


I found internet on American vs Japanese 1930s and 1940's.
Fun engine to build too.
The other not in artical by time of ww2 American had a new Explosive Charge 1.5 time of Japanese so the Mark 15 825 pound compair to Japanese is 1,400 pounds . ​

At the outbreak of the war, the Japanese Navy possessed some of the world's finest torpedoes, including the fabled Long Lance. The quality of these weapons was no accident, but rather the result of Japan's intensive efforts during the 1920's and 30's to make good the shortcomings of her battle fleet. Laboring as she did under the unfavorable 5:5:3 ratio of capital ships imposed by the Washington Naval Treaty, Japan would most likely be at a disadvantage in any Pacific conflict with the United States. She also knew well enough that the U.S. modeled its fighting doctrine on the famous 'Plan Orange', which called for an advance of the American battle fleet across the Pacific to relieve the Phillipines. It was anticipated that at some location in the Western Pacific a decisive battle would be fought. In Japan's view, some means must be found to offset its disadvantage in capital ships before this battle occurred, or its inferior batle line would be destroyed by the American force. Torpedo tactics and night combat were seized upon as one way to whittle down the American battle line as it made its way across the Pacific. Accordingly, Japan worked diligently to develop the tactics needed to implement this new doctrine, and also to create the weapons with which to carry it out. The result was that Japanese torpedoes showed a steady progression of improvements throughout the 1930's, culminating in the devlopment of the famous 'Long Lance' in 1935.
Designing and perfecting the Long Lance required solving some extremely difficult technical problems, most of which centered around the usage of pure oxygen as a fuel (rather than compressed air). Compressed air is nearly 77% nitrogen, which is useless for combustion, and also contributes to the visibility of the torpedo by leaving a bubble track on the surface. The usage of pure oxygen promised far greater power and propulsive efficiency, but it came with certain costs. The most glaring of these was how to use pure oxygen safely aboard a ship or submarine, given its inherently inflammable nature. Premature detonation of the torpedo upon firing was also a problem. However, the Japanese overcame these hurdles. Further, through meticulous live-testing of their weapons against ship targets, they perfected a warhead detonator that was rugged and reliable (The U.S. Navy's BuOrd could certainly have taken a lesson or two here). The resulting weapon, the Type 93 torpedo, was fantastically advanced in comparison with its Western counterparts, possessing an unequaled combination of speed, range, and hitting power. This weapon, coupled with the flexible battle tactics practiced by Japan's cruisers and destroyers, led to victory after victory in the early stages of the war. Only as American radar and gunfire control became increasingly sophisticated would the Japanese advantage in night battles begin to disappear, and even then a Long Lance-armed Japanese destroyer was still a thing to be feared.


Ship and Submarine Torpedoes

Model	Diameter	Length OA	Total Weight	Explosive Charge	Range	Wander (max)	Comments
6th Year Type	21"	22' 5"	3157 lbs.	441 lbs.	7,000m @ 36 kts 10,000m @ 32 kts 15,000m @ 26 kts​	?	An older torpedo still used in some of the older RO-class submarines.​
8th Year Type	24"	27' 7"	5207 lbs.	761 lbs.	10,000m @ 38 kts 15,000m @ 32 kts 20,000m @ 28 kts​	?	A large conventional wet-heater torpedo still used aboard some older cruisers and destroyers, notably Nagara.​
Type 92	21"	23' 5"	3792 lbs.	661 lbs.	7000m @ 30 kts​	120m / 7,000m	An electric torpedo for submarines, used extensively throughout the war.​
Type 93	24"	29' 6"	5952 lbs.	1080 lbs.	20,000m @ 48 kts 32,000m @ 40 kts 40,000m @ 36 kts​	500m / 20,000m 1000m / 32,000m 1500m / 40,000m	The Long Lance. 'Nuff said.​
Type 95	21"	23' 5"	3671 lbs.	893 lbs.	9,000m @ 49 kts 12,000m @ 45 kts​	170m / 9,000m 250m / 12,000m	A smaller version of the Type 93 intended for submarines.​
Type 97	17.7"	18' 5"	2161 lbs.	772 lbs.	5,500m @ 44 kts​	80m /5,500m	A miniaturized Type 93 intended for midget submarines. Very unsuccesful (its oxygen flasks leaked a lot), it was used operationally only once - at Pearl Harbor.​

Just for giggles, let's take a look at the statistics on the standard US Navy destroyer torpedo of the war, the Mark 15.

Model	Diameter	Length OA​	Total Weight	Explosive Charge	Range	Max Launch Speed	Comments
Mark 15	21"	24' 0"	3841 lbs.	825 lbs.	5,500m @ 45 kts 9,150m @ 33 kts 13,700m @ 26 kts​	?	​

Bottom line: the US fish had a decent-sized warhead, but nowhere near the range of the Long Lance, and the reliability


Airborne Torpedoes
I'm not really an expert on Japan's airborne torpedoes, so I don't have much in the way of enlightenment to dole out on the subject. I mean, they worked, and went 'Boom' and so on. The Japanese managed to deploy them in some pretty interesting places, most notably in Pearl Harbor, where the shallow depth of the water necessitated the modification of the existing torps with wooden fins so as to as make them dive less deeply upon entry into the water.

Model	Diameter	Length OA	Total Weight	Explosive Charge	Range	Max Launch Speed	Comments
Type 91 Mod 1	17.7"	17' 4"	1728 lbs.	331 lbs.	2000m @ 41 kts​	260 kts.	An older torpedo that was still being used in some land-based JNAF torpedo-bomber squadrons at the beginning of the war, including some of the units ('Nells') which attacked and sank Repulse and the Prince of Wales.​
Type 91 Mod 2	17.7"	18' 0"	1841 lbs.	452 lbs.	2000m @ 41 kts​	260 kts.	First deployed in April, 1941. Carried by the 'Kate' torpedo bombers which attacked Pearl Harbor.​
Type 91 Mod 3	17.7"	17' 4"	1872 lbs.	529 lbs.	2000m @ 41 kts​	260 kts.	First deployed in mid- to late-1942.​
Type 91 Mod 3 Improved	17.7"	17' 4"	1889 lbs.	529 lbs.	2000m @ 41 kts​	300 kts.	First deployed in 1943. Strengthened to allow higher launch speeds.​
Type 91 Mod 3 Strong	17.7"	17' 4"	1872 lbs.	529 lbs.	1500m @ 41 kts​	350 kts.	First deployed in 1944. Strengthened to allow higher launch speeds.​
Type 91 Mod 4 Strong	17.7"	17' 4"	2030 lbs.	679 lbs.	1500m @ 41 kts​	350 kts.	First deployed in 1944.​
Type 91 Mod 7 Strong	17.7"	18' 9"	2319 lbs.	926 lbs.	1500m @ 41 kts​	350 kts.	First deployed in 1944.​

Here's an interesting (if a little bit beaten up) picture of the 'Kate' which finished off the already damaged USS Hornet on October 24, 1942. The splash of the torpedo (which most likely would have been a Type 91 Mod 2 or 3) can be seen at the lower right. This weapon struck Hornet at 1523 hours, and ended any hopes of saving her. (Scanned from Frank, "Guadalcanal")

some artical was short because it is to big

Dave

 

[SmithDoor]

SmithDoor and Friends,

I was reading an account of the pre-WWII submarines, and came across a description of a device that was also a paper "computer" referred to as an "Is-Was" that was used to project location from known historical sub position data. I think that was replaced by the torpedo-setting mechanical computers and plotters used in WWII. Do you know anything about that?

--ShopShoe

I just post on Japanese vs the USA torpedoes.
It does not tell hole story but good reading. Here link to site
http://www.combinedfleet.com/torps.htm

What is interesting is how American used mechanical computers and tube computers vs Japanese and Germany.
They did have there computers like the E6B and specialized slide rules.
FYI I done with sliderule what E6B does something fun when going to school.
In photograph I have made my own slide rule foe developing time and temperature handy to have.

Dave