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| Woodworking (rec.woodworking) Discussion forum covering all aspects of working with wood. All levels of expertise are encouraged to particiapte. |
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#1
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HOW TO FIND LONGITUDE WITH YOUR VIKING SHIELD
http://www.sjolander.com/viking/sketches/shield/body/
I enjoyed the thread on plywood armour so much, decided to post something more in the same vein. Everyone already knows that Viking shields were made with wood. Doesn't everyone? Well, if you didn't, you do now. So, I'm not posting shield plans. I hope that as soon as you finish your longitudef inding shield you will post pictures. I'll be waiting with bated breath. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews |
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#2
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The recommended method quickly gets into trouble. A swinging pendulum on a
moving boat, with pitch, roll and yaw accelerations, isn't a reliable measure of time. See: Longitude : The True Story Lone Genius Who Solved Greatest Scientific Problem his Time by Dava Sobel. Steve "J T" wrote in message ... http://www.sjolander.com/viking/sketches/shield/body/ I enjoyed the thread on plywood armour so much, decided to post something more in the same vein. Everyone already knows that Viking shields were made with wood. Doesn't everyone? Well, if you didn't, you do now. So, I'm not posting shield plans. I hope that as soon as you finish your longitudef inding shield you will post pictures. I'll be waiting with bated breath. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews |
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#3
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On Sun, 01 May 2005 18:28:29 GMT, Steven and Gail Peterson
wrote: The recommended method quickly gets into trouble. A swinging pendulum on a moving boat, with pitch, roll and yaw accelerations, isn't a reliable measure of time. See: Longitude : The True Story Lone Genius Who Solved Greatest Scientific Problem his Time by Dava Sobel. I thought the Vikings sailed by latitude alone, hoping their food would last until they got to Nova Scotia (whichever name they called it) |
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#4
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#5
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Charles Krug wrote:
On Sun, 01 May 2005 18:28:29 GMT, Steven and Gail Peterson wrote: The recommended method quickly gets into trouble. A swinging pendulum on a moving boat, with pitch, roll and yaw accelerations, isn't a reliable measure of time. See: Longitude : The True Story Lone Genius Who Solved Greatest Scientific Problem his Time by Dava Sobel. I thought the Vikings sailed by latitude alone, hoping their food would last until they got to Nova Scotia (whichever name they called it) While they didn't have the compass, they did have a Sun compass which would tell them where North was during the day. it was a sundial used in reverse. They didn't really sail by latitude becasue they had no angular measurement instrument to tell them what latitude they were on. The Arabs did (Kamal), but the Vikings hadn't seen that. -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#6
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Call me obtuse, but if I was going to build meself a precision measuring
instrument, upon which my life might depend, I don't think I'd build it into the edge of something that another guy was going to whackin' some sharp metal bits into. Then again, a helmet would look pretty bitchin' with a sextant bolted to the top. -Tim "Charles Krug" wrote in message ... On Sun, 01 May 2005 18:28:29 GMT, Steven and Gail Peterson wrote: The recommended method quickly gets into trouble. A swinging pendulum on a moving boat, with pitch, roll and yaw accelerations, isn't a reliable measure of time. See: Longitude : The True Story Lone Genius Who Solved Greatest Scientific Problem his Time by Dava Sobel. I thought the Vikings sailed by latitude alone, hoping their food would last until they got to Nova Scotia (whichever name they called it) |
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#7
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On 1-May-2005, gregg wrote: The Arabs did (Kamal), but the Vikings hadn't seen that. The Vikings had made it at least as far as Constantinople. I would have guessed they had seen the kamal. Mike |
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#8
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#9
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Michael Daly wrote:
On 1-May-2005, gregg wrote: The Arabs did (Kamal), but the Vikings hadn't seen that. The Vikings had made it at least as far as Constantinople. I would have guessed they had seen the kamal. Mike Well yes but that was late in the "Viking Age" as I recall. But when they made their voyages West, it was without anythign but a Sun Compass. -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#10
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J T wrote:
Mon, May 2, 2005, 4:56am (EDT+4) (Michael Daly) The Vikings had made it at least as far as Constantinople. I would have guessed they had seen the kamal. Probably. But, as I understand it, a kamea was used to determine star positions. The Kamal was used to determine whether or not you had reached a latitude. It is essentially a piece of wood with a hole in the center. In this hole was a string - stopped at one end. You can see a picture of one on my web page below. You pre-calibrated it at your destination: You held it up to your eye and moved it out until the bottom edge was on the horizon and the top edge was on, say, the North star. you place a knot in the string such that that was the distance the kamal was from your eye when you held the knot behind yoru front teeth. Now it's calibrated for that destination. You cna put a knot in fro several. So when you left a port and headed TO one of those destinations, you ran North or South until the North Star and horizon was lined up with that knot behind your teeth. Then you hung a left or right to get into port. If the run was a long one you kept checking to be sure you maintained that latitude., Sun compass and kamal were supposedly developed around the same time, anyway. Both used to determine latitude. the Sun Compass was not used to determine your latitude, as I understand it. it was used to figure out which way was North. It was essentially a sundial used in reverse. Basically, they would head north, or south, until they got to the latitude of their destination, then turn, and sail to it - simple, effective. Longitude wasn't able to be accurately determined until the 17th century. Agreed with the above paragraph. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#11
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How to find longitude with this shield. While sailing, longitude may be found in the following manner: 1. Find noon to find midnight. Using a piece of wood with a straight hole bored in it. This hole would need to be large enough so that the Vikings could sail as far north as they wished and the hole would still let daylight pass thru at the noon hour. This piece of wood needs to be suspended such that the hole is at 90 degrees to the center of the earth. In other words, the piece of wood needs to be flat with the surface of the earth. However since we are on a heeling boat, we can not just lay this piece of wood on the deck. I think suspending it by three strings would do. Held by a person so as to dampen all rocking motion on the piece of wood. Thus to find noon with this hole we need to start counting as soon as any sun starts to pass thru the hole. Then stop counting when the sun stops passing thru the hole. Half way between these two times is exactly noon. Now to use this information to find midnight is as follows. When the sun starts to shin thru the hole, the man of the watch starts to count EVERY OTHER SWING of the pendulum. Thus the number of swings counted is exactly the count from noon to when the sun stops passing thru the hole. Which is exactly what we want. Now to continue. When the sun stops passing thru the hole the man on the watch starts to count EVERY SWING of the pendulum. He continues this count until he reaches his midnight total count. end quote This clearly depends on the use of a pendulum to measure time, which is the problem that prevented anyone from determining longitude until Harrison invented a clock that was sufficiently accurate and stable, free from inaccuracy due to ship motion. His invention allowed the British a great advantage in marine navigation, both Naval and commercial, until others figured it out too. Steve "J T" wrote in message ... Sun, May 1, 2005, 6:28pm (EDT+4) (Steven and Gail Peterson) burbled: The recommended method quickly gets into trouble. A swinging pendulum on a moving boat, with pitch, roll and yaw accelerations, isn't a reliable measure of time. See: Longitude : The True Story Lone Genius Who Solved Greatest Scientific Problem his Time by Dava Sobel. Hmmm. I would suggest you go back to the link, and reread it very carefully. Then think about what you read. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews |
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#12
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#13
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J T wrote:
Mon, May 2, 2005, 4:53am (gregg) says: snip the Sun Compass was not used to determine your latitude, as I understand it. it was used to figure out which way was North. It was essentially a sundial used in reverse. snip Easy enough to find north without any gadgets. At sea? During the Day? The Sun Compass was used to determine True North, which is a bit trickier. I have to disagree - the Vikings weren't aware of magnetic variation. They had no magnetic compass. They didn't know there was True vs Magnetic North. And, apparently was "set" for a specific latitude. It was marked out at a specific latitude, yes. They had no math to mark the Sun Compass out without using the sun in the first place. So, like the Kamal it was calibrated for latitudes. So, if you wanted that latitude, you could use a Sun Compass to find it. How? What actions were taken with ta sun compass to determine your latitude? Another latitude, another Sun Compass. Supposedly is was within a few degrees as accurate as a magnetic compass - which is not bad for those times. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#15
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I'm thinking this thread is getting bogged down. I think you
should all go back and read the site again. Four years to complete it? Count every other pendulum swings from noon to noon? Then that number of swings is the time from noon to midnight? Yah, right. First that would assume the count was started, and ended, at true noon. And, the counter didn't lose count, etc., etc., and a lot of other stuff. Whan I found the site, I read it. Then read it again. Then I started ROTFLMAO. It all might work on dry land, but on a ship, at sea? I don't buy it. Personally I think it's all just a big joke. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews |
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#16
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J T wrote:
Tue, May 3, 2005, 4:57am (gregg) advises: At sea? During the Day? snip They had no magnetic compass. They didn't know there was True vs Magnetic North. snip Yeah, at sea, during the day. You wait until the sun is at it's highest, you look at a shadow, the shadow points north. Then you point, and say, "Hey, that way's north". Simple. However, not exactly precise. The Vikings didn't need to know about "True North", what they needed was a consistent reference point, this allow them to have just that. You conveniently snipped the essential part of the question. You said they used the Sun compass to find variation. Tellme how they used the Sun compass to find the variation. Yes they DID use it to find True North - but that's what I've been telling you for 2 days now Toward the end of the Viking age, they did have access to magnetic compasses. Check this. http://members.aol.com/jvlambert/Norman/SunCompass.htm JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#17
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J T wrote:
Tue, May 3, 2005, 4:57am (gregg) advises: At sea? During the Day? snip They had no magnetic compass. They didn't know there was True vs Magnetic North. snip Yeah, at sea, during the day. You wait until the sun is at it's highest, you look at a shadow, the shadow points north. Then you point, and say, "Hey, that way's north". Simple. However, not exactly precise. The Vikings didn't need to know about "True North", what they needed was a consistent reference point, this allow them to have just that. No. You snipped out the REAL question that was posed to you. But here it is: You said: Easy enough to find north without any gadgets. To which I asked: At sea? During the Day? Explain to me HOW they found Norht WITHOUT ANY GADGETS... Bear in mind that the Viking Sun Compass is...a GADGET. Next you said: The Sun Compass was used to determine True North, which is a bit trickier. Trickier than WHAT? I've been telling you that the Vikings used the Sun compass to find North, now for two days. The "North" it finds is True North. It's not "trickier"...it's only "trickier" to find True North *IF* you are using a magnetic compass. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#18
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#19
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J T wrote:
Tue, May 3, 2005, 6:02pm (gregg) burbled: No. You snipped out the REAL question that was posed to you. But here it is: You said: Easy enough to find north without any gadgets. To which I asked: At sea? During the Day? Explain to me HOW they found Norht WITHOUT ANY GADGETS... Bear in mind that the Viking Sun Compass is...a GADGET. Next you said: The Sun Compass was used to determine True North, which is a bit trickier. Trickier than WHAT? I've been telling you that the Vikings used the Sun compass to find North, now for two days. The "North" it finds is True North. It's not "trickier"...it's only "trickier" to find True North *IF* you are using a magnetic compass. Nah, I answered the "real" question. You just ignored the answer. I said (and you copied it): "Yeah, at sea, during the day. You wait until the sun is at it's highest, Explain to me how you know the Sun is at it's highest....without a gadget... you look at a shadow, the shadow points north. Then you point, and say, "Hey, that way's north"." WHICH IS USING A GADGET...which is in direct contradiction to what you said: Easy enough to find north without any gadgets. See. Simple, no gadgets. A bit vague perhaps, but still north. The Viking Sun Compass is not a gadget? Perhaps you would have understood if I'd said "more accurate", instead of "trickier", or maybe you're just nit-picking. No I'm trying to make sense of what you are saying which is very difficult. -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#21
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J T wrote:
Wed, May 4, 2005, 5:52pm (gregg) burbled: Explain to me how you know the Sun is at it's highest....without a gadget... WHICH IS USING A GADGET...which is in direct contradiction to what you said: The Viking Sun Compass is not a gadget? No I'm trying to make sense of what you are saying which is very difficult. Just for the Hell of it, I'll run thru it quickly, with no anticipation of you claiming understanding. Like anyone else, I would look at the sun, and decide when it was at it's highest. Of course, that would probably be a bit inaccurate. No biggie, it would all balance out in the end. HOW woudl you decide it was at it's highest? How would you "look at it"? I would have said no gadget, but apparently you're now claiming shadows and fingers are gadgets. No I'm saying a Sun Compass is a gadget. I already clearly stated that a Sun Compass "is" a gadget, so you can't read, or what? You haven't stated anything clearly. Nope, I don't buy that, I think you do understand. I considered the possibility you're really that obtuse, but decided probably not. Rather, I figure my earlier suspicion is correct, that you're just playing silly buggers. So, since you're claiming fingers are gadgets, I have a question for you. I have five gadgets, which one am I holding up? Answer: the one stuck up your nose, since I never said fingers are gadgets. Enough. You are trying too hard to cover up what was probably only lousy language. JOAT A highbrow is a person educated beyond his intelligence. - Brander Matthews -- Saville Replicas of 15th-19th century nautical navigational instruments: http://home.comcast.net/~saville/backstaffhome.html Restoration of my 82 year old Herreshoff S-Boat sailboat: http://home.comcast.net/~saville/SBOATrestore.htm Steambending FAQ with photos: http://home.comcast.net/~saville/Steambend.htm |
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#22
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You don't.
Explain to me how you know the Sun is at it's highest....without a gadget... snip You don't. You need a sextant, a very accurate watch and a set of Bowditch tables. Bowditch's skill as a mathematician permitted him to demand exhorbantent fees for his services from the shipping company, since without him and his tables on board, nobody knew where they were. Today, a $100 GPS receiver has made the whole process mute. Lew |
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#23
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Lew Hodgett wrote:
You don't. Explain to me how you know the Sun is at it's highest....without a gadget... snip You don't. You need a sextant, a very accurate watch and a set of Bowditch tables. If you're not too near the equator, put a stick in the ground (obww - make it a pointed stick) and when the shadow is shortest, the sun is highest. Bowditch's skill as a mathematician permitted him to demand exhorbantent fees for his services from the shipping company, since without him and his tables on board, nobody knew where they were. Bowditch's translation of Laplace showed his skill as a mathematician (but obviously nowhere near that of Laplace himself), but his editorial work on Moore's New Practical Navigator wasn't earthshattering. Other publisher's tables were just as good; the nautical almanac was the essential item. Besides, celestial navigation only works well if you already know where you are (at least approximately). Today, a $100 GPS receiver has made the whole process mute. Mute, but fun. Ken Muldrew (remove all letters after y in the alphabet) |
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#24
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Today, a $100 GPS receiver has made the whole process mute. Mute, but fun. Moot! |
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#25
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The word is MOOT.
"Ken Muldrew" wrote in message ... Mute, but fun. |
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