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Author Topic: The Dole Derby  (Read 134288 times)

Harry Howe, Jr.

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Re: The Dole Derby
« Reply #150 on: March 23, 2012, 01:23:14 PM »


Gary
Do you, have you, hiked?  I have and I made it a point to know the length of my pace.  I did this by walking a known distance (measured in feet) and counting the nmber of paces that it took to cover the distance, thus determining the length of my pace (30 inches).  Then, when hiking an unknown distance I counted the number of paces and multiplied by the known length of my pace to estimate the distance travelled.

Similarly, in my canoe I determined how many strokes it took to cover a known distance on a lake ( approx 4-1/2 feet per stroke) and then when counting strokes and multiplying by the distance per stroke I could estimate the distance travelled on another trip on another lake.

The Voyaguers in the Canadian Fur Trade specified distances as the number of "Pipes" smoked in covering a distance at a certain stroke cadence.  The pipe was made of clay and was of a consistent volume to allow a relatively fair measurement of time.

They measured distances on a portage  by the number of "poses" (pauses) it took to carry their load over the portage.  Each voyaguer was contracted  to carry two 90 lb packs over each portage.
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Gary LaPook

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Re: The Dole Derby
« Reply #151 on: March 23, 2012, 03:26:51 PM »


Gary
Do you, have you, hiked?  I have and I made it a point to know the length of my pace.  I did this by walking a known distance (measured in feet) and counting the nmber of paces that it took to cover the distance, thus determining the length of my pace (30 inches).  Then, when hiking an unknown distance I counted the number of paces and multiplied by the known length of my pace to estimate the distance travelled.

Similarly, in my canoe I determined how many strokes it took to cover a known distance on a lake ( approx 4-1/2 feet per stroke) and then when counting strokes and multiplying by the distance per stroke I could estimate the distance travelled on another trip on another lake.

The Voyaguers in the Canadian Fur Trade specified distances as the number of "Pipes" smoked in covering a distance at a certain stroke cadence.  The pipe was made of clay and was of a consistent volume to allow a relatively fair measurement of time.

They measured distances on a portage  by the number of "poses" (pauses) it took to carry their load over the portage.  Each voyaguer was contracted  to carry two 90 lb packs over each portage.
I pace 122 per 100 meters, that is what it was when we determined it in basic training in the army in 1966 and it is still exactly the same 122 paces today.

gl
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Harry Howe, Jr.

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Re: The Dole Derby
« Reply #152 on: March 23, 2012, 04:41:51 PM »


gary

mmm  32.3 inches per pace, I wiuld guess your height as  5'-9 1/2" to 5;-10".  ??
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Gary LaPook

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Re: The Dole Derby
« Reply #153 on: March 23, 2012, 06:18:28 PM »



It's a lot like the famous Michelson-Morley experiment that was done to determine the presence of the Aether thought to be the medium for propagating light.  They split a light beam into two parts and directed them over a fixed, known distance at right angles to each other and looked for a difference in time for each part to travel the distance.  That difference would tell them of the presence of the Aether.  They didn't find a difference and Einstein used their results to deduce that there was no Aether and no speed greater than the speed of light.
I am familiar with that experiment.  Hmmm... then how do they get the modern ring gyros to work?

gl
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Gary LaPook

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Re: The Dole Derby
« Reply #154 on: March 23, 2012, 06:34:15 PM »

Quote from: Harry

Gary
Making two measurements over a fixed distance, say the length of your canoe or raft, one with the current and one against the current allows the estimation of the speed of the current.  It's equal to the distance measured divided by the difference between the two measurements divided by 2 and then converted into mph using the conversion 22 feet per second equals 15 mph.
Here's how ya do it.
Ya put the floater, say a red and white bobber in the water at the nose and paddle with the current and timing how long it takes to pass the bobber till it is at the stern, i.e. the length of the canoe, raft.  Then ya turn the canoe, raft around and do the same thing against the current.


O.K. let me make sure I've got this right. You have a canoe that is 18 feet long. You throw out a bobber well in front of the canoe (so that you can establish a steady speed prior to reaching it.) You then paddle steadily past the bobber and it takes 4 seconds for the bobber to move from the bow to the stern. You continue downstream a bit, turn around and then paddle steadily, using the same rhythem,  back upstream past the bobber and it again takes exactly 4 seconds to go past the bobber. So you are going 18 feet in 4 seconds, 4 and a half feet per second, 3 mph in each direction. Since there is no difference in the time and the speed I assume you would calculate zero current. But using your formula 18 feet divided by zero and then divided by 2 causes the dreaded "divide by zero error" on a computer since that is not allowed since the result of that operation is not defined. So it looks like my formula is better for this than yours. So with no current the times and the speeds will be the same, right?

gl
« Last Edit: March 24, 2012, 06:15:02 PM by Gary LaPook »
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Harry Howe, Jr.

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Re: The Dole Derby
« Reply #155 on: March 23, 2012, 09:45:57 PM »


Ring Laser Gyroscope, not familiar with how it works.  Saw where it is based on the Sagnec Effect (Sagnec Interferometery.  Interesting and I gotta look at it some more before I can say I understand it.
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Jeff Palshook

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Re: The Dole Derby
« Reply #156 on: March 24, 2012, 07:36:43 AM »

Sagnac_Effect and ring laser gyroscopes .... It's been a while since I brushed up on the specific details of the Sagnac Effect, but I think the description I will give here is correct on most of the particulars.

A ring laser gyroscope works by sending two separate laser beams in opposite directions around a closed optical path.  This optical path is basically a "channel" inside a glass block.  Mirrors at each corner of the block re-direct the laser light beams into the next leg of the path.  The block can be either triangular, rectangular, or hexagonal.  A longer path length (i.e., a physically larger optical block) produces more accurate measurements.

The two laser beams, each traveling around the optical path in a direction opposite to the other beam, interfere with each other.  A sensing element detects the resulting interference pattern at the opposite side of the optical block from the injection point of the two beams.  If the optical block has a rotation rate in inertial space, the frequency of one beam will slightly different than the frequency of the second beam.  The sensing element measures the Doppler shift between the two beams.  The detected Doppler shift is proportional to the angular rate of rotation.  This is the Sagnac Effect.

A key difference between a ring laser gyro and the older technologies involving "conventional" spinning mass gyroscopes is that a spinning mass gyroscope measures angular displacement, while a ring laser gyroscope measures angular rate.  Thus, some extra math is needed to turn a system using a ring laser gyro into an inertial measuring unit or inertial navigation system, compared to the math needed in an inertial navigation system using spinning-mass gyroscopes.  But both systems are very complicated and require a lot of math anyway!  The big advantage of an inertial system using  ring laser gyroscopes is that the gyroscopes have no moving parts and thus the system is easier and cheaper to maintain compared to a system using coventional spinning-mass gyroscopes.

There is also an optical gyroscope called a fiber optic gyroscope (FOG),  which uses a very long fiber optic thread wound around a central core.  A laser beam is injected into one end of the optical fiber and sensed at the other end of the fiber.  I forget the optical principle which allows a FOG sense rotation.  I know it is different from the Sagnac Effect.  I do know a FOG is more accurate than a ring laser gyroscope.  This is why FOG's are used in the current generation of inertial navigation system for our ballistic missile submarines (SSBN's), while ring laser gyros are used in the inertial navigation system on attack submarines (SSN's).  An SSBN has more stringent requirements on navigational accuracy than an SSN has.
 
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Re: The Dole Derby
« Reply #157 on: March 24, 2012, 10:08:30 AM »

This has likely been mentioned already, but I am of the impression that the "Miss Doran" was a fabric aircraft.  What then would explain the pieces of aluminum that seems to have been showing up around Gardner?
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Harry Howe, Jr.

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Re: The Dole Derby
« Reply #158 on: March 24, 2012, 10:30:54 AM »

Dr Jim
I don't think that anyone is suggesting that the Miss Doran and its occupants Flew to Gardner. The discussion is centered around them possibly running out of fuel and "ditching" and floating (paddling, sailing) in the life raft they had aboard.  Is that possible?  Well, Gary LaPook reminds us that Eddie Rickenbacher survived at sea for over 20 days, and in 1944 Zamperini, and Phillps survived for 47 days (2000 miles) on a raft  and floated to the Marshalls where they were captured by the Japanese.  Their companion, McNamara perished after 33 days.  The book describing the adventure is "Unbroken" authored by Hillebrand (sp?).  Haven't read it yet, I have it on order.
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Re: The Dole Derby
« Reply #159 on: March 24, 2012, 10:51:20 AM »

The Dole birds took off August 16, 1927
Amelia took off from Lae  July    2, 1937
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Castaway for 10 years?  Am I missing something?  I'd think cast away for 10 years there would have been enough debris found on the island to fill a land fill, enough crab/lobster and bird skeletons to build a small fort. 

Someone once wrote,"simpler explanations are, other things being equal, generally better than more complex ones."

On an overflight looking for AE a pilot described Gardner as showing signs of recent habitation.  That would not seem to fit with any from the Dole race.
« Last Edit: March 24, 2012, 10:54:07 AM by Dr James Younghusband, D.C. »
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Harry Howe, Jr.

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Re: The Dole Derby
« Reply #160 on: March 24, 2012, 11:01:15 AM »


Jeff P.
A picky point re: the RLG.
"A ring laser gyroscope works by sending two separate laser beams..."
Actually it is one laser beam split by a half-silvered mirror at 45 degrees to the laser's direction thus allowing one half of the beam to pass thru the mirror undeflected and move counter-clockwise around the "ring" path while the other half of the beam gets reflected and moves in a clockwise direction.  Normally there wouldn't be an interference pattern set up since bothe beams come from the same source and travel the same path length.  But, when the "ring" is rotated, say in the clockwise direcrtion, the clockwise beam travels slightly farther and the counter beam, slightly shorter to get to the detector and thus the interference pattern, fringes,  is set up and is a function of the speed of rotation.  Complicated mathematics of course, nothing is simple anymore, LOL.

Another disadvantage of a mechanical gyroscope is that as the  speed of its rotation slows its axis precesses, i.e. no longer remains pointed in its original direction (conservation of angular momentum in a reotating system).  Our earth's axis of rotation does the same thing, it precesses with a period of about 56,000 years  and the North pole "wobbles".  Super imposed on this wobble, whicn is caused by the gravitional force acting between the earth and sun and because the axis is tilted about 23-1/2 degrees from being perpendicular to the plane of the earth's orbit, is a "wobble" about the precession.  This wobble is  caused by the gravitational force between the earth and the moon.

Welcome to the adventure.
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« Last Edit: March 24, 2012, 01:48:37 PM by Harry Howe, Jr. »
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Heath Smith

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Re: The Dole Derby
« Reply #161 on: March 24, 2012, 11:08:12 AM »

Quote
Castaway for 10 years?  Am I missing something?

We were discussing the artifacts, primarily the skeleton that perhaps was a woman, located near what appeared to be the sole of woman's shoe. This was the judgement of the guy who found the bones. The bones appeared to be very weathered, only 4 teeth remained in the skull. It could be possible, however unlikely, that these were the remains of Mildred Doran and not Earhart.

No one is suggesting that this castaway was alive for years.
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Re: The Dole Derby
« Reply #162 on: March 24, 2012, 11:17:29 AM »

I guess anything is possible.   Given that Hawaii is about 2556 miles east of Gardner, if the Ms Doran had made it within sight of Hawaii before going down, I'm not sure of prevailing winds or ocean currents, but traveling at a speed of 4mph it would have taken about 26 days to reach Gardner.  Given that they had little water, few provisions, a small life raft it would be quite a long and hot trip.  I would think a simpler explanation would be that the person who observed the skeleton misjudged the date of death because of the rapid destruction of flesh by the island crabs, sun, wind, storms, etc.
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Harry Howe, Jr.

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Re: The Dole Derby
« Reply #163 on: March 24, 2012, 11:20:21 AM »


Dr. Jim
"Someone once wrote, "simpler explanations are, other things being equal, generally better than more complex ones."

It's referred to as Occam's Razor and you will  see it cited on here many times.  It's modern equivalent is KISS (Keep it simple, stupid.) Somewhere, in this thread I think, Marty put it into wonderful Latin.  I'll have  to look for it.

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Harry Howe, Jr.

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Re: The Dole Derby
« Reply #164 on: March 24, 2012, 11:35:14 AM »


Dr Jim
Links to information, including a youtube video, can be found in the early posts in this thread discussing the equipment carried by the DoleBirds.  Life raft, sextant, "water machine" i.e. a device to allow re-breathing of the water vapor exhaled as one breathes and thus reducing the need to drink a lot of water to replace the moisture lost by the body.

I think that we all realize that it was an unlikely event, perhaps a wildly unlikely event, for Mildred Doran to have been on Gardner.  We're discussing a remote possibility.
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« Last Edit: March 24, 2012, 11:04:57 PM by Harry Howe, Jr. »
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