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  #21  
Old December 22nd 15, 01:01 PM posted to rec.bicycles.misc
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default O/T: knots

On Tue, 22 Dec 2015 02:51:04 +0000, Phil W Lee
wrote:

John B. considered Mon, 21 Dec 2015 08:01:54
+0700 the perfect time to write:

On Sun, 20 Dec 2015 20:04:43 +0000, Phil W Lee
wrote:

John B. considered Sun, 20 Dec 2015 17:50:33
+0700 the perfect time to write:

On Sun, 20 Dec 2015 02:25:09 +0100, "Jakob Krieger"
wrote:

- John B. / Tue, 15 Dec 2015 11:49:53 +0100

Of course with plastic ropes and fixtures,
you don't need a knot any more for many things.

But for rescuing »man overboard« or joinig ropes
for more length, classical knots are still used.

What ropes would that be? The main halyard? About 80% wire rope? The
main sheet? Wire again, or the jib sheet... wire once again.

Well, it used to be considered as a good precaution to
have a roll of rope lying somewhere in the boat.
Even in cars, towing-ropes can be found.


May be except for GPS sailors, they don't know
what a knot or even a rope is.

Sort of snarky remark isn't it? After all big ships navigate with GPS,
airplanes navigate with GPS. It has been quite a number of years now
since anything commercial used the stars.

Nobody with a little bit of experience (bike or car drivers
included) relies on GPS only.


I see. Do you really think that the 1st officer on, say the Emma
Maersk" is out on the bridge wing every day taking his noon sight? Or
that a B-52 comes equipped with a sextant? Or that any modern
commercial or military vehicle comes with a copy of the six H.O.
tables?

The U.S. navel Academy stopped teaching celestial navigation nearly 20
years ago stating that while celestial was accurate to a 3 mile radius
that GPS was accurate to a 60 ft. radius.

Almost everything of any size used inertial navigation in between
traditional and GPS, and certainly until VERY recently, it was not
legal to use GPS as the primary means of navigation in an aircraft of
UK registry.
That's what radio beacons are for, in all their various types - VOR,
DME, NDB, and ILS (and yes, I know how to use them all, although not
for all the various functions required for a full UK instrument rating
- the NDB approach is notoriously difficult). I'm fairly sure that in
coastal waters, ships use a similar system of beacons, mostly housed
in what used to be primarily lighthouses (and sometimes still perform
that function as well).


So, do you navigate across the Atlantic, or even worse, across the
Pacific with radio beacons?


Actually, you can.
DR gets you close enough to pick up beacons in plenty of time to avoid
bumping into anything and correct your course to make landfall where
you need to.


That isn't the way that you described navigation in the U.K. :-)

Re costal radio beacons. It might be an anomaly but I certainly have
never seen them anywhere in Asia, nor have I seen a reference to them
and certainly if they were in common use navigation charts and sailing
directions would have reference to them. Any active light house is
marked on the chart and it's light signal described.



Bubble sextants were certainly part of the standard equipment on the
Vulcan, so why not the B-52?


The last (I believe) U.S. made aircraft that had the ability to use
celestial navigation were early models of the Boeing 747, which were
phased out in the 1960's. The SR071 had a automated celestial and
inertial navigation. The last SR-71 left service in 1989. The last
Vulcan was delivered in 1965.

You are talking about old technology.


Which you certainly CAN use in anything which has outside windows big
enough to give horizon and solar/star sighting at the same time.
There are even specialist gyro stabilised bubble sextants designed for
the purpose, and tables to offset horizon angle by altitude.
Battery life isn't really much of a problem in the duration of any
normal aircraft flight, and on water you can pick your moment over a
much larger timescale.


Yup, certainly. But no windows :-) And, without a bubble sextant it is
awful hard, at 30,000 ft to get a good horizon. And if a fancy
electronically stabilized sextant then why not just use GPS.

By the way, to accurately locate the seismic lines used in oil field
exploitation they haven't used a sextant in years and years. All GPS
these days.

But why all the excitement about sextants? Just use your D.R. and when
you get close look for a landmark. All sailing directions have a
wealth of descriptions of landmarks.

And, there are days, sometimes weeks, that you can't see well enough
to get a sight, and other days when it is too rough to get a good
sight and even when you do your "cocked hat" is probably a mile on
more on a side... if you are really good and more then likely, in a
small boat, a lot bigger.

Even in rough weather and a solid overcast a GPS will give you a
location within feet :-)



Note that INS units had to be "borrowed" from some old airliners in
museums to strap down in the crew compartment of the Vulcans used in
the "Black Buck" operations of the (pre-GPS) Falklands war. In their
original (nuclear) role, they were expected to navigate by DR and
celestial, as it was assumed that most beacons would be off air or out
of range, and the DR part is kind of difficult over a featureless
ocean like the South Atlantic, as it relies on position checks (which
were carefully surveyed for the routes the Vulcan force was assigned
to on their nuclear role). All INS units are large, as they have big
gyros in them, so aren't suitable for small craft, and have to be set
up with accurate starting positions - in aircraft this is done by
positioning the craft on a carefully plotted navigation marker painted
on the hardstanding and hand entering the exact latitude and
longitude. The aircraft has to be kept completely still for several
minutes while the internal gyros spin up to speed and self-tests are
performed. They also accumulate errors over time, as they have to
make a "best guess" approach to precession.
I had no idea that US naval navigators were so badly trained - aren't
naval forces supposed to be able to operate in time of war, when EMP
could have killed the GPS constellation, along with most other outside
reference signals?
Or maybe they rely on being able to scavenge some old kit out of
obsolete vessels in that situation?

Of course, on smaller craft, the bigger problem is likely to be
reliance on power - particularly on sailing vessels.
One of the major certification requirements for aero engines is that
they be electrically self-contained, usually achieved by using magneto
ignition.





I hate to be the one to disillusion you but I don't believe that any
operational U.S.A.F. engine today uses magneto ignition :-)


I think you'll find that some of the smaller trainer aircraft do use
piston engines, complete with magnetos.


I made a very quick check and I don't believe that the USAF has any
reciprocating engine aircraft in use. At least every thing I see with
a propeller is a turbo-prop.


I did, how ever, work on what may have been the last of the
reciprocating powered bombers that the USAF had - the B-50 which did
have magnetos.... however to start the engines the system used
"voltage boosters" that served to feed a higher voltage to the
ignition system than the magnetos could produce at starting RPM. The
"voltage boosters" were operated by the air craft's electrical system,
that for starting was powered by an external power supply.


Nope. A voltage booster. the P&W 4360 had a low voltage magneto system
to avoid voltage leaks at high altitude and they definitely had a
voltage booster for each of the two mags.

The old tried and true of making a rough check of whether the mags are
putting out was to grab a spark plug lead and tell the guy to "hit the
starter". The shock was enough to jolt you but it did make for a quick
check.

I once watched a bloke try the same thing with the R-4360, which had
voltage boosters, and it almost knocked him off the stand :-)

IIRC, magnetos don't lose much in the way of sparks at low revs - it's
more to compensate for the voltage sag that engaging the starter
causes.


Nope, magnetos produce a lower voltage at starting revs. Way back they
used what was refereed to as an "impulse coupling" to sort of kick
start the mag to get enough voltage to fire the plugs at starting.

Magnetos, you may recall, work perfectly well on motorcycles with
kickstarters!


But, you get more revs from the kick starter on a bike than the
starter on a large aircraft engine.

That goes pear-shaped pretty quickly if you then can't find
a runway to land on as soon as the power goes off! This is also why
at least a basic set of primary instruments are vacuum powered, so you
can at least keep the aircraft flying the right way up and in the
right direction if all the smoke comes out of the electrical system.


Come now. I flew with my father when I was just a lad, in a Piper J-3
and it didn't have any vacuum instruments in it.


The snarky remark was meant about people who have
no orientation at all without GPS (can't even find
their own bathroom)

Yes, a good sailor should be able to maintain and repair the boat, as
well as drive it. Anything can break if sufficiently abused over a
long enough period, and extended abuse is not a bad working
diefinition of a trans-oceanic voyage in a small boat!
Of course, if you creep around the coastal areas, you can generally
find a port to put into if (when) something goes wrong or the weather
turns nasty.


That sounds like a very logical argument... Until one discovers that
few if any commercial shipping carry sufficient personal and/or
equipment to "to maintain and repair the boat". The Emma Maersk, for
example carries a crew of 13, 4 Deck Officers, 2 Engine Officers, 3
ABs, 2 OS, 2 Oilers. Who do you think repairs the navigation gear? Or
the bow/stern thrusters?


If a navigation antenna gets blown off, who do you think replaces it?
Or do you think they just keep going and play blind-mans-buff?
Who replaces the lamps in navigation lights if (when) they fail?


Which navigation antenna is that? The GPS antenna? Or the big radome?


Of course, a yacht is a rather different proposition. Not many yachts
(and even less of their normal equipment) are really designed with
genuinely extreme weather in mind, so if you're going to use one for
trans-oceanic voyages (or anything too far out to be able to run for
the nearest port at the first hint of a bad forecast), you do need to
be able to make-do-and-mend, unless you only sail in events with
safety rescue boats available.


If you are crossing oceans there is no running for harbour so you try
to make your crossing in the benign seasons :-) Talk to anyone who is
doing a sailing circumnavigation and you find that they seem to spend
lots of time in harbour. You get to Thailand and you have to wait for
the monsoons to change before you can set out for the Indian Ocean.


To a large extent, similar constraints apply to those of bicycle
components, as weight and size matter. And the biggest market for
equipment is the weekend user who spends as much time looking after
their equipment as they do actually using it.

--
cheers,

John B.

Ads
  #22  
Old December 23rd 15, 03:14 AM posted to rec.bicycles.misc
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default O/T: knots

On Tue, 22 Dec 2015 23:03:27 +0000, Phil W Lee
wrote:

John B. considered Tue, 22 Dec 2015 19:01:17
+0700 the perfect time to write:

On Tue, 22 Dec 2015 02:51:04 +0000, Phil W Lee
wrote:

John B. considered Mon, 21 Dec 2015 08:01:54
+0700 the perfect time to write:

On Sun, 20 Dec 2015 20:04:43 +0000, Phil W Lee
wrote:

John B. considered Sun, 20 Dec 2015 17:50:33
+0700 the perfect time to write:

On Sun, 20 Dec 2015 02:25:09 +0100, "Jakob Krieger"
wrote:

- John B. / Tue, 15 Dec 2015 11:49:53 +0100

Of course with plastic ropes and fixtures,
you don't need a knot any more for many things.

But for rescuing »man overboard« or joinig ropes
for more length, classical knots are still used.

What ropes would that be? The main halyard? About 80% wire rope? The
main sheet? Wire again, or the jib sheet... wire once again.

Well, it used to be considered as a good precaution to
have a roll of rope lying somewhere in the boat.
Even in cars, towing-ropes can be found.


May be except for GPS sailors, they don't know
what a knot or even a rope is.

Sort of snarky remark isn't it? After all big ships navigate with GPS,
airplanes navigate with GPS. It has been quite a number of years now
since anything commercial used the stars.

Nobody with a little bit of experience (bike or car drivers
included) relies on GPS only.


I see. Do you really think that the 1st officer on, say the Emma
Maersk" is out on the bridge wing every day taking his noon sight? Or
that a B-52 comes equipped with a sextant? Or that any modern
commercial or military vehicle comes with a copy of the six H.O.
tables?

The U.S. navel Academy stopped teaching celestial navigation nearly 20
years ago stating that while celestial was accurate to a 3 mile radius
that GPS was accurate to a 60 ft. radius.

Almost everything of any size used inertial navigation in between
traditional and GPS, and certainly until VERY recently, it was not
legal to use GPS as the primary means of navigation in an aircraft of
UK registry.
That's what radio beacons are for, in all their various types - VOR,
DME, NDB, and ILS (and yes, I know how to use them all, although not
for all the various functions required for a full UK instrument rating
- the NDB approach is notoriously difficult). I'm fairly sure that in
coastal waters, ships use a similar system of beacons, mostly housed
in what used to be primarily lighthouses (and sometimes still perform
that function as well).

So, do you navigate across the Atlantic, or even worse, across the
Pacific with radio beacons?

Actually, you can.
DR gets you close enough to pick up beacons in plenty of time to avoid
bumping into anything and correct your course to make landfall where
you need to.


That isn't the way that you described navigation in the U.K. :-)

I don't believe I ever did describe navigation IN the UK, just that
required for a rating under UK regulations. I'm fairly sure that
celestial navigation is still taught in the Royal Navy - it certainly
is in the Merchant Navy, and it would be a bit strange for Naval
Reservists to out-qualify their full time Naval counterparts.
Nearly all training is about what you need to do when things go wrong,
not when they are going right, and electrical failure is certainly not
an unanticipated failure mode.

Re costal radio beacons. It might be an anomaly but I certainly have
never seen them anywhere in Asia, nor have I seen a reference to them
and certainly if they were in common use navigation charts and sailing
directions would have reference to them. Any active light house is
marked on the chart and it's light signal described.

They certainly do have radio beacons in Asia - they may not be
intended primarily for maritime use, but can be used by suitably
equipped craft. You can even DF on commercial stations fairly easily
if you have the (not particularly expensive) equipment.


Come now. You wrote, "I'm fairly sure that in
coastal waters, ships use a similar system of beacons, mostly housed
in what used to be primarily lighthouses".

I reply that I've never seen such a thing and then you tell me that,
"They certainly do have radio beacons in Asia".

Well, of course they do. Intended for aircraft use, not in light
houses. And of course, if one has the required equipment one can get a
direction fix from any radio transmitter.

But how many ships and boats have radio direction finding equipment.
In fact, how many commercial ships still carry a Radioman or have a
"radio room".




Bubble sextants were certainly part of the standard equipment on the
Vulcan, so why not the B-52?

The last (I believe) U.S. made aircraft that had the ability to use
celestial navigation were early models of the Boeing 747, which were
phased out in the 1960's. The SR071 had a automated celestial and
inertial navigation. The last SR-71 left service in 1989. The last
Vulcan was delivered in 1965.

You are talking about old technology.

Which you certainly CAN use in anything which has outside windows big
enough to give horizon and solar/star sighting at the same time.
There are even specialist gyro stabilised bubble sextants designed for
the purpose, and tables to offset horizon angle by altitude.
Battery life isn't really much of a problem in the duration of any
normal aircraft flight, and on water you can pick your moment over a
much larger timescale.


Yup, certainly. But no windows :-) And, without a bubble sextant it is
awful hard, at 30,000 ft to get a good horizon. And if a fancy
electronically stabilized sextant then why not just use GPS.


Well, a military aircraft should anticipate the possibility of the GPS
constellation being knocked out.


But there is no necessity. You said, above, that you could use radio
beacons and other radio stations to navigate by.

By the way, to accurately locate the seismic lines used in oil field
exploitation they haven't used a sextant in years and years. All GPS
these days.


Well, that's a commercial decision, so you use the cheapest that works
(or your shareholders are going to complain).

But why all the excitement about sextants? Just use your D.R. and when
you get close look for a landmark. All sailing directions have a
wealth of descriptions of landmarks.

And, there are days, sometimes weeks, that you can't see well enough
to get a sight, and other days when it is too rough to get a good
sight and even when you do your "cocked hat" is probably a mile on
more on a side... if you are really good and more then likely, in a
small boat, a lot bigger.

Even in rough weather and a solid overcast a GPS will give you a
location within feet :-)

After an intermittent soaking with seawater?


Well, an intermittent soaking with sea water will pretty much destroy
your charts and your H.O. tables and having a sextant without these
two accessories is pretty much a futile exercise in navigation :-)

But more realistically, most yachtsmen, on offshore voyages, carry at
least two GPS receivers, and sometimes even more. I've even got a
wrist watch device that includes GPS. Some boats carry "chart
plotters" and don't use paper charts at all any more.




Note that INS units had to be "borrowed" from some old airliners in
museums to strap down in the crew compartment of the Vulcans used in
the "Black Buck" operations of the (pre-GPS) Falklands war. In their
original (nuclear) role, they were expected to navigate by DR and
celestial, as it was assumed that most beacons would be off air or out
of range, and the DR part is kind of difficult over a featureless
ocean like the South Atlantic, as it relies on position checks (which
were carefully surveyed for the routes the Vulcan force was assigned
to on their nuclear role). All INS units are large, as they have big
gyros in them, so aren't suitable for small craft, and have to be set
up with accurate starting positions - in aircraft this is done by
positioning the craft on a carefully plotted navigation marker painted
on the hardstanding and hand entering the exact latitude and
longitude. The aircraft has to be kept completely still for several
minutes while the internal gyros spin up to speed and self-tests are
performed. They also accumulate errors over time, as they have to
make a "best guess" approach to precession.
I had no idea that US naval navigators were so badly trained - aren't
naval forces supposed to be able to operate in time of war, when EMP
could have killed the GPS constellation, along with most other outside
reference signals?
Or maybe they rely on being able to scavenge some old kit out of
obsolete vessels in that situation?

Of course, on smaller craft, the bigger problem is likely to be
reliance on power - particularly on sailing vessels.
One of the major certification requirements for aero engines is that
they be electrically self-contained, usually achieved by using magneto
ignition.





I hate to be the one to disillusion you but I don't believe that any
operational U.S.A.F. engine today uses magneto ignition :-)

I think you'll find that some of the smaller trainer aircraft do use
piston engines, complete with magnetos.


I made a very quick check and I don't believe that the USAF has any
reciprocating engine aircraft in use. At least every thing I see with
a propeller is a turbo-prop.

They still have at least one Slingsby Firefly, with it's Lycoming
engine, based at Edwards AFB, and believe it or not, an AN-2, but the
main reason so few piston engine aircraft are still officially used is
that they outsourced nearly all of their primary training, and the
aircraft that went with it! Despite that, there are still 25 T-53As
(Cirrus SR20) in the inventory, and I believe a few T-52As (Diamond
DA40), although these may have all been replaced by T-53s now.
There are even 3 T-51As (Cessna C150) still in use.


The USAF has done, probably the majority of their primary flight
training, through outside contractors for years and years. My first
job after school was at an airfield in a small town in Georgia
operated by Southern Airways Corp. that provided primary flight
training for the Air Force... using the original T-6.

As for Edwards AFB, they have a lot of odds and ends of aircraft
there. Some, and I suspect the Slingsby Firefly, as there were a
couple of crashes with that aircraft, that Edwards did some flight
testing to see if the aircraft would recover from one particular
maneuver. The aircraft passed the tests I believe :-)




I did, how ever, work on what may have been the last of the
reciprocating powered bombers that the USAF had - the B-50 which did
have magnetos.... however to start the engines the system used
"voltage boosters" that served to feed a higher voltage to the
ignition system than the magnetos could produce at starting RPM. The
"voltage boosters" were operated by the air craft's electrical system,
that for starting was powered by an external power supply.


Nope. A voltage booster. the P&W 4360 had a low voltage magneto system
to avoid voltage leaks at high altitude and they definitely had a
voltage booster for each of the two mags.

The old tried and true of making a rough check of whether the mags are
putting out was to grab a spark plug lead and tell the guy to "hit the
starter". The shock was enough to jolt you but it did make for a quick
check.

I once watched a bloke try the same thing with the R-4360, which had
voltage boosters, and it almost knocked him off the stand :-)

IIRC, magnetos don't lose much in the way of sparks at low revs - it's
more to compensate for the voltage sag that engaging the starter
causes.


Nope, magnetos produce a lower voltage at starting revs. Way back they
used what was refereed to as an "impulse coupling" to sort of kick
start the mag to get enough voltage to fire the plugs at starting.

Magnetos, you may recall, work perfectly well on motorcycles with
kickstarters!


But, you get more revs from the kick starter on a bike than the
starter on a large aircraft engine.


On large aircraft engines, maybe, but I've not had much to do with
them. I do know that motorcycle kickstarters are very variable,
partly depending on size. Big singles (500+cc) are particularly slow.


Really, I had a Harley 80 cu. inch, flat head, and had no problem kick
starting it. I never owned a 500 c.c. bike but I did ride a mate's 500
c.c Norton single and it started easily. (In fact, the first
motorcycle I saw with an electric starter, I wondered about whether it
was intended for the ladies :-)



That goes pear-shaped pretty quickly if you then can't find
a runway to land on as soon as the power goes off! This is also why
at least a basic set of primary instruments are vacuum powered, so you
can at least keep the aircraft flying the right way up and in the
right direction if all the smoke comes out of the electrical system.


Come now. I flew with my father when I was just a lad, in a Piper J-3
and it didn't have any vacuum instruments in it.

Only because it only had pitot/static instruments and a turn & slip
indicator!


No turn and slip indicator. An altimeter, magnetic compass and air
speed was all the flight instruments it had.


some snipped
--
cheers,

John B.

  #23  
Old December 25th 15, 02:28 AM posted to rec.bicycles.misc
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default O/T: knots

rOn Thu, 24 Dec 2015 20:47:53 +0000, Phil W Lee
wrote:

John B. considered Wed, 23 Dec 2015 09:14:08
+0700 the perfect time to write:

A great deal of redundancy snipped


Well, a military aircraft should anticipate the possibility of the GPS
constellation being knocked out.


But there is no necessity. You said, above, that you could use radio
beacons and other radio stations to navigate by.


Or INS, or celestial navigation.


Are you serious? Celestial navigation? In an airplane? It probably
takes 10 to 15 minutes to actually make a minimum of two star sights
and work out a position. Which is possibly accurate to, say a 2 mile
radius. In an aircraft flying at, again say, 500 MPH (Boeing 747
cruise M-0.85)?

In 10 minutes the airplane travels ~80 miles while you are fanatically
making a series of fixes. All accurate to a location 75 miles behind
you.

More snipped
But more realistically, most yachtsmen, on offshore voyages, carry at
least two GPS receivers, and sometimes even more. I've even got a
wrist watch device that includes GPS. Some boats carry "chart
plotters" and don't use paper charts at all any more.

What kind of battery life does your wrist GPS have?

A rechargeable one :-)

Which can be re-charged from either the solar panel or the wind
generator.

and yet more snipped

As for Edwards AFB, they have a lot of odds and ends of aircraft
there. Some, and I suspect the Slingsby Firefly, as there were a
couple of crashes with that aircraft, that Edwards did some flight
testing to see if the aircraft would recover from one particular
maneuver. The aircraft passed the tests I believe :-)

Yes, the aircraft didn't have a problem - the crashes were all put
down to pilot error. But I don't know why they retained that
aircraft, let alone the AN-2.


At least when I was stationed there were a lot of old aircraft
scattered around. At one time - maybe in the very late 1960's - I saw
what may have been a Hiller X-18, which flew its last flight in 1961.
And of course the B-52A (only 3 ever built) that had carried the X
aircraft :-)


But, you get more revs from the kick starter on a bike than the
starter on a large aircraft engine.

On large aircraft engines, maybe, but I've not had much to do with
them. I do know that motorcycle kickstarters are very variable,
partly depending on size. Big singles (500+cc) are particularly slow.


Really, I had a Harley 80 cu. inch, flat head, and had no problem kick
starting it. I never owned a 500 c.c. bike but I did ride a mate's 500
c.c Norton single and it started easily. (In fact, the first
motorcycle I saw with an electric starter, I wondered about whether it
was intended for the ladies :-)

Did your Harley have magneto ignition?


Nope, but your remark about the "big" 500 cc bikes I assumed that you
were referring to engine size.

The Norton's (and similar BSAs, Matchless, etc) difficulty in starting
was almost directly determined by the state of tune - the higher the
power it was tuned for, the more difficult it was to start.
But the point (pardon the pun) is how fast the engine needs to spin to
give a useful spark. I'll bet that it was too slow to even register
on the rev counter until the thing was running. It has been on every
four stroke I've ever owned with a kickstarter.


Yes, likely due to advanced Ignition timing. I once helped to push
start a Norton 500 cc "feather bed" racing bike at the Daytona Beach
races that the rider said was impossible to kick start.

Come now. I flew with my father when I was just a lad, in a Piper J-3
and it didn't have any vacuum instruments in it.

Only because it only had pitot/static instruments and a turn & slip
indicator!


No turn and slip indicator. An altimeter, magnetic compass and air
speed was all the flight instruments it had.

Yeah, I knew they didn't have a lot.
The continued existence of aircraft like that is one reason why it's
still legal to operate NORDO (outside controlled airspace) - because
you can't fit a radio to something without an electrical system.
Of course, the same is true of some yachts, and the conditions under
which they can operate is potentially far more hostile to electrical
systems, both in severity and duration.


The preferred navigation method was to follow the railroads :-)

By the way, there is a research paper titled "Vision-Based
Road-Following Using a Small Autonomous Aircraft" done at the AINS
Center for Collaborative Control of Unmanned Vehicles, University of
California, Berkeley, which apparently is dated 2003, which describes
the method :-)
--
cheers,

John B.

  #24  
Old December 27th 15, 06:39 AM posted to rec.bicycles.misc
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default O/T: knots

On Sat, 26 Dec 2015 18:02:59 +0000, Phil W Lee
wrote:

John B. considered Fri, 25 Dec 2015 08:28:15
+0700 the perfect time to write:

rOn Thu, 24 Dec 2015 20:47:53 +0000, Phil W Lee
wrote:

John B. considered Wed, 23 Dec 2015 09:14:08
+0700 the perfect time to write:

A great deal of redundancy snipped


Well, a military aircraft should anticipate the possibility of the GPS
constellation being knocked out.

But there is no necessity. You said, above, that you could use radio
beacons and other radio stations to navigate by.

Or INS, or celestial navigation.


Are you serious? Celestial navigation? In an airplane? It probably
takes 10 to 15 minutes to actually make a minimum of two star sights
and work out a position. Which is possibly accurate to, say a 2 mile
radius. In an aircraft flying at, again say, 500 MPH (Boeing 747
cruise M-0.85)?

In 10 minutes the airplane travels ~80 miles while you are fanatically
making a series of fixes. All accurate to a location 75 miles behind
you.

But you know how fast you are flying, and in what direction, so just
making occasional fixes allows you to correct for the difference
between forecast winds aloft and actual - which is all you need.
Unless you are skirting very close to controlled or restricted
airspace, you only need to know where you are to within a couple of
miles, at least while you are at altitude and over featureless terrain
or ocean.

More snipped
But more realistically, most yachtsmen, on offshore voyages, carry at
least two GPS receivers, and sometimes even more. I've even got a
wrist watch device that includes GPS. Some boats carry "chart
plotters" and don't use paper charts at all any more.

What kind of battery life does your wrist GPS have?

A rechargeable one :-)

Which can be re-charged from either the solar panel or the wind
generator.


Either of which can be damaged or destroyed by adverse weather.
It's a bit like self-steering gear. Nice to have, but a good sailor
should know their boat well enough to be able to balance it on most
points of sailing, or if it is badly balanced, at least know which
points of sailing it will or won't hold without manual steering and
sheet management. Heck, even roller reefing (or more particularly,
the gooseneck it uses between boom and mast) is a weakness that a good
sailor should be able to manage without if necessary.


Frankly, I hear that a lot, from shore bound folks, but in reality
when you go to sea there are a lot of things that can't be repaired
without outside help. I've never seen a sailing yacht with more then
one auxiliary motor and the cry, "Oh! I'll just sail it." is not
really a solution, in some cases when the engine fails. I knew a bloke
who's transmission failed about 10 miles out from Phi-Phi Island, in
Thailand, when he was trying to get to Langkawi in Malaysia - about a
hundred miles - during the S.W. monsoon when there are very light to
no winds in that region. It took him nearly two weeks and much of the
time he was drifting with the tide and anchoring when the tide turned.
The VL cargo ships have only a single engine and propeller.

If the gooseneck breaks, depending largely on the type of rig, the
boat could probably be sailed with the main loose footed as the boom
actually only serves to make the sail easier to handle - single sheet
- and allows for more control of sail shape - out haul.

Self steering :-) ever try hand steering a boat for days and days? I
have and it is not really something that I care to repeat.

As for "balanced without manual steering", very few sloops - probably
the most common yacht - can be sailed that way. And saying "which
points of sailing it will or won't hold without manual steering" is
even worse. The N.E. Monsoon will blow for the next 5 months and I
want to, have to, go north. No sloop I've seen will sail to windward
hands off.


and yet more snipped

As for Edwards AFB, they have a lot of odds and ends of aircraft
there. Some, and I suspect the Slingsby Firefly, as there were a
couple of crashes with that aircraft, that Edwards did some flight
testing to see if the aircraft would recover from one particular
maneuver. The aircraft passed the tests I believe :-)

Yes, the aircraft didn't have a problem - the crashes were all put
down to pilot error. But I don't know why they retained that
aircraft, let alone the AN-2.


At least when I was stationed there were a lot of old aircraft
scattered around. At one time - maybe in the very late 1960's - I saw
what may have been a Hiller X-18, which flew its last flight in 1961.
And of course the B-52A (only 3 ever built) that had carried the X
aircraft :-)

All the large and medium sized aircraft are now turbine, yes.
They tend to be more expensive initially, but with much lower running
costs, so if you keep them long and do lots of hours, the total cost
of ownership is lower.


They also produce far more power from a smaller, lighter package :-)

Some of the H-34's (I think it was) were converted from Recip engines
to turbo and had a rather surprising amount of ballast added to
compensate for the reduced power plant weight.

But, you get more revs from the kick starter on a bike than the
starter on a large aircraft engine.

On large aircraft engines, maybe, but I've not had much to do with
them. I do know that motorcycle kickstarters are very variable,
partly depending on size. Big singles (500+cc) are particularly slow.

Really, I had a Harley 80 cu. inch, flat head, and had no problem kick
starting it. I never owned a 500 c.c. bike but I did ride a mate's 500
c.c Norton single and it started easily. (In fact, the first
motorcycle I saw with an electric starter, I wondered about whether it
was intended for the ladies :-)

Did your Harley have magneto ignition?


Nope, but your remark about the "big" 500 cc bikes I assumed that you
were referring to engine size.


It's more individual cylinder size, as that's what you are compressing
in one go in order to start it. And of course, if it's not magneto
ignition, the minimum speed at which a magneto will give a spark is
irrelevant, as you have a battery to do that.


Well, the 500cc single engine has a 30.5 cubic inch cylinder while the
80 cubic inch Harley twin had a 40 cubic inch cylinder, and, to the
best of my knowledge the Harley "80" was made only with a manual kick
starter :-)



The Norton's (and similar BSAs, Matchless, etc) difficulty in starting
was almost directly determined by the state of tune - the higher the
power it was tuned for, the more difficult it was to start.
But the point (pardon the pun) is how fast the engine needs to spin to
give a useful spark. I'll bet that it was too slow to even register
on the rev counter until the thing was running. It has been on every
four stroke I've ever owned with a kickstarter.


I never owned a "big Bike" that had a "rev counter"

Yes, likely due to advanced Ignition timing. I once helped to push
start a Norton 500 cc "feather bed" racing bike at the Daytona Beach
races that the rider said was impossible to kick start.


It's only partly ignition timing - compression ratio and valve timing
are also significant factors. Pure racing machines often did away
with the kickstarter altogether, because it was both useless and added
extra weight.
But you can get a spark from magneto ignition down to about 100rpm -
so if you can make the kickstarter turn it, you can usually start it.
If it cranks much below that, then yes, you probably need an impulse
coupling, so aircraft which are hand started by swinging the prop, or
large piston engines pretty much need them. But even on those, the
ignition system is self-contained, and has no connection to any
external power or even the battery.

To drag this slightly close to being on topic (warning - thread
collision possibility), bicycle generators are technically (low
tension) magnetos, as they don't have field coils but permanent
magnets.

Come now. I flew with my father when I was just a lad, in a Piper J-3
and it didn't have any vacuum instruments in it.

Only because it only had pitot/static instruments and a turn & slip
indicator!

No turn and slip indicator. An altimeter, magnetic compass and air
speed was all the flight instruments it had.

Yeah, I knew they didn't have a lot.
The continued existence of aircraft like that is one reason why it's
still legal to operate NORDO (outside controlled airspace) - because
you can't fit a radio to something without an electrical system.
Of course, the same is true of some yachts, and the conditions under
which they can operate is potentially far more hostile to electrical
systems, both in severity and duration.


The preferred navigation method was to follow the railroads :-)


That only works in VFR below the clouds.


Piper Cubs were only flown VFR!!!!


By the way, there is a research paper titled "Vision-Based
Road-Following Using a Small Autonomous Aircraft" done at the AINS
Center for Collaborative Control of Unmanned Vehicles, University of
California, Berkeley, which apparently is dated 2003, which describes
the method :-)


There's also a whole set of RFCs on the carriage of datagrams by avian
carrier, with and without quality of service and even encryption -
bandwidth is quite high, but latency issues make it unsuitable for
most applications
But while such things are amusing, there are actually some genuine
rules for following what are termed "line features" in aircraft
navigation, mostly to avoid meeting another aircraft following the
same feature in the opposite direction. This can result in a rather
bad landing for both aircraft (a good landing being one you can walk
away from, and a great landing being one where the aircraft is
reusable). In a nutshell, you keep the line feature on your left
(giving horizontal separation), and choose your height according to
your magnetic track (giving vertical separation) - meaning you need to
get at least two things wrong before there is any danger. Well, three
really, since looking where you are going is also highly recommended

--
cheers,

John B.

  #25  
Old December 29th 15, 01:24 AM posted to rec.bicycles.misc
John B.[_6_]
external usenet poster
 
Posts: 2,202
Default O/T: knots

On Sun, 27 Dec 2015 23:46:43 +0000, Phil W Lee
wrote:

John B. considered Sun, 27 Dec 2015 12:39:16
+0700 the perfect time to write:

On Sat, 26 Dec 2015 18:02:59 +0000, Phil W Lee
wrote:

John B. considered Fri, 25 Dec 2015 08:28:15
+0700 the perfect time to write:

rOn Thu, 24 Dec 2015 20:47:53 +0000, Phil W Lee
wrote:

John B. considered Wed, 23 Dec 2015 09:14:08
+0700 the perfect time to write:

A great deal of redundancy snipped


Well, a military aircraft should anticipate the possibility of the GPS
constellation being knocked out.

But there is no necessity. You said, above, that you could use radio
beacons and other radio stations to navigate by.

Or INS, or celestial navigation.

Are you serious? Celestial navigation? In an airplane? It probably
takes 10 to 15 minutes to actually make a minimum of two star sights
and work out a position. Which is possibly accurate to, say a 2 mile
radius. In an aircraft flying at, again say, 500 MPH (Boeing 747
cruise M-0.85)?

In 10 minutes the airplane travels ~80 miles while you are fanatically
making a series of fixes. All accurate to a location 75 miles behind
you.

But you know how fast you are flying, and in what direction, so just
making occasional fixes allows you to correct for the difference
between forecast winds aloft and actual - which is all you need.
Unless you are skirting very close to controlled or restricted
airspace, you only need to know where you are to within a couple of
miles, at least while you are at altitude and over featureless terrain
or ocean.

More snipped
But more realistically, most yachtsmen, on offshore voyages, carry at
least two GPS receivers, and sometimes even more. I've even got a
wrist watch device that includes GPS. Some boats carry "chart
plotters" and don't use paper charts at all any more.

What kind of battery life does your wrist GPS have?

A rechargeable one :-)

Which can be re-charged from either the solar panel or the wind
generator.

Either of which can be damaged or destroyed by adverse weather.
It's a bit like self-steering gear. Nice to have, but a good sailor
should know their boat well enough to be able to balance it on most
points of sailing, or if it is badly balanced, at least know which
points of sailing it will or won't hold without manual steering and
sheet management. Heck, even roller reefing (or more particularly,
the gooseneck it uses between boom and mast) is a weakness that a good
sailor should be able to manage without if necessary.


Frankly, I hear that a lot, from shore bound folks, but in reality
when you go to sea there are a lot of things that can't be repaired
without outside help. I've never seen a sailing yacht with more then
one auxiliary motor and the cry, "Oh! I'll just sail it." is not
really a solution, in some cases when the engine fails.


That depends partly on how far you are going and how well you can sail
it, maybe?


Not really. It depends very much on where you are. My understanding is
that in the British Isles wind is practically an every day occurrence
but in the monsoon areas it may hardly blow at all for months out of
the year.

Sir Robin Knox-Johnston never once used his engine on his ketch
Suhaili all the way from Falmouth to Falmouth, 313 days at sea, 30,123
nautical miles. When he tried to turn it over fairly early in the
voyage (to use as an auxiliary battery charger), he discovered it had
seized.


Yup, and I mention below about the guy that takes almost a month to
drift something less then 100 miles.

His self-steering broke before he was half-way, and his gooseneck
after only a third. He ended up doing without the former altogether,
but kept repairing the latter, although of course there were lengthy
periods while it was being repaired when he was managing without,
usually in the worst weather conditions.


One can only speculate. I know probably 20 people who have made a
circumnavigation and neither their wind vane nor their gooseneck
broke.

I knew a bloke
who's transmission failed about 10 miles out from Phi-Phi Island, in
Thailand, when he was trying to get to Langkawi in Malaysia - about a
hundred miles - during the S.W. monsoon when there are very light to
no winds in that region. It took him nearly two weeks and much of the
time he was drifting with the tide and anchoring when the tide turned.


That's a situation where he should have turned back.
He could have got it fixed and still arrived at Langkawi sooner than
he did, and far more safely.


How?

The VL cargo ships have only a single engine and propeller.


And thrusters, which although they are intended for use when mooring,
can also be used to keep the ship from ending up broadside to the seas
if the prop or shaft are damaged.


The point is that there is little forward motion without the motor
driving the propeller and I doubt that one can cross the pacific using
only the bow and stern thrusters :-)


If the gooseneck breaks, depending largely on the type of rig, the
boat could probably be sailed with the main loose footed as the boom
actually only serves to make the sail easier to handle - single sheet
- and allows for more control of sail shape - out haul.


Or you can lash the boom to the mast, depending on the rig and the
circumstances.

Self steering :-) ever try hand steering a boat for days and days? I
have and it is not really something that I care to repeat.


RKJ reckoned he spent more time sewing than steering, but Suhaili was
a very well balanced boat.

As for "balanced without manual steering", very few sloops - probably
the most common yacht - can be sailed that way. And saying "which
points of sailing it will or won't hold without manual steering" is
even worse. The N.E. Monsoon will blow for the next 5 months and I
want to, have to, go north. No sloop I've seen will sail to windward
hands off.

Well, that's an inevitable consequence of having only one mast and two
sails - you have less choice of balance available. And having such
relatively large sails makes them more difficult to handle if things
are going pear-shaped.


I don't believe you have ever sailed, or at least not much :-) One
doesn't have large sails when things are going pear shaped.

and yet more snipped

As for Edwards AFB, they have a lot of odds and ends of aircraft
there. Some, and I suspect the Slingsby Firefly, as there were a
couple of crashes with that aircraft, that Edwards did some flight
testing to see if the aircraft would recover from one particular
maneuver. The aircraft passed the tests I believe :-)

Yes, the aircraft didn't have a problem - the crashes were all put
down to pilot error. But I don't know why they retained that
aircraft, let alone the AN-2.

At least when I was stationed there were a lot of old aircraft
scattered around. At one time - maybe in the very late 1960's - I saw
what may have been a Hiller X-18, which flew its last flight in 1961.
And of course the B-52A (only 3 ever built) that had carried the X
aircraft :-)

All the large and medium sized aircraft are now turbine, yes.
They tend to be more expensive initially, but with much lower running
costs, so if you keep them long and do lots of hours, the total cost
of ownership is lower.


They also produce far more power from a smaller, lighter package :-)


Well, yes - that's partly what makes the running cost lower.

Some of the H-34's (I think it was) were converted from Recip engines
to turbo and had a rather surprising amount of ballast added to
compensate for the reduced power plant weight.


Yes, depending on how the overall weight and balance is originally,
that can be a problem with conversions.

But, you get more revs from the kick starter on a bike than the
starter on a large aircraft engine.

On large aircraft engines, maybe, but I've not had much to do with
them. I do know that motorcycle kickstarters are very variable,
partly depending on size. Big singles (500+cc) are particularly slow.

Really, I had a Harley 80 cu. inch, flat head, and had no problem kick
starting it. I never owned a 500 c.c. bike but I did ride a mate's 500
c.c Norton single and it started easily. (In fact, the first
motorcycle I saw with an electric starter, I wondered about whether it
was intended for the ladies :-)

Did your Harley have magneto ignition?

Nope, but your remark about the "big" 500 cc bikes I assumed that you
were referring to engine size.

It's more individual cylinder size, as that's what you are compressing
in one go in order to start it. And of course, if it's not magneto
ignition, the minimum speed at which a magneto will give a spark is
irrelevant, as you have a battery to do that.


Well, the 500cc single engine has a 30.5 cubic inch cylinder while the
80 cubic inch Harley twin had a 40 cubic inch cylinder, and, to the
best of my knowledge the Harley "80" was made only with a manual kick
starter :-)

But not magneto, so no minimum speed to get it to spark, which means
you can just use low gearing on the kickstarter.
And the Harley 80 was a pretty soft state of tune anyway, at least
compared to the sportier of the 500 singles.


Well "soft" maybe. It was a lot of years ago now but my 80 cu. inch
bike (actually bored and stroked to 92 cu.in.) was, at the time,
unbeaten in quarter mile drag racing, in the Miami Florida area. Be
either 2 or 4 wheels :-)



The Norton's (and similar BSAs, Matchless, etc) difficulty in starting
was almost directly determined by the state of tune - the higher the
power it was tuned for, the more difficult it was to start.
But the point (pardon the pun) is how fast the engine needs to spin to
give a useful spark. I'll bet that it was too slow to even register
on the rev counter until the thing was running. It has been on every
four stroke I've ever owned with a kickstarter.

I never owned a "big Bike" that had a "rev counter"


So not all that highly tuned then?
More highly tuned engines tend to need them, as one result of tuning
them to give a higher output is to narrow the engine speed range over
which it's produced.


But why bother? Just built a bigger motor :-)

Come to think of it, I've only ever owned one 4 stroke motorcycle
without a rev counter, and that was a 50cc moped!


snipped

That only works in VFR below the clouds.


Piper Cubs were only flown VFR!!!!

Of course.
You can't fly IFR without instruments and a radio.

--
cheers,

John B.

  #26  
Old December 30th 15, 01:11 AM posted to rec.bicycles.misc
Jakob Krieger
external usenet poster
 
Posts: 145
Default O/T: knots

- Frank Krygowski / Sun, 20 Dec 2015 06:41:53 +0100

The snarky remark was meant about people who have
no orientation at all without GPS (can't even find
their own bathroom)


[sorry for not responding for quite some time]


I'm just back from an almost-an-hour drive to attend a friend's party.

On my way there, the country highway to his house was unexpectedly
closed. I think it may have been due to a bad car crash, since it was
open on my way home, and there was no sign of construction work. Oh,
and there were no detour signs, which would have been normal for
construction work.

So I made my way by dead reckoning over very minor country lanes. I was
interested to note that I was navigating - or at least, confirming my
direction - by looking at the stars. First time in a long time!



So you are not an Englishman. They doubt the existence of
lights in the sky behind the fog.


But you do confirm my thesis that a sailor / navigator
should have more skills than relying on GPS only.


jk


--
no sig
  #27  
Old December 30th 15, 01:21 AM posted to rec.bicycles.misc
Jakob Krieger
external usenet poster
 
Posts: 145
Default O/T: knots

- John B. / Sun, 20 Dec 2015 11:50:33 +0100

[sorry for late reply]

Nobody with a little bit of experience (bike or car drivers
included) relies on GPS only.


I see. Do you really think that the 1st officer on, say the Emma
Maersk" is out on the bridge wing every day taking his noon sight? Or
that a B-52 comes equipped with a sextant? Or that any modern
commercial or military vehicle comes with a copy of the six H.O.
tables?


I definitely know that at least one Apollo mission (13?)
did it's return by using a sextant after computers had no
more enrgy to work.


The U.S. navel Academy stopped teaching celestial navigation nearly 20
years ago stating that while celestial was accurate to a 3 mile radius
that GPS was accurate to a 60 ft. radius.


That's a fault.


If you don't know a fall-back at all when electronics strike,
you are not a navigator.


I begin to understand why MH370 drowned.


jk



--
no sig
  #28  
Old December 30th 15, 01:27 AM posted to rec.bicycles.misc
Jakob Krieger
external usenet poster
 
Posts: 145
Default O/T: knots

- John B. / Fri, 25 Dec 2015 02:28:15 +0100

Are you serious? Celestial navigation? In an airplane?


Without instruments, you have no orientaion.

If you can spot the North Star, you have principial
orientation (if seen starboard, you fly to west).

Nobody talks about _exact_ celestial positioning,
but I'd never trust a pilot who doesn't even know
the basics.


jk


--
no sig
  #29  
Old January 1st 16, 01:46 AM posted to rec.bicycles.misc
Jakob Krieger
external usenet poster
 
Posts: 145
Default O/T: knots

- Phil W Lee / Wed, 30 Dec 2015 18:40:03 +0100

.... happy new year to everyone ...


So I made my way by dead reckoning over very minor country lanes. I was
interested to note that I was navigating - or at least, confirming my
direction - by looking at the stars. First time in a long time!


So you are not an Englishman. They doubt the existence of
lights in the sky behind the fog.


It's mostly light pollution that kills our view of the stars these
days, and it affects vast areas, including nearly all cities and
conurbations, not just in the UK, but in most developed countries.
Regular atmospheric pollution makes this worse.


True, light pollution is very impressive when coming home to the
city after a mountain tour.

The night sky is a mystery to MOST people these days, as most live in
those very cities and conurbations that are producing the pollution.


I don't find the link right now -- on youtube, there is a very funny
story told by Neil deGrasse Tyson (the NY astronomer) how, as a boy,
his parents wanted to show the planetarium to him. His (if not true
then well-invented) answer was: »but I already know all four stars
there are in the sky« ...


... In Namibia, I found it was possible (with about 5 minutes
of adjustment for my eyes) to walk safely outside at night by
starlight, with no moon visible.


I can even read in total darkness. At least since I got an iPad
;o)

.... which by the way offers (even free) basic astronomy apps.
A lot easier to learn about star constellations than by books.

But you do confirm my thesis that a sailor / navigator
should have more skills than relying on GPS only.


Even the most simple minded should have a basic knowledge of celestial
navigation - even if it is just locating Polaris (the northern pole
star) or an approximate location of Sigma Octantis (the southern pole
star) - even though that star is not normally visible, it's position
can be located with sufficient accuracy for any normal purpose from
it's fixed position relative to the Southern Cross.


That's what I think about this, too.

It's unbelievably easy to accidentally misdirect a compass with the
strangest of objects ...


.... or GPS. Our city busses have an info system (»next stop: xyz«)
based on GPS. When there is fog or snow in the air, the system tends
to talk total crap.

... so having an absolute reference for direction is
essential, and those two references are visible without too much
difficulty in all but the worst conditions unless obscured by clouds.



Electronics is good, but I'd never trust on it alone.
Even if there are redundand systems. Planes crashed because
pilots were unable to judge which one was defect and which
one to trust.


jk



--
no sig
  #30  
Old January 5th 16, 04:49 AM posted to rec.bicycles.misc
Jakob Krieger
external usenet poster
 
Posts: 145
Default O/T: knots

- Phil W Lee / Fri, 01 Jan 2016 20:40:10 +0100


Electronics is good, but I'd never trust on it alone.
Even if there are redundand systems. Planes crashed because
pilots were unable to judge which one was defect and which
one to trust.


JFK Jr. to cite a well-known example, but there are many others.


Or AF-447, the Airbus A330 that came down half way between Rio and Paris

https://en.wikipedia.org/wiki/Air_France_Flight_447


jk

--
no sig
 




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