Navigation?

[MajorChaos]

After a bit of a search and getting lost in the threads, I decided to just ask a new the questions I was searching.

1. Who was in charge of navigation on a pirate ship?

2. What about a privateer?

3. What navigational aides would be used?

4. Where would these navigational aides be acquired?

5. How often would navigation be checked?

I could probably come up with more questions, but I figured I'd start there, since it's probably a lot of information.

Also, yes I know I could search the web, but I know there are a lot of knowledgable folks here and if they'd be so kind to answer or point me to some good research, I'd appreciate it.

Some items I've read about are:

Astrolabes, backstaff, Davis Quadrant, traverse boards and of course charts.

[Capn_Enigma]

ad 1: Captain or mate.

ad 2: same as 1.

ad 3:

What Instruments are necessary for the execution of this excellent skill?

THe Instruments necessary for a skilful seaman are a Sea Compasse, a Crosse Staffe a Quadrant, an Astrolaby, a Chart, an Instrument magneticall for the finding of the variation of the Compasse, an Horizontall plaine Sphere, a Globe, and a paradoxall Compasse. By which instruments, all conclusions and infallible demonstrations, Hydrographicall, Geographicall, and Cosmographicall, are without controlement of errour to be performed: but the Sea Compasse, Chart, and Crosse staffe, are instruments sufficient for the Seamans use: the Astrolabie and Quadrant being instruments very uncertaine for Sea observations.

John Davis, "The Seamans Secrets", ed. 1633

Apart from the instruments mentioned, a seaman would also have used the Davis quadrant, also called backstaff, invented by John Davis, and the chip log for measuring speed.

ad 4: From instrument makers or by stealing them from prize ships.

ad 5: Daily at noon time, if shooting the sun was possible. Else, dead reckoning was used, the uncertainty of a fix increasing in proportion with the time that passed since last shooting the sun.

The Davis quadrant is the same as a backstaff, as already mentioned above.

A traverse board makes dead reckoning a bit easier, cause you don't have to take notes while being on watch but intead plug the pegs according to your course and speed at each hourglasses 30- minutes interval and read it off later after your watch and enter the readings into your log.

A traverse board is not vital for navigation.

[MorganTyre]

1. Who was in charge of navigation on a pirate ship?

Whomever was qualified which could be a real problem there was a time (don't know if it was this case in the GAoP) that a common sailor learning to navigate was almost a floggable offense in the navy. I think the idea was that if only the officers could navigate then a mutiny was less likely. If I remember correctly it wasn't until the publication of Bowditch that things really began to change.

2. What about a privateer?

Navigation on most ships through history was pretty much solely the responsibility of the captain and I imagine that privateers were no exception.

3. What navigational aides would be used?

The backstaff or cross staff are going to be the most common tools of the era for celestial navigation. Despite what you may read to the contrary quadrants (not to be confused with the davis quarant) were not used much aboard ship as the motion of the sea in all but a dead calm renders then useless. A chiplog is a reliable method of estimating speed but I don't know if they were period, the same with traverse boards. Most ded-reckoning was based on estimated speed and time as measured by hourglass and so was frequently wrong which historically led to some amazing screw-ups. On the barbary coast the kamal would also have been used for celestial navigation. I'm not sure about the far east navigation practices, that would be interesting to learn more about.

4. Where would these navigational aides be acquired?

Wherever possible. These were specialized instruments at the time and were made by craftsmen, probably on an order by order basis. Any ship captured will have some instrumentation on board.

5. How often would navigation be checked?

Whenever practical. The noon sight was the most common at the time but I believe the polaris shot was already in use at the time. One is more or less the inverse of the other. The closer you are to the equator the higher the sun is over the horizon at noon and the closer polaris is to the horizon at night. With the crude, error-inducing instrumentation available at the time the conditions played a huge part in whether or not a reliable shot could be taken. At best you can only really count on a degree or so of accuracy which is a 60 mile radius of error. Between that, imperfect charts and questionable ded-reckoning it's not exagurating to say that the only real time a pirate knew exactly where he was was when he was in port.

[jim hawkins]

blackjohn get in on this thread!

Sounds like Chip logs are period:

A major advance that made dead-reckoning much more accurate was the invention of the chip log (c.1500-1600). Essentially a crude speedometer, a light line was knotted at regular intervals and weighted to drag in the water. It was tossed overboard over the stern as the pilot counted the knots that were let out during a specific period of time. From this he could determine the speed the vessel was moving. Interestingly, the chip log has long been replaced by equipment that is more advanced but we still refer to miles per hour on the water as knots. Using the sun and the stars, the navigator knew his beginning and ending latitude – now he could determine the distance he had traveled to estimate his east/west position.

[blackjohn]

blackjohn get in on this thread!

hell no! too much like my day job. ditto that cartography thread!

[Sir Eric]

Some vessels had a crew member other than the captain or the mate who was assigned navigation responsibilities... men such as William Dampier became quite well known and coveted for navigational ability. This may have been the exception as opposed to the rule. Likely on pirate vessels it was whoever seemed to be best at it and kept the ship off the rocks the longest...

It was also a common occurance for ships in unfamiliar waters to stop at port and pick up a Pilot who knew the local waters.

There are also reports of pirates pressing navigators into service on their ships... I believe this is how Bart Roberts came to be a pirate.

[Capn_Enigma]

A chiplog is a reliable method of estimating speed but I don't know if they were period, the same with traverse boards.

Chip logs and traverse boards are definitely period.

A kamal is not of much use because each is made for a specific latitude. It only tells you whether you are on certain latitude, but cannot measure it. This is only practical if sailing to the latitude of the desired port and thereafter tuning east or west and follow that latitude.

However, by the 17the century, navigation had evolved beyond that. With the rhumb line and the "paradoxall" sailing, the kamal was obsolete.

.. but I believe the polaris shot was already in use at the time.

The Polaris shooting had already become obsolete, too. Because the backstaff attains a much higher precision than the quadrant and astrolabe (see also my quote of Davis a few posts earlier), Polaris shooting was only used to ascertain the rough latitude.

Also, it is very difficult to shoot a 2nd magnitude star (like Polaris) from the deck of a swaying ship with an astrolabe. I have tried this myself and had errors in the magnitude of degrees (= 60 nautical miles off for each degree). "Navigation" like this is just advanced guesswork.

[Fox]

Too much for me to answer from me netcaff, but here's a few thoughts.

During the GAoP the navigation was usually the responsibility of the master or pilot rather than the captain (although on smaller vessels the master was frequently the captain as well so...)

One of the many criticisms levelled at Walter Kennedy was that although he was an apparently brave fellow he couldn't navigate for toffee - yet he still made it to captain.

Also, it is very difficult to shoot a 2nd magnitude star (like Polaris) from the deck of a swaying ship with an astrolabe. I have tried this myself and had errors in the magnitude of degrees (= 60 nautical miles off for each degree). "Navigation" like this is just advanced guesswork.

Now here I have to wonder whether we're talking about the level of accuracy we would hope to achieve now or the level that it was practical to achieve then. There are numerous accounts of period navigators being way out in their guesstimated positions, often with tragic consequences. The appalling loss suffered by Shovel's fleet in 1707 on the Scilly Isles was a result of the wrong answer being picked after a debate amongst the fleet's navigators about their position - some of them had it right but were over-ruled. Yes, advanced guess work is FAR from ideal, but a lot of the time it's what they did. :)

[blackjohn]

It was also a common occurance for ships in unfamiliar waters to stop at port and pick up a Pilot who knew the local waters.

Very good point Sir Eric! Not only did this happen with the buccaneers and pirates (both often taking involuntary pilots onboard) it continues to be practiced today in commercial shipping.

[Story]

Something to chew on, navigation wise.

http://www.nature.com/nature/journal/v444/...ll/444534a.html

[MorganTyre]

Here are some neat links showing it in motion. Neat mechanism but WAY more advanced than anything available (again) until the 20th century.

http://www.etl.uom.gr/mr/index.php?mypage=640x480

http://www.math.sunysb.edu/~tony/whatsnew/...0400/kyth5.html