[HN Gopher] To study ancient seafarers, researcher built a repli...
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To study ancient seafarers, researcher built a replica ship - and
sailed it
Author : benbreen
Score : 37 points
Date : 2022-09-17 17:14 UTC (5 hours ago)
(HTM) web link (www.washingtonpost.com)
(TXT) w3m dump (www.washingtonpost.com)
| vixen99 wrote:
| Along these lines let's not forget the Kon Tiki expedition. In
| 1947 Heyerdahl & crew wanted to show if, using a simple raft,
| South Americans could have reached Polynesia in the era prior to
| Columbus in 1492. Modern genetic analysis now seems to back up
| his idea long after he made his successful voyage.
|
| https://www.kon-tiki.no/expeditions/kon-tiki-expedition/
| https://en.wikipedia.org/wiki/Kon-Tiki_expedition
| ericd wrote:
| There was a great movie shot by the sailors before and during
| their voyage, I think called Kon-Tiki, and released in 1950 (
| https://en.wikipedia.org/wiki/Kon-Tiki_(1950_film) ). It used
| to be up on Youtube, but I can't seem to find it. If anyone can
| dig up a link, it's very worth a watch. IIRC, they're almost
| hilariously casual about the whole thing, and they just went
| and crossed the Pacific on a raft of logs, with little support.
| eesmith wrote:
| It was a bit more than "could have reached Polynesia."
|
| As your Wikipedia link points out:
|
| > Heyerdahl's hypothesis was part of early Eurocentric
| hyperdiffusionism and the westerner disbelief that (non-white)
| "stone-age" peoples with "no math" could colonize islands
| separated by vast distances of ocean water, even against
| prevailing winds and currents. He rejected the highly skilled
| voyaging and navigating traditions of the Austronesian peoples
| and instead argued that Polynesia was settled from boats
| following the wind and currents for navigation from South
| America.
|
| As a sort of mirror image of Kon-Tiki, the 1976 Hokule`a trip
| from Hawaii to Tahiti - using traditional non-instrument
| wayfinding methods from one of the last Polynesian master
| navigators, Mau Piailug - conclusively demonstrated that
| viewpoint wrong.
| eitland wrote:
| I think modern genetic analysis has proven Thor Heyerdahl
| wrong. From the linked article:
|
| > Heyerdahl's hypothesis of Polynesian origins is
| overwhelmingly rejected by scientists today. Archaeological,
| linguistic, cultural, and genetic evidence all support a
| western origin (from Island Southeast Asia) for Polynesians via
| the Austronesian expansion.
| RjQoLCOSwiIKfpm wrote:
| A must-watch in that context is the Oscar-nominated 1972
| documentary on Thor Heyerdahl's Ra expeditions.
|
| They attempted to cross the Atlantic on papyrus boats, based on
| drawings and models from ancient Egypt.
|
| Here's a good picture of their second boat:
|
| https://upload.wikimedia.org/wikipedia/commons/0/09/19-08-28...
|
| Here's the documentary:
|
| Part 1: https://www.youtube.com/watch?v=EJDYiTYoaLE Part 2:
| https://www.youtube.com/watch?v=hb6Jsudv7lg
| gerdesj wrote:
| His (Thor's) books are a cracking read too.
| [deleted]
| ChrisMarshallNY wrote:
| Yeah, I came to mention the Kon-Tiki:
| https://en.wikipedia.org/wiki/Kon-Tiki_expedition
| ghaff wrote:
| These are things that National Geographic readers of a
| certain age were all very familiar with.
| otabdeveloper4 wrote:
| I think this is pretty common.
| WalterBright wrote:
| It took me a loooong time to intuitively understand how a ship
| can sail upwind. The diagrams and explanations made no sense to
| me.
|
| I finally figured it out, though. Take a drafting triangle, which
| has 30-60-90 degree angles. Place the 30-90 side against a wall
| or something rigid. Take a block (wind) and press on the 30-60
| side. The triangle will squeeze "upwind" in the direction
| perpendicular to the 30-90 side (in addition to a larger movement
| sideways towards the 60-90 side).
|
| The keel of the boat plays the role of the 30-90 side against the
| wall, the sail the 30-60 side.
| bicx wrote:
| I got into sailing for a bit (poor man's sailing in a 16'
| sailing kayak), and it took a lot of mental processing for me
| to realize how the keel (or a form of hull acting as a keel) is
| essential for sailing upwind. The physics are really
| interesting.
| Prcmaker wrote:
| I used to sail and fairly quickly got the understanding for
| sailing up-wind. The thing that blew my mind, and continues to,
| is that the top speed you can reach is dependant upon the
| length of the boat and not the weight. This obviously excludes
| modern things like motorised craft, planing, foiling etc.
| hutzlibu wrote:
| "The thing that blew my mind, and continues to, is that the
| top speed you can reach is dependant upon the length of the
| boat and not the weight"
|
| Is there a simple explanation for this to share?
| leetcrew wrote:
| you might find this video helpful:
| https://www.youtube.com/watch?v=URgSFglbl5g
| gerdesj wrote:
| Longer => greater surface area in contact with the water.
|
| Friction and stiction due to area is a greater killer of
| speed than weight, which will only put you a bit lower in
| the water.
|
| It is obviously a lot more complicated than that. Enough
| weight will sink you and more length will slow your descent
| to the depths a bit. Greater weight will increase inertia
| so acceleration will take a hit. Depending on how the
| weight is distributed you risk turn over due to your meta
| centre being in the wrong place in relation to your centre
| of gravity.
| closewith wrote:
| > Longer => greater surface area in contact with the
| water.
|
| >Friction and stiction due to area is a greater killer of
| speed than weight, which will only put you a bit lower in
| the water.
|
| The opposite is true.
|
| The longer a hull, the faster a displacement vessel can
| travel. Here's an MIT explanation:
| https://engineering.mit.edu/engage/ask-an-engineer/what-
| is-t...
| mhandley wrote:
| As a boat moves through the water it creates a bow wave.
| The wavelength (ie crest to crest) of the bow wave
| increases with boat speed. Once the wavelength of the bow
| wave equals the hull length, the boat will start climbing
| the front of the bow wave and will be sailing up hill.
| Unless you've got a lot of power and can climb on top of
| the bow wave and plane, this is the maximum hull speed.
| chrisweekly wrote:
| When it comes to explaining how keels allow sailboats to point
| close to the wind, I always liked "squeeze a watermelon seed,
| it shoots forward" as a way to make it more intuitive.
| gerdesj wrote:
| If you look down on a bermuda rigged (big triangle) sail from
| above, it looks suspiciously like an aerofoil and those things
| fly. There is an angle away from the wind coming towards you
| which is as "close as you can get to the wind". At that point
| you are "close hauled", Try and go closer to the wind and your
| leading edge will collapse (luffing) and you will slow down
| rapidly and it gets a bit rubbish.
|
| As you move away from the wind your speed will increase because
| of several things: less of the wind vector is trying to blow
| you sideways and more is actually pushing you. The aerofoil
| lift thing is less important compared to being pushed. The
| sweet spot is at around 120 degrees off the wind - there is
| loads of push and loads of "lift" and a minimal amount of
| sideways force being counteracted by the hull. This is called a
| "broad reach".
|
| When the wind is behind you "running", there is a lot of push
| and no "lift" but instead you get drag due to the break up of
| laminar flow over the wing errr sail. However, in a run you
| send up spinnakers and "big boys" which are all basically
| bloody great bags to capture the wind and massively increase
| speed. Even a small yacht can "goosewing" by putting up two of
| the front sails - one on each side to increase sail area.
|
| I've done about 30mph on a wind surfer in a broadreach - my mum
| drove along a road parallel to the beach and the wind was just
| right to do a broad reach roughly parallel to the beach and
| road. A car speedo is usually 10% shy of reality.
|
| Sailing is great fun and can be really complicated but once you
| know your halyard from your sheet and all that stuff and get to
| the point where you can feel the wind and can see the
| conditions on the water and all the other things going on it is
| rather rewarding. The point of going from novice to supervised
| fun is quite quick - a weekend or so in a dinghy. A couple of
| weekends to be confident solo inland and a bit longer at sea.
| You do need to think safe.
|
| Get it wrong and it can be a right old downer!
| alanning wrote:
| "Modern mariners can tack against the wind by setting the sails
| at sharp angles. That wasn't feasible 2,400 years ago because
| sails were fixed then."
|
| From the picture it seems the sail on the replica can pivot
| around the mast but looks like it would take a lot of work (and
| time) with all the rigging.
|
| So is this quote's meaning that modern sailboats can change the
| angle of its sail fast enough to be useful while the ancient ones
| couldn't?
| codeduck wrote:
| square rigged vessels cannot make way upwind; they are limited
| to approximately 60 degrees either side of the wind, and would
| have terrible sailing characteristics in this position that
| would push them downwind to the level that they could probably
| not travel a true course within even 90 degrees of the wind.
|
| lateen (think dhow) sails were around from about 200 bc but
| only became widespread later. They are more efficient efficient
| upwind and permit a boat to point close enough to the wind to
| move a meaningful distance "upwind"
| sandworm101 wrote:
| There was more to it than just sails. Keel and rudder tech had
| to evolve too. Tacking a ship upwind is a special thing that
| involves every aspect of sail and hull to accomplish. And the
| equipment to do it comes with drawbacks.
| ourmandave wrote:
| In the Mediterranean Sea the winds predictably reverse (and have
| for centuries) so sailors would schedule around when they were
| blowing favorably in the right direction.
|
| They might wait days within the cycle to get the best conditions.
|
| You're welcome.
| gerdesj wrote:
| The Middle of the World sea is mostly land locked. Close to
| land the winds run off shore (away from the shore) in the
| morning and then back to on shore (point towards the shore) in
| the afternoon. This is because in the morning the land is
| relatively cool and in the afternoon it is relatively warm. The
| thermal gradient above the land and sea then determines the
| wind direction. This pattern is mostly seen in the summer and
| less so in the other three seasons, when it gets a bit more
| random.
|
| Now it all gets a bit complicated depending on which bit of sea
| is being affected by which bit of land. On top of that the Med
| has weather systems just like everywhere else and they can get
| a bit feisty. Early in the (Christian) New Year you get the big
| old winds like the Ghibli and co dumping sand into your Brandy
| Sour.
|
| I lived in Cyprus for two years back in the 1980s and spent
| quite a lot of that time in and on the water.
| gerdesj wrote:
| I have now actually read the article. It seems that no
| sailors were harmed in it.
|
| I really don't buy this article's premise.
|
| Even a vessel with run only sails can plot a course by
| working out which bit of land is affecting the patch of sea
| they are traversing. In the areas where land doesn't have a
| direct effect, you get to play the usual lottery with wind
| and weather. Even when the wind is against them, they should
| be able to manage slightly better than a "abeam close reach"
| so go slightly against the wind.
|
| "Modern mariners can tack against the wind by setting the
| sails at sharp angles. That wasn't feasible 2,400 years ago
| because sails were fixed then."
|
| No they were not "fixed" at all - look at the picture of the
| replica - it is running close hauled. The sail is tied off
| fore and aft and not at right angles to travel. The article
| literally contradicts itself with photo evidence. If you look
| really closely at the modern yacht with a Bermuda rig - it's
| sails are luffing!
| ChrisMarshallNY wrote:
| Before the lateen sail.
|
| https://www.britannica.com/technology/lateen-sail (and a deep
| keel)
| ip26 wrote:
| Yet, without such favorable conditions to _develop_ sailing,
| would the lateen have been invented? (technology ladder
| theory)
|
| The more we learn about the Mediterranean, the more I am
| struck that it was the perfect crucible, and that it is no
| accident it was the epicenter of so much in human history.
| samatman wrote:
| Maybe, maybe not, but there are other ways to sail upwind,
| such as the proa https://en.wikipedia.org/wiki/Proa .
|
| When it comes to basic applications of fundamental machines
| (this is ultimately a use of leverage), humans have a way
| of figuring it out.
| epilys wrote:
| The sea peoples are back!
| fredsmith219 wrote:
| Run!
| ThinkBeat wrote:
| I would like to mention Thor Heyerdahls expeditions
|
| In 1947 he crossed the Pacific Ocean on the balsawood raft Kon-
| Tiki.
|
| This was his first expedition to be captured on film, and was
| later awarded Academy Award for best documentary
|
| In 1951. He later completed similar achievements with the reed
| boats Ra, Ra II and Tigris.
|
| https://www.britannica.com/biography/Thor-Heyerdahl
|
| https://www.kon-tiki.no/thor-heyerdahl/
|
| https://en.wikipedia.org/wiki/Thor_Heyerdahl
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