Jump to content

Rich D

What is the function of the Bifurcated bow?

Recommended Posts

I've often wondered but could never see the reason for the bifurcated bow, except, possibly, to stay true to tradition. What purpose does it serve? There must have been a reason for it for the original builders to build them that way but I have never seen an explanation for it.

Share this post


Link to post
Share on other sites

Joe Greenly of Redfish Kayaks in Port Townsend, Washington says it is not for more effeciency as it cuts through the waves.  His theory is that it is the shape required because of the seal skin you are using limits you to this option only.  How that is the case I do not understand.  I would like to someday see a seal skinned bidairka.  One documentary from the early 90's I remember seeing said they managed the waves of the ocean better when built this way.

Share this post


Link to post
Share on other sites

I've heard that too Rex. To explain it a little more as best as I can, it allows for slightly more hollow at the bow when viewed from a cross section. The bottom split is skinnier so it allows the boat to slice through the water in smooth conditions. The upper part of the split creates a wider section of the skin. The wider more buoyant section allows the front end to bob over waves. So the idea is to have a front end with good flat water speed that doesn't sacrifice seaworthiness. This couldn't be easily achieved without the split as the skin would naturally stretch taught and even out the width differential. Now for the disclaimer: this is purely speculation from smarter people than me who have observed the boats. We can't talk to the developers of the original concept and ask them why for obvious reasons.

Share this post


Link to post
Share on other sites

  Hirilonde I think you hit on a possibility.  I once attended an event called something like the Native Inuit Kayak Symposium in Washington State, along the West Coast.  Those guys were

teaching kayaking skills and my wife and I were able to make a nice Greenland paddle and a sprayskirt.  What I was interested in was the Inuit type of kayaks and paddling and so on.

What I found was they should have been called the Greenland Kayak Symposium because all they new could be traced back to instructions given by an old fellow in Greenland whose skills were nearly lost before he passed away.  The kayaks had made their way east over hundreds of years and had been tailored for their particular needs.

  The answers for questions we have about Inuits were lost because of the speed in their demise at he hands of Russian and European cultures.

Whatever their methods, I have learned to respect their 'Kahunas' for being willing to hook up to a whale in the open ocean while in a kayak.  I know motivation is intense when your family is

hungry.  Still, I can remember the fear I encountered while being in waves on Lake Michigan way beyond my skills and I wasn't hooked up to anything.  Hats off to the original kayakers.

Share this post


Link to post
Share on other sites

The bifurcated bow probably works like the bulbous bow found on most newer ocean-going vessels. The theory is that this bow shape causes a secondary bow wave further out, which partially cancels out the principal bow wave, thereby reducing wave-induced drag. The effect is most noticeable at velocities approaching hull speed, which makes sense for large, ocean-going vessels, as well as for kayaks. For vessels that operate at lower velocities, the bulbous bow is not efficient as it increases drag due to greater wetted area.

Fair winds, Andy

Share this post


Link to post
Share on other sites

I believe that Professor Irwin P. Corey may have said the slight turbulence created by the bifurcated bow ionizes the water and the negativity of the ionized H2O results in an infinitesimal magnetic field that is repellant to the hull material thereby reducing resistance and producing a small retropulsive force at the stern resulting in a small additive propulsive effect that increases the efficiency of the occupant.  He also theorized that the ionization of the H2O adjacent to the hull has a attractive gathering effect on certain ocean fish and mammals.

 

But I could be wrong. :D

  • Like 1

Share this post


Link to post
Share on other sites

Well I think is was to appease some of their Gods.  Or some significance like that.  I don't think they were into all the wave resistance, being the coefficient of .... stuff, 

just my opinion...  :)

Share this post


Link to post
Share on other sites

If you are going to make up a reason then make up a good one  :P

I believe that Professor Irwin P. Corey may have said the slight turbulence created by the bifurcated bow ionizes the water and the negativity of the ionized H2O results in an infinitesimal magnetic field that is repellant to the hull material thereby reducing resistance and producing a small retropulsive force at the stern resulting in a small additive propulsive effect that increases the efficiency of the occupant.  He also theorized that the ionization of the H2O adjacent to the hull has a attractive gathering effect on certain ocean fish and mammals.

 

But I could be wrong. :D

Share this post


Link to post
Share on other sites

 

I believe that Professor Irwin P. Corey may have said the slight turbulence created by the bifurcated bow ionizes the water and the negativity of the ionized H2O results in an infinitesimal magnetic field that is repellant to the hull material thereby reducing resistance and producing a small retropulsive force at the stern resulting in a small additive propulsive effect that increases the efficiency of the occupant.  He also theorized that the ionization of the H2O adjacent to the hull has a attractive gathering effect on certain ocean fish and mammals. But I could be wrong. :D

Yeah - I'm going with this one :>) If I can just remember it when someone asks...

Share this post


Link to post
Share on other sites

Touche, Bcone1381!  I couldn't have said it better (actually, I couldn't have said it).  Great laugh.  And thanks for the vote and wonderful sportsmanship, Rich D.  I just couldn't resist.  Was simply meant in fun. You all make this a wonderful forum. 

Share this post


Link to post
Share on other sites

I have been waiting on this.  There are several different styles so that makes answering the "Why" even more complicated.
 
One thing never tossed out is that maybe some was a joker and have some fun. Or a builder had an artist eye.  :unsure:
 
Just to add a little confusion to this discussion. 
 
Polynesian examples of bifids.
 
Posted Image
 
Posted Image
 
Posted Image
 
 
Even the Alaskan version has several versions. Unfortunately I can't find images online of all of them.
 
Posted Image
 
 
Posted Image
 
So when you talk about them it is kind of like saying kayak, it covers a lot of ground!

Share this post


Link to post
Share on other sites

Scientific American Frontiers had a nice section on this in 1991 on episode 203 -The Baidarka : A Legendary Aleut Kayak  It shows the cool Aleut hat as well. 

They uncovered one on Anangula Island that was built about 8,750 years ago (3,000 years before the Great Pyramids).  It tells of George Dyson reconstructing one.

I googled the episode at Scientific American Frontiers episode 203.  George Dyson says the reconstructed versions behaves well in waves.  He also mentions that

stealth was one of the Aleuts main objectives.

Share this post


Link to post
Share on other sites

Rex thank you for that!  Here's a transcript:

 

NARRATION An Olympic champion and his raring kayak help solve the mystery of this ancient boat - and bring it back to its Aleutian home. Also - the spider says "goodbye" with silk - but it says 'hello" with flowers. Babbling babies - they can't speak, but they can tell us how we talk. And a new cure for brain tumors - it takes just twenty minutes. All coming up, on Scientific American Frontiers.

back to top

THE BAIDARKA REBORN

WOODIE FLOWERS Hi. I'm Woodie Flowers, and welcome to Scientific American Frontiers. You know, a canoe is a nice boat Lightweight, efficient, easy to paddle. But where did the canoe come from? I don't mean who manufactured it, but where did the design come from? The answer is - we really don't know! It's the same with kayaks. Although nowadays we mass produce boats like this, canoe and kayak designs were developed by Native Americans so long ago - many thousands of years - that their origins have been completely lost. This great boat building tradition flourished all across the continent. But we're just discovering that it was most refined was on the remote Aleutian Islands, halfway to Siberia, a piece of America a thousand miles from the mainland.

WOODIE FLOWERS (NARRATION) A funeral for thirty native Americans. But these remains are seven hundred years old. Ancestors of these Aleut people who live in the village of Nikolski. The nearby burial cave, discovered a year ago, contained the remains. The Aleuts decided an investigation was justified. It meant no disrespect for the dead, because the aim was so vital - to rediscover their own history. To help reveal the past, anthropologist Bill Laughlin has worked alongside the people here for the past fifty years. These 1948 home movies show one of Laughlin's earliest digs at the site of an ancient village. His discoveries have steadily revealed a way of life that has thrived here for 9000 years. The key to this achievement was not on the land - it was out at sea.

 

BILL LAUGHLIN "This is an especially good place to see the historical panorama of the interaction between the Aleut hunters and collectors and the sea from which all their resources came. Everything they needed came out of the ocean. And the biggest challenge of course is to go out on the open sea and harpoon a sea lion or a whale."

NARRATION The treeless tundra of these islands holds Little that sustains life. While the surrounding ocean is rich in whales, seals, fish of many kinds. But to hunt and travel year-round required an ocean-going vessel that could stand up to the roughest waters and worst weather in the world. The Aleuts developed a sophisticated boat design that met these challenges for thousands of years. Their invention was an ocean kayak, named the baidarka by Russian explorers. Fast... sea-worthy ... it was the crowning achievement of the Aleut hunters. Boat builder George Dyson is out to learn the mysteries of baidarka design and performance. Accounts by 18th century Russian colonists describe extremely fast boats - but no examples survive. To recreate how the high-speed baidarka worked, George's only guide is this tantalizing sketch, two centuries old, of an odd looking craft.

 

GEORGE DYSON From these sketches and from what is being discovered in burial cases and so on, archaeological evidence, how do we reconstruct the dynamics of boat budding at that time from what really is only fragmentary evidence. And the only way to do that is by reconstructing the vessels themselves.

NARRATION The original frames were made of pieces of driftwood, a scarce and precious building material. In his workshop north of Seattle, George Dyson has other choices. He's trying out aluminum tubing while colleague Joe Lubischer experiments with the same design made from wood. The flame presents some perplexing features. A bow like an open jaw - was it functional or purely decorative? The stern ends not in a point, but in a square. Why? Inset in places - bone bearings where the parts rub together. The ancient boat builders obviously didn't want a rigid structure. They used loose lashings as well. The result is a very flexible skeleton. Over this frame, Aleut Mike Lekanoff sews on a nylon covering - a substitute for the sea lion hide his ancestors used. A flexible skeleton wrapped in soft skin - just like the sea mammals the Aleuts hunted. For the first test they've chosen a calm fresh water lake, where it will be easy to measure speeds on a quarter-mile run. Recruited to paddle is Greg Barton, world record holding Olympic gold medallist. He'll run the course first in his own racing kayak. Greys strength roughly matches a typical Aleut hunter who, like Greg, kayaked every day. But his kayak is radically different from the Aleut baidarka.

GREG BARTON This kayak is designed specifically for racing on calm water in a straight line. It's very narrow, that's the main difference between this kayak and the others. This is much skinnier, it has much less resistance in the water.

NARRATION Resistance is created when a boat pushes water aside, forming waves at the bow and stern. The faster it goes, the larger these waves grow. The paddler has to climb up his own waves. So as the boat makes big waves, it reaches a sort of natural speed limit that's tough to beat. Greg's racing boat is more streamlined than the average kayak. You can see the small waves it's creating. Full out, he hits ten miles an hour... Olympic class sprint speed. Now the baidarka. Based on its larger hull it's bound to be slower. But how much slower, no one knows. Greg puts out all he has and hits nine miles an hour - extremely fast for a kayak this size, matching the best high performance commercial models. But the two-piece bow seems to be doing little - it's right out of the water! In fact what's happening is the boat is planing - skimming the surface. It's a way to beat the speed limit of its own waves, a trick well-known to modern boat designers. But it looks like the Aleuts got there first. The trials were revealing - but not realistic. Baidarkas were meant for different conditions.

GREG BARTON If you took these same boats and put them in some six foot swells, I'd be swimming ashore with my race boat and I'd still be paddling the other boats. And also the speeds may vary. The other boats probably wouldn't slow down nearly as much whereas the race boat would be floundering and you'd be spending a lot of time just trying to keep the boat upright.

NARRATION So for the ultimate test, Frontiers has arranged to bring the baidarka back to its roots in the Aleutian Islands. It's high summer here but the weather is still cool and the waves are still ominously large. We're going back to the village of Nikolski, ancient center of traditional Aleut boat building. They still depend on the sea for their livelihood. But no one's hunted in a baidarka for 80 years. George Dyson and Bill Laughlin are on hand for the baidarkas' arrival. The boats will have come 3000 miles from Seattle - first by commercial jet to the nearest fishing port, then three days at sea on board a fifty foot trawler. Finally, they're transferred to small boats out in the bay - and then the baidarka is home at last. For the Aleuts it's a time of rediscovery.

BILL LAUGHLIN That's marvelous. I think that's the first time now since 1910 that real baidarkas have been brought ashore here. It's a historic moment.

NARRATION The young people have never seen a baidarka before - but for the older men the memories come flooding back.

BILL ERMELOFF They had a piece of sea lion hide about this wide and about five feet long that they put in there and that's where they sat They used grass for putting under their behind.

SCOTT Did they carry a lot of stuff in the old time baidarkas?

BILL ERMELOFF Yeah, they did carry quite a bit of stuff. They carried provisions and stuff to eat. Sometimes two or three baidarkas in a group would tie together and spend the night on the open sea when they were hunting sea otters.

NARRATION For George it's the moment of truth - the water is forty degrees, and it's going to be rough out there - dangerous waters for the boat's first ocean test. But he's a skilled kayaker and this, after all, it's where the boat belongs. As it works its way onto the open sea, the mysteries of the baidarka's strange design will be mysteries no longer. The open jaw bow has an obvious sanction: the lower section pierces the surface, providing dean entry into the water. The wide upper bow gives the boat lift as it crashes into swells. Without it the baidarka would nose dive into the waves. So the ancient designers managed to combine different qualities in a single craft high speed during the hunt, safety and comfort cruising in big seas.

GEORGE DYSON It feels real nice in the rough water, feels like it was made for rough Water. The fact that it could achieve significant times on a flat water race course and also cut into this sloppy water as cleanly as it does definitely shows the real virtues of a versatile design.

NARRATION Another virtue is the flexible frame. Working in rough conditions every day, a rigid boat would wear out quickly. But with a shock-absorbing hull the baidarka can bend with the waves instead of straining against them. The Aleut designers could also turn the dangerous surf to their advantage. The wide square stern catches the energy from following waves pushing the boat on its way.

GEORGE DYSON This thing would surf like crazy if you had the power to get on top of these waves.

NARRATION With an experienced kayaker like George making it look simple, it isn't long before everyone wants a go at it.

 

LARRY PLETNIKOFF:: Let's try it out, eh? I'd like to try it out.

NARRATION Larry Pletnikoff has never gone kayaking before. And remember, this is an expert level boat - it's very tippy. But even a tumble into the frigid bay doesn't phase the brave at heart.

LARRY PLETNIKOFF: Oh, it was great?

GEORGE DYSON I couldn't believe he stayed up as long as he did! I've never found anybody who's never kayaked before who stayed up that long!

LARRY PLETNIKOFF: I did it today, ehhh?

NARRATION In the hands of its inventors, the baidarka is back in home waters.

WOODIE FLOWERS Now that the baidarka has returned to the Aleutians, the local people are determined to revive their boating traditions. And it's not too late. As we just saw, there are still a few older people who remember what it took, especially the extraordinary physical skill and stamina. Young boys started training from their earliest years - at age four or so. They played with model baidarkas... They even had miniature harpoons like this to get ready for the real thing. And all the time they did exercises .... Like hanging by your fingers to develop the muscles that hold the paddle.., and sitting with legs straight out - like you would in a baidarka - and leaning forward, to develop flexibility.., or stretching exercises like this... All designed to ensure that the abilities of the Aleut paddler matched the abilities of their wonderful boat, which is now back in its original home.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.