Placement of seat in a kayak?

Petros,
There's been a lot progress in boat design since "native watercraft" and rudders is element of progress. We can learn a great deal from them however. Balanced kayaks w/o rudders can work quite well but put a bigger or smaller person in them and maybe not so good. Mainly the rudder allows us to have powerful directional control that can help us overcome the excessive directional
stability in most "touring" kayaks. Rudderless designs were tried and now I think most designers have decided rudders are a good thing.

Easy

 

origami layout updated

I have updated the origami layout to be suitable to build from 1.25m strips.
I am very hesitant to actually choose the building material, but everything I have considered so far comes in 1.25m size

The considered choices:
- FRP: It is the most possible choice. I am experimenting with flax composite right now, I will see its outcome. If it won't come out good, I can still use glass, which is more than twice cheaper (I find this fact a proof of how sick is the world we live in.).
- steel: yes, but made from 1mm it would be some 40kg. I guess building from anything thinner would be fool.
- alu: I don't even know what would be the suitable thickness if using alu. As it's density is nearly half of steel, anything above 1.5mm would be too heavy. But what would be mechanically adequate?

 

You could do a 3-section boat, with a front end, cockpit and rear end, but that would involve other problems.

Also I am not real attracted to origami for such small boats as this. Trying to cut from a single sheet seems to leave a lot of waste. The large boats are "built flat", with the sheets welded together as needed to avoid waste, they don't try to start with a 20m x 12m sheet of steel just so they can cut the whole pattern out in one piece. But to weld the sheets together, you would need to use metal that was thick enough to reliably butt-weld (weld it edge-to-edge).

Many larger aluminum canoes use .050" (1.25mm), with some vintage and smaller models using .040" (1mm). These boats were always riveted together, and had some internal stiffeners. Some flat-bottom (paddled) boats that are built extra-heavy-duty or for small-engine use, will use .065" (1.65mm) for the bottom and thinner metal for the sides.

I do know that there are inland motor boats in the 6-7m range that have hulls built entirely out of .080" (2mm), so that would seem to be overkill for a single-person rowed boat.

----------

Really the main problem with aluminum is what you could join reliably. The easiest way to join thin aluminum would probably be riveting, but you'd need to be able to reach the back side of the rivet to do that. So you would need to make a "canoe" and then make a "lid" to close in the top of the boat.... {-which could make the boat a lot more convenient to use overall, but involves a whole different design-}.

You could weld the aluminum also, but a TIG is expensive and using a gas torch on aluminum that thin is a skill all in itself. With no easy way to reach the back side of much of the weld seams, patching any holes you blow would be difficult.
Another consideration is that welding aluminum provides a certain waterproof join, but also softens it along the weld as well. (I am planning on "trying" to build a small aluminum row boat.... I at first thought I would weld my entire boat, but now think I will weld it below the waterline, and rivet it above)

One reason to use thicker aluminum is that (if you are welding it) thicker aluminum is drastically easier to weld. Most commercially-made welded aluminum boats use metal that is at least .100" thick, just because they can reliably MIG-weld sheet of that thickness..... I bought some .050", .080" and .100" pieces of sheet to practice gas-torch welding on, and noticed early on that welding on the thicker sheet is much easier to do than the thinnest sheet.
~

 

This is exactly the kind of modern thinking that dismisses some 2000-3000 years of development by native kayakers. Like somehow because we use computers to draw pictures now it means we are smarter than the people who used them everyday to stay alive for thousands of years. This is just modern arrogance, and really more like modern people being impressed with their own inventions and dismissing ancient technology as if it is unworthy of consideration. It is very difficult to improve on that well developed a design, computer analysis or not, especially since it was a matter of survial, not recreation.

The computer is not a substitute for knowing your subject. This I say as a modern engineer that uses computers daily to do my job. I have had computer wiz kid engineers working for me that made very fundamental errors in their analysis, and assumed that the answers were correct because that is what the computer output indicated. They could not even tell that the output was off by whole orders of magnitude because they had no feel for what they were doing. The same is true with hull designs, especially for something as small as a kayak.

I have been using canoes and kayaks for almost 40 years, paddled many hundreds of miles in all kinds of conditions. I have paddled just about every manufacturer's modern design, none perform as well as a typical native design in my experience. Most of the modern rudders were poorly designed, as were the hulls and paddles. Most of the people in the business of making production kayaks do not have enough knowledge to know if their hulls are really better or not, they are mostly products of marketing to consumers who mostly do not know what to look for in a kayak. There are good designers out there, but like most everything else these days, the majority of stuff out there is junk.

A rudder is not "progress" if it is not necessary. A design is best when there is nothing to remove from it, not when there is nothing left to add to it. More useless junk hanging off a kayak (or any boat for that matter) is only something else to malfunction, maintain, and drag along on the trip. Nothing good comes of it when it is not necessary. The best hull design is one that DO NOT NEED a rudder to control it. Rudders are adaptations from larger "white man" boats scaled down to fit on a native water craft. I have rudders on many of the other boats I have owned, but not on a kayak or canoe.

Sorry for the long rant, but that is my experienced and professional opinion. Do not dismiss something just because it was used by our ancestors.

BTW, that kayak can be built as a skin-on-frame: Use 20 mm square wood stringers, plywood bulkheads, lash the frame with polyester lacing cord (or even dental floss works good) and heavy nylon or even cotton fabric skin (hand stitch it closed), and paint with polyurethane or oil based paint. Inexpensive, fast to build, and very light.

 

Petros,
Thanks for your well thought out and well presented response. I understand
what you have said and frequently have similar thoughts. However turn signals, windshield wipers, lightweight diesels, fiberglass boat construction, GPS and 10s of thousands of other things that almost all people think of as progress are not necessary but useful and worth the effort. Just because it took these ancients 3000yrs to design and make a Kayak dosn't mean they are superior.
The ancients did however spend much much more time developing their boats and were so intimate with them they understood things that we haven't got the time or drive to find out. Think about all the time we waste working at our jobs that aren't directly related to our well being (other that the money), driving cars, fixing and otherwise maintaining our extensive infrastructure ect ect. All these things the ancients didn't need to do. I sometimes think of the philosophers of old, most of them were elite and had no chores to do. They spent all of their time with the questions of life. I think they discovered and learned things that modern man can't get near because we spend so much time in the great machine that sustains our lives there's not enough time or/and focus to relate to that kind of knowledge. The ancient kayakers were largely like that except using, developing and building their boats was more like work but the drive to make them as good as possible was borne out of survival and necessity to an extent that no modern man, thinking about his next BigMac and his drive home will ever have the opportunity to excel as the ancient philosophers and kayakers did.
I still think a modern kayak is best equipped with a rudder and/or foot pedals.
By the way I lived on 188th by the ultralight airfield for 20 yrs.

 

So get one with a rudder/skeg, or don't. And get one with a flat bottom, or choose one of the (few) that are still made with rounded bottoms.

But many kayak owners seem to think that flat bottoms and rudders/skegs are a pretty good idea, and companies only build what sells. I dare say those owners are probably not as concerned with looking like an Eskimo as they are having a boat that tends to stay upright and that points where they want it to, particularly in rough conditions.

I don't disagree with any of this advice, but I would still point out that an authentic kayak is made only from driftwood ,sealskins and other parts of available animals. It seems a bit odd to insist that adding a rudder is totally unacceptable while using all this other modern stuff is perfectly reasonable.
~

 

Since two or three comments I am thinking whether to declare the rudder and skeg issue to be beaten to death. But it is at least in a civilized manner, and anyway I cannot resist to further drift away from the original subject

Yes, companies only build what sells. But what sells is often not the most efficient one. The wide public is not an expert in any areas, and any feature, even the most counterproductive one is a selling point in the marketing brochure.
If you are well in something, you may have noticed that really good stuff is either unavailable or have exorbitant prices.
So the fact that it is hard to buy a kayak without rudder is not a proof for the fact that it is superior. And neither a proof that it is not. Actually I think - as I said before - that it is a matter of personal taste and abilities.
In my case my son can paddle better than I can build and maintain a rudder or skeg. Well, the building and maintenance is my responsibility, paddling is his, and the decision is mine

 

As an former race canoer footrests and rudders are essential in any performing kayak. I will not argue that those are items Inuits are in no requrement of, but if speed is by any priority those are a must. Modern long range canoes is however outside my knowlede.

Not said that you should build one but a proper racer is hard to handle but it´s like riding a bike and after you learned you will do very well even in rough conditions. The bottom is not v-shaped but rather somewere
between V and U.