Can a kayak be designed not to weathercock or leecock?

[mitchgrunes]

Please correct any errors I have made, and answer my questions:

Most sea kayaks are designed to weathercock in the wind when used without a skeg or rudder, and if you don't adjust the trim using weight or seat position, and don't have any hulltop objects, the bow rides lower with respect to the water surface when you are moving forwards, and is therefore less exposed to the wind. Hence the stern is blown more sideways by the wind than the bow, which means the boat tends to turn into the wind.

The same response tends to be true for surface waves. Riding higher means the bow has more cross section to the parts of waves that are above the waterline, so such boats also turn into waves.

A few sea kayaks leecock - the exact opposite. The stern tends to ride lower, and it blows in the wind sideways more than the bow, so you turn out of the wind.

All sea kayaks I know of are displacement hulls. (Though I'm not sure that is true of "surf boats". Perhaps they are more like whitewater playboats, which are mostly planning hulls, though I think whitewater racing boats are almost all displacement hulls. BTW, I don't race.) That means as they move forwards, they effectively pull water up from below, and push it to the sides. This both creates the drag and means the end that has more drag (if there is one) is drawn downwards more than the end that has less. It also means end with more drag has a bigger bow or stern wave than the other.

Most sea kayaks have a bigger bow wave than a stern wave, and there is more drag up front - and that means they weathercock.

You can change trim any number of ways in a given boat. You can alter the trim by adding weight to the front or rear. Or by adjusting the seat position to the front or rear. If there is no seat per se, by adjusting your position.

You can also alter the things you have strapped to your front and rear deck. (E.g., spare paddle, water pump, in some cases a paddle float, water bottle.) These things typically have more cross section to the wind than a bare deck, hence they can be used to make the boat weathercock or leecock. All these things are typically kept on the deck for safety, with the possible exception of the water bottle, which is much more useful on the deck than below. (I've tried do tubes attached to backpack or sterntop water sources, but so far haven't found one that works well.)

A kayak designed to be controlled without a skeg or rudder can be neutral in the sense of neither weathercocking nor leecocking in the wind.

As best I understand it, the tendency to weathercock is optimal for kayaks to be controlled by a skeg or rudder. Because the skeg or rudder are only effective when submerged.

Hence kayakers who routinely use a skeg or rudder tend to pick boats that need skegs or rudders, and often believe they all do. But maybe this is circular reasoning. They pick a boat designed to need them, hence they use them. And they use them, hence they pick a boat designed to need them. Perhaps it's somewhat like having a drug addiction? (You don't need to respond to that question. It was only asked in fun. )

I have no rudder or skeg. Frankly, I fear to make a mistake that would damage a rudder or skeg, by hitting a submerged object, or by forgetting to raise it before launching or landing. I deliberately chose one of my boats that was fairly close to neutral (a roughly 1998 era Current Designs Caribou - not a Caribou S, which had a skeg), though it isn't perfect. I think it comes close to neutral in the wind, but it sometimes turns in waves, from some directions. I haven't figured out the full pattern.

I also worry that if a skeg or especially a rudder is damaged, it might get stuck, and cause the boat to turn forever in circles. (Remember the Bismarck?) So one would need to exit the boat to bring it up, which could be somewhat unsafe in dangerous conditions, because it would be harder to re-enter the boat from the water. (Yes, I know you should never paddle alone. But most of us do sometimes anyway. Likewise we should try to avoid dangerous conditions, especially when paddling alone. But sometimes dangerous conditions blow up without your expecting them to.)

1. Is there a tradeoff? I.E., are boats that are designed to be neutral in the wind and waves necessarily less efficient? E.g., must they have more drag, from the water or air?

2. Another big question: Is it possible to design an efficient boat so that it is neutral in the wind, and also neutral in waves, from all possible directions?

(Obviously, you can't make a boat completely neutral, when launching and landing. Because near shore, the wind and waves may not be the same in the front or rear. E.g., shorebreak. So this is all an idealization. And the greatest control problems I have had are in shorebreak. But those are exactly the times when a skeg or rudder is least safe to use.)

 

[gonzo]

Kayaks, like all small boats' behavior is hugely influenced by the crew position and movement. That is what makes them agile and quick to respond. It is possible to design a neutral kayak, but then the crew will have to be trained to be neutral also.

 

[mitchgrunes]

Yes, I understand that and I clarified that later by saying you can adjust your seat position, trim and aerodynamics. The main question I really meant to ask was whether can they be designed to be efficient and neutral. I.E., is there a tradeoff. But I couldn't figure out how to change the title to include "efficient".

I guess some kayak seats are easy to adjust in position. Mine isn't.

I didn't mention that I was basing what I was saying partly on
How Important Is A Rudder On A Kayak? Here's What To Know - Paddling Magazine https://paddlingmag.com/stories/columns/rock-the-boat/how-important-is-a-rudder-on-a-kayak/
and that he mentioned you can also lean your boat to adjust for turning forces. Any boat that doesn't have completely circular cross sections can be turned somewhat that way. E.g., by adjusting the position of your butt. (Because I find it uncomfortable AND inefficient to lean to one side for a long period. Plus my seat tends to lock me into a fairly specific position. And my relatively inflexible body also makes leaning forward or back much difficult.)

And of course there are many ways to use paddling strokes to adjust direction - but that is inefficient, in the sense that it reduces how much forward paddling power you can generate.

 

[mitchgrunes]

I should also explain that I am the crew. I can be trained - but don't want to waste effort on what good design creates naturally. Of course, this is all completely different than what I would want from a whitewater playboat, where the whole point IS modifying the way the boat responds. In contrast, I sea kayak to play tourist, to get exercise, and to try to keep up with a group of potentially younger and more athletic paddlers. If I waste energy on playboat style maneuvers, I won't keep up with them.

(A person in a sea kayak club I belong to claimed that the definition of a sea kayak necessarily includes a skeg or rudder, and originally specified that as a requirement for joining a trip. Interesting idea. AFAIK, skegs and rudders weren't introduced to kayaks until the 19th century, whereas traditional arctic sea kayaks probably go back for millennia, and many, perhaps most, still don't have them - though of course one can define terms like "sea kayak" any way one wants and a trip leader can choose what is allowed. E.g., recently surf skis and other sit-on-top boats, stand up paddleboards, and boats that look like open canoes and small sailboats and small motorboats that can also be paddled or pedaled are sometimes called kayaks, sometimes "sea kayaks".)

I realize that much of what I said is generic, and applies to boats that are not single person kayaks. Even big boats with large crews. But that's not my interest.

 

[gonzo]

I can categorically afirm that the original kayaks had no rudders. The Innui did not used them. Also, they original ones were rather short and narrow by todays standard of a sea kayak. When the weight of the crew is more than the weight of the boat, then a kayak withoug a skeg can be made to weathercock bow up or downwind by changing position.

 

[mitchgrunes]

By arctic kayaks, I wasn't just referring to Inuit boats. I meant all close deck boats used by various circumpolar peoples. I did a very quick non-authoritative web search, and found claims that Inuit, Greenland and Aleutian boats did not traditionally use skegs or rudders.

But
Modern invetions for ancient kayaks https://kajakkspesialisten.blogspot.com/2023/02/modern-invetions-for-ancient-kayaks.html
said

The kayak skeg or rudder, was invented late in the 19.th century by a Greenlandic seal hunter named Jens Reimer. It was further refined and developed by his hunting mates to the skeg we still see in Greenland today: A narrow wooden fin tied underneath the kayak's rear end. The reason for the invention was the introduction of rifles in kayak hunting...

I suppose the original absence might have been a consequence of materials and/or technology, or the need to easily launch and land. E.g., someone once told me that one major point of Greenland kayak design (with bow and stern above the waterline) was so they could easily glide onto an ice sheet. If so, having something fragile beneath the boat could have been counterproductive, for reasons I'll leave you to imagine. And for skegs, having something on the bottom that might leak might also have been counterproductive.

I have asked places that rent kayaks about them. They said rental boats with rudders or skegs spend a significant amount of time being repaired. Stores that sell kayaks also are able to get additional income by repairing them. And I know I make mistakes.

But Greg Barton said that Epic boats have them because they are much more efficient than having to correct for sea conditions. Though I wonder how much of that relates to racing, and to boats designed for racing. E.g., leaning would presumably be less effective for steering with an approximately circular cross section. My very brief attempts to using racing kayaks and surfskis made it clear to me I would have trouble remaining upright while leaning those boats too.

 

[portacruise]

Having a Rudder or skeg that can be easily/ quickly manually retracted or that automatically retracts, pivots, spins or otherwise moves in response to damaging pressures to hull or appendage -might be the way to go? Assuming such a thing hasn't already been tried, or can even be designed? I'm aware of dagger boards and kick up pivoting rudders, but perhaps there's further innovation possible with newer materials and design/simulation tools? Another approach is cheating; by using an extremely lightweight motor system- which is what I use to keep up with the young and the strong in non-sea kayak applications.. Best of both worlds.

 

[mitchgrunes]

Having a Rudder or skeg that can be easily/ quickly manually retracted or that automatically retracts, pivots, spins or otherwise moves in response to damaging pressures to hull or appendage -might be the way to go?

I think most kayak rudders can be manually retracted. So can all the adjustable skegs I have seen.

The problem is that people (including me!) make mistakes. Also that the mechanisms to retract them sometimes fail. E.g., a rope or cable breaks, or gets tangled in something.

I don't know automatically retracting rudder or skeg. Perhaps they exist? But I wonder if the conditions (e.g., large waves, current boundaries) under which rudders and skegs might be most useful would be conditions under which there might be large hydrodanmic forces on them - which might cause them to automatically retract, and lose their usefulness?

But my original main question was whether kayaks designed to neither weathercock nor leecock are inherently less efficient. Can you answer that?

It seems to me that is the optimal solution. Plus, some of us have paid extra and made other compromises in order to shave a few pounds off the weight of our boats. Rudders and skegs goes in the opposite way. And adjustable skegs also reduce the storage capacity of a boat, which reduces its usefulness for long trips. (OTOH, one could argue that long expeditions might accidentally lead to altering trim in such a way that a rudder or skeg would become useful.)

Another approach is cheating; by using an extremely lightweight motor system- which is what I use to keep up with the young and the strong in non-sea kayak applications.. Best of both worlds.

In states like mine, you need to register (and pay for) annual registration of the kayak if it has a motor (though maybe there is a minimum horsepower for that - not sure).

My personal feeling is that motors reduce the whole point of paddling. Also, many fellow kayakers consider it cheating, and I might not be welcome on their trips. (Unless they don't know the motor is there.) And motors are at least as easily damaged as rudders and skegs, and are inclined to become tangled in vegetation. Kayakers frequently boat in very shallow water, to the point that they brush the bottom surface, and paddle through light seaweed, etc. Motors and batteries also significantly increase weight.

And in sea water, batteries can be hazardous: e.g., unsealed lead acid batteries may generate chlorine gas when contacting salt water. Sealed batteries sometimes rust or corrode to the point of becoming unsealed, especially in sea water. (Note that water does sometimes enter the storage compartments in sea kayaks, perhaps because the seals are imperfect, but also because the bulkheads (if any) need to have small holes in them so the boats aren't damaged by temperature & pressure changes.) Lithium ion batteries can be explosively flammable when they develop leaks. (A person who sells and services electric bikes warned me of this when I became curious about them. I gather there are some lithium ion chemistries for which this is less true than others - but it is still a problem. Sometimes EVs stored in garages cause the garages and the homes they attach to to burn down or explode.)

Obviously, the marine community accepts and tries to compensate for all these battery safety issues. But it harder to do this on kayaks, because waves often wash over kayaks, and kayaks are specifically designed to roll for safety, and many of us practice that. Plus, in a larger more stable boat, such as typical motorboats, since there will hopefully be no washing over, and no rolling, the batteries can get much more ventilation, which eliminates the chlorine gas problem for lead acid batteries, and at least some of the rust and corrosion problem.

To give you some idea of how easy it is for sea kayaking equipment to be exposed to salt water, sea kayakers I knew tested safety equipment such as flares and epirgs. They failed within a few weeks or months, even if packed in the "waterproof" boxes sold at marinas, or kayak storage bags. (Tied off condoms work better. Maybe dive certified containers would too? And maybe that info is out of date with the best marine boxes? But my own experience is that marine storage boxes and kayak storage bags eventually leak.)

All that said, some people do what you say. And personal watercraft have pretty much the same issues as kayaks, yet they have batteries.

 

[Milehog]

I'm no expert but have built a couple very good handling touring kayaks. A 14' version for my wife and a 17' for myself.
A few inches of seat travel, assuming an intelligently placed cockpit, can affect the wind-water couple. A hard chine Greenland inspired hull can, IMO, yield less resistance and easier handling in open water than a round chine boat with the bothersome complexity of a retracting skeg.

 

[Skip Johnson]

Efficient is a tricky word when discussing handling of small paddle craft. Most of my experience is with racing canoes and in that venue some classes prohibit rudders. Classes that don't prohibit rudders all have rudders.
To your original question I've designed a few sea kayaks without rudders and there is a minuscule penalty in drag to insure that the craft will track straight in normal use.
Over the years I've paddled a lot of miles with and without a rudder. For a 14' solo canoe I prefer double blading rudderless. I no longer adventure race but a longer hull with a good rudder is a rush when that little bit of opposite rudder coming out of a sweeper accelerates the boat.

 

[portacruise]

For me, the most important question would be how much difference in efficiency it makes in either loss or gain direction, 5% may not matter? If someone in the sea kayak Club has used one, maybe you can get an idea about it from them. If no one uses that type of sea kayak hull, that also says something. If someone does design one that is significantly more efficient, I would expect everyone else to follow suit and get one, but then those participants that are older and weaker would still Trail behind? The annoyance of having to slow down for someone that is struggling to keep up has to be traded against the annoyance of cheating, when using a power assist? I don't know sea Kayaks and all the details about rules / conditions/ distances / when /where they are being used, but maybe someone else can help if given a detailed SOR.

But my original main question was whether kayaks designed to neither weathercock nor leecock are inherently less efficient. Can you answer that?

 

[gonzo]

But my original main question was whether kayaks designed to neither weathercock nor leecock are inherently less efficient. Can you answer that?

The answer depends on too many factors; it is really vague. You need to define efficiency before you question can be answered. For example, a kayak that requires less effort to move in a straight line in flat water, may need a lot of effort to maneuver between rocks.

 

[BlueBell]

But my original main question was whether kayaks designed to neither weathercock nor leecock are inherently less efficient.

Yes, generally speaking.

 

[BlueBell]

Most sea kayaks are designed to weathercock in the wind when used without a skeg or rudder

This is incorrect.
Kayaks weathercock as a result of their design not because they are designed to.

 

[mitchgrunes]

I asked

But my original main question was whether kayaks designed to neither weathercock nor leecock are inherently less efficient.

Yes, generally speaking.

Can you explain why? Or can you give me a reference (ideally free on the Internet) that does so?

E.g., is there some reason that bow wakes waste less energy than stern wakes, which might mean you want the bow to ride higher than the stern?

I saw one source that said something that wasn't clear to me, I guess implying that flow next to the bow is mostly laminar, but that flow separation occurs by the time you get to the back of the boat. I get that has some relevance, in the sense that, if I remember right, completely laminar flow has no net drag (except for skin friction), because the energy lost pushing water apart at the bow is regained by letting it push the boat forwards at the stern.

Is flow separation the factor that makes such boats inefficient?

Regardless, how significant is the difference? E.g., about how much more energy (percentage wise) is needed to make a relatively thin (I'm still thinking about 16" x 16' for me, nearly full length waterline) kayak go, say, 5 knots, under typical somewhat sheltered sea conditions (say, tidal rivers or Chesapeake Bay, zero to several foot high waves) if the kayak is designed not to weathercock or leecock in wind or waves without having to use a rudder or skeg? Assume relatively open conditions, not dodging rocks or submerged logs.