Keel Reality

[sbroam]

Two ways to test the theory:

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Sea kayaks often have drop skegs, which are almost like adjustable keels. They're a fin just behind the cockpit that can be raised or lowered by a deck control. At 1/4 skeg (about 1" down fin) there is a change in handling over no skeg or full skeg.

...

I've got such a sea kayak and in normal straight ahead, calm conditions paddling, I don't really notice the skeg all that much. It is about 3.5' back from the cockpit, maybe a little less from the end of the water line. Maybe it is my technique. When I *do* notice it is in the wind or waves coming from the side or an angle - I think that is called weathercocking or weathervaning? Then, the skeg helps keep the boat from turning into the wind/waves.

Oops, I admitted to kayaking - another reason for a bag over my head!

Speaking of the Coleman - it's certainly not a wonderful boat but it does have one undeniable attribute - it is better than having no canoe at all. [And, believe it or not, it is better than some things called canoes - check out Dick's Sporting Goods sometime and look at one of those 100# monstrosities with built in coolers and cup holders.] Two times in my life I have used a Coleman to my benefit. First, when I was starting paddling, one given to me set the whitewater hook. Believe it or not a Coleman *with* floatation got us down a big water III (Saluda at 21K CFS) in one piece. Within a month or two, both of us had "real" boats. Later, while on an extended consulting gig in NJ there was one that came with the apartment I rented in the basement of a lake house. It was no Bell Flashfire, but hey, if you can't find joy in summer twilight sharing a lake with a collection of birds varied enough even to peak Audobon's interest, you are too much the snob for me.

[sbroam]

You a funny man KNeal.

...

Yeah, that KNeal is quite the comedian, but I think he has it all wrong this time. His little experiment would measure resistance to *lateral* movement. I think tracking is more about resistance to *turning*. Have teams of paddlers spin their boats for a half hour, take a break, switch boats and repeat, then compare the revolutions for keeled and unkeeled boats. The team that is too dizzy to stand buys the cold beverages.

I agree that other factors *could* be stronger than a keel. It's all about resistance to turning - water line length and other aspects of cross section come into play. I'm sure there is some naval architecture based method of calculating "resistance to turning" as there are ways of calculating the "righting moment" (stability).

Another thought is that a keel on a given shape would introduce drag, too - you would be increasing wetted surface area. Would any gains in tracking be offset by that? Would reduced frustration offset the drag?

I still say give minicell or another (cheaper) foam a try - easy to shape and attach (duct tape!) and lighter than clay or many other materials.

[bathtuboy]

I'm afraid this is a no brainer for me, keels completely destro the handling of a whitewater boat. The first canoe I built was from a design with a keel. Although I really liked the design otherwise, the keel made handling very difficult, it also made me feel I had no control over the way the boat tracked in a straight line, those little changes of diraction which were previously only a flick of the wrist became really hard work.

All subsequent boats I have made in a similar way and shape but without the keel. Control is now precise, quick and easy.
Paddling on windy lakes I could see the benefit of a keel, and this is where they should be used.

Having said that, one of the important things about boat design, is that everyone has different opinions, likes and dislikes. It would be very boring if we were all paddling the same boat because it had been empirically proved to be the best.

[PAC]

It was a hope that some of the designers from DC / Penn State of past would post on this. I'm sure they, in their efforts to build the fastest slalom boat, toyed with the idea of a keel or keels. Maybe even tested them in the Navy tank.
But since we don't see keels on any of the more high performance designs (OC or C) I have to think there are a number of rationales for that.
IMHO keels work like a "V" hull in a power boat. Great for straight line performance but add too much drag laterally. Can't see anyone wanting a play boat or creeker with one.
That said there are keels out there in play.. well sort of.. in the shape of chine lines and rails (my view of course).
Example in C1 would be the Finkenmeister, or OC1 the Viper, where by setting a hard edge the paddler can set a track line.
Slalom and Cquirt boats have this too (using their sides / seamed areas) but to lesser degrees (since they tend to be rounded out). And although they are not true keels they are an edge the paddler uses as a knife to "cut" the water so as to place the boat were the paddler wants it to go - sort of the same type of application as a keel.
Nothing is cooler than watching a good boater use an edge to rip it up a rapid by bang'n eddies. My $.01 - Paul C.

PS - I also just want to point out its much easier to discuss Keels verse KNeals! We don't want to go THERE!

[Open Gate]

On the flats with my CU Fly(slowest boat on earth ) if I want to keep up with the weak paddlers, I really lean the boat on my strong side and use the V Shape it now makes to cut through the water instead of plowing throug it(it really feels as if a scraper was mounted to the front of this beast...).

That's as close to a keel I ever got, and the limit of my expertise on this flat water subject.

Keels and White water don't mix, like drinking and driving(where the keel is the drinking...)

[John Coraor]

It was a hope that some of the designers from DC / Penn State of past would post on this. I'm sure they, in their efforts to build the fastest slalom boat, toyed with the idea of a keel or keels. Maybe even tested them in the Navy tank.

Paul:

I had been keeping out of this discussion as the original post asked for empirical data on the effect of a keel. Having none, I didn't feel that I had much to add. However, as not having anything intelligent to say has never kept me from opening my trap in the past, why break with tradition!?!

I would agree with the remarks made in several posts that the presence or absence of a keel impacts any given boat's performance less than other major factors of the boat's design like rocker, waterline length & width, and wetted cross section. Put a keel on any OC slalom boat and it will still turn more readily than a Jensen cruiser.

However, does any of us really doubt that the same OC slalom boat without a keel would turn more readily than its keeled cousin? If you think about it, a keel extends the profile of a canoe deeper into the water, providing more surface area in the water (i.e. friction) to resist lateral forces, while only nominally increasing friction when moving forward, the same principles that Jensen used in design of his long, lean, cruisers. Hence the effect of a keel in lessening lateral drift on a windy lake and to a certain extent in facilitating tracking when moving forward.

A keel's effect on lateral drift is probably somewhat similar to adding enough additional weight to a similar keelless boat to sink it the same distance lower in the water as the height of the first boat's keel. However, weighting a keelless boat would also reduce its forward speed due to increased drag. Typically you only find keels on general purpose/multi-purpose (i.e. "do no purpose well") canoes, usually with relatively flat bottoms (for good primary stability), in order to make such flat-bottomed boats track a bit better than the design would otherwise achieve. Adding a keel to a Jensen cruiser would be superfluous and to a slalom boat, counterproductive.

Of course, there are other ways to achieve the same purpose as a keel, including using a shallow vee hull, which also increases resistance laterally, but has the advantage of being able to constructively negate this effect when laid over on its bilge, thus making for both better tracking and better manuvering if paddled properly.

Getting back to slalom boats, they are an interesting case study as by definition slalom boats are designed to maximize two characteristics that are typically antithetical - maintaining good tracking to increase forward speed while enabling quick turns upon demand. While you won't find a traditional bow to stern protruding keel used, there are some examples of shorter keel-like elements being used from time to time. Beginning in the late 90s it became fairly common to design slalom boats with "rails." These can be seen as short, shallow "keels" typically located at the chines. Often the "rails" don't protrude deeper than the rest of the hull as much as the hull between the rails is raised somewhat higher (like a very shallow catamaran). However, the amount of change in hull cross-section is usually pretty small, on the order of 1/4 to 3/8 of an inch, and is almost always limited to the center section of the hull. The intent is to facilitate tracking and thus speed when paddling forward, without hampering the ability to turn quickly when needed. Because a good deal of turning in slalom involves stern pivots - small, short rails restricted to the center portion of the hull don't seem to have much adverse effect on turning. Whether they actually help much with tracking is, of course, much debated.

So much for my free observations, which are, of course, worth every penny that you've paid for them.

John

[KNeal]

You a funny man KNeal.

I'm glad you appreciated the humor. I am serious that you posed a good question to check our understanding.

Yeah, that KNeal is quite the comedian, but I think he has it all wrong this time.

You think I'm wrong being a comedian?!

I do think the lateral drift test is accurate for the effectiveness of the keel versus a smooth bottom that allows lateral slipping. The hypothesis is that the keel aiding tracking also minimizes lateral slipping. So, anybody (Paul) game for a wind/drift test?

I also just want to point out its much easier to discuss Keels verse KNeals! We don't want to go THERE!

Hey Paul, you stll mad that I haven't run over Ohiopyle Falls in a tandem c-2 with you?

KNeal

[sbroam]

You think I'm wrong being a comedian?!


KNeal

No, you're just fine as a comedian - no worse than the rest of us.

[Eric Nyre]

I've got such a sea kayak and in normal straight ahead, calm conditions paddling, I don't really notice the skeg all that much. It is about 3.5' back from the cockpit, maybe a little less from the end of the water line. Maybe it is my technique. When I *do* notice it is in the wind or waves coming from the side or an angle - I think that is called weathercocking or weathervaning? Then, the skeg helps keep the boat from turning into the wind/waves.

Try turning the boat with the skeg up, quarter, half, etc. It will turn much better with the skeg up.

Skegged kayaks are designed to weathercock. When you have the skeg all the way up it should turn into the wind, and as you drop the skeg it will turn away from the wind. To run in specific conditions, you just adjust the skeg until the boat goes where you want to.

However in calm conditions where the boat won't weathercock, the skeg will affect how the boat turns. Easier with none than full.

For the most part, I think keels are antique. They were great to help protect wood canvas boats from having their skins wear, they were basically full length skidplates. Also good for construction methods that wouldn't allow for a nice V entry, reduced rocker, or other designs that help a boat track.

[sbroam]

Skegged kayaks are designed to weathercock. When you have the skeg all the way up it should turn into the wind, and as you drop the skeg it will turn away from the wind. To run in specific conditions, you just adjust the skeg until the boat goes where you want to.

Thanks for the explanation! I usually just try dropping it if I feel I'm being blown around, now I'll be a little more methodical and informed.

[PAC]

John thanks for the response and it was worth way more than I paid for it!
Your Jansen analogy is a perfect example of what value a keel adds. Having paddled a 17' cedar stripper with and without a keel years ago (since I made the boat I figured it was okay to tinker with it) I agree that a 3/4" keel did very little to change its tracking characteristics. Although as you noted it was somewhat helpful when working against a cross wind when there was no load in it. It also was a lot more friendly to get somewhere when there was some weight in it.
As for Slalom boats - I remembered that some designers started to incorporated rails back when... but I thought it was earlier (my how time flys).
Again thanks for the thoughts and keeping the billing low! Paul C.

PS: As for you KNeal.. your time will come to take a drop with me in a C2!

[sbroam]

Someday we will have boats with variable geometry - you will be able to dial in a modification that fits your current, momentary need - I can see my boat going from sort of creekishly configured at the end of Chattooga Section IV to a longer, skinnier boat, maybe with a keel for that paddle out across Tugaloo. Would that be cheating? Even if I didn't have a bilge pump or nose plugs?

[jscottl67]

Someday we will have boats with variable geometry - you will be able to dial in a modification that fits your current, momentary need - I can see my boat going from sort of creekishly configured at the end of Chattooga Section IV to a longer, skinnier boat, maybe with a keel for that paddle out across Tugaloo. Would that be cheating? Even if I didn't have a bilge pump or nose plugs?

Hmmmm...adjustable thwarts...hmmmmm

[Eric Nyre]

Variable boats:

Ok, don't shoot me since this is a kayak.

http://www.rethinkkayak.com

Folding kayak where you can adjust rocker as needed. Seriously pricy, but an interesting idea.

I think the closest C-boats come right now is leaving a Skeeter on a roofrack mid summer in 100 degree temps. Though that's not very adjustable once it starts to deform.

The adjustable thwarts might work. Tuck in to reduce rocker and make an easier to paddle flatwater boat, make them wider to increase rocker and flare for dryer times on the river. Hmmm....

[sbroam]

That is seriously cool - skin on frame has a lot of appeal, plus it is adjustable?! But yowza on the price - $5,500?!

I have seen plans online for a skin on frame boat, but certainly not adjustable. Might be interesting to make a touring C-boat with that method, though...