I stipulate that the following has nothing to do with the usual use of a skeg to balance wind, or for better control in following seas.
I have found that on calm water deploying the skeg on my Seda Ikkuma provides a small efficiency benefit.
Consider two boats with identical drag at a given speed, but one stiff tracking and the other loose. The stiff tracking boat will be more efficient at that speed because it will not ‘waggle’ side to side with each stroke. In other words, the waggle causes inefficiency. Plus, with the looser tracker one will be modifying the stroke a bit more for steering and/or leaning a bit more, both adding a bit to inefficiency.
So dropping the skeg on flat water adds a bit of drag, but makes the boat straighter tracking. The skeg on the Ikkuma is small and well shaped, so its drag is very small. The waggle of the Ikkuma is also small, but I sense that, with my stroke, I am a bit more efficient with the skeg deployed.
This will differ for particular boats and paddlers. Deploying the skeg on flat water in an already stiff tracking boat will add drag and not reduce the already small waggle very much. On a loose tracking boat, but using a high stroke with the blade very close to the hull, there may not be much waggle anyway. On a loose tracking boat like the Nordkapp LV, it may be more efficient to deploy the skeg on flat water. Especially with a longish paddle and a low stroke.
Skeg
A lot of energy is wasted making correcting strokes and wind and stroke imbalances may exist when paddling, even on flat water.
A skeg is probably the best method of both reducing the required number of correcting strokes during any distance paddling. They also provide the benefit of resisting whatever mild wind may affect tracking. Skegs tend to have surprisingly mild effects on overall drag, so deploying them in flat water is something I’d recommend.
Rick
I can address the Tempest RM
(not sure about other boats)
I have to put the skeg down frequently, if I want to line up a picture, or do anything else while not paddling, since the Tempest will otherwise drift off in one direction or the other. And, almost as often, I forget to bring the skeg up when I’m back under way. So, I’m paddling along and start to wonder, “Why am I slogging?!” D’oh, skeg down, again. It’s very noticible, if you’re paddling with any vigor.
Why?
My thoughts are to use flat water days as training days. It may be a tiny bit more efficient with the skeg down (I’ve heard 5%), but what happens to your skills and muscles? I would rather struggle a little more on a calm day so that I’m in shape with sharpened skills when I need it most.
A friend and I used to throw a tennis ball back and forth on calm days. We would toss it in front of each other’s boat and the receiver has to edge and use steering strokes to grab the ball. It broke up the boredom of flat crossings and increased skills. We would do it in rough water as well, but has a few pleasure boaters coming over to see if we were OK. I guess the throwing motion looking like panicked waving sometimes.
I’m sure using the skeg is more efficient (and a rudder even more so), but unless you’re a racer, I don’t see the need.
Partial Deployment
Many people put the skeg down a small amount. That improves tracking and reduces correction strokes, but you still need to edge, etc., to do maneuvers. Putting the skeg down all the way makes the boat turn off the wind or waves, even if they are very mild.
forward stroke practice
If you are concerned with efficiency, you would be better off focusing on improving your forward stroke which will keep the boat straight without the skeg. It will also improve your speed because your effort will be going into making the boat move forward not sideways.
That tendency for your boat to veer back and forth is from turning every forward stroke into a sweep stroke. Pulling past your hip instead of exiting earlier or sweeping out at the start.
Rowing shells, which do not suffer from
the waggle forces of kayaks, and are both longer and more directional than sea kayaks, have big fixed skegs underneath.
But I would be careful about over-valueing skegs for any kayak. I have read Grand Canyon kayakers raving about running big rapids with skegs down in their XP10s or Fusions, but I think they have just gotten lazy. At any time, a situation could occur when the skeg would be a liability. You certainly can’t run technical rapids with a skeg down.
If one is reaching forward with a good catch, and not prolonging the stroke improperly, the boat should go straight as if pulled by the nose. If it won’t do that unless the skeg is down, it’s back to technique.
Technique and equipment
Many will claim that the amount of "help" from a
skeg or rudder decreases the need for correctional strokes.
Hence more power, more forward thrust, more efficiency
Humans are not robots, strokes "wiggle" a bit.
Drag
I use my skeg as little as possible, even in wind, because it creates very noticeable drag. I would say it reduces my speed by about 20%.
I would rather correct my course by shifting my weight or leaning so that all of my energy is going into moving forward rather than correcting sideways drift. But of course there are times when leaning and corrective strokes are not enough and then a skeg is a good thing to have. But I would never use it on flat, windless water. And I wouldn’t own a kayak that needed a skeg in those conditions.
But as you say, it depends on several factors. Over time I’ve made peace with my kayak’s tracking and now adjust unconsciously.
that’s the best part about a skeg
just deploying it in an “on/off” fashion is really shorting the benefits of the skeg.
Consider Olympic flatwater kayakers
They paddle kayaks that have deployed rudders. All of them.
Anyone think those guys and gals have poor stroke mechanics?
Don’t know, but single sculls don’t have
rudders, and I never heard rudders discussed as an option.
Eight oared shells have rudders, but it’s just to make sure the coxwain doesn’t have his hands in his shorts.
no need
If a skeg reduces speed by 20%, you need a new boat. Did you check this with a GPS?
Any motion of your body, or stroke variation for steering, will create inefficiency. Whether this exceeds the skeg drag or not depends on the particular boat and the particular paddler.
One should not use the word ‘need’ in this context. The question is whether a modicum of efficiency/speed is provided. No kayak should need a skeg in flat water.
scull shell vs kayak
scull shells have 2 oars that goes into the water at the same time. kayak only has one blade in the water at any given time.
Motorcycles have kick stand. Cars don’t.
Skegs increase waterline length?
From a hydrodynamic perspective, does a deployed skeg increase the effective waterline length of a boat, and thus increase the (effective) maximum speed and/or add more efficiency? Does this balance the negative effects of added drag?
No, I think the kayak is fine. Maybe it’s that in flat water on a windless day you feel drag easily when you don’t want to feel any drag at all in those conditions. I “estimate” that my skeg slows me down about 20%. I would call it significant. Significant enough that I avoid the skeg if at all possible. But if the end result without the skeg is that I’m exerting effort unnecessarily to stay on course, then I would use the skeg.
My over the stern skeg probably does
a little as I would guess a partially deployed rudder. Little skeg experience till now but seems from the posts “it all depends” on the boat, conditions, skeg style/shape, paddler, etc. Just got my Easy Ryder Dolphin with an over the stern skeg and like it so far. Thin metal (rudder-like) blade, wider at the bottom than top so counter balanced and deployed by its weight from a line to the cockpit - very simple. Down it tracks very straight on all points of wind, up very maneuverable, in between can be tuned as you like. Thinking about one for my canoe. Just thoughts, R
Brilliant. Irrelevant.
exactly!
.
I doubt it
"From a hydrodynamic perspective, does a deployed skeg increase the effective waterline length of a boat, and thus increase the (effective) maximum speed and/or add more efficiency? "
Increasing the waterline length itself won't give you more speed/efficiency.
It's when your increase in length resulting in decrease of waterline width (given the same displacement volume), then you'll have a more efficient hydrodynamic shape.