Anytime you add more directional stability you will make the boat less maneuverable. The 2 are opposites of each other.

Stability also changes depending on how much weight the boat is carrying and how it's distributed. It's also affected by the wind and wave conditions at any particular time.

Because of all these reasons it's hard to find an ideal location and size for a fixed fin. A retractable skeg would work better because the amount of stability enhancement could be adjusted in real time for local conditions.

Laszlo

I'd put the skeg about halfway between the rear edge of the aft hatch and the stern.  Too far back and you just can't turn the boat when you want to.

That's the big appeal of a retractable skeg---you can tune the tracking so you have it when you need it.

revensdale, there's no way to use a smaller skeg, is there?  Rather than relocating it?  (Assuming you don't go to the retractable skeg solution).

Smaller skeg means less drag, I think.

I do belive the answer to the problem is called a paddle

Adding a fixed skeg makes a kayak track more i.e. makes it harder to get bumped off course by waves or wind and just plain makes it harder to turn.  However, skegs primarily are added to reduce a kayak’s tendency to weathercock (turn into the wind).  So take your kayak out in a brisk crosswind and if it weather cocks install a larger skeg or move it back, if it leecocks (turns downwind) file it smaller.  A wind neutral kayak is much more enjoyable to paddle in blustery conditions.   

I've read on this forum in the past that moderate weathercocking is normal and desirable on a kayak, just as in a sailboat.  Sailors call it "weather helm" but it is the exact same thing.

Of course in sailboat, slight weather helm is not just desirable--the boat would be dangerous without it, and scarcely anyone would design or sail a boat that didn't have it.

In a kayak, perhaps it is less critical to have some weather helm.  I just futz around back bays, creeks, and small lakes with my kayak, and I am not any kind of expert.   But my understanding from this forum is that it is still pretty important, especially for a kayak used in open waters.

You want a kayak to turn into the wind if you become momentarily or permanently unable to paddle it.  This will reduce the chance of capsizing.

I will speak from my experience.  Others will have their experiences and probably different thoughts on the topic.  Nothing is more exhausting than getting caught in a kayak that leecocks or weathercocks too much in a brisk crosswind.  And once you are exhausted from paddling on one side your only hope is if the wind is toward shore (or to get help, a common reason to use a tow line).  I like a kayak with no moving parts (other than the paddle) and I day paddle a lot with little cargo.  So optimized trim is a real concern when conditions arise.  So I trim the kayak for no cargo.  Then when I do pack gear I distribute it to maintain trim (about twice the weight in the rear hatch as in the front).  I have found a wind neutral kayak to be ideal in a crosswind, easily managed in a headwind, and manageable in rear quartering winds.  Having a little weathercocking makes paddling in a headwind easier but adds to the workout in the wallow producing rear quartering winds (and waves).  So to keep most corrections to properly timed edging (a knee lift), I like a neutral kayak.  I think every paddler should play with the trim to find his or her preferred trim in his or her particular kayak.  Moving the seat back reduces weathercocking.  So moving your seat around plus or minus a couple inches before gluing it down is a good idea.  Also adding rear ballast is a temporary method of trimming a kayak.  The easiest method, to add ballast on the fly, is to fill a waterbag with seawater and clip it under the deck rigging (aft to reduce weathercocking or forward to increase weathercocking).  After paddling six hours on one heading during a channel crossing one quickly appreciates not having to make regular sweep strokes from quartering winds.