Updated Summer 2020
Short answer: Yes.
It’s easier to go straight while paddling as hard as you like, and since 2014 all Gumotex come with them, as do many other IKs. Some can be mounted or removed by hand even from an inflated boat.
And if not, it’s easy to glue a kit to any IK (see below).
A few years ago Gumotex introduced a slip-on skeg which was near identical in shape to one I’d had made in the alloy-skeg days, but in tough plastic and with clever tool-less mounting (above). I’ve fitted these plastic skegs to older Gumotex IKs and other IKs. The kit is under £20 + glue, and the skeg is tough. Just make sure you glue it on really well; it helps if your boat is made from a matching rubber fabric as the supplied Nitrilon patch. or make your own patch from same fabric.
I fitted the tough Gumotex skeg to my Grabner Amigo IK (above) and at sea used it all the time. But on the shallow Spey (below) that boat didn’t handle at all well without a skeg, possibly because the a tailwind pushed the high back around. It was really quite annoying as a few years earlier my broadly similar Sunny managed the Spey fine, so it clearly varies from boat to boat.
If you’re an experienced paddler you’ll have acquired the knack of going straight without a skeg – handy for paddling shallow rivers where the skeg would drag. A little more paddling finesse and small constant correction is required, especially if powering on.
It’s good to learn the technique: fix your eyes on a tree or marker on a distant bank and paddle as gently as you like towards it, not looking away and keeping the nose of the boat in line with the marker. By using very light strokes you’ll see it can be done if it’s not too windy when again, a skeg helps with tracking (going straight).
I even found I could paddle a ten-foot Solar (below) without a skeg. Once you know you can go straight without a skeg, it’s just a matter of adopting the same finesse but with a bit more power. Only when you attempt the speeds of a Maori war party will the deflection get too much because you can paddle faster and still go straight with a skeg. Out at sea or on busier rivers, I always use a skeg.
I’ve often thought a hinged retractable skeg with a spring or just weight could be a good idea: it would pivot backwards when dragging in shallows, then drop back down when there’s enough depth. Seems SUPs also have this problem and in the US, FrogFish have made such a thing for boards, but they say the spring can be a weak point. I’ve envisaged something more normal skeg size as I can imagine in rapids drifting sideways into a rock or something might put a lot of leverage on such a long skeg. SUPs don’t normally do rapids.
Especially if your kayak has a rudder mount, I think it would be quite easy to make one, if you think it’s worthwhile.
On a shorter, wider, slower packraft the consensus seems to be skegs make little difference. I can believe it before I knew it and now I know it. The bow still yaws or pivots a little left to right as you paddle; less so with a load mounted on the bow. Tracking – going straight – is not the same thing and not a problem on a packraft because you can’t go that fast. You move along with a moderate left-right bow shuffle which it’s true, does limit your speed – but speed is limited by a packraft’s hull shape anyway. Or is it?
If anything, a packraft skeg fitted under the bow rather than the stern might limit this yawing, but I imagine you’ll destroy the instant turning ability for little actual benefit. Good for crossing a long lake in a hurry maybe. Can’t say I’ve seen this idea mentioned, though I am sure someone’s tried it.
In 2011 Alpacka invented the extended stern (right; bottom) which has the same effect as a skeg. It’s been widely copied by other manufacturers and it definitely works.
below; clip on skeg on my MRS Nomad. Tried it once but generally not needed.