On my Hybrid Cormorant, I built a retractable skeg whose mechanism
was a stiff stainless steel wire running in a tube from the skeg to
a sliding control next to the cockpit. This is the same sort of design
used by Valley and North Shore (and no doubt other commercial kayak
builders). Its neat, reliable, but a bit of an effort to build, and
perhaps a little prone to jamming.

I've seen two other methods of deploying a skeg, both relying on bungie
cord. In one case (Masterlite plastic kids river boat), the bungie pulls
the skeg down, and a cord and cleat pulls it up, whilst in the other case
(Nigel Dennis Romany) the bungie pulls the skeg up, whilst the cord and
cleat pulls it down. This seems a poorer way to do it - if the skeg hits
a rock, either the skeg or the cord will be damaged, whilst on the plastic
boat, the skeg is just pushed up into the boat against the tension of the
bungie and pops back into use again when the rock is passed. On the other
hand, if a stone jams the skeg up, the NDK method allows you to put more
force into deploying it, whilst the plastic boat relies entirely on the
strength of the bungie. The other disadvantage is that if the skeg is
mostly up, the bungie remains stretched most of the time, which will lead
it to deteriorate sooner.

There may be other potential mechanisms that I haven't seen or thought of.
The requirements I see are:

Not to complex to build - field serviceable
Skeg/mechanism not readily damaged by rock-hopping errors
Skeg easy to free from jamming by stones/sand
Easy to see how far the skeg is down by looking at the control
Design minimises routine wear (wire cutting into wood/plastic, or cord
wearing where it goes round corners or into a cleat).

I'm planning to put a drop skeg on a boat which will be used by kids,
so it needs to be simple and tolerate carelessness, rather than being
hydrodynamic perfection.

Any thoughts / experience / alternative designs ?

Andy