First off, how heavy is your dinghy and where do you plan to sail? The
davits that most people put on their boats are way too small for the shock
loads generated by pounding through seas and you'll end up bending them.
Personally I think that you need davits which are rated at 4x the actual
weight of the dinghy if you expect to have them survive in rough seas.
I use Atkins and Hoyle (
http://www.atkinshoyle.com/) davits and have been
quite happy with them. I started out with their model 1800 davits, which
are rated for 180 lbs/davit, and I found that they weren't sufficient in
big seas. I then upgraded to their model 5000, which are rated for 500
lbs/davit or 750 lbs/pair, and these have been rock solid. Note that I
only lift a 120 lb dinghy without a motor.
Pay close attention to securing the dinghy to keep it from swinging from
side to side. I use SS coated cables which crisscross, from the bow
lifting point and the D-ring on the dinghy transom, to the opposite davit.
I also have a SS cable which goes from the other transom D-ring, which is
closest to the big-boat, up to the davit arm. All of the SS cables have
turnbuckles to tighten them and carabiners on the ends. It's taken me a
long time to come up with this solution, but the dingy remains solid even
in big seas.
-- Geoff
www.GeoffSchultz.org