In search of the perfect hatch system
After trying the standard Pygmy gear, bungees and hooks, rare earth magnets, and three different gasket types on my Arctic Tern, I went off in a completely different direction with Holly's Redfish Silver by adding the ability to adjust the tension from the cockpit on each "Leidy" style hatch lid.
One side of each hatch has the typical loop and hook structure. The other side has a bungee running through tiny blocks on the hatch and hull and then back to the cockpit to a jam cleat. By first letting off tension from the cockpit it's very easy to tilt the hatch open to remove it. Tensioning the bungee makes the hatch very secure. There's no reason for the complete line to be a continuous section of bungee, so the bulk of it is small dacron cord. Since the bungee is lead through blocks on the lid, the lid is effectively "leashed" to the boat.
I've heard of hooks pulling off from other peoples hatches in hot weather, so I built the hooks (two layers of 1/8th birch plywood) all the way across the lid to increase surface area. They form two ribs that reinforcement the lid quite nicely.
Every method has its compromises. While the hatch was water tight and has proven trustworthy, Holly found it annoying and impractical. The magnetic hatches I put on my Tern worked so well that I have since retro fitted this boat to the same system. The tensioning device has been left intact and functions very well for a hatch leash and increased security for rough water and highway wind buffeting.
By the way, "Leidy Lid" refers to Ross Leidy's innovative method for securing a hatch from underneath so that the deck is clean of straps. You can find more information at his web site, Blue Heron Kayaks.