Boat Building Forum

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Other: Magnetic Hatch closures- consensus?

For the past few years I've been suing SeaLect 'rubber' type hatches in deck recesses in my boats.
I'm thinking about putting a home-made hatch into a boat project in the future, and magnets seem like a way to ensure that the hatch is 'pulled down' on to the seal.

I have found via internet search some good info (from this forum and also other websites).
Rod Tait has a very helpful building guide:
http://www.orcaboats.ca/howtopdf/MagneticHatches.pdf

Rob Macks has done a lot of work on magnetic hatches and posted information here, but I couldn't find much info on his website; perhaps the magnet hatch tips are in his building guide.

I have a bunch of epoxy-coated magnets that I bought from K&J Magnetics a few years back. They are 19mm diameter discs, 3.5 mm thick (3/4" x 1/8").

What's the consensus (if there is one) on magnet spacing and number around the hatch perimeter?
I want to have a good seal, but still be able to open the cover! :-)

I'm assuming webbing loop(s) as pull tabs, or are people successful getting fingertips into a recess at the edge? The water here is cold, and my hands are often cold when opening hatches

Has anybody done a magnetic hatch in a glass (not wood core) boat? All-glass laminates are much more flexible than cored layups.

Has anybody done a magnetic hatch in a peaked deck?

Consensus on the best seal type? I'm thinking of the 'ridge in the lid pressing into a foam gasket' style.

Ideas about optimum hatch opening size and shape? Ledge/sealing area width?

Compass interference is a concern; comments?