Not the design itself you refer to, no. Never built nor seen one. But I've been using supermagnets for some years in various ways to 'keep things closed' that otherwise would have required some mechanical means I'd rather not have had to incorporate.

They are useful for this purpose; everything I've done w/'em has been successful. With a hatch design though there's more to it involving properly effective sealing that has to come from other design aspects. Closest thing yet I've built is a ventilation hatch in my garage/workshop, hinged to close a large hole over the inlet to a solar-powered exhaust fan on the roof. Hatch is well-insulated & weather-stripped to seal tightly when closed. The RE magnets placed in the hatch itself and the base do a proper job of pulling both parts tightly together during the winter. It takes several pounds's pull on an attached line to pop it open. In all I think I used maybe eighteen of the round ones about 7/8" dia. to effect a strong attraction so the EPDM weatherstrip would compress tightly when closed.

(Design also includes a magnetic reed switch that disconnects solar panel from fan motor when hatch is closed so fan won't run when there's no airflowing past to cool it.)

So to my mind the concept is a sound one. The engineering however must bear scrutiny for your choice to prove its value in use over time.

Hi w.mass, 

while i have not done the rare earth magnet hatches, i studied the idea extensively.  you mentioned laughing loon....and wanted to make sure you saw a very detailed construction video for magnetic hatches at https://www.youtube.com/watch?v=0j-2uPy68H0

in a nutshell, for me, while very slick, they are a lot of work and require a lot of precision...note in his video for example...the approach you need to take with gasketing that is different than how you would approach it on other hatch configurations.

but if you have the time and skill...they looks great.

h

   I'm thinking about doing it on the next boat. Here is a place for the magnets. 

https://www.homedepot.com/s/rare%2520earth%2520magnets?NCNI-5

It won't help with the accuracy of your compass, though.

Another thing to worry about is beach sand. In Southern California, at least, as kids we used to drag magnets on a string through the sand to collect iron filings. You may get black abrasive fuzz on your hatches depending on the iron content of the sand where you paddle.

Laszlo

What Laszlo's saying has merit. There's a lot of iron-bearing junk out there, magnets will tend to attract it at every opportunity. That wasn't an issue with my ceiling hatch or other stuff I've used these things for but should be considered for a boat.

I was gonna post a link to where I source mine but stopped when I looked at that HD link; they offer one with a countersunk hole in middle, make more secure attachment than simply epoxying them into place as I've been doing. Letting the epoxy fill the countersink avoids using a separate fastener.

On my Chesepeak 18 I made a custom day hatch and used magnets to keep it closed.  I used 12 round magnets around 12" od hatch.  I drilled the holes in the plywood doubler for the hatch before attaching to the hatch cutout to prevent drilling thru the cover.  the doubler was nearly the same thickness as the magnets I used.  For the "flange" where the gasket attaches I did the same, used a double thickness, drilled the top one before gluing together.  After epoxying the magnets in and filling to flush, I added a layer of fiberglass.  The magnets were aprox 3/16" thk.

Make sure before epoxying the magnets in that they are all in the correct orientation. 

The other 2 hatches are the standard design from the kits using webbing straps to hold closed.  I also added a bulkhead between the dayhatch and the rear hatch as I wanted some storage for food and other items accessable while on the water and if it got some water in it while open it wouldn't flood my rear compartment.  I don't remember exaclty how I aligned the the base with the hatch when I assembled it.  Missalignment of the magnets would be less critical in a round hatch then a more oval or retanglular hatch

I purchased the kayak from the builder who built it without hatches and used it for some time.

   Hello all, As usual the forum provided much useful info. Thanks everybody. The magnet idea does seem very cool but also alot of work, I think I will go with the standard flush hatch that is provided with the shearwater kit. Does anyone have ways of doing those differently or anything additional to make them "better" or do they work just fine they way they are supplied.  Maybe save the magnet thing for the next boat. Thanks.

T

This is how I've been doing hatches on strip built and hybrid boats. While the deck is off I'll build up a layer on the underside with carbon fiber and fiberglass to about a 1/16" thickness. I put plastic under it so it doesn't stick. After it cures I clean up the edges, cut the hatch opening and the scribe a 3/4" lip. I'll then cut out the middle and use this piece to reinforce the hatch cover. I then bond the rim to the underside of the deck. I also fabricate CF hooks and padeyes that I bond to the under side of the cover and the sides of the hull. Bungees are used to keep it down. I used a very thin 1/8" foam gasket. The result is an almost fush cover.  What I find it that the hatch cover is very stiff and the hatch rim has some flex. This allows a very water proof seal. Not 100% but pretty darn good.

Does this make sense?

Dan