Will:

Radio Shack magnets are what I use. Yes, they are strong, but you can take advantage of that in your design. My favorites are the round ones, (about 3/16", I would guess). Just drill the right sized hole and epoxy them in. Make sure you get the polarization correct (don't ask me how I know). A magnet immediately under your pick hole will offer the most resistance (well, two would offer more). If you feel that would be too strong of a resistance, move the magnet to a position away from the pick hole. In other words, let a little lever action help in overcoming the strength of the magnet. They are really not that difficult to work with. Definitely use the rare earth magnets. No weight, lots of strength. Definitely do not use the ceramic magnets. They weigh a lot and are comparatively weak.

Jim Fruit

Will,
I have used magnets to hold cowls on two airplanes and been very pleased. They are a lot less of a problem then screws. The first ship was a Still Stuka converted to electric. I used a top load hatch for the battery. The hatch was  held by two K&S 3/16" diameter neodymium magnets, one at the front in the center and one at the rear in the center. I used a 1/32" plywood contact tab holder under each magnet that was attached to the fuse. I drilled a 3/16" hole in each of the contact tabs and set it so the magnet would smoothly fit through it. On the bottom of the contact plate I epoxied a 1/4" sq of tin plate (any steel coffee can type material will do). The contact plates act to both hold down the hatch but the holes keep it in place. It was a little tricky to get the tab attached to the fuse top block at the correct height to get the hatch tight on the fuse and have enough hold from the magnet. What I did was a little cut and fit. I glued the tab in the center of the top opening then slowly sanded out a slot so it fit on the tab and just touched the fuse sides. After I got that to fit I measured the center location were each magnet would sit and marked the hatch. I then used a dremel end mill (the larger 1/4" one) to make a flat spot in the hatch. Fit the magnet and adjust the depth of the flat until it lets the hatch just touch the fuse. Then put a small drop of epoxy on the top of the magnet and put the whole thing together to cure. If you have the fit correct once the epoxy cures just lift off the hatch.

On the second ship my OTS El Diablo I used two 3/16" K&S magnets to hold the fuel hatch. This time I used a piece of 1/32" plywood on the bottom of the hatch that slip under a front planking strip of 1/8" lite ply (it is a box fuse with a flat top). I put the magnets at the back corners, I made two corner blocks of 5/16" sq hard wood and installed a flat head sheet metal screw in the end of each, put the magnets in place on the hatch put some slow cure epoxy on the sides of the blocks and put it all together with a scrape piece of wood to between the blocks along the rear fire wall to push them into the sides and hold them. When installing start by setting the blocks in the corners with the shim stick holding them in place a little higher then the final location, then install the hatch and push the blocks down the the final position. This worked really well and holds the hatch just fine.

Good luck, let us know how you install yours.

Bests,          DennisT

Will, were the magnets plated (did they look shiny-chrome or shiny-gold)?

If they weren't (i.e., if they had a dull finish) then you may want to make sure they're painted with something.  The steel mix that they use for rare-earth magnets corrodes easily.  This is why so many of these suckers are plated, but I'm not sure what Radio Shack gets.

There's a bazillion magnet sellers out there; if you want to get a bunch of them cheap search on "rare earth magnets" and follow your nose.  I think I bought from "magnet boys".

My local hobby shop (Tammies) in Beaverton (Portland area) OR, has a very nice selection of plated super magnets in various sizes, and shapes. Apparently, rare earth magnets are popular with other hobby venues as well.

Bill