I read where folks are using the "rare earth" magnets for attaching hatches.

Does one just recess an area in the hatch and expoxy in place, then building a small ledge from behind the firewall for the plane attached mating magnet?

On my trainer... I put a lip on the aft end of the bottom of the hatch to slide under the front window.. and put servo mount screws in the corners by the firewall. But I'm trying to move into nicer construction techniques and looking for something cleaner. The plane is a 4* .40 and although plans call for glueing the hatch cover... I prefer removeable.
Thanks...
Mike

Magnets work great for hatches. I use some a friend got for that are 1/16" thick by 1/4" diameter. Strong little magnets. I use them on my smaller electric planes. Planning on trying it on my bigger 1/5 scale war birds.
Edwin

I've had times where magnet-magnet connections were too strong, and I'd almost crush part of the airframe with the force it took to open the canopy/hatch. Sometimes a magnet on one side and a washer on the mating surface are enough.

What Dfalcon says is true. I busted a 1/16" sq stringer on my little electric pitts trying to man handle the motor compartment hood.
Edwin

I'll add that if you can, to make your hatches with the magnet side towards the rear of the plane. Air will have a harder time trying to get under the magnet, losing your hatch.

Sorry double post

I was going to say what deadeye said. Put a tab in the front of the hatch that will fit under a lip on the fuse, then use magnets to hold down the back

It's also worth considering to do what Minn and deadeye suggest only with a twist.

Hinge on one side and magnets on the other.

Airflow over fuselages often create areas of negative pressure and areas of positive pressure. Darn if it's a puzzle most times predicting where the pressures are going to help hold the hatch down and where they're going to try a pull them open. Put the hing on one side and since very few airplanes experience sideways airflow on the fuselage, the magnet on the other side probably won't see just negative or positive. (Unless the attitude in flight gets REALLY bad, and then you won't care if the hatch is found at the crash site or some distance away.)

good point

I was thinking about this the other day in a Turbine Application. So I looked it up and here we are.

Any reason not to give this a shot at 200MPH?

thanks for the pic... and daroc for the side mount suggestion.... I'll feel like i'm working on a ford model T. I was thinking about the little shelf for the bottom magnet and i'll give it a try.. getting close now !! ... down to covering... to bad I can't fly it naked since i build soooo much better than i cover ![&o]

How are you attaching the rare earth magnets to the fuselage? I have tried epoxy and hot gluing small rare earth magnets in an EPP foam plane, using two magnets to make the connection but the magnets connect and one is pulled from the adhesive. I tried placing some adhesive slip resistant tape on the back of the magnets then hot gluing it in place but the magnet is still pulled free of the mount. I have not tried using only one magnet and a thumb tack or washer.

Epoxy works for me. I dont know why it didnt for you. Maybe some skin oils or something like that? As for 200mph hatch covers, I've been thinking on that a bit and I guess you would have to make sure the hatch has good airflow over it. Just speculating but turbulance at high speed might buffet enough to blow it off. On the other hand, with the up wind side of the hatch pegged and a detent on the down wind side in addition to the the magnets, might just hold. There are some pretty strong magnets out there.
Edwin

I don't use 2 magnets together but instead use one magnet and one very thin piece of shim stock (about .005") on the other surface. One thing to keep in mind too is to make sure you have the polarity right before you glue them in or they will repell from one another.

Where do youm buy them?

Here is "a" source. But I have not settled yet on the technology:

http://www.magnetsource.com/Solution.../rareerth.html

Go to eBay and do a search for 'Rare Earth Magnets'. You should be able to find cubes (that's what I prefer) in sizes ranging from 3/16" - 1/4" (bigger as well, but your not going to hang you plane from an I-Beam are you?) Actually, I've seen 2" cube REM's that can handle 200+ lbs and then cost about $40-$60 each!

I've had very good luck with this seller.

http://stores.ebay.com/Emovendo

Michaels Craft store is stocking them..

You'll find them with the other ceramic magnets.. They have 1/4" in packs of 6 or 1/2" in 4 packs for $2.99

Check your magnets before installing.. I had one 1/2 strength dud in my pack.

I guess Michaels will work - never looked. It all depends on how strong of a magnet your looking for, the smaller the mag, the more power rating you'll need, IMO. As fas as I know, the strongest we consumers can get are N48 strength. At least that's all I've seen so far, but haven't done much research. I

An excellent and inexpensive source for very good magnets is Lee Valley. The magnets are far better (stronger for their size) than most other sources and very inexpensive plus a large choice of sizes. Just check out leevalley.com and go to "magnets".

http://www.kjmagnetics.com/products.asp?cat=11


If you look below you'll know why I get the feeling my posts are actually invisible. Happpens alot!

Another source - the one I use - is www.kjmagnetics.com

I suggest passing on the magnets from Michales. I bought the only ones that look like rare earth and I truly doubt they are. They are about ½” in diameter and one is not nearly as strong as the 3/16” diameter rare earth I have.

After installing two of those “Michales” magnets so they would work face to face to hold down the back part of a canopy that is pinned in the front, I doubt it’s going to work. I can see that canopy coming off in an inverted loop.

A guy at local hobby shop told me Radio Shack sells them, however at a premium price.

You can get magnets here. They also have cups and washers for them too. These intensify the magnets like the metal plates that are used with rectangular ceramic magnets.

http://www.rockler.com/product.cfm?p...&filter=magnet

Scott

The suggestion of Lee Valley tools is a good one. They stock a large range of rare-earth magnets, as well as magnet cups and matching washers.

I put a pair of 1/16 x 1/4 rare earths into cups that were in turn epoxied into the bottom of my cockpit/hatch, and then screwed the washers to blocks at the aft end of the fuselage compartment. You can turn the fuselage upside down and give it as hard a shake as you want and it doesn't move. In fact, as has already been pointed out, it can be a problem to get the hatch open and I'm thinking of putting a "hard point" into the underside of the cockpit opening so I can pull it up from there without breaking the balsa skin