Magnets for holding cowls on airplanes

[frank mccune]

    Hi:

    I would like to have some information regarding using magnets for holding cowl on airplanes.  Information such as placement, strength size etc.

                                                                                                          Tia,

                                                                                                          Frank

[Dennis Toth]

Frank,
I have used small round magnets from K&J Magnetics (http://www.kjmagnetics.com).

I have used them to hold cowls on electric and IC ship. I use 1/4" round ones. I use epoxy to hold them in place in the cowl. I use 1/16" plywood triangles in the corner of the tank area with a 1/4" hold to allow the magnet to pass through and position the cowl. On the back of the plywood plate I epoxy a piece of tin plate for the magnet to hold to. I use 4 for a full cowl and for just a tank hatch (or battery hatch) I use a plywood tab along the front edge with two magnets on the back with the triangles as above. I have also used some where the hatch has side rails and put small blocks with flat head screws into them to allow height adjustments.

Best,     DennisT

[FLOYD CARTER]

Radio Shack carries nice magnets called "rare earth".  This is a samarian-cobalt mix that is very strong.  The magnets are about 1/8" diameter.  The only problem is getting them to stick to balsa.  I have used JB Weld.  Cowlings should also be "keyed" to maintain alignment, but at the same time allowing the part to "slide" in one direction. This seems to be the best way to remove a cowling.  You will find it hard to remove a cowling by pulling straight up and against the pull of the magnets.

Floyd

[Mike Lauerman]

Good thinking, Floyd. 'Turning' or 'sliding' cowl makes sense.
 
(I attached a 'keyed' cowl that slid straight on/off a longitudinal key...LOL Never thought I could pull glued magnets right out of the balsa! And they weren't the strong 'Rare Earth' type)

[George in Cedar]

I found rare earth magnets at Harbor Freight.  1/8" thick x 5/16 diameter.  Ten for $2.99.  Seem to work just fine.

http://www.harborfreight.com/catalogsearch/result?q=rare+earth+magnet

George

[Dennis Toth]

Guys,
I found some 1/4" diameter Neodymian magnets that have a counter sunk hole through them. This makes it easy to mount with a #2 screw and also allows you to position and use it as a template for positioning it in the mount, then just mark the center and secure it with JP Weld and the #2 screw. They are from K&S magnetics, part number R422CS-P-N52 (http://www.kjmagnetics.com) the cost 81 cents for package of two.

Best,    DennisT

[Shorts,David]

I think Joe Daly was using magnets to hold his wing on. 

[Brett Buck]

I think Joe Daly was using magnets to hold his wing on. 

   Not that funny.

     Joe was "going for it", as was appropriate given the high level of competition, and even pretty sturdy construction let go. Most people can't appreciate the kinds of loads you can put on these airplanes with modern cornering and engine/motor capabilities. It's *far more load* than you could possibly have generated before about 1990, and we have had a spate of similar failures since then, despite building them stronger and stronger.

   +-60-70 lbs, cyclicly, over and over, for months/years can take its toll.

     Brett

[Shorts,David]

If memory serves, I've only folded two wings and with far less g loads I'm sure. But I've ripped out two belcranks now. Those aren't fun either.