Mike Hardy Posted July 29, 2014 Share Posted July 29, 2014 Hi, I am making a small hatch. In the fuselage body I have let in 4, 5mm magnets. In the hatch itself I can use two thin strips of metal or 4 countersunk head screws to engage the magnets, using screws (head flush with the balsa) is going to be easier to adopt but the metal strip will connect with both magnets on each side. Which is the better idea.? Mike. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted July 29, 2014 Share Posted July 29, 2014 I always use another magnet, pole-to-pole is much stronger than pole to metal. Quote Link to comment Share on other sites More sharing options...
Mike Hardy Posted July 29, 2014 Author Share Posted July 29, 2014 Thanks Phil, never thought of that!! With 4 pole to pole magnets will the pull be 'too strong' the nose hatch is 70 x 60 12 to 15 mm thick medium balsa. - separation. Mike. Quote Link to comment Share on other sites More sharing options...
Plummet Posted July 29, 2014 Share Posted July 29, 2014 It depends on the magnets... What I do is to cut out a depression in the surface that just fits the magnet. Rub the magnet well with something abrasive. Then I fill the hole/holes with slow drying epoxy and insert and sink the magnets (the right way up) in the glue and cover them with cling film, plastic, or masking tape. Assemble the lot. Make sure that the canopy/hatch or whatever is well clamped closed. The magnets will be attracted by their mates and the glue will hold them in their correct position. When set, remove the covering. There should be a thin skin of glue over the magnet, and a tiny gap between the mating magnets. A quick rub to clean up the glue surface is sometimes needed. I have found that just gluing the back of the magnets will fail sometimes. Putting them in the puddle of glue is a lot stronger. Does this make sense? Plummet Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 29, 2014 Share Posted July 29, 2014 I'm surprised a Yorkshireman has suggested doubling up on the magnets over the cheaper methods. I use scraps of soft iron on several models to hold the hatch/canopy & the (cheese)heads of 4BA screws for the cowl of my Jnr 60, never had any problems with any of them. Remember that it's important that the magnets & metal actualy make contact when in place, even thin film of epoxy between them will greatly reduce the pull strength. Quote Link to comment Share on other sites More sharing options...
Mike Hardy Posted July 29, 2014 Author Share Posted July 29, 2014 Thanks guys, Hope I have not started another 'war of the roses' Mike. Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted July 29, 2014 Share Posted July 29, 2014 Horizontal dowells at the front of a hatch, and magnets on magnets at the back for me I sink the magnets into a puddle of epoxy, with clingfilm between surfaces while it dries, just as Plummet describes above. Quote Link to comment Share on other sites More sharing options...
Plummet Posted July 29, 2014 Share Posted July 29, 2014 Posted by PatMc on 29/07/2014 17:25:41: I'm surprised a Yorkshireman has suggested doubling up on the magnets over the cheaper methods. I use scraps of soft iron on several models to hold the hatch/canopy & the (cheese)heads of 4BA screws for the cowl of my Jnr 60, never had any problems with any of them. Remember that it's important that the magnets & metal actualy make contact when in place, even thin film of epoxy between them will greatly reduce the pull strength. Well... It all depends... If I hadn't 'acquired' a stack of tiny neodym magnets some time ago I might think differently. The magnets are more available to me than steel strip. (I would guess that you need something a bit thicker than tin can steel.) Magnet to steel I think I would agree - they need to be touching. Magnet to magnet however - it can be too strong for the balsa, and a tiny gap can be good. Plummet Edited By Plummet on 29/07/2014 19:52:48 Quote Link to comment Share on other sites More sharing options...
PatMc Posted July 29, 2014 Share Posted July 29, 2014 The soft iron I use has generaly been cut from the blanking bit's removed from the back of PC towers when any extras are fitted but there are plenty of other everyday sources. The only model I have with magnet to magnet is my EG Pro hatch. I deliberatley left a slight gap & although the hold is good enough for all aeros etc the hatch does sometimes fly off in a bumpy landing. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted July 29, 2014 Share Posted July 29, 2014 The story is that apparently I'd shown a bit too much enthusiasm helping my little nephew with his new "Magnetrix" set, its a construction set based on magnetic sticks and ball-bearings, kids can build 'outline' models with it really quickly. Anywho, when it came to my own birthday, guess what, a Magnetrix set! So, curiosity & all that, turns out each magnetic stick is a short length of soft iron with a 5mm neodym at each end, all held together with a thin plastic coating. This coating split easily with a craft knife, and the magnets can then be pulled off the metal stick. Consequently, I have a ready supply of 5mm supermagnets!!! so two per catch is fine, even for a Yorkshireman! Cheers Phil PS Mike: >> Hope I have not started another 'war of the roses' Nah, Pats on the proper side of the pennines! Edited By Phil Green on 29/07/2014 21:43:22 Quote Link to comment Share on other sites More sharing options...
John Privett Posted July 29, 2014 Share Posted July 29, 2014 When I wanted some magnets for canopies etc. I bought some on eBay. They're 6mm diameter, 2mm thick and didn't cost very much. I still have 44 left - I think I bought a bulk lot of 50! Quote Link to comment Share on other sites More sharing options...
Dave Bran Posted July 29, 2014 Share Posted July 29, 2014 As sold for model railways............................. Quote Link to comment Share on other sites More sharing options...
Mike Hardy Posted July 30, 2014 Author Share Posted July 30, 2014 Hi I have used the 4 magnet approach hatch fits nicely and is firm (too firm!!) and does not move about. It is difficult to open any ideas? thought about letting in an M3 nut on the CL and using a screw as a grab. there is no dowel at the moment - do I need a locating dowel? Mike. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted July 30, 2014 Share Posted July 30, 2014 slide it sideways to get it off. I strip the magnets out of 'retired' motors, they work a treat for hatches. Quote Link to comment Share on other sites More sharing options...
Mike Hardy Posted July 30, 2014 Author Share Posted July 30, 2014 Thanks Bob, yep that works!! Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted July 30, 2014 Share Posted July 30, 2014 No dowel needed if you have the 4 magnets Mike. I use dowels instead of magnets at the front. My thinking, is that no amount of propwash etc can get under the front of a hatch and lift it off, then, even if my magnet installation is poor or fails. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted July 30, 2014 Share Posted July 30, 2014 To go against the grain, I use a peg (front or rear - whichever is most convenient) and (normally) 2 (10mm) magnets in a cross member that latch onto thin tinplate strip epoxied to a matching cross member. Haven't lost a hatch yet.. But there is plenty of time for that. My Flea Fli uses a single magnet against a vertical strip. The hatch simply slides off. No sign of it coming adrift Martyn Quote Link to comment Share on other sites More sharing options...
Mike Hardy Posted July 30, 2014 Author Share Posted July 30, 2014 Thanks guys, I have another problem - gluing canopies to balsa - another post. Mike. Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted July 30, 2014 Share Posted July 30, 2014 For what it's worth I have found snap off craft knife blades as a good option to use in combination with magnets. I have quite a few of theses cheap knives. Quote Link to comment Share on other sites More sharing options...
Phil Green Posted July 30, 2014 Share Posted July 30, 2014 But... a good few slope-soarer hatches have been eaten by sheep. Button magnets will pass right through, whereas segments of craft knife could do some damage. CheersPhil Quote Link to comment Share on other sites More sharing options...
i12fly Posted July 30, 2014 Share Posted July 30, 2014 For me its button magnet one side and a washer on the other -they're nice and flat, not sharp and very thin, no preparation required other than rebate the magnets in Quote Link to comment Share on other sites More sharing options...
Delta Foxtrot Posted July 30, 2014 Share Posted July 30, 2014 Posted by Phil Green on 30/07/2014 13:18:02: But... a good few slope-soarer hatches have been eaten by sheep. Button magnets will pass right through, whereas segments of craft knife could do some damage. CheersPhil Fair point Phil. Ingestion by sheep has not been one of my design criterion to date, but now you mention it. I do grind the sharp edges and corners off, but even so I would not want to swallow them personally. Quote Link to comment Share on other sites More sharing options...
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