Magnetic double glazing

[stannn]

I've just received 10 neodymium button magnets, 10mm dia x 5 thick. They attract each other with about 3kgf when touching (a lot). More to the point, the force is still considerable and adequate when they are on opposite faces of a 3mm thick acrylic sheet.
There's a gap in my knowledge because the attractive force is much less than 3kgf for one magnet holding a steel screw. Worse, when the magnet and screw are on opposite faces of the acrylic, the force is too low for my purpose. The plan was to place 6 tiny countersunk screws (painted) into the wooden window frame and use 6 magnets to hold each 1200 x 600 acrylic sheet. The bottom of the acrylic will sit on the cill to take the weight. This face to face contact works well in preventing air passage, as I have found elsewhere.
Anyway, it's back to the drawing board.
I also received 3 off 3mm x 1220 x 2000 sheets of clear cast acrylic from Robert Horne for £40 plus VAT each and free delivery. This is a very good offer. They are now cut down to size though they will do it for you.
Stan

[Katy]

Check out the magnets on my previous link - try using a magnet on the frame and a magnet on the acrylic sheet - there are lots to choose from, inc. countersunk ones http://www.first4magnets.com/counter-sunk-magnets-9-c.asp

[AndySussex]

Taking the magnet approach, how do you make a seal?
If you were to put a line of steel tape around the window frame then attach perspex sheeting on the corners and maybe the middle of the strips, would this be enough to create a seal of the perspex against the steel tape?

[stannn]

Katy
I have looked at your posts and very interesting they are. However, your magnets with self adhesive are 1mm thick and so would lead to a 2mm air gap, would they not? Also, the magnets on the window frame would be very obvious when I remove the acrylic for summer. I could paint them though.

Andy
Why use steel tape if the window frame is reasonably flat? If it's really poor joinery then you have a problem anyway.
 In the last fortnight, I carefully planed to size 2 sheets of acrylic, 3mm x 1000 x 600, for the bathroom window and 'boy' did I make a good job. The 2 sheets  touch the reveal on all 3 edges and come within 1mm of each other. They look really professional because they shine and cover all of the frame. They even stayed up and in contact with the frame because they were such a good fit.
However, after 2 days the acrylic started to sag in a single bow so that a gap appeared at mid height. Well, I did something really naff. I drilled a 3mm dia hole at mid height on each vertical edge (2 per sheet, 10mm from the edges) and used 4 x 1/2 inch BMA (bronze metal antique) screws to pull the sheet to the frame. The screws are so small that you do not notice them. The BMA matches the frame colour.
However, contact with the frame is not good enough and I may have to add more screws. The ideal position for the fasteners is probably at 1/6, 1/2 and 5/6 of the height. It would be the same for magnets if I could wangle it.
Stan

[Katy]

Stan, you could countersink them as you were planning to do with the screws - just a little more fiddly, possibly. I've painted out the magnets on some of my frames, though not bothered to countersink them as I'm working with soft fabrics.

[stannn]

Katy
My neodymium magnets could indeed be fitted flush into shallow drilled holes in the wooden frame (10mm dia by 5mm deep) and epoxy used to secure them before painting. The bare sheet could then be offerred up and the companion magnets fitted loosely. They'll find their own positions pretty sharpish. As I said earlier, the attractive force is very strong through 3mm acrylic. I think that I will try this. It's quick and cheap.
Even the orientation of the magnet pair doesn't matter as the outer one will flip ovet to the correct attitude on its own. My apologies to Shambles who earlier described something similar but not with loose magnets.
Stan

[AndySussex]

Hi Stann. I think I might be missing a step here. So we have a sheet of acrylic, but how are you going to magnetically attach that to the window frame (made of wood).
I get that it could be done if you sunk some magnets into the wood and then had some on the other side of the acrylic, but even then, it wouldn't be air tight would it?

[stannn]

Andy
You have understood the principle. Now I realise that the result is not hermetically sealed but it has been good enough in the bathroom to stop condensate forming on the outer glass panes. There is just a bit of mist on the acrylic after we shower in the morning and that soon clears. So, pools of water are history and that is a result!
Incidently, I do not like conventional double glazing units because I have had several fail in the conservatory and that was expensive.
Stan

[stannn]

Well, can you believe it, the system works. I removed one of the bathroom panels and drilled 2 off 10mm dia holes with a dowelling bit (drill with a spike) at 1/6 and at 5/6 height. These holes are as near to the edge of the reveal as possible. So, because the Makita drill has significant body width, the holes have to be drilled at a slight angle. A magnet was pushed flush into each hole and had enough friction to do the business. I replaced the acrylic sheet and the mid height screws, threw on 2 more magnets and they pulled the panel snug to the frame.
I am gaining an advantage by having the magnets on the very edge of the acrylic sheet because some of the field is able to go around the edge through air, creating a greater force than if it were in the middle of a sheet.
The stainless-steel-coloured magnets even look trendy. I still have to epoxy the frame magnets.
Stan