Foil Glue Test

Discussion in 'Coaching stock' started by JimG, 16 November 2012.

  1. JimG

    JimG Western Thunderer

    I have made a quick setup which might answer your question. I've made a basic coach side section with tumblehome from Plastikard. I've cut a piece of 10thou nickel silver sheet to fit on the tumble home and shaped it to suit. I've also cut some strips of 5thou and 10thou nickel silver to see how it works with narrow strips.

    Here are the bits of nickel silver with the glue applied and still showing its milky appearance, which disappears when it has "set" ready for application. I had cleaned the nickel silver with a fine bristle glass fibre brush and it has quite a polished finish and you can see that I was running into problems with surface tension in spreading the glue thinly and evenly. A matt finish would probably help and I think I remember seeing something during my web surfing that a very small drop of Fairy liquid might help.

    FoilGlue01.jpg

    The next picture shows the panel stuck to the tumblehome and the strips stuck to the flat upper side.

    FoilGlue02.jpg

    All the pieces were placed on the Plastikard and pressure was applied with my fingers. About half a minute after sticking them down, they wouldn't move with my trying to pick the edges up with my fingernail. I was surprised how well the thin strips stuck down. I thought the lack of area of material might be a problem - apparently not.

    The one problem I think I have with the larger sheet is that there is air trapped in the middle of it. I dropped the sheet straight onto the tumblehome and pressed it down and I think I would have to roll a piece like this onto its position to avoid trapping air.

    But the adhesive seems to work well and certainly grips metal to plastic much better than I thought it would. I'll leave it to harden for a day then maybe do a test to destruction to see how strong the bond really is.

    Jim.
     
    tomstaf likes this.
  2. tomstaf

    tomstaf Western Thunderer

    Jim,

    Thanks for this great bit of research bearing in mind I've got several etched parts to attach to plastic coming up in the near future:thumbs:

    Cheers

    Tom
     
  3. Dog Star

    Dog Star Western Thunderer

    A very interesting result. Lowering the surface tension of the fluid seems a good step, given that the solution is water based then maybe IPA could help.

    The reason that I posed the question, see post no. #1, was the comments which you made in the thread about slating the goods shed. In the light of this experiment with the metal/ plastic, gowdo you view those comments now?

    thanks, Graham
     
  4. JimG

    JimG Western Thunderer

    I did some tests to destruction a short while ago and the results were not too good.

    The larger sheet of 10 thou came unstuck with not too much force using a fingernail under one corner. The adhesive layer was still tacky and it would stick down again, but would come unstuck again with the same force under a corner.

    The tests on the strips were a bit more inconclusive. With the thicker 10 thou strips, about the same force as the sheet under one end with my fingernail broke the joint and the whole strips came loose. With the 5 thou strip, my fingernail under an end, lifted a few millimetres of the end, but the rest of the strip remained firmly in place. I tried a pull on the loosened end and the rest of the strip seemed quite firmly held although I suspect that a greater amount of pull would probably have peeled it off. I think I would be happy with the amount of adhesion of the 5 thou strip, especially if it could be further protected with a coat of paint.

    But I suspect that the adhesive doesn't really work well with stiff materials where good contact over every part of the piece cannot be guaranteed. When I formed the sheet to match the plastic tumblehome, I got it close to the curve, but not exactly, so it would probably have fitted where it touched leaving areas of the adhesive with little or no contact with the other material. Similarly with the 10 thou strip which was probably not dead flat, and from my experience with milling Plastikard recently, that can also not be considered as dead flat. The 5 thou strip would have been flexible enough to provide a good contact over its length. On my shed roof, the 5 thou lead foil is even more flexible than the 5 thou nickel silver, so it works well too, even though there are a multitude of different mating surfaces with all the slates.

    The adhesive does feel similar to the Post-It adhesive - maybe just a bit stronger, and it dries and sets to a very thin film so would not fill any gaps between mating surfaces.

    I suspect that the adhesive action also resembles that of the Seklema Multimat which I used on the milling machine - which had a tacky surface which would hold flat sheet material very firmly for milling but which would release the material quite easily if a corner was gently prised up.

    So my test looks as though it confirms that the adhesive works well for flexible materials (like foil!! :) ) but with poor results for stiffer materials where an exact surface match cannot be guaranteed.

    Jim.
     
  5. Dog Star

    Dog Star Western Thunderer

    A slightly disappointing result for the big or thick stuff.

    I think that using the product for the flat etches which were described by Steph (and included in his links) is probably reasonable. I am not sure that I wish to trust the etch window frames for 7mm Mk.1s especially as the glazing is inserted into the body opening and needs to be pushed up against the rear face of the etch frame.

    A contact adhesive for the frames is desirable, preferably one which does not string and which can be cleaned away easily. Time to go back to the Mk.1 thread.

    thank you, Graham
     
  6. JimG

    JimG Western Thunderer

    Graham,

    I thought it might be window frames that you were thinking about and I don't think there would be enough area of contact to give a good adhesion, although if the etches were about 5 thou thick brass, it might be worth a try if you could find a way of restricting the amount of insertion of the glazing.

    Jim.
     
  7. Steph Dale

    Steph Dale Western Thunderer

    Guys,
    I'm wondering whether you migt be in the process of attempting to solve a problem that doesn't exist?
    The area around the window frames of a Mk1 is pressed to present a flat surface to the glass isn't it? I must admit it's not a feature I've seen modelled, but it is there. Afterall Mk1 carriages have flat glazing; rather than, say, a Bullleid coach which genuinely has curved panes.
    Forming the panel shape around the windows won't be exactly easy, but I suggest some care is taken to avoid falling back on assumptions which might not be correct.
    Your thoughts please?
    Steph
     
  8. Steve Cook

    Steve Cook Flying Squad

    I think Fred Phipps is the only one to have modelled that feature on his Mk1's - there is probably a photo of it in the 1/32 section...

    Edited to add photo of feature on second to last post on this page