Covering Blue Foam

[Piecost]

Jeremy,

Thanks for your interest and thoughts. You may well be right that there may be better alternatives to the Czech methods. Perhaps; it is up to us to find them!

I have not experimented with tissue over mylar, even though I own various grades of film. I even own one of the lighest; OS film. I had wondered about using it under condensor tissue, but have not tried it. It might be worth trying with one of the lighter Kozo Shika tissues. I am nervous about trying to heat shrink it, though. Perhaps I will give it a go on my next peanut model.

I am primarily interested in sealing foam surfaces with double curvature. As I previously stated; my experiments have been unsuccesful in producing a flexible sealed tissue. But, I have just bought a varnish called Polycrylic. Various threads on RCGroups suggest that it has similar properties to the Czech Balakryl. It is not a polyeuthane, is rubbery and takes a long time to dry. I really hope that it produces sealed tissue which is flexible. If not, that might be the end of that line of investigation.

Thinking of applying plastic film over solid surfaces reminds me that the Czech forum stating that Tonda Alfrey really did use microfilm on a couple of models. And that this was not a Google translation error! Talking to one of the senior UK indoor duration fliers put me off of even considering making my own microfilm. I think that microfilm might remain sticky and can imagine coming home from an outdoor trimming session with the model covered in grass seeds.

I agree that the thinner films may well be thin enough that pleats or lap joints will not show under the tissue.

I think that the critical thing is the adhesive. Do you have any experience with Deluxe Foam 2 Foam? It resembles Uhu U-Por from what I can tell on Youtube. As such, It would need thinning. This would need to result in a perfectly smooth and thin liquid to be applied uniformly. Maybe lighter fluid would work, as per Uhu Por.

As you likely appreciate; it is as vital that the coating deforms with the substrate rather than delaminating and creasing. I experienced this problem on a Peanut Nolan Aero Bristol scout, see photo below:




I had applied very thin aluminium foil, from chocolate wrapping, to 1mm thick blue foam. I used a light application of spray glue on the foam before applying the foil. Upon application, the foil was smoothed down carefully and was wrinkle free. But, after attaching to the model, wrinkles appeared and ruined the look. A thicker monocoque foam front fuselage might have helped. The thicker foam would deform less.

I found that spray glue can be relatively heavy and difficult to control the amount applied.

Perhaps canopy glue might stick shiny plastic film to foam?  But, I do not see how the moisture can escape to enable the glue to dry. I anticipate further experiments being needed.

Other thoughts are appreciated.

[Jmk89]

I'm afraid all I know about Foam 2 Foam is from reading the ads in AeroModeller. And I know even less about Uhu U-por!

As for the appropriate solvent or thinner, if there is one, I have absolutely no idea.

Sorry

[Jmk89]

This thread discusses using thinned U-Por to attach Mylar:
https://www.rcgroups.com/forums/showthread.php?1568062-Using-diluted-UHU-Por-to-attach-Mylar-covering

[RolandD6]

[quote author=Piecost link=msg=6477
Perhaps canopy glue might stick shiny plastic film to foam?  But, I do not see how the moisture can escape to enable the glue to dry. I anticipate further experiments being needed...
[/quote]

Try 'Weld Bond', it is supposed to bond most materials.

Pinprick the foam to create escape holes for the moisture; a technique used by some people who still build balsa models.


Paul