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[rickles23]

Hi all,I am having Plastic sheet problems.I glued together four small sheets to make a box for a model I am building.I used all the usual tools to ensure all was straight.Now I find each sheet is bowed inwards to adepth of two millimetres.It's enough of a bow to be noticeable.What am I forgetting to do?Regards

[Geoff]

The only thing I can think off is that you used very thin sheet. If using solvent weld glue it can exert a small but meaningful pull in at the joints (meniscus) so, this could just make all the surfaces slightly concave.


Cheers


Geoff

[Colin Bishop]

Are you using transparent or white plastic? If opaque plastic then you can use some plastic strip on the inside to straighten and reinforce the sides. If you are using transparent sheet then you could add a base strip to straighten the sides along the bottom. Presumably you are putting a top on it? If so that will stabilise the upper part of the sides.

You don't mention how big the box is.

Colin

[rickles23]

Hi both,


I am using 2mm white sheet and the box is 7.5cms X 5cms.


Regards

[Colin Bishop]

2mm sheet is quite thick really. Unfortunately plastic is inclined to do this unless backed or stiffened in some way. It must be due to the way the adhesive melts the joins and evaporates to weld them together.

I have recently had a similar problem in building some benching for my paddle steamer model. Th supports are slices of square box tube overlaid with strip. The strip I used initially proved to be too thin and bowed between the supports so I had to double the thickness and also add a stiffener along the inside base of the box section supports to get a stable structure.

The longer sections are 12cm.

Colin

[nemesis]

you can get this affect if using "Hips",the highly polished surface exerts the pull. I have noticed the plastic you get in kits is not "Hips", just the plain matt surface. It is more forgiving as well, imho, nemesis

[Akira]

I tend to reinforce my walls with angle stock, set diagonally. Whiel it may not take all the bow out, it certainly makes it harder to notice.

[John W E]

hi there,


one of the methods I have used in the past - it may or may not suit yourself.   I build the box that I am wanting from either plywood or balsa wood first.   I then cover that with thin plasticard, glued with superglue.


Here is one I made for Exeter on the funnel - and the ammo boxes are made in the similar method, only using solid balsa wood core instead of plywood.

[Big Ada]

Pop in on to a Radiator, it may help.

[Circlip]

For a 3"x2" box 0.3cm would have been a better choice?


  Regards  Ian.