HOW TO: Improving/replacing clear parts

I thought I would share with you some thoughts I had over the weekend about clear parts and some ideas I tried out to improve them. A summary of my thoughts can be found here (http://www.automotiveforums.com/vbulletin/showpost.php?p=3768680&postcount=21)

I was working on a Fujimi Dino 246GT and was really annoyed with the clear parts:

Basically the plastic part is WAY out of scale. Looking through them is like peering through a pair of Mr Magoo’s spectacles. I asked myself what’s the point of trying to detail an interior of you can’t see it clearly after installing the tub into the body?


Apart from being so thick, they are invariably scratched before I even open the bag


The fit of the clear parts leaves a lot to be desired and in fact impacts on assembly of the whole car.

With regards scale, I measured the thickness of the Dino clear parts – at it’s thinnest it was 0,67mm and 1,0mm at it’s thickest (measurements taken AFTER sanding the part!). If we take an average thickness of 0,84mm this scales out to glass 20mm (3/4”). Bullet proof glass isn’t much thicker!

I tried two approaches to remedy this:
1) Thinning and polishing the part
2) Making a replacement part.


1) Thinning and polishing:
For this I used squadron sanding sticks (medium, fine, polishing), various grade sand papers, micromesh system, Tamiya compound (fine, final polish), Maguire’s Carnauba Wax.

http://img386.imageshack.us/img386/898/polish012zv.jpg

First I used the medium and fine polishing sticks to thoroughly sand down the piece on both sides. I went a bit further than just removing scratches and actually thinned out the part somewhat. After this stage the clear part was predictably opaque and look like a disaster. Do not despair!!

Then I began the polishing stage. On one side I used the full Micromesh system (3600-12000) while on the other side, for comparison, I used only a 2-sided squadron stick. After polishing out there was IMHO no noticeable difference between the 2 effects obtained. The only difference was in time and effort required – the squadron polishing stick method was quicker and easier.

After polishing, the clear part was still not crystal clear so I worked further - first with Tamiya compounds followed up with the application of carnauba wax. After this the clear part was sparkling and clear.

I was totally happy with the effect and found that it was worth the effort. However, IMO it is not possible to thin the part very much and it still remains out of scale albeit significantly clearer.



2. Making a replacement part
This approach was more or less forced upon me when I snapped a clear part in half while polishing it and was unwilling to accept a glue line in the middle of the rear window

First I took a piece of clear plastic from some bubble packaging (something I stole form my wife :wink: ) and cut out a suitable large piece for my needs. This plastic was 0,16mm thick (3,8mm/0,15” in 1/1 scale) much better!

http://img386.imageshack.us/img386/9468/newwindow017hx.jpg

Before starting work, I cleaned the piece up with Tamiya fine and finishing compounds and then rubbed it with carnauba wax which removed all fine scratches. I felt that it would be much easier to do this while I had a large, flat surface to work with rather than a small, curved part.

http://img386.imageshack.us/img386/1219/newwindow023jv.jpg

Next I made a covered the original part with Tamiya 40mm masking tape and contoured the shape to make a template/mask.

http://img386.imageshack.us/img386/3923/newwindow038vb.jpg

The template was transferred to prepared sheet of plastic and then I cut out the template. I started first with scissors, cutting about 5mm away from the template and then cut carefully along the line with a nr 11 scalpel. The template will inherently give you a new piece slightly larger than the original which is fine. You can adjust to fit later by carefully sanding with fine grit paper or sanding stick.

http://img386.imageshack.us/img386/1151/newwindow048qq.jpg

http://img386.imageshack.us/img386/8223/newwindow057xo.jpg

Once I had the shape cut out, I put the new part up against the original in order to establish where the curves should be. I bent the part in the appropriate places around gradually thinner paint brush handles (without heat).

At this stage the key is test fit, test fit, test fit and test fit again. TBH I was lucky and got it right first time but I don’t suppose I will get that lucky again.
Also, I now know it is important to get any curves just right at this stage. The material is quite springy you cannot expect the glue to hold a part to the body that is pulling too much in the opposite direction. My estimate is at 0,5mm tolerance.

http://img386.imageshack.us/img386/2345/newwindow064wo.jpg

http://img386.imageshack.us/img386/5264/newwindow072yj.jpg

The final part was treated with wax again to clean it up and then fixed in place with GS hypo cement. I think that the final result is excellent. The clear part is now clear and to scale. When looking through through the new window, you can’t see it and that was the point!! :iceslolan

http://img386.imageshack.us/img386/5281/newwindow095fb.jpg

I’m pretty sure that I will be using this technique more in the future. The whole operation took me about 30 minutes which is about what it took me to sand and polish old part before I broke it. Also, the Dino rear window is an exceptionally difficult piece because it has lots of curves and is fitted at an angle so I am sure that regular windscreens and windows shouldn’t present any problems.

I hope that this (rather long :uhoh: ) post will encourage some people to look critically at their clear part sprues and do something about it.

Disclaimer: I accept no responsibility for any broken or damaged clear parts! :biggrin:

That was a really good post, I need to make a few sets of "windows" for some of my builds and I found your method to be really well thought out and you presented it in an excellent format, 10/10 for a really good "how - to"

Cheers, I'll try this method, with the missing part from my model. Use the masking tape over the gap as apposed to around the piece, it should work.

Excellent tutorial and a great idea. Thanks for sharing :)

Mick Sz.

Wow, That is so great. I've wondered about trying this before. Now after seeing this I know it can be done. Mods, make sure this gets put in the how to section for sure.....

So you take the clear plastic from packages?
Also, won't the plastic bend back to a flat piece? So what can you do to get a hard, solid piece?

Excellent tutorial Stevenski

you never fail to surprise me, Stevenski. what a great thread! i dont think i have ever had a model where there wasnt some problem with the windows and now i dont have to give it another thought. problems solved! the part of this i really can appreciate is the much more accurate scale appearance. thanks again for this. looking forward to your tutorial about making robots to paint car bodies without running the paint.

Fantastic tutorial steve, really a real improovement.

You can also use clear thermaform type plastic sheets to copy kit windshields and windows. http://www.squadron.com/ItemDetails.asp?item=SQ9003

Take the windshield to be copied, and mount it pedistle style face up on your workbench. A big chunk of modeling clay and a large sized bottle of Tamiya acrylic works fine for this. Gently heat a piece of thermaform at least several inches longer and wider than the windshield, until it's nice and flexible. Then, place it over the windshield, and pull it's edges down past the windshield. It cools pretty rapidly, and will hold the shape it cools in. This is called 'smash' molding, and works essentially like a poor man's vacuum-former. Trim it to shape, and install.

Totally awsome tut man! Gonna use it to fill the windows that tami's enzo left out:grinyes: !

nice tutorial, how do you get the clear part to hold the curve though?

Glad you found this thread of interest and I hope it will be useful to you all in some way.

So you take the clear plastic from packages?
Also, won't the plastic bend back to a flat piece? So what can you do to get a hard, solid piece?

nice tutorial, how do you get the clear part to hold the curve though?
In this instance I found that I didn't have any problem with getting the plastic to hold its shape.

I had been prepared to use heat to soften the plastic as MPWR points out in his post but in the end it turned out that I didn't need to - the plastic held its shape well with just "mechanical" bending around round paintbrush handles.

There is a springyness to the material which is why I mentioned that it is important to test fit and make sure that the curves are fiting closely to the body part before glueing. This wasn't a big problem though.

I once tried the "smash" molding method MPWR mentioned (although I didn't know then that it had a name :biggrin: ) but I had real problems getting the plastic warm enough to be soft and allow me the time to transfer it to the master before it cooled out. My previous frustrations with this method are why I looked for an alternative this time round.

Les - Before the robot tutorial I have to finish a special request tutorial for Gridgirl ;)