how to accurately cut out and clean up vac-form clear parts?

[jjp_nl]

I've been working on my Spitty MK.22/MK.24 lately (see 'whats on the workbench) Among the aftermarket stuff I used is a vac-form canopy because especially the back sliding hood kitpart sits way too high on the fuselage (nowhere near the guiding rails)

So I got me some Squadron vacu-form replacements (the came in two's in my case). And out of the sealbag they look something like this. It comes with a good amount of excess clear plastic film. While I managed to remove the excess clear plastic somewhat OK following the Squadron instructions, I've found it to be a rather daunting task taking up quite a bit of time. I have to admit I have very little experience in handling vac-form clearparts, so I'm already glad I got away with how I did it, but looking at other peoples work I feel I could have done better.

So, I was wonding how some of you guys might go about removing any excess clear plastic and work it into a nice and smoothly cut out and well fitting clearpart. I understand the delicate nature of these vac-form parts makes working with extreme caution a necessity, but perhaps I have missed a special trick or technique to make things a bit easy.

Any advice would be greatly appreciated!

Thanks in advance

 

[Wayne Little]

having been there done that....i have used a pair of scissors to trim away the main sections of excess plastic, followed by a SHARP knife to trim down close to the edges, following up with sandpaper and sometimes a file to carefully get down to the final edgeing of the frame. I usually take it VERY slowly with lots of dry fitting as I get the final shape right, this can take a while to get right due to the thin nature of the vacform canopy.

 

[mikewint]

I agree with Wayne, I seldom use these myself but on those occasions where I have, I have used a dremel rather than a file or sandpaper as I feel I have more control and can angle the tool so as not to accidentally scratch the canopy. I also dip the canopy in Future and let it dry thoroughly before final trim and fit

 

[Airframes]

I haven't used many vac-form canopies, but I have moulded a lot of my own, with the same problems of trimming. In all cases, I brace the inside of the canopy (using the mould for home made ones, and Plasticine or Blu Tak for vac form), then, with a NEW blade, carefully and gently score (not cut) continuously around the part until it is separated from the excess plastic.
Where a canopy and windscreen need to be separated, I place a strip of Tamiya masking tape over the 'cut line', marking the actual line to be cut with a fine pencil, and repeat the above actions. Any rough edges are carefully, and gently, sanded, with the remainder being blended into the fuselage with PVA when attached.

 

[jjp_nl]

Thanks for the advice guys. Seems like I was on the right path after all. Making a make-shift mold with blu-tac seems like a good additional measure to take in order to make it a little more 'solid' when working on it and cleaning it up. I will try using my motor tool on a piece of scrap vac-form clear part to see how that goes down.

 

[mikewint]

If you are goint to use a rotary tool watch your speed. friction causes heat and heat melts plastic so generally a low speed and light pressure, let the tool do the work

 

[jjp_nl]

Check! Ik can change rpm on my motor tool, so I'll start at the slowest speed possible

 

[A4K]

Good advice guys!

I pretty much use Terry's method (nimus the mould for bracing), and cut with a new blade, holding the scalpal at a 45 degree angle to perpendicular. I find this helps guide the blade without risk of slipping and damaging the canopy.

 

[N4521U]

I have buggard up a few of these devil things............. Have given up on them.

 

[Zaggy]

My technique has always been to leave between 5-10mm of plastic around the 'bottom' of the part, then use 200-320 grit sandpaper (glued to a board or hard, flat surface) to sand the plastic away from the bottom of the part. The old rule that I always followed was, sand until the 5-10mm of excess plastic 'falls off'. If the part is fragile or flexible, as above, pack it out with something... What used to work well for me was some balsa wood, carved generally to shape and pressed into plasticine, with something between 2-5mm between the base of it and the bottom of the finished part - I would find just plasticine on its own was not firm enough and likely to ooze out onto your sand paper...

Vacuform kits are fun I kinda miss them!

 

[Capt. Vick]

Good info guys, thanks!