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BiggTim

Vac forming advice needed

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I'm preparing to try my hand at vac forming some clear parts again, and could use some pointers in type of plastic to use (be very specific, i.e. brand, thickness, etc.)

I also had trouble last time getting the plastic to pop off my masters without damaging either of them. What do you use as a mold release medium, if any? Thanks in advance 

 

Tim

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Use a UV stabilised PETG - 0.5 mm/20 thou Vivac is a good brand here in Europe - not sure if available in the US?

 

No mould release - but don't polish the surface of the pattern - if polished surface then flat back a little - I use 2000 grit wet and dry, but have heard of scotchbright etc used.

 

That's with a cast polyeurethane resin master - as that's what I use - and don't get any separation issues.

 

Iain

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Iain, 

 

My masters are also resin, but required a bit of priming and sanding to get put some blemishes out. Do you suppose a final primer coat of Tamiya fine gray would be sufficient?

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1 hour ago, BiggTim said:

Iain, 

 

My masters are also resin, but required a bit of priming and sanding to get put some blemishes out. Do you suppose a final primer coat of Tamiya fine gray would be sufficient?

 

Take care with the primer.  The primer may stick to the hot plastic during the forming.  It was painful but I cleaned up and primed my Malcom hood pattern and then recast it so there would be no need for primer.

 

HTH

 

Rick

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5 hours ago, Iain (32SIG) said:

Use a UV stabilised PETG - 0.5 mm/20 thou Vivac is a good brand here in Europe - not sure if available in the US?

 

No mould release - but don't polish the surface of the pattern - if polished surface then flat back a little - I use 2000 grit wet and dry, but have heard of scotchbright etc used.

 

That's with a cast polyeurethane resin master - as that's what I use - and don't get any separation issues.

 

Iain

Ordered some of it today, thanks!

2 hours ago, Dandiego said:

Tim I had another LSPer do a canopy for me. I sent him a resin master and he first vaced my master with some thin white plastic and then he formed the clear plastic over the white plastic.

 

Dan

Good idea!

2 hours ago, Rick Griewski said:

 

Take care with the primer.  The primer may stick to the hot plastic during the forming.  It was painful but I cleaned up and primed my Malcom hood pattern and then recast it so there would be no need for primer.

 

HTH

 

Rick

Another excellent idea! I will try that, too.

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As others have said - I've learned from experience - don't use any primer - just raw resin.

 

Don't be tempted to fill any pin holes on the surface with filler/paint/superglue - in my experience it doesn't work and you'll get imperfections on any moulding.

 

Best sand these back until gone - or cast another copy.

 

Iain

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Posted (edited)
6 hours ago, Iain (32SIG) said:

Just to add - I've used the 0.5mm on the Spitfire canopies - I'd use 1mm for anything larger.

 

But 0.5 has been perfect for these:

 

Those turned out extremely well, Iain! I hope I can do it half that well. 

 

The .5mm should be perfect then. I am having a go at vac forming the rear canopies for my Ju87G-2 build, since I buggered the original trying to "improve" it. Another Fantastic LSP member pulled my toast out of the fire by offering a new set of clear parts, but I thought I might as well give this a shot too, for practice. I am attempting to make the rear canopy out of two overlapping clear pieces and a tube frame, as the original was made - the kit molds them as a single piece withe no frame. I do not know if I have the skills to do it, but I'm gonna try. 

stuka-5.jpg

 

Incidentally, does anyone have any pics of the rear guns form inside the pit with the canopy slid open? All the photos I can find from the exterior with open canopies seem to show the guns either slid back with the canopy and pointing at roughly a level attitude, or not sticking out at all - as if they stayed in place and the canopy slid back without them. When the canopy is closed, they usually point upward. I'm sure this is due to the springy thingy they were mounted on, but I'd like to understand it a little better. Any help would be appreciated.

 

Tim

 

Edited by BiggTim

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Posted (edited)
1 hour ago, D.B. Andrus said:

Great idea, Tim. Should improve the look a great deal.....and thanks for the beautiful shot of the D model.

 

Cheers,

 

D.B.

 

 

D model? Forgive my ignorance, but are the G models the same as D, just with gun pods? That photo is of the bird at Herndon,  in the UK, and they advertised it as a G, and it seems to match all the G photos I could find, with no pods. Please fill me in.

Edited by BiggTim

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D model same G but for guns and pilot's cockpit details, as far as I know. I looked in my files and could only come up with a drawing of the gunner's position for the B model. If you think that would help I can post it.

 

Cheers,

 

D.B.

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Tim

 

I did find 2 shots of the gunner's position for the D, which should be same as the G. They're in Junkers Ju 87 "Stuka", Part 2, by Manfred Griel; Air Doc, ADC 009, 2011; ISBN 978-3-935687-48-5; page 19. Shots are pretty cramped, but....... Let me know if you need a scan.

 

Cheers,

D.B.

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