Jump to content

As a result of the close-down of the UK by the British Government last night, we have made all the Buy/Sell areas read-only until we open back up again, so please have a look at the announcement linked here.

This site uses cookies! Learn More

This site uses cookies!

You can find a list of those cookies here: mysite.com/cookies

By continuing to use this site, you agree to allow us to store cookies on your computer. :)

Recommended Posts

"Well Oliver that's another fine mess you've gott'n us OUT of!"

Looks marvellous, was that your first pull?

If so it proved the concept immaculately

I had doubts about the extension frames, but they have worked rather nicely

You see, here I am already learning how to do it

:thumbsup2:

Edited by perdu

Share this post


Link to post
Share on other sites

Looks like proof of concept to me :)

Doesn't look like the filler/primer transferred with heat - or that the master degraded (?)

One of the frustrations is that any speck of dust etc. can ruin (depending on your standards - and we know yours are the highest G) a canopy.

Have to say tho' that even your first effort looks to compare well with the Pavla offering for clarity.

Share this post


Link to post
Share on other sites

Thanks guys. Yes, that was the first one - shoulders of giants and all that... I just did another, but have still got little pimples all over it on the inside. Might try re-flatting the mould. I think static attracts dust to the sheet too. I wonder if I could leave the backing film on...?

Share this post


Link to post
Share on other sites

Just tried one with the backing film on - works OK, but still getting the flaws - which look like bubbles in the canopy. The plug itself is fine. Strange.

Share this post


Link to post
Share on other sites

Looks good to my newbie eyes... what a great WIP thread for education.

Also looks as though the creature from 'Alien' is looking over your shoulder in the second picture, reflected in the sheet you're holding. Dangerous stuff.


Share this post


Link to post
Share on other sites

I've had bubbles form in PETg sheets on heating.

When it has happened they have appeared very quickly and it has always seemed to me to be as a result of over heating or perhaps too rapid heating as it occurred when I'd allowed the heating element of my dental vac machine to get red hot before presenting the PETg to it for heating.

I've generally avoided it by not switching the heating element on until I'm actually trying to heat the PETg.

Could the oven temperature be a bit high? I know that you chose a sensible temperature - but?

It's also right to say that any pinprick like dimple in the master will get transferred.

Frustrating aint it :)

Share this post


Link to post
Share on other sites

Just tried one with the backing film on - works OK, but still getting the flaws - which look like bubbles in the canopy. The plug itself is fine. Strange.

This is the problem I am still trying cure, I think its called blooming and occurs only where the PETG has physically contacted a surface. Even does it when it contracts pure metal like the base place of the vac machine, but any area that has been heated but didn't touch anything is unaffected.

Share this post


Link to post
Share on other sites

Does it look like this? ignore the bigger bubbles that was muck. the smaller imperfections. If you are able to look at a Rob Taurus canopy they have managed to solve it somehow. click for bigger

14470394184_59ff2df2d8_b.jpg

Share this post


Link to post
Share on other sites

Not quite as bad as that, the bubbles don't seem to break the surface, but form small lumps, just one or two noticable ones.

Share this post


Link to post
Share on other sites

Did the canopy arrive mate?....Should have gotten it by now as I gave it to the postie to put in the bag as he was emptying the postbox last Saturday lunchtime...

Share this post


Link to post
Share on other sites

Did the canopy arrive mate?....Should have gotten it by now as I gave it to the postie to put in the bag as he was emptying the postbox last Saturday lunchtime...

Nope, nothing as yet. Still hopeful though because I'll use it if it's better than these vacform ones.

Share this post


Link to post
Share on other sites

Nope, nothing as yet. Still hopeful though because I'll use it if it's better than these vacform ones.

Its been used on the postmans tonka!

Share this post


Link to post
Share on other sites

I wonder if there's a need to raise the temperature more slowly?

You showed us a warm up blower to use first, might it be an idea to use that to soften the PETg, maybe getting a slower heat transfer would reduce the bubblings

Not being as good or careful as you I didn't notice bubbles on the Scout

I wonder if attempting to use ordinary acetate sheet in your rig would be better

I got a sheet of A1(? blo-dy big) sized acetate from my local artist's supply shop

They sliced it down to A4 size for me and I found it worked better than PETg

p.s. just searched my off cuts box for unused vac'd Scout cockpits, yes in the PETg ones some signs of internal bubbling

The odd acetate ones seem clearer

Share this post


Link to post
Share on other sites

Does the heat gun warm up the mould significantly? I wondered if the temp of the mould might be something to do with the slight bubbles in the transparency.

Very very impressive results, can't believe how clear this is.

Eng

Share this post


Link to post
Share on other sites

My friend and branch mag editor John D who posts here occasionally uses a heat gun for vac moulding demos at the club premises

Plenty of heat from one of those

Share this post


Link to post
Share on other sites

I tried again this afternoon, without the heat gun, oven on direct heat, not fan, plus I lowered the temp a bit. I also dusted the sheet with a microfibre cloth before putting it in the oven. Pretty much eliminated the bubbles, at the expense of slightly worse conformance to the lower flared frames.

I've got two ones that might pass. I can try again maybe tomorrow I guess, until I get bored.

Next job is to find some very, very thin plastic strip for the frames. Tamiya tape didn't really work for the riveting tool, so I need something between plastic and tape. Maybe the Tamiya stuff posted previously might be OK.

Share this post


Link to post
Share on other sites

Can you cut thin strips of plasticard for that?

I used it on my Jaguar canopy to reasonable effect

Good news getting a better version

All techniques need practise, and often fortunate conditions ;)

Share this post


Link to post
Share on other sites

It needs to be about twice as thick as tamiya tape at the most I'd think.

Been painting the pilots tonight...never been very good at modelling figures, but I thought these would give some scale.

Share this post


Link to post
Share on other sites

I tried again this afternoon, without the heat gun, oven on direct heat, not fan, plus I lowered the temp a bit. I also dusted the sheet with a microfibre cloth before putting it in the oven. Pretty much eliminated the bubbles, at the expense of slightly worse conformance to the lower flared frames.

I've got two ones that might pass. I can try again maybe tomorrow I guess, until I get bored.

Next job is to find some very, very thin plastic strip for the frames. Tamiya tape didn't really work for the riveting tool, so I need something between plastic and tape. Maybe the Tamiya stuff posted previously might be OK.

I wonder if a tack cloth on the mould and sheet would do the same???

I'm trying making the frames on the Meteor canopy from a very thin vinyl paint mask on a digital cutter at the moment. If your able to come up with a pattern with the curve that you need I could cut it for you and you can see how that goes. Alternatively there are rolls of very thin self adheasive aluminium tape on ebay you could cut to the right shape that might work.

Share this post


Link to post
Share on other sites

I wonder if a tack cloth on the mould and sheet would do the same???

I'm trying making the frames on the Meteor canopy from a very thin vinyl paint mask on a digital cutter at the moment. If your able to come up with a pattern with the curve that you need I could cut it for you and you can see how that goes. Alternatively there are rolls of very thin self adheasive aluminium tape on ebay you could cut to the right shape that might work.

I doubt I'll need to profile the hoops - they are near enough straight for all practical purposes, and at the thickness I'm looking at, they should bend out of plane easily (if required!). Not sure how to stick them yet, maybe pva, cyano wicked around the outer edges, then dip in Klear.

Edited by dr_gn

Share this post


Link to post
Share on other sites

Do dip in Klear before getting cyano near them G

I lesson I had to work hard to understand :(

Share this post


Link to post
Share on other sites

I've got two ones that might pass. I can try again maybe tomorrow I guess, until I get bored.

I now what you mean. It can be hard to know when to stop in the pursuit of the holy grail of a perfectly formed, perfectly clear canopy. I think it's probably a a race between boredom, awareness of the just how much expensive PETG is being wasted, and dawning realisation that there's always something wrong with the canopy you've just does - and maybe the second or third one wasn't so bad after all......

If you've got a couple that are just about good enough then I'd put one of them to one side for safety and choose the other (or one that's nearly as good) and see if you can improve it by smoothing and polishing with micro mesh followed by a dip in Klear. If you can - Bingo. If not then no harm done.

Share this post


Link to post
Share on other sites

I really advise trying acetate sheet instead

The PETg setup you have achieved is ideal for a materials changeover

I still haven't seen any bubbles in my acetate mouldings

Edited by perdu

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...