Hot pressing

[al49]

Hi everybody,
I need some help on something I never did before.
For the Macchi C 200 I'm building in 1:32 (follow this link if you wish)
http://www.ww2aircraft.net/forum/start-finish-builds/macchi-c-200-w-i-p-22455.html
I'm still in troubles with the cowling.

Cutting into separate elements and empting the bulges, doesn't work well enough and it will be my latest option.
The reason is that besides the diameter of my engine is correct (1200 mm : 32 = 37.5 mm and my engine is 36.00 mm) the outside diameter of the resin piece is 38 mm, so it will be tough, at least for me, to make it fitting.
So I have two options.
The setting I'm thinking is something like this:

I could, 1) leave the cowling pieces on the floor or, 2) make larger cowling pieces.
To do the latter I thought to use the originals as masters to make new ones from plastic sheet, but as said above, I never did something like this.
Because I cannot do vacuforming (my vacuum cleaner is strange), the idea was of hot pressing.
Can anybody tell me how to do it?
Many thanks in advance and best regards
Alberto

 

[Wurger]

Alberto, if I have understood correctly - you need to make a new engine cowling of a smaller diameter am I right?

 

[al49]

Alberto, if I have understood correctly - you need to make a new engine cowling of a smaller diameter am I right?

Hi,
sorry, probably I didn't explained well: I need to do individual cowling parts larger then those obtained by simply cutting this resin item

in order to obtain the components shown on the top of this drawing

I remember reading somewhere that if I heat a .5 mm plastic sheet and, while it's still hot, I press on it the original, I should get a copy just .5 mm larger but, before I start doing trials, I would appreciate some more precise guidances, if available.
Cheers
Alberto

 

[Wurger]

Oh.. I see now. Of course it is possible. But I must worn you that the resin part as the former can be damaged or even destroyed by the warm. Unfortunately the rasin used for making aftermarket parts is not warm-proof and can be shaped ( bent for instance ) with warm water. So I don't suggest using it as the former. Of course you can mould it again with epoxy rasin. But it is better to use wood, balsa for instance. If I were you I would divide the cowling into a few parts. The part one - the front ring. It can be moulded with the epoxy.When hardened , warm up the plastic sheet and stretch on the former. The second part - the mid ring with bulges.For that I would use balsa for making a cilinder of the inner diameter of the ring.Of course you can use a half of the cilinder for the former. And again stretching plastic on this. All these bulges I would make separately, making epoxy formers for them. And the third part - the rear ring . It might be made with a plastic strip ( strips) formed with warm using the balsa former for the middle ring. The air intake and the rest small parts have to be scratch-built certainly.

 

[Airframes]

That's the basic idea Alberto. It's best to also make a female mould to ensure a more accurate alignment and shape, but I'll let Wojtek explain, as I'm a bit bogged down at the moment!
EDIT: Oops! Sorry Wojtek, we posted at the same time!

 

[Wurger]

Yep.. sorry Terry.

 

[al49]

Oh.. I see now. Of course it is possible. But I must worn you that the resin part as the former can be damaged or even destroyed by the warm. Unfortunately the rasin used for making aftermarket parts is not warm-proof and can be shaped ( bent for instance ) with warm water. So I don't suggest using it as the former. Of course you can mould it again with epoxy rasin. But it is better to use wood, balsa for instance. If I were you I would divide the cowling into a few parts. The part one - the front ring. It can be moulded with the epoxy.When hardened , warm up the plastic sheet and stretch on the former. The second part - the mid ring with bulges.For that I would use balsa for making a cilinder of the inner diameter of the ring.Of course you can use a half of the cilinder for the former. And again stretching plastic on this. All these bulges I would make separately, making epoxy formers for them. And the third part - the rear ring . It might be made with a plastic strip ( strips) formed with warm using the balsa former for the middle ring. The air intake and the rest small parts have to be scratch-built certainly.

Many thanks.
My concern are only the four parts with bulges.
The front ring will work and the back ring I will do with plasticard.
For the four parts mentioned above, I made already several resin copies, so I will not touch the original, but how should I do to make the "larger" copies?
If I got it well, you suggest to fix the resin copy of each single panel on a solid surface and then stretch on it the warmed-up plastic sheet?
Thanks again

 

[Wurger]

Exactly , I suggest that.