DMC

Editing in text After reshaping the canopy and windshield moulds and plunging another set I’m satisfied with the shapes. I plunged the windshield .020 PETG and I think it’ll be okay. The canopy might be another story, however. The problem with plunging a deep mould into thin styrene is that the stretching of the hot styrene stops at the edge of the female mould. Only the styrene within the opening is stretched. Consequently, as with the canopy mould, the first part of the mould to contact the hot styrene remains fairly thick but as the mould is plunged it becomes almost paper thin. That’s not much of a problem with, say, .040 material, as in the cowling in the photo above, because of the extra thickness. Forty thou is good for cowlings, spinners and the like but is too thick for canopies. I have been been unable to find any PETG thicker than .020 anyway but will have another look on the Web. If I could find .030 PETG I’d give that a try. Another .010 would make a difference. My my best shot at getting an acceptable canopy is probably to vacuum form one. When vacuum forming the whole area of the hot styrene is used and is pulled down over the mould so the thickness remains constant instead of thining out as it does with plunge moulding. Cheers and and thanks for looking Dennis

Editing in text in a few minutes Okay, cowlings are another kit replacement part that are fairly easy to do. Top left: this one that I made out of clay but didn’t get quite right. Good enough for a demonstration, however. This will be a two step plunge. Note how sharp the edge is on the opening. Top right: first plunge using .040 thick styrene, enough for a little filing or sanding if needs be. Bottom left: flipping the assembly over while the styrene is still very hot, and using this length of aluminium tubing, which is conveniently the right size. I pressed into it to get the rolled edge. Bottom right: After the second step. Surprised to get the “spinner” as I hadn’t done this with tubing before. I first experimented with this method on the intakes for the SH-2G and then used it for the Monogram F4U-4 intakes. I expect there are other ways it could be useful. Cheers, and thanks for looking Dennis

Thanks for that, really appreciate it. Must have bee a EUREKA! moment. Good that you were able to find it and I agree about the site.. Cheers Dennis

Text in a few minutes. First photo is of the old toaster oven I use. I’ve marked the dials with two settings, one for baking the clay and the other for heating the styrene for plunging. I used the meat thermometer at first when I had the oven in the garage and it got quite cold out there. The styrene takes anywhere from 12 to 15 minuets to heat up depending on the thickness. Not sure what material the white pad is but I use it to keep the balsa, or clay, from coming in contact with the tile. Doesn’t melt or burn. Second photo top left: in, top right: not ready although the styrene has started to sink into the opening, bottom left: better, styrene should be very wet looking with a slight yellow tinge, bottom right: plunge Let it cool a bit then remove clips and separate from the mould. Looks ok but, as you can tell by the crease on one side, the mould wasn’t equal distance around the opening. Try again. Thanks for looking Dennis Apologies for the poor quality of the photos but it was a bit tricky trying to do this in front of the hot oven.

I’ve been running a plunge moulding tutorial over on the Scratch Building page and am working on a canopy for the Corsair. Thanks for looking Dennis

Okay, not bad for the first plunge but I'm going to reshape the moulds a little and try another set. These were done using .030 white styrene. Using white initially gives me some idea of any changes I need to make. In Detail & Scale I learned that the canopy actually raises up a couple of inches as it slides back. Good book that! Thanks for looking Dennis

Big enough, four engined. Apparently it was a DC-6B from the Red Bull’s collection. ( How much of that darned stuff do they sell anyway?) Dennis

Why clay? I like using it simply because I like sculpting with it. Also because I find it very versatile. Make a mistake and it's easy to add a bit and re-bake it. Polymer clay can stand several bakes without burning or crumbling. The small bust of Pallas Athena was done in several stages. But wood, or some other material, can also be used. The curved mould in the second photo was easier to carve from balsa then sculpt from clay. I used it to plunge the concave section that the flaps mate up with on the Corsair wing. Some moulds would be difficult, for me anyway, to carve from wood. The mould for the Corsair wing intake is an example. Plunging the intake was a two step process. After the first plunge, I had to flip it over while still hot and plunge the rolled in intake. I admit it took me several tries before I got something usable. Second photo: Canopies and windscreens are probably the most often plunge moulded replacement, or new, parts of a model kit. Canopies that are too thick, lost or damaged can be replaced by plunge moulding a new one. Canopy moulds can certainly be carved from wood but I think there might be some issue with the wood grain showing on the clear PETG. Because I altered the fuselage of the Monogram Corsair I'm building, the kit canopy couldn't be used. An aftermarket replacement would have saved a lot of time, and would have been the chosen way to go for most modellers, but I had to sculpt and plunge a replacement. Using the kit canopy, with a little petroleum jelly as a release agent (necessary), I pressed a thin layer in first to get a good fit and then added a, shaped, larger piece. I got something like this after baking: third photo I then enlarged those two pieces with more clay, baked them and shaped them using the fuselage as a guide. I've made the female moulds to fit and later today I'll plunge the moulds in white styrene to see how close I was to getting a good fit. (Might have to edit this also as I can barely read the print using my laptop) Cheers and thanks for looking. Dennis

Hi Rob, Big four engined Douglas taxied by at Duxford yesterday. Buffed to a chrome like finish and all four radials ticking over nicely. Sweet, thought of your build. Cheers Dennis

Well now you’ve done gone and started a nostalgia reverie. I seem to remember doing one or two like this those many years ago. No bandsaw and templates cut out and stuck to cardboard with mucilage glue. I think the vertical stab might have been glued on, crookedly no doubt, later, however. Cheers Dennis

Excellent! Those Speedbirds are really starting to get their claws in me. Especially the Macchi Castoldi types. Thanks for posting. Dennis

Thanks for that. Troy also provided a link for access to the book. Worth a look. Dennis

Hi Ian I have done something similar with polymer (bake to harden) clay. It was a kit canopy and I filled it wth clay and carefully removed it (it took a few tries) and baked it. I then covered it with a thin layer of clay to enlarge it slightly and baked it again. This was just an experiment, however. So, yes, you could try it but as I have never used air dried clay I wonder if it would be difficult to remove from the canopy without destroying it. Is it a bubble canopy? Bulged at the top? You might have a problem getting the bubble shape by plunge moulding if the base as much narrower than the top. Hope this at least partly answers your question. I plan on on dealing with this very problem in a future post. Cheers Dennis

Shaping up, Rob Dennis

Just curious, how big a disc? Dennis