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How to replace or fix a bad Vac canopy?

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Not sure whether this goes down the path of exotic restorative techniques, or creative commerce:

 

Have had an Anigrand 1/72 C-124 in work (shelf of doom, technically) for over a year, now. While the quality of the kit's resin castings is excellent all around, the canopy is not. It is distorted and pitted far beyond my ability to Micro-mesh/polish it to a suitable state. I ordered two replacements online from Anigrand in Hong Kong and it either got lost in the mail, or was too small an item for them to bother with. My $6 was refunded after a 6 mo. no-show, but still be-no canopy.

 

The clear plastic part is a single, large section of fuselage that includes the whole area above & around the flight deck of the big bird. I built up the 'pit, as it is big & visible enough to justify the work and don't wanna just hide it under painted panels.

 

Suggestions appreciated.

 

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Suggestion 1:

Bob, do you have any vacuforming capabilities, like a Mattel machine? If so, simply smooth out the kit canopy and vac over it, using it as the master. If your kit canopy IS a vac (as your title suggests); dam up the rear and pour it full of plaster of Paris. THIS becomes your new "master". It can also be sanded and polished smooth, erasing any bad framing; or even reshaped to correct a bad contour if needed. This is what I had to do for the C-119 I'm currently building (see below).

 

Suggestion 2:

If you don't have a vac machine, you can "push mold" a new canopy. There's an example of this down in the "On the bench" topics where I molded a new canopy for the C-119 I'm building.

1) You still use the kit canopy as your master

2) You need a way to hold the plastic that's heated (clamps, or pinning to a board as I did)

3) You need a cut out in that board, just slightly bigger than the mold, to push the mold through, helping stretch it and "pull/push form" the new canopy

4) You need a heat source to heat the plastic. I used a stove burner.

5) You need a way to hold the plastic while heating it, either clamps or oven mitts, AND you have to be able to use that way of holding it to also push the canopy through the molding hole, as you won't have time to "adjust your grip".

 

This is a hit and miss way of doing things, but it's also a method almost anyone can use without any "machinery".

 

Hope this helps!

 

GIL :smiley16:

Edited by ghodges

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Squadron used to make clear sheeting that you could heat, then stretch it over a master pattern. IF they still make the stuff, you might try filling the old canopy with epoxy putty making sure it fits right before it hardens, then stretch form over it. Just a suggestion.

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But, bear in mind that the male master MUST be smaller than the final part. This discrepancy will vary with the thickness of the clear sheet plastic you are using, but the final product is always larger than the male mold. Now, if the part tapers from bottom edge to top, then sometimes, all you need do is sand a little from the bottom. However, for example, if the width of the part is constant, then it will always be too wide, no matter how much you lower it from the bottom. If you can use the unusable kit part to creat a male mold by pouring something in it that will harden but still allow you to remove the kit part, that would be ideal. Otherwise, I would be inclined to carve and sand a new, slightly smaller male mold from styrene ( or bass or balsa wood, thoroughly sealed) and vacuuform over it. Nick Filippone

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I'm afraid I'll have to disagree with James on the Squadron Thermaform. I have some and have had NO luck with it at all. It immediately clouds up when heated and then seems too rubbery to be stretched or sucked over a mold.

 

The same goes for Evergreen brand clear styrene. It will not react properly when heated and is useless for vacking or push molding (but good for cutting windows from).

 

What you need is Pet-G type plastic. K&S brand clear sheet seems to be Pet-G, and works very well in my experience. It's available at Hobby Lobby stores too, in case your local hobby shop doesn't carry it. .15 or .20 seems to work best for push molding, and .15 and .10 works best on my old Mattel machine.

 

Nick is correct in that your vac copy will be slightly larger than the kit part you start with. If you make the plaster of Paris mold I suggested, this can be sanded down a bit overall to help make the new canopy closer to the size needed. However, The overall size difference will be almost negligible and the flexibility of the vac copy will help adapt it to fit too. But, as Nick points out, you will have to be prepared to deal with that difference.

 

GIL :smiley16:

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I order my clear plastic sheets from MicroMark. Their current catalog has the following stock numbers for Clear Vivak:

 

85881 -- 8.5" x 11", 0.010" thick, 6 per package, $15.75 (on sale from $19.35)

85882 -- 8.5" x 11", 0.150" thick, 6 per package, $17.50 (on sale from $21.50)

85883 -- 8.5" x 11", 0.030" thick, 6 per package, $17.50 (on sale from $21.50)

 

I have used the above 0.010" stock in my vacuform machine very successfully. It produces a very clear piece that is even thinner when stretched and very flexible, but still quite sturdy when handled. Dip it in some Future. Trim your part off of the sheet with a sharp knife or scissors, and you can sand the edges using a fine grit and careful support when handling.

 

These sheets are made by K&S, so you may find other sources as well.

 

Good luck.

 

Ed

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Vivac is the only way to go on Vac Canopies. Micromark does carry it and it's a bit pricey but it's what companies like Falcon/Squadron use for their moldings. Cheers

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