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How To Duplicate Vac-U-Formed Canopies


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It comes up now and then, whether it is possible to duplicate vac-u-formed canopies.  The answer is yes!  I will show you how I do it.

 

First off, the canopy you wish to replicate has to be closed at both ends.  If it has already been cut out of it's plastic sheet, you are going to have to devise a way to make it hold a runny sort of product.  One way might be to glue plastic pieces to the part that needs to be sealed off, using a glue such as G-S cement, which can later be dissolved with 91% rubbing alcohol, without harming the plastic.

 

BEWARE --  THIS METHOD WILL NOT WORK ON ANY SORT OF "UNDERCUT" CANOPY!!!  -- but then, I don't think the vacuform process would either!

 

Next, I dip the canopy into a paper cup full of Future or Pledge or whatever it is now, wherever you are. I do this twice, dipping into the cup, holding the part with tweezers, and allowing to dry on a paper towel for an hour or so between coats.  After each dip, I pour the left-over Future/Pledge back into the bottle, then place the now empty paper cup upside down over the canopy, while it dries, to deter any dust.  The reason for the Future is twofold.  First, to help make certain that the surface of the cast part will be smooth, and also because later on, if the casting doesn't want to come out of the canopy (mold), you can dissolve the Future with Windex with Ammonia D, as it is now called.  Don't know why that call it that, but they do.  You can also use plain or diluted ammonia, but it will smell really bad!

 

Anyway, except for the Future and ammonia product, our needs are simple:

 

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The canopy we wish to copy, and a can of Durham's Rock Hard Water Putty.  What it was used for originally, I don't know, but it works great for this.  I got mine at Home Depot, you mileage may vary..

 

I just dump some of the Durham's fine powder into a plastic cup, then add a few drops of water, and stir with a cocktail stick.  The stuff stirs much like Plaster of Paris, but dries harder (and yellow).  You want to mix it until it has a consistency  somewhere between chocolate syrup, and pudding.  That is, you don't want it too runny, as it will take forever to be dry (and be weak), but also, you don't want it to be so stiff that you have to scoop it into the mold (canopy).  Fortunately, it's cheap enough to experiment with!

 

Anyway, just make sure that your canopy will hold water, but your putty mix is more like pudding...  Next, mix up the putty and pour it into the mold (canopy).  Make certain that the canopy is level. 

 

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I usually make sure to fill the canopy a bit above level, as the putty will shrink slightly as it settles.  I also run a cocktail stick back and forth, to make sure that no bubbles are left against the canopy surface.  Getting the right consistency will go a long way toward that goal.

 

Here is what mine looks like, after drying, usually about two or three days:

 

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Usually, the Durham's will just pop out with a tiny bit of prying, preferably in an area that is not critical, as the stuff WILL scratch.  If not, here is where the Windex D is your friend.  Run a few drops along the edge between the canopy and the Durham's, and after a few seconds, you should be able to pop it right out. 

 

Lastly, the finished product:

 

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Note that any fine rough edges (arrow) can be sanded right off, and the bottom can be sanded flat, if need be.  Note the perfectly smooth surface of the molded part, which is of course, a perfect copy from the inside of the canopy, so that after you vacuform it, should create a copy perfect to use -- plastic thickness being about the same as the original copy.  If there is a little Durham's residue on the original canopy that you copied, again, the Windex D and a toothbrush will get it right off!

 

Duck Soup, as they say...   Now, where did I put that Vac-u-former?

 

Ed

 

 

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Looks like a very good product. Not seen it over here in England, but it looks a better bet than accurately mixing smelly resin together.

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Durham's is a DIY filler.  The beauty of it is that you can control the consistency of it by mixing in more or less water.  Less water, you get a thick putty; more water, you get a pourable, pancake-batter consistency.  Each has their uses. 

Back in the day, FineScale Modeler ran a series of articles by Ray Anderson called "The Art of the Diorama" (and later compiled them into a book).  He would use Durham's for his groundwork.  We followed suit on our 1/72 scale Fire Support Base now located at the South Carolina Confederate Relic Room and Military Museum.  Read about it here (click through the pages for the full story):

https://www.ripcordassociation.com/ripcord-diorama-part-1/
 

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