March FSM

i wonder if you can heat and smash those? anyone try?

Well, for starters, per the article, he filled the inside of the "kit" canopy with water based filler. A vac canopy master is very thin, thus the resulting dried putty master would be the right size for another vac replacement.

If you were to use a injection molded kit canopy, it would be several times thicker. Thus a casting of the inside would be considerably undersized. Then, when you vac a new replacement over the undersized master it will be much too small.

As an example, the math might work something like this.

The original kit vac canopy is probably made out of .010 clear plastic. While a kit injection molded one would be more like .020-.030. thus the replacement vac would probably be about .010 to .020 undersized.

A better process with a poor kit injection molded canopy is to use the kit canopy itself as the master. Simply carefully reshape and smooth the kit canopy. Using the same water based filler on the inside to strengthen it helps. You need to be very careful to finish it glass smooth because every flaw will show on the finished product. So will every speck of dust. When you are happy with the shape and finish, just mount it on the vacuform machine and proceed just like the article shows.

One note of caution. Like most cheap materials, bottles and already used clear plastic does not always yield very satisfactory results. The heating and stretching process will remove some of the flaws, but often not all. Thus the little pits and dings and bumps can end up recast right in the middle of your hard work. I would suggest staying with the good commercially available products like the Evergreen sheets shown in the picture of materials.

Norm

in article 3qFMd.4368$uc.2988@trnddc02, Norm Filer at snipped-for-privacy@cbrnp.com wrote on 4/2/05 7:23 am:

Snip

I have used the original canopy to produce male/female vac form like replacements using the plastic trays from multy packaging found under boxes of small items ( or small boxes OF items ?) in the local supermarket . Most of the trays are dimpled which gives an extra bit of "give " when moulding.

Rory Manton

Oh gods, why me?

Not usually the case. Consider carefully the original kit injection canopy - it fits the OUTSIDE dimension of the cockpit nicely in most cases. However, the inside is considerably undersized (by the thickness of the canopy). If you make a mold of the inside, you will end up with an undersized canopy. The thinness of the vac canopy will not be noticably thicker than the original and it is much easier to get to fit than trying to pull an undersized canopy out to the rails.

I have only done this a couple of times, but in each case, I used the original kit canopy as the master and had ZERO fit problems.

John W. Alger IPMS 10906 Charlotte Scale Modelers

John,

You quit reading too soon. The very next sentence says exactly that. Then the rest offers a similar solution.%^)

Norm