Age of Strife


http://www.ageofstrife.com/blog/Spack/172_bf_109_propeller_repair_b-147_sid-8deb103228a5bcf37fe5ec2c205da522.html

Author:  Spack [ Sat Apr 13, 2013 2:00 pm ]
Blog Subject:  1/72 BF 109 Propeller Repair

Some time ago my son and I built a Revell 1/72 scale Messerschmitt Bf 109 G-10 model kit. The canopy has not been glued on as I wanted him to paint it first, but it ended up sitting on a shelf for months and at some point one propeller blade has broken off and been lost. This month my son wants to paint it, so it's time to repair it as it'll look odd with only two blades instead of three. I was first going to try to use some plasticard to repair it, but that was a non-starter as the blade is very thin and has a twist to it that would be extremely to replicate in this way.

Luckily I have some Oyamru "instant mold" that I bought a few years ago, and has previously been used in other projects. This stuff is great, as it's a thermal setting plastic - when it's put in boiling water for about a minute it goes very soft, and then hardens as it cools. Once cool it holds a perfect impression of the item it has been molded around. I couldn't find any "green stuff" putty kicking around (it's hiding somewhere in the house, but I can't remember where!), and once it sets it's quite brittle. I wanted something that would hold a smooth surface and be slightly flexible, and as an experiment I've decided to use some "no more nails" type DIY adhesive - the particular one I've used is Wickes own brand.

First job was to make some molds - as they will need to be cut open to extract the blades I've made three, that way if the first one doesn't work I've got a chance that the other two might. The first piece of instant mold was pushed onto the blade and squeezed, you need to make sure there are no air bubbles on the area that will hold the part. This was left to cool and then carefully pulled off; the molding material is flexible enough to handle this without ruining the mold if you're careful. A pin was then pushed in at the closed end of the mold to allow air to escape when the adhesive was squirted in, without this an air bubble will form at the tip of the part and ruin it.

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For the other two blades I decided to use a "two part" mold rather than the single block for the first one. I folded the molding material around the blades, and after cooling carefully pried them open along the seam where it had been pushed together. Adhesive was then placed on one half and the mold squeeze together tightly, forcing the excess out of the hole at one end and through the seam. This will likely result in a very thin flash or mold line at the seam, but this should be simple to remove once set.

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The blades will be left overnight to set, and tomorrow I'll open them up and see how they turn out. If they all fail then I'll try again with "green stuff" or a similar epoxy putty.

Tags: OyamaruInstant Mold1/72Casting



Comments

Author:  Spack [ Sun Apr 14, 2013 8:49 am ]

And the result is ... utter failure. The liquid nails didn't dry out! Time to hunt for the green stuff that I know is sitting in a box somewhere in the house.

Author:  estarriol [ Thu Apr 18, 2013 9:05 am ]

Piece of advice, when you do it with green stuff, push a pin onto the bottom of the blade as it will then give you a stub to fix into the plastic.

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