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One of the problems you run into when building masters is sometimes you have to build a master one way, to get it done, knowing the final version will probably have to be a different configuration. This floor piece is a very good example of this.


The floor piece was made so that I could figure out exactly how the walls would fit and exactly what diameter the finished floor had to be for the walls to fit correctly. Keep in mind the walls connect the floor and the bottom of the window area. Those two are different diameters, creating an inward slant to the wall, so it was very important to get the angle of the walls and the diameter of the floor just right.


Here you can see how I had to add to the overall diameter of this piece by cutting a ring of plastic. Actually, this is just one of several rings I had to cut, each one getting closer to the final one you see here. Using this piece as a master is a problem, for several reasons. First, it is not the correct thickness to make a reliable casting. Second, it is just too large to make as a single-piece casting. Resin shrinks as it cures, which will throw off the fit of the final part. This lead me to the decision that part of the floor will be a casting, the rest will be sheet plastic cut to the correct size.


One of the things that works against making the floor a large casting is the depth of the center.


Looking at the underside of the floor, you can see there are other unneeded features. Neatly removing what isn't needed would be very time consuming and probably wouldn't work. And since the floor needs to be thicker anyway, it only makes sense to save what would be the hardest to recreate and make a mold of it. In this case, that would be the center, with its steps and conical walls.


Here I've made note of the overall diameter of the floor, which will be important to know later; and determined the best place to separate the center from the floor. The block in the middle was placed to accurately reposition the center-point to the level of the floor, so a compass could be used to draw the separation line accurately.


The bandsaw is the best tool for this job.


Here we have the center of the floor after removing some extraneous material. I've left just enough of the background for the steps and cut down a flange that was in the way (compare with Photo 4). I've also cut the piece that will be added to thicken the floor from .080" to .125". Since the remaining floor area, the part that was cut away earlier, is completely flat, sheet styrene .125" thick will be supplied in the kit to complete the part.

I didn't quite finish reconfiguring this master today, so there will be more to come, continuing the coverage so you can see how the finished parts go together. Stay Tuned!

Scott