In the realm of the astromech building world, the most popular choices for skin material are styrene, which cost the least, and aluminum, again, the more expensive option that seems to rise proportionally with the price of gas. Both have their pros and cons, but we'll save that for another discussion. Since I was on a budget, I chose the former and to keep the spirit of "building" alive, I decided to hand cut them from scratch.
The skins can be generally divided into four parts: front-inner, front-outer, rear-inner and rear-outer. The four parts are categorized further into two different layers, hence "outer" and "inner" (total of 2). According to the club specs, the accepted thickness of each layer of skin is 0.04". Just to get an idea how inexpensive styrene plastic was, I spent no more than $25 for two sheets of 0.04" x 48" x 96" at my local plastics supplier.
Regarding the order of the build, I chose to construct the skins first because I wanted to use them as a guide when I later made the wood frame. More specifically, the completed skins showed me exactly where to place the "uprights" and how far to space the "rings" (I'll cover this later on).
Materials & Tools:
2 -sheets of 0.04"x 48" x96" Polystyrene
1 -11oz can Duro All-Purpose Spray Adhesive
-Adobe Reader 9
-Computer & Printer
1 -ream of white printer paper
1 -heavy duty box cutting knife with extra blades
1 -Xacto Knife with extra blades
1 -4 foot metal ruler
1 -1 foot metal ruler
1 -Klean Strip Low Odor Paint Thinner
1 -Transparent Scotch tape
1 -utility light with low wattage bulb
1 -15" x 40" clear plexy glass
1 -assortment books of even thickness
1 -roll of paper towels
1- pack of 600 grit sandpaper
Dave Everett, founder of the R2 Builders Club, created full-scale cutting templates for styrene skins and has kindly made them available to the group. Rather than going to a Kinko's or other large office supply store and spend a fortune have it printed "professionally," I decided to stay home and save some major bucks by using my own printer. Using Adobe Reader and its Snapshot Tool feature, I was able to span the templates onto several 8.5" x11" sheets of paper.
I created a makeshift lighted view box by using books to prop up a scrap of plexi glass with a utility light placed underneath it. This little gizmo allowed me to accurately join and tape all the printed sections into one complete full scale template. During this process, I double and tripple checked that the templates were accurate by measuring several sections and comparing them against the club blueprints.
After the templates were created, I lightly misted the backs of them with an all-purpose spray adhesive (repositional type of bond used for scrap booking) and being extremely careful not to create air bubbles, I attached them to the blank sheets of 0.04" styrene using my hands to smooth them out. A heavy duty box cutting knife was used to make the long straight cuts and an Xacto knife was used for the smaller curved sections :
...and here's a completed portion of the front outer skins cut:
After all the parts were cut, the paper was peeled away and the excess residue from the adhesive was cleaned up with a non-toxic, low-odor paint thinner. The cut pieces were washed with water to remove any remaining paint thinner on the styrene. 600 grit sand paper was used to smooth any sharp edges and burrs created by the cutting blade. Although this hand cramping experience was long and tedious, the end result was self-rewarding and well worth the effort. ...and because I was so excited and impatient, as I already wanted to see the light at the end of the tunnel, I had to stand it up to make a more tangible example. Wow! I see you Artoo!
