Sirius Rocketry - For the Serious Rocketeer!

- Working With Moldin' Oldies Parts

While quite strong, these polyurethane castings are just a bit "softer" than standard polystyrene plastic parts. If sanding is necessary, they sand beautifully. They should be finished with enamel-based primers and paints. (Experience has found out that lacquers don't work as well and should probably be avoided.) Due to the possibility of a thin film of mold release, these parts should be washed with soap and water to remove this film, which may interfere otherwise with the bonding of paint. These parts are also resistant to solvents, so typical plastic cement or plastic welder will not work on them, as those types of glues are meant for polystyrene and not polyurethane plastics. Epoxy is ideal for bonding these parts. Use sandpaper to slightly rough up any surface to which you want epoxy to adhere to to give the surface a little “tooth” on which the epoxy can “bite”. CA glues (like our Bob Smith Products) also work well as adhesives on these parts.

These parts have all of the detail of the originals but they may not have all of the strength in the shock cord mount. On some pieces we have deliberately removed the shock cord mount for this very reason. You may want to consider alternate methods of attaching shock cords and parachutes, just to be safe. On some cones, you can drill a hole in the end and insert a screw eye, on others you can drill two holes and loop some Kevlar cord or other strong cord through, epoxy a loop of Kevlar to the end of the cone or epoxy a loop of kevlar to the inside of the cone. DO NOT rely on the molded shock cord mount, because although it may be a faithful reproduction, the resin shock cord mount may not hold like the originals. Also note that due to occasional part shrinkage, a wrap of masking tape around the nose cone shoulder may be required to correct a very loose fit..

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