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Greetings Fellow Water Rocketeers. This is a method I developed in keeping up with the good performance and technology of the Bigfoot Water Rocket Launcher. 
In this update, I will mostly cover the recent discoveries in attaching the styrofoam fins to the plastic rocket body. This new method is faster, cheaper, stronger, and oderless. Basically, with a new type of glue chemistry we will be able to make PLASTIC RIVETS that will effectively fasten the fins to the body.
PL Premium Construction Adhesive has opened up some new opportunities and strategies for solving adhesive problems. This new glue is made of polyurethane. It sets up by absorbing moisture in the air, so it doesn't release smelly solvents like other common adhesives. When fully cured, it is semi-ridged, which is important because the walls of the rocket expand during pressurization. Hot melt glues are too stiff, and break loose.
Generally, you'll find it in your local hardware store, next to the famous (and not to be used in this application) "Liquid Nails" in the paint department. Currently, a local "Home Depot" Hardware Store charges $2.47. PL Premium is made by ChemRex Inc., in Shakopee, MN. Their technical service # is (800) 243-6739, in case you want further information and availability in your area. I called this number and found their representative very helpful and genuinely interested in our unique use of their product.
PL Premium can also be used to join plastic body parts (and nose cose) together. Previous rocket construction literature suggest the use of clear "GOOP Household Adhesive", which is still a good selection. However, GOOP can not be used for attaching the fins because it desolves styrofoam. PL Premium sets up faster, and half the price of GOOP.
For good adhesion, the golden rule to remember (for all adhesives) is that surfaces should be CLEAN, free of grease and dirt, and surfaces should be SANDED, especially something smooth like plastic. I've had good luck with 240 grit sandpaper.
Another extra method of achieving extra hold is to prime the (sanded) surface with a very thin film of PL Premium, and let is dry for about 1/2 hour. The film will become very tacky, and become a great foundation for joining.
Of course, take precautions not to breath vapors, or smoke (if your awl is too hot), and work in a ventalated area.
Use a 1/4" awl, or 16 penny nail, to melt a passage from OUTSIDE of fin to INSIDE edge. Use a medium heat for best results. If heat is excessive, the hole will melt larger than diameter of awl, and the process is uncontrolable. If awl is too cool, it will stick. Minimal practice and skill can get good results.
Reheat awl,or nail, as required. I use a propane torch with trigger (instant on), but even a candle would work. It doesn't take much heat to reach the correct temperature for the awl to (melt) drill the holes.
Awl is removed, leaving TAPERED hole.
On a standard sized fin, burn three holes on each side of the fin, making six total holes. Burn the holes at about 45 degree angle. Holes should be evenly spaced apart.
Looking at edge with 6 holes burned through stryofoam fin. This is the edge that will touch and join the surface of the rocket body.
