Thermal Formed Rockets - Using Hot Laundry Iron
I developed this method of thermoforming a soda bottle using a hot laundry iron.
This is the easiest, fastest, and safest methods of creating rounded bullet shaped noses from the bottoms of soda bottles.
This shaped nose has been called the "GUPPY NOSE". It was first introduced to us and named "GUPPY NOSE" by Clifford Heath. He uses a method of holding the bottle in hot boiling water to achieve this rounded nose.
SHRINKING the entire bottle is also possible, giving it thicker wall thickness and a less aerodynamic resistance.
If you are attempting to make rockets with parachutes and find that all your bottles are the same circumference, you could use this method to shrink your booster just a tiny amount, so you can have a slide off nose cone.
Look At The Difference In Size Between Before (Left) And After (Right).
Here's the changes:
- Capacity - 2 liter to 1.5 liter (25% shrinkage).
- Circmference - 13.625 to 11.875 inches (12.8% shrinkage).
- Wall thickness - .0123 to .0142 inches (13% INCREASE)
- Height - 3/8 to 1/2 inch shorter.
Don’t run off in a hurry now and get an iron and start ironing soda bottle. If you did, this is what you will have. A wrinkled up mess of a soda bottle.
The trick is to hold some pressure inside the bottle, using a tire valve stem.
Drill a 35/64 inch hole thru the center of soda bottle cap. Press valve thru hole. Use soap or any lube to help if it is difficult to install completely through cap hole.
Use a SAFE air pressure of about 10 - 15 psi pressure!!
I set the temperature setting on the laundry iron to HIGHEST SETTING. My iron is rated at 1200 watts.
Don't stay in the same area very long. Roll the iron on a section once or twice, and move somewhere else.
Note in the movie above that I use a rolling motion of the iron while in contact with the PETE plastic. This is to eliminate scratching of the outside surface of the bottle.
Stay away from the neck and flange. When near completion, you can iron out any wrinkles, and blend surfaces to match. You really have a lot of control of the outcome and how nice the finished product will look.
The rounded bullet shaped nose is achieved by simply pressing and rolling the iron against those five raised areas (feet). Again, don't work on the same area to long, rotate often, and move to the next foot. Eventually they will shrink like shown above.
Ready for some CREATIVE Thermoforming?
On this 2 liter bottle, a smaller WAIST in the middle & rounded the bottom.
Body is TAPERED & rounded bottom.
This one is slightly different in shape form the one above.
Here are two 20 ounce "SPRITE" soda bottles. I ironed the bottom to a more rounded profile in the left bottle in picture. The ironed bottle has a better profile for traveling through the air. Many times, I've used these smaller bottles for 2nd stage rocket deployment, because they are smaller & lighter.