This blog covers the day to day progress of water rocket development by the Air Command Water Rockets team. It is also a facility for people to provide feedback and ask questions.

Saturday, February 07, 2009

FTC Nosecones

Since we are rebuilding the FTC payload, we've decided to replace the Kinder surprise egg nosecone with a more streamlined one. I machined up the nosecone mold out of a solid piece of plastic and polished it.

The nosecone mold prior to final polishing.

Attempt #1 - Heated the base of a small PET bottle and forced it over the nosecone mold and tried to heat shrink it over the top. Heat gun was too close and the base started crystalizing. The nosecone ended up flying quite nicely into the rubbish bin.

Attempt #2 - Heated the base of another small PET bottle more gently this time. This was only a slightly better result than the previous one. Before long he joined his friend in the bin. It just could not be shrunk down enough to the 30mm diameter.

Attempt #3 - Coated the mold with release agent and impregnated fiberglass matting with resin and then started wrapping it on the mold, but as you can imagine a nosecone isn't easy to round off with flat matting. Before long I had a nice mess on my hands with lots of bubbles, folds, and the rounded front was anything but. After another 5 minutes of trying to correct it, I finally pulled the whole mess off the mold and guess where it went?

Then I emptied the bin ready for more nosecones.

Attempt #4 - I went to the local supermarket and bought a couple of pairs of pantyhose (nylon stockings) and a shoe polishing brush. Okay I did get strange looks at the checkout counter as they were the only things I purchased. Little did they known those stockings will do over 200km/h one day. Instead of the release agent, I stretched the thumb section of a disposable rubber glove over the mold and tied it off. This made sure there were no creases anywhere. I then proceeded to stretch 8 layers of pantyhose over the top of that again tying it off at the bottom. I then simply poured the fiberglass resin all over it and worked it in with a brush and with my gloves. The nosecone is now drying so I will know in the morning if it worked. Otherwise it looks pretty good.

... Oh and the shoe polishing brush I bought earlier I had cut into about 20 strips each with 5 sets of bristles and use them as disposable brushes for the fiberglass. At 10c per strip they can be thrown away after each job.

I'll post results of attempt #4 when it dries and assuming I can get it off the mold.


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