.::. Frequently Asked Questions

1. I'm 11 years old and plan to join the B division which is middle school division. It has a activity called Bottled Rocket and I really want to win that medal. Can you give me some tips on how to build a good rocket?

   The most important piece of water rockets is actually the launcher. You said that they would be providing the launcher for you? Is this correct? If that is the case, then your work is greatly simplified, but you've also lost an opportunity to gain an advantage through greater technology. :)

   I was poking around the site and I was looking for the rules. I couldn't find them outright but I did find an order form for them on http://www.soinc.org/store/tguides.htm

   If I remember correctly, from reading rules from other science fairs, they require a 2 liter bottle, with an attached parachute, where the launch pressure is 60lbs, launched at some pre-determined angle? Is this all correct?

   Perhaps I should just list out some questions that may help me help you:
   1. Do the rules dictate a 2 liter soda bottle like one would buy Pepsi or Coke in? Another advantage is that you could make your own 2 liter bottle from a florescent tube cover (FTC). The bottle would be longer and thinner than the typical 2 liter soda bottle which would turn into increased altitude. Much more difficult but the current world record holders design their rockets this way.
   2. Is there a required recovery mechanism? "Recovery mechanism" is a fancy word for parachute. Designing a parachute can be difficult. In some water rocket competitions, judging is based not only on altitude, but flight time. The right parachute can mean a huge flight time.
   3. When is the Science Olympiad? I think the site says May 17-20, 2006?
   4. How motivated are you? How much time do you think you will spend on this? Sometimes simple is better. Other times, technology really lets you make leaps in altitude and flight times.
   5. Is there a budget? I don't want to recommend buying items if we're going to blow the budget. One of the most expensive items I might suggest is a heat gun to melt some of the plastic. It can be had for about $30 from Home Depot or Lowes, though.
   
   

   That's all I can think of right now. I hope I haven't scared you away from this great hobby. I know I've asked a lot of questions but, after all, this is rocket science!

2. I have been hunting all over for a #94 o-ring. Home Depot doesn't carry it, Lowes doesn't ... specifically what are the ID and OD measurements on the o-ring supposed to be?

   I'm looking at one of my packages of #94 O-Rings. I don't remember if I bought it at Home Depot or at Lowes. On the package, it says:
   

   7/8 x 5/8 x 1/8
   #94 O-RING
   STK NO 35874B
   DANCO COMPANY CONCORDVILLE PA 19331

   From my own measurements with a caliper:
   

   OD: 22mm
   ID: 15mm
   Thickness: 4mm
   

   
   My suggestion is that once you find them, buy a lot of them. The rubber o-ring will dry out and ultimately crack (or fail) at some point.

3. I was looking into your clark cable tie launcer design and i was wondering exactly what the size for the pvc collar that goes over the cable ties. It wasn't specified and i was trying to figure out exactly what size i would need to ensure a strong hold of the cable ties. Any advice would help me out.

   I don't recall where I actually purchased the collar that I'm using. It should be commonly available at most any hardware store that carries commonly used PVC pipe. It says 1 1/4" and "SCH 40" on the end. The outside diameter is 2" (51mm) and the inside diameter is just over 1 5/8" (42mm). I use about 14 or 15 cable ties and the collar with just fit over them and hold them in place.