Egg-O-Naut C

[scienceolympiadist]

Wouldn't it be fair to say that if you add the same proportion of water, the 2L rockets will have twice the force?

[rocketman1555]

No, F=ma, so force depends on the mass of the rocket too. You can get the same height out of a 6L rocket as you can out of a 2L rocket. Yes, 1L rockets usually don't go as high as a 2L, but if you build one right it can go as high, as long as you are not building it to a set of rules.

And the other advantages of 2L is that they are cheaper to buy and you have more space for the egg capsule.

[scienceolympiadist]

hmm, that makes sense. only that the 2L isn't twice as heavy as 1L. think of the surface area of the bottles

true there are more space for the egg capsule. but from last year, I didn't feel the egg capsule was a real concern

[rocketman1555]

A 2L alone isn't twice as heavy, but the fins are usually larger, making them heavier, and so are cones and such.

And the extra space is really just more room for a parachute, it allows you to make the egg capsule a little bigger to accommodate different designs.

[jazzy009]

Anybody have any advice on string to use for the parachute? I tried fishing wire but I'm not a fan. Thread maybe?

[rocketman1555]

I normally use 100% polyester sewing thread, but Nylon also works. I've also used Bamboo Crochet Thread which works, but is a little heavy.

[andrewwski]

I used thread, it worked fine. Beware that it's not terribly strong though, you could rip a few shrouds getting caught in a tree, or in my case, holding the capsule while the wind gusts into the parachute. Worked fine for what I needed it for though.

Fishing line is a pain as it is too stiff.

[calgoddard]

A 2 L bottle rocket theoretically can store twice the energy of a 1 L bottle rocket.

However, the 2L bottle rocket will not go twice as high as the 1 L bottle rocket at the same launch pressure, for a variety of reasons.

The main reason is that the 2 L bottle rocket has a much larger cross-sectional area than a 1 L bottle rocket. Therefore the drag of a 2 L bottle rocket at very high launch velocity is substantially higher than the drag of the 1 L bottle rocket. Bottle rockets probabably launch at over 80 mph.

Back when we did 2 L backsliders, they did not go much higher than a 1 L backslider of the same design, each being launched at 60 PSI. My recollection is that the 2 L backsliders went about 20% higher.

Does anyone know if the 2010 Egg-O-Naut rules specify 2 L bottles? Did anyone get the tentative rules from the Summer Institutue?

[Celeste]

Anybody have any advice on string to use for the parachute? I tried fishing wire but I'm not a fan. Thread maybe?

I've been using fly line backing. It's used in fly fishing, but it's a lot more like thread than regular fishing line. I've used it for my chutes most of the year, because I had regular thread break on a test flight early on. The fly line backing doesn't seem to tangle too easily and it's never broken on any of my rockets. It's also neon colored, so that makes me happy! Google "Cortland Micron Fly Line Backing". You'll probably be able to find it, or something like it, at an outdoorsy store like Cabela's, Canfield's or Scheel's.

Also, no matter what kind of string you use, you should put a dab of clear nail polish on any knots you tie. It'll keep them from coming undone.

[starpug]

I normally use 100% polyester sewing thread, but Nylon also works. I've also used Bamboo Crochet Thread which works, but is a little heavy.

Make sure to use the correct knot for tying, a normal square knot might not be sufficent