Scioly.org

jason60069 wrote:Is there anything that we should be adding other than fins and a nose cone?

More bottles could be added to help build a good backslider (see rest of forum and wiki for more details).

jason60069 wrote:Also, what kind of times are you getting on your rockets?

I have not tested a rocket because of this MI weather.

I'm not trying to rub it in, but I've been getting times around 17 to 18 seconds (thanks to the sunny San Diego weather) except when my rocket hits a tree, but the national time is around 25 to 30 seconds

What bottles are you using?

What is the best suggestion for a rocket design? I just want to now?

hello, I'm wondering if I could make a nose cone that goes out farther than the bottle thus acting like a parachute on the way down, would that work , I also wanted to say that I tested water amounts and found more like 3/8 to be the best

scientist wrote:hello, I'm wondering if I could make a nose cone that goes out farther than the bottle thus acting like a parachute on the way down would that work

I would not advise it. It would create drag on the way up thus not going as high. It would require the it to be unstable thus not going as high. The center of gravity would be behind the center of pressure other wise it would tip and not go down with the "parachute" up. This is a lose lose situation. I would highly recomend a backslider. I hope this anayisis helped.

scientist wrote:I also wanted to say that I tested water amounts and found more like 3/8 to be the best

The best amount of water is about 1/3 depending on the rocket. 3/8 = 0.375 2/3 = 0.333 This is not much of a difference. Your rocket may require a little more water.
EDIT: Sorry I meant 1/3. It is fixed now.

2/3 sounds high. When it was 1 L bottles a few years ago, the optimal amount of water seemed to be about 1/3. I suppose with 2 L bottles, it could be different, but I still expect the optimal amount to be in the vicinity of 1/3. 3/8 is close to 1/3 (about 11% difference), but not very close to 2/3 (78% difference).

But as with anything, your mileage may vary. You will want to conduct your own tests and use the data you've found to optimize the design.

I'm still confused on how to build a backslider rocket, even after clicking the links on the bottom of the Bottle Rocket wiki. Any help?

scifipi wrote:I'm still confused on how to build a backslider rocket, even after clicking the links on the bottom of the Bottle Rocket wiki. Any help?

Adjust the center of gravity to be the same as the center of presure.
You can do this by:
Making rockets longer
adding weight to nosecone
making fins larger
I prefer the first as it gives you the best times.

Does anyone have an opinion on forward fins? They might be a good idea to bring the CLA forward.