Ping Pong Parachute B/C

[MichaelGier]

It’s possible I am a little dense, but I’m amazed this question/problem has not come up:

Depending on the tolerances of 1/2 PVC and the I.D. of random bottles, it seems to me that only a small percentage of competitors would show up to competition day with a bottle which will provide a useable airtight seal over the 1/2-inch PVC launcher tube. Is there some sealing mechanism or gasket or fudge factor that I am overlooking here?

I am building a launcher in my garage. I’m getting a completely failed seal on about half the bottles I’ve tried, and a more-or-less unacceptable seal on the rest.

[andrewwski]

A fairly common method to make a better seal is to heat the PVC over a candle at the point where the neck of the bottle will contact, and then as the pipe softens, push the two ends together to make a slight bulge in the pipe. This bulge helps seal as you push the bottle down against it.

[MichaelGier]

A fairly common method to make a better seal is to heat the PVC over a candle at the point where the neck of the bottle will contact, and then as the pipe softens, push the two ends together to make a slight bulge in the pipe. This bulge helps seal as you push the bottle down against it.

Good information, thanks. It just fascinates me that this event seems to completely depend on this seal being "just right" and all we have to make it so is the luck of the uncontrolled tolerance.

[Dreamz]

Would 3D printing a "shell" to contain the ping pong ball be legal if the strings from the parachute are still attached directly to the ball with tape?

[DatSciolyBoi]

So from my interpretation/understanding of the rules, we need to have a nose cone that will cover the ping pong ball, but it is ok for this nose cone to separate from the rocket so that the ping pong ball can detach?

[Airco2020]

So from my interpretation/understanding of the rules, we need to have a nose cone that will cover the ping pong ball, but it is ok for this nose cone to separate from the rocket so that the ping pong ball can detach?

I don't see that a nose cone is mandated at all, it just says the nose of the rocket must be blunt or rounded. I was thinking the ping pong ball can be the top of the rocket. Am I reading this wrong?

[knightmoves]

So from my interpretation/understanding of the rules, we need to have a nose cone that will cover the ping pong ball, but it is ok for this nose cone to separate from the rocket so that the ping pong ball can detach?

I don't see that a nose cone is mandated at all, it just says the nose of the rocket must be blunt or rounded. I was thinking the ping pong ball can be the top of the rocket. Am I reading this wrong?

The rocket must be rounded without the ping-pong ball present. It's a safety rule - nobody wants pointy missiles flying around, and when your rocket descends, it won't have the ping-pong ball. You can certainly mount the ping pong ball as the top of the rocket, but your rocket must meet the bottle cap test without the ball or parachute present.

I don't understand why DSB thinks there must be a nosecone covering the ping-pong ball - there isn't anything like that that I can find in the rules.

[Airco2020]

So from my interpretation/understanding of the rules, we need to have a nose cone that will cover the ping pong ball, but it is ok for this nose cone to separate from the rocket so that the ping pong ball can detach?

I don't see that a nose cone is mandated at all, it just says the nose of the rocket must be blunt or rounded. I was thinking the ping pong ball can be the top of the rocket. Am I reading this wrong?

The rocket must be rounded without the ping-pong ball present. It's a safety rule - nobody wants pointy missiles flying around, and when your rocket descends, it won't have the ping-pong ball. You can certainly mount the ping pong ball as the top of the rocket, but your rocket must meet the bottle cap test without the ball or parachute present.

I don't understand why DSB thinks there must be a nosecone covering the ping-pong ball - there isn't anything like that that I can find in the rules.

Still a little confused on this one. The ping pong ball as the top would pass the cap test. Any rocket with a nose cone or something covering the ping pong ball and parachute would have to come off to release the parachute, so the rocket coming down won't have the nose cone anymore and would be just the blunt end of the bottle. I don't see how you keep the rocket with rounded nose intact on descent if you have to release the parachute?

[knightmoves]

Any rocket with a nose cone or something covering the ping pong ball and parachute would have to come off to release the parachute, so the rocket coming down won't have the nose cone anymore and would be just the blunt end of the bottle. I don't see how you keep the rocket with rounded nose intact on descent if you have to release the parachute?

Would the blunt end of a 1L bottle not pass the cap test? I don't have one here, but I think it would.

[Airco2020]

Any rocket with a nose cone or something covering the ping pong ball and parachute would have to come off to release the parachute, so the rocket coming down won't have the nose cone anymore and would be just the blunt end of the bottle. I don't see how you keep the rocket with rounded nose intact on descent if you have to release the parachute?

Would the blunt end of a 1L bottle not pass the cap test? I don't have one here, but I think it would.

I think it would. I guess I misread what you said earlier, I thought you said the blunt top of the rocket had to come down intact.

I guess the question is, if we pass the cap test before and after, can we use the ping pong ball as the top of the rocket?