Some questions about thrust and my new rocket

Discussions about rockets, construction materials, adhesives, nozzles, nosecones and fin design.
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Some questions about thrust and my new rocket

Post by Water Rocket Expert »

Okay so I am getting into some "big" rockets, or at least big for me. 6 liters. 3 sections of 2, 1liter bottles coupled together by 1/2 inch PVC Pipe. Is the PVC a good coupleing method with glue or should I use something else? Also, is the standard 22mm nozzle going to produce enough thrust to get 2 liters of water into the air, the altimeter, the rocket, and the camera, and the parchute deploy mechanism and parachute? Will I need boosters? Do you think they will hold 100 psi, I used JB Weld Clear and sanded the contacting parts? I hope this rocket goes 550'-700'. The perpose of this rocket is to build one that has a lot of volume. All the other ones were pretty small or FTC which has hardly any capasity.
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Rocket Splices
Rocket Splices
RK000258.JPG (84.04 KiB) Viewed 92 times
Detachable Fins
Detachable Fins
RK000257.JPG (85.97 KiB) Viewed 92 times
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Re: Some questions about thrust and my new rocket

Post by arjan »

If you splice two 1 L bottles you're most likely going to end up with a volume of approximately 1.6 L per splice instead of 2 L per splice this is because of the overlap and because you cut the bottom from the bottles. So you're rocket's total volume will be around 4.8 L (3*1.6) instead of 6 L.

I've never seen a rocket with a 22mm nozzle being unstable due to the lack of thrust, so with a "full bore nozzle" (=22mm) you'll always be on the safe side I think.

Not sure what you exactly mean with the PVC coupling. Can you explain that?
Most people connect their splices with the so called "Tornado tubes".
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

Take 1/2 inch PVC and glue it into the neck of the bottles like the launch tube.
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Re: Some questions about thrust and my new rocket

Post by Blenderite »

That might work, WRE, but the problem is that if one of your spliced pairs develops a leak, you have to get rid of both, not just one. I would recommend the tornado tubes. They work well. However if you have a lathe or know someone with a lathe, you can see about making some Robinson couplings, or if you are really adventurous, your own custom tornado tubes. That will be harder cause you would have to match the thread that the bottles have, which is not a standard thread i believe.

Another thing you could try is to make your own Robinson couplings using the method shown here: http://www.uswaterrockets.com/construct ... torial.htm

That is a good method if you can find the glue that they use, since it is a special glue specifically for bonding PET plastics.

If you can come up with a method that allows you to have a PVC connector that can screws together, then by all means use it, and share it here!!!
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

DogLover wrote:That might work, WRE, but the problem is that if one of your spliced pairs develops a leak, you have to get rid of both, not just one. I would recommend the tornado tubes. They work well. However if you have a lathe or know someone with a lathe, you can see about making some Robinson couplings, or if you are really adventurous, your own custom tornado tubes. That will be harder cause you would have to match the thread that the bottles have, which is not a standard thread i believe.

Another thing you could try is to make your own Robinson couplings using the method shown here: http://www.uswaterrockets.com/construct ... torial.htm

That is a good method if you can find the glue that they use, since it is a special glue specifically for bonding PET plastics.

If you can come up with a method that allows you to have a PVC connector that can screws together, then by all means use it, and share it here!!!
Isn't that what the robinson coupling does?
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

Do my fins look good?
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

Are there any ways to slow down a "Water" Tomy timer? One that runs real fast. I think it should last about 4 to 5 seconds. Not 1 and 1/2 seconds.

Thanks. What about the fins?
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

Too late! I already glued those splices. Although my next rocket may use a different technic similar to the USWR's method. How long does a water rocket typicaly take to make like one of your guys. Also please answer the above questions because I find most people just answer the last question.
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Re: Some questions about thrust and my new rocket

Post by Blenderite »

The fins look good. As for the tomy timer, there is no way, that I am aware of. Back when I was experimenting with tomy timers, when I went to buy a toy to rip apart for it, I would only buy walking toys, as their timers are much slower.
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

What do you use now? Instead of a Tomy timer. Do you use the servocron method? I used JB Weld Steel Stick and Loctite to glue on the fins. I have spliced the rocket, coupled the splices, made the fins supported the rocket with rods and am now working on the parchute and I have finished the nose cone.
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Re: Some questions about thrust and my new rocket

Post by arjan »

Water Rocket Expert wrote:Do my fins look good?
What material are your fins made of? Looks like it's some kind of Styrofoam, if they are then I'm afraid they won't last long. If they are made out of coriflute then it's okay.
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

They are made out of some type of foam but it's pretty durable and when it bends it can easily be stratend. It's like poster board from Wal-Mart.
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

Okay I know some of you probably want better pictures. Well here you go!
Attachments
Rockets Stature
Rockets Stature
102_8285.JPG (664.67 KiB) Viewed 64 times
Nose Cone with Tommy Timer
Nose Cone with Tommy Timer
102_8281.JPG (664.33 KiB) Viewed 64 times
Fishing Swivel and Shroud Lins
Fishing Swivel and Shroud Lins
102_8280.JPG (622.67 KiB) Viewed 64 times
Parachute; I added a fishing swivel
Parachute; I added a fishing swivel
102_8279.JPG (535.96 KiB) Viewed 64 times
Single Fin Up Close
Single Fin Up Close
102_8278.JPG (460.53 KiB) Viewed 64 times
Better Image of Fins
Better Image of Fins
102_8277.JPG (673.52 KiB) Viewed 64 times
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Re: Some questions about thrust and my new rocket

Post by arjan »

My thomy timers come from those swimmer toys called "Zippy bather" (image search on google and you'll see what I mean). The timers I use are very reliable, never had a deploy failure because of a thomy timer. It takes ~6 seconds for 1 turn of the timer and it can be wound up quite a few turns so this is more then enough.
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Re: Some questions about thrust and my new rocket

Post by Water Rocket Expert »

where do you buy yours?
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