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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Val4 and booster prototype

Discussions about rockets, construction materials, adhesives, nozzles, nosecones and fin design.
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retrotec29
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Val4 and booster prototype

Post by retrotec29 » Thu Oct 19, 2017 11:51 am

After the success of Val3 I decided there was room for improvement. Val4 is 10g lighter and 40mm shorter than Val3. Volume has been increased to 1.5L. Several test flights on Val1 has also yielded a new nose cone design. With that much loss in length coupled with the new nose cone the drag coefficient should drop to the 0.05 to 0.06 range. Numbers look good to go 500+ feet. As I tinkered with the numbers and a couple sims in Open Rocket I realized if I could boost this version to 45-50 m/s something interesting would happen. I could almost double the altitude. So I began the work on a booster. The staging coupler is based on the Mark3 used by Air Command. I did tweak it a bit to shorten the length and shave a few grams. Everything on the booster is built for speed. Recovery deployment will all be internal. Shroud venting will have a blow away cover to keep the air frame smooth before staging. Capacity of the booster is 4L. Everything has been pressure tested to 120psi. Compete dry weight for booster and sustainer should be around 500g. Being the prototype I have already come up with some ideas to knock off another 10mm of length and 50g of weight off the final version. With the weather closing in testing may need to wait for spring but I will update as things progress.
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anachronist
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Re: Val4 and booster prototype

Post by anachronist » Sun Oct 29, 2017 2:38 am

Nice. Not enough for the class B record, but those rockets don't use soda bottles, which to me sort of takes the fun out of the challenge. I've advocated to WRA2 in the past to expand the competition rules to include more unreinforced bottle classes (see this thread). I hope to see something soon.



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retrotec29
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Re: Val4 and booster prototype

Post by retrotec29 » Wed Nov 01, 2017 7:04 pm

We’ll see on the class B record. There are still a lot of “if it works” in this project. If I can shave the weight by 50g. And if the prototype works 1100 feet is achievable. I may not have the weather to prove it until spring.


No matter where you go, there you are. Buckaroo Banzai

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retrotec29
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Re: Val4 and booster prototype

Post by retrotec29 » Wed Nov 01, 2017 7:04 pm

We’ll see on the class B record. There are still a lot of “if it works” in this project. If I can shave the weight by 50g. And if the prototype works 1100 feet is achievable. I may not have the weather to prove it until spring.


No matter where you go, there you are. Buckaroo Banzai

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retrotec29
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Re: Val4 and booster prototype

Post by retrotec29 » Sun Nov 26, 2017 11:07 am

The prototype booster is complete. Final dry weight of booster and sustainer is 530 grams. So the sub 500 gram target weight of the final version looks achievable. Numbers on the sustainers apogee look well over 900 feet without the addition of the staging event. The actual altitude of the staging has many variables so that part is a wait and see.
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Latest challenge is the launcher. My current launcher works very well but is just to small.
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So the plan will be to build a new launcher and double the size. No elevation adjustment but the center post will extend to the ground with a ball joint adjustable foot. That will give the tripod and additional point of contact and directly transfer the energy of the rocket to the ground. Plan B would be to use my small mid-high power launcher with an adapter mounted to the rail for the launch tube. Another tripod design this launcher also uses a direct contact point in the center.
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retrotec29
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Re: Val4 and booster prototype

Post by retrotec29 » Wed Jan 24, 2018 4:49 pm

The acquisition of supply’s for the new launcher have begun. Everything was on hold the last month as I moved into a new house. Hopefully the shop will be back up and running next week. Being a little curious of the actual scale I rough cut all the PVC last night.
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Center post will extend to the ground and end in a 3 1/2” adjustable ball foot. Legs will be slip fit for easy transport. For added stability they will be reinforced with chains and filled with sand. A three way valve will allow fill and purge with pressurized air separate. The launch tube will screw directly into the base to add stability. To reinforce the o ring sleeve I machined it from a solid pice of PVC. Wall thickness is over a 1/4”. Should be interesting at the very least.
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Re: Val4 and booster prototype

Post by retrotec29 » Sun Feb 18, 2018 9:37 am

The launcher is almost complete. I have a removable 1/4” rod holder still in the works. Legs are a slip fit for transport. But I would not call it easy to move around. All three legs are packed with sand for added stability. Launcher core and fittings were also pressure tested to 150 psi for half hour.
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Weather here has been dry but still cold. Soon as it warms up we will be ready for a test flight.
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retrotec29
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Re: Val4 and booster prototype

Post by retrotec29 » Sun Feb 18, 2018 9:49 am

D3B3C40A-D02B-4B53-A983-BCFC69F23B8D.jpeg
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Re: Val4 and booster prototype

Post by anachronist » Sun Feb 18, 2018 2:31 pm

Nice. What's that small tank under the stand for?



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Re: Val4 and booster prototype

Post by retrotec29 » Mon Feb 19, 2018 12:05 pm

Adding water to the booster with a filled sustainer became very problematic. So I decided to fill the booster on the pad. The sprayer tank allows me to push the water in through the launch tube. Once filled I can purge the remaining water in the tube back into the sprayer. A three way valve keeps the water out of the air line. When everything is set I turn the vale to air and I am ready to start pressurizing for launch. If I take my time and try not to fill the booster all at once the pressure build up while I am at the pad only reaches 15-20 psi.


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Re: Val4 and booster prototype

Post by retrotec29 » Tue Feb 27, 2018 12:08 pm

The new pad went through some testing last week. With loads similar to the Val4 and booster launch I was getting some movement on release. The culprit was the floating center anchor for the chains. So I replaced the ring with a fixed 3” pvc cap. Problem solved.
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Re: Val4 and booster prototype

Post by retrotec29 » Thu Mar 08, 2018 4:00 pm

Forgot to add a ready to travel photo.
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