Nozzle vs Nozzleless

[nater]

Making sodium salicylate from aspirin sounds like a chore. If it is what you have available, I recommend using Steve LaDuke's Hybrid motor method. Like Dag mentioned, start with a 50/50 blend of BP and Sali whistle. Make each fuel and blend like salt and pepper.

 

These rockets do not have impressive tails or sound, but tails can be improved by changing your delay fuel. They are impressive lifting rockets.

[innervision]

It's just a disclaimer because it's whistle propellant aka organic flash.

 

It's good for work... not sound.

 

Good to know. I would have guessed that merely 5% charcoal wouldn't affect the sound too much.

 

 

 

Making sodium salicylate from aspirin sounds like a chore. If it is what you have available, I recommend using Steve LaDuke's Hybrid motor method. Like Dag mentioned, start with a 50/50 blend of BP and Sali whistle. Make each fuel and blend like salt and pepper.

 

These rockets do not have impressive tails or sound, but tails can be improved by changing your delay fuel. They are impressive lifting rockets.

 

Should the spindle for this be similar to a BP spindle or somewhere between whistle/BP?

Also, I assume that even wide nozzles on these would be guaranteed CATO?

 

It takes a little time to make the salicylate, but It is a pretty simple 2 step process, and I like the chemistry behind it. Another benefit is that I make POTASSIUM salicylate. No sodium involved.

[ddewees]

5% of almost anything will affect the sound...

 

I remember adding fine titanium once to standard 76/23/1 whistle, and the sound all but went away! I think it was closer to 10%, but you get the idea.

 

I would recommend making as many varieties of whistle as you can... and you yourself will eventually decided on a favorite or favorites. I personally didn't like the Dan Thames whistle, but not because of the sound... i found that it was brittle and didn't store well.

 

This is still my favorite of all time, for both sound and performance... tough to beat. Twenty six second flight is nothing to shake a stick at either...

 

[Video]

[DavidF]

Innervision, I have experimented with KHP whistle, the formula from Rembert Amons. When I made it as directed, it would not maintain combustion. The burn was choppy and it seemed to 'blow itself out'. This happened with and without a core. I tried various things to correct this, all successful. All that is needed is something to 'hold the fire'. I used powdered charcoal, and also powdered perlite. When I used 1% copper oxychloride, I got the most powerful whistle I had seen. But, I had not used copper oxychloride before with whistle of any kind. With the KHP whistle, I got 40 pounds of peak thrust and a burn time of .15 sec. With no core it has a very shrill whistle.

 

I have made my own sodium salicylate before. With my caveman pots and pans method, I found that it was darned near impossible to dry it! It worked well though.

[nater]

 

Good to know. I would have guessed that merely 5% charcoal wouldn't affect the sound too much.

 

 

 

 

Should the spindle for this be similar to a BP spindle or somewhere between whistle/BP?

Also, I assume that even wide nozzles on these would be guaranteed CATO?

 

It takes a little time to make the salicylate, but It is a pretty simple 2 step process, and I like the chemistry behind it. Another benefit is that I make POTASSIUM salicylate. No sodium involved.

 

Potassium salicylate might pique my interest, when I can start building again I might have to give it a try. I have made aspirin before, but never the reverse. I don't care for the sodium yellow flame. I have enough potassium benzoate to last me a long time, so I have been using that almost exclusively.

 

The spindle for a hybrid rocket is the Hybrid-Universal spindle as designed by Steve LaDuke, he also recommends using a nozzle. Firesmith's Universal spindle is a similar concept with different dimensions. They are closer to a BP spindle than a Whistle. They are a little shorter and fatter than a BP spindle. To be honest, just try a BP one if that is what you have. The beauty of the hybrid design is easily tweaking the fuel for your needs. When you mix up both fuels, don't mix it all right away. Try a 50/50 blend without a nozzle and see what happens. If you need more power, try 60/40 whistle / BP and so on. You could also just think of it as making a nozzleless BP motor and spiking the fuel with whistle to get the performance you want.

Edited May 29, 2016 by nater

[dagabu]

Aaron Hull at the IPA did a class on nozzleless hybrid #2ers this weekend. They sure do fly very well! I was holding rocket sticks no no video yet but I will look.

[AlteredMatter]

Is using PVC as a rocket casing really an issue when it is nozzleless? I know about the chance of injury due to a CATO, but I have a hard time believing it would explode if it is nozzleless.

[dagabu]

There is n o rule about using PVC in pyro BUT I don't know of a single club that allows it and the shards it can produce are just too dangerous to use for day to day rockets. Also, it gets really soft when warm, is a terrible casing and its plastic, it's plastic garbage and litters the land.

 

For model rocketry with the proper nozzles, it has found some favor and comes back to the user so no litter. Early on, I too used PVC until I got a piece of shrapnel from a Cato in my arm. Paper is my go-to now and you can always roll your own.

[Mumbles]

I still wouldn't. Not worth the risk. Faults in manufacturing, grain cracks, etc. can still cause issues.

[dangerousamateur]

 

I have a hard time believing it would explode if it is nozzleless.

 

I had a 1lb BP rocket cato on me, it was nozzleless and made with very good willow blackpowder, ballmilled very long.

 

The bang was shocking loud!

 

 

 

Is using PVC as a rocket casing really an issue

Apart from the residue in the countryside it is not.

The parts wont fly farther than the stars of a shell. You dont want to be around so near anyway.

Keep your distance, collect your garbage afterwards and have some fun. Thats my opinion.

Edited July 13, 2016 by dangerousamateur

[Redrocketman]

I know there is a great shadow of doubt in relation to using PVC as motor casings. I can advise you web search Jacobs Rocketry experimental rocketry site. It focuses completely on the correct construction of PVC motors from 1/2 & 3/4" up to 1.5" motors including both case bonding single full length grains through to bates grain configuration, nozzle design and retention. Covers all maximum case pressures, quoting all the maximum pressures the different sizes can take, and the safe pressures that shold be aimed for. I must emphasise that as Dave said, they will not be accepted at clubs, simple as that. But experimental rocketry takes a slightly different approach. Look up that site and spend the time to read it properly before attempting any of the projects. It honestly is a gospel. One thing I must state that if constructed correctly, the nozzle or end cap will fail before a case rupture. Using inhibited bates grains ensures a ' neutral ' burn rate, not progressive rise in pressure. there simply is not the burn time for heat to transfer to the case to weaken it. In 9 static J class tests, I've only ever had a nozzle fail ( at the point it was pushing 21 + kg thrust! ) the site has all the proven max safe pressures for each size pvc, so with a bit of sitting down on huopen rocket ( others there is heaps )program you can determine roughly the pressures that will be experienced and load your motor accordingly. Hope this helps, please don't hesitate to ask if you need anymore help, good luck, Luke

Ps, dags was right though, distance is you best safety net, cause to be honest I would not like to be near one if it did let go!!!

[AlteredMatter]

Well the reason I ask about PVC, is because I've been rolling my own tubes out of paper(which I agree is much safer) but they still seem to explode. I don't know if the fuel is burning with too much pressure or the quality of my tubing is not up to par. I rolled them with about 1/8 of an inch thickness using wooden dowels. I didn't have this problem when I was using 3/8" diameter tubing, but when I sized up - I started getting Booms rather than woosh and going up into the sky. Perhaps my black powder is burning a little too fast, but which I know is necessary with nozzleless rockets.

[dagabu]

Lots of reasons why they may be Catoing. One is that the pressure per square inch may rising beyond its abilities to hold the thrust. Another may be small air pockets in the tube. Not enough pressure consolidating the fuel or even fissures or cracks in the grain.

 

Not all things can be sized up directly and black powder is certainly one of those things. I can use hit fuel up to 3/4" but my 1" rockets have to use a cooler fuel.

[OldMarine]

I use hot 75/15/10 in my 1 and 3lb rockets and have not had a cato since I started waxing my tubes. I did have some nozzle failures but switching to nozzleless rockets solved that with no perceptible loss of oomph. I still don't understand why nozzleless rockets perform so well.

[AlteredMatter]

I know this may sound like an easy question, but how exactly do you wax tubes? Do you just simply put paraffin wax on a q-tip and apply it to the inner tube?

[OldMarine]

I have a small crock pot and a dauber that i use to coat all but the nozzle area of the tube. I had to change the thermostat on the pot to get the wax almost to the smoking point to keep the wax from building up too much and making insertion of a rammer a PITA. Dave Forster has an excellent tutorial on FW and I think there's a thread here as well.

The tube waxing virtually eliminates tube shrinkage/shortening during pressing which I think helps to stop the little fire paths along the tube surface that cause catos

http://www.amateurpyro.com/forums/topic/9372-wax-coating-rocket-tubes/page-2?hl=+dave%20+forster

Edited July 14, 2016 by OldMarine

[Seymour]

 

 

One thing I must state that if constructed correctly, the nozzle or end cap will fail before a case rupture.

 

NO!

 

This is a huge claim. In some cases it is be true, but please let me assure you that there are many motors that go bang so much more powerfully than this.

 

This does not mean that they are built badly, it's simply that this rule of yours has exceptions. Lots of exceptions. So many that I don't think it is worth considering a rule.

 

For example, find me an effective nozzleless rocket that goes bang in the way you describe when they fail. It doesn't have to be whistle. As has already been mentioned, BP ones go bang more powerfully than may be expected.

 

Indeed, I often joke that if you try and make a BP salute it won't ever be as good as a hot BP motor cato-ing.

 

I've heard another rule. This rule says that if your nozzle or end cap are shot out it means that they were not pressed hard enough. Of course there are exceptions to this rule too, but my point is that when you are thinking about the possibility of fragments of motor casing becoming dangerous, deciding that they should never be created because motors should pop the ends out without having the casing fragment is not a safe assumption, or an accurate one.

Edited July 19, 2016 by Seymour

[dagabu]

...One thing I must state that if constructed correctly, the nozzle or end cap will fail before a case rupture. Using inhibited bates grains ensures a ' neutral ' burn rate, not progressive rise in pressure...

 

Just got off the phone with an old friend Ted that I used to do HP rocketry with and this thread popped up, I asked him about the PVC caps and nozzle being ejected and his response was, "The adhesive (glue) and the distance the caps are made to cover ensures that the tubing will fail before a properly glued joint will fail. So it is with the case of threaded inserts, plugs and depending on the construction type, nozzles as well."

 

This is backed up by the technical white papers each of the manufacturer provide for tubing specifications, so Ted says. He is a licensed hydraulic engineer for the sate and does approves the drawings for the waste treatment for Minneapolis.

 

Grain of salt...

[OldMarine]

I don't know squat about pvc rockets but as a Master Plumber, Pipefitter and Steamfitter, I'll tell you that a properly cemented (fused) pvc fitting is almost 3 times as strong as a longitudinal pipe section. Any air test explosions we've had were not in the fittings but in the center area of longer runs of pipe. It may be de rigueur for model rocketry but I'll not be convinced it's safe. I've never seen a ball mill explode but common sense tells me it can so I practice safe milling. Same with pvc, I've not had a rocket shotgun me with shards but I know it's completely possible. I think I'd rather use thinwall aluminum tubing because of all I've read..

Edited July 19, 2016 by OldMarine

[dagabu]

I keep a quarter in the freezer for plumbers that dont know how to tuck in their t-shirts!

[OldMarine]

I wear Duluth Trading No-Crack Tee Shirts so no worries mate! After the first few years of fiberglass insulation down the crack I learned to protect myself and consequently others from the crack epidemic.

[dagabu]

Just say NO to crack!

 

I got a plumber with the frozen quarter where I worked, LOTS of teenage girls and they would FREAK out if they saw the Chunnel on a plumber. He never wore a belly shirt again...

[OldMarine]

We had a Bosnian Furbeast working for us a few years ago who insisted upon duffing his shirt whenever in a ditch. I went the opposite route you chose and flipped a torch heated penny down his crack. He followed company and OSHA rules thereafter!

[chuckufarley]

a Bosnian Furbeast

I think there may be a reward for documenting the exitence of one of those. 😀

[OldMarine]

I think there may be a reward for documenting the exitence of one of those.

We had twin brothers so they're either very rare or more likely killed at birth. Most stubborn bastards I ever met.