Wanting to get into hybrids....

[ephantom1]

Hello all, long time reader, first time poster here.

I've been flying HPR now for about a year and have been loving every minute of it. I've gotten my Tripoli L2, but instead of going on to L3, I'd like to get started with hybrids(54mm). No one at my local club flies hybrids currently(although there is one guy who is working towards it) so I'd like to give it a shot. I know, I know.....I shouldn't do hybrids to save money, and there are AP reloads that have higher impulse at less weight, but I still want to do hybrids because I just think they're awesome!(and because I can only dream about doing liquids....)

I've read most of the threads here about hybrids, and based on the posters' suggestions I'm leaning towards Contrail Rockets. I have a few questions before I start planning/designing though:

1. Does anyone know if the Contrail GSE is a good system? I couldn't find anybody discussing it in a thread here.

2. Where can one acquire a tank of Nitrous Oxide? (Auto shop? I really have no idea on this one....)

Also, if anyone has any advice or concerns in using hybrid motors, I'd love to hear it.

Thanks,
Elijah

 

[jderimig]

For tanks are you asking where you can get a tank or where you can get a refill?

For a tank go to CatalinaCylinders.com and buy direct. If you're flying 54mm hybrids I would recommend at least a 20# tank. You want to specify a CGA326 (or CGA660) value with a dip tube.

For refills, auto performance shops are the most common and most expensive. You may find a specialty gas supplier in your area that will do refills but that is less common. Sometimes you will can get lucky and find a medical N20 supplier to fill your tank.

If you want a turnkey system and recommendation I would recommend contacting Doug Pratt at Pratthobbies.com.

 

[sumo310b]

Hybrids are great, they take a little bit more effort to set up than an AP motor but I like the fussing required.

Im in Australia so can't comment on nitrous supply, nor have I seen the Contrail GSE used. Ron from Black Dog Rocketry has been more than helpful to me with hybrid motors, he's worth contacting for GSE and motor supplies. https://blackdogrocketry.com/ . I started off using the Pratt Hobbies GSE and it does the job but I moved to the BDR GSE to fly Hypertek motors.

I've flown smaller Rattworks and Contrail motors and found the Rattworks was generally better made. I love the Rattworks K350 tribrid, its my favourite motor. The RATT motors are an odd size (64mm) but Aeropack make adapters for them to fit 75mm tubes.

Make sure you follow the manufacturers advice regarding fill pressure, you may need ice / thermal blankets around your fill tank depending on your location. Treat filled motors with respect, remembering they operate at 650-900psi. Keep an eye on your vent tubes and expect a white vent plume when the tank is full, I've seen someone fire their Contrail K motor after 10 seconds when the unsecured vent tube started flailing around because of its long length as the motor filled.

Make sure you have the line right fittings and spares before you get to the field. Weigh your tank before use and after each flight so you can monitor how much nitrous you're using (and wasting), and if you get a tank with a dip tube you won't be able to use the last pound or 2 of the bottle.

You should be comfortable with altimeter deployment also. Oh yeah, keep your vent tube away from your electronics or else you might find you get deployment on the pad Just take my word on that one.

 

[boomtube]

Hybrids??
You want to get into Hybrids??
Did you learn nothing from watching “The X-Files” or “Stargate: Atlantis”?
It never goes well for the creator when you are dealing with Hybrids.

PML lists a couple of their rocket kits as “Hybrid Ready” I ‘m not sure what they mean by that as I have enough trouble just getting my Cert 2 AP rockets to fly.
Listening to hybrids fly is almost as enjoyable as watching them fly.

 

[ephantom1]

I looked into the Rattworks motors, and their 64mm motors seem pretty cool. What is the state of Rattworks though? I've read that Contrail is still going strong but I'm not sure about Rattworks. The Black Dog Rocketry website says that Rattworks components are in low supply.....I don't want to buy all the hardware then not have any reloads available to fly.

 

[brianc]

++1 on the Pratt recommendation! Since you're planning on 54mm, get the BFV- it'll be worth it.

Contrail used (or used to) a resistor and pyrodex pellet ignition system that required 24Volts. But
that is easy enough to swap to an e-match/ignitor and use standard 12V.

Welcome to the dark side!

 

[legranddudu]

Agree with Brian, ++1 on the Pratt GSE. It is modular, well built and Doug Pratt's service is just outstanding, even for us international customers.

The contrail reloads now comes with 12V ignitors (black). At least the ones I get from them. Love my contrails, they just always work and resist to everything I do wrong, even crashes *lol*

Denis

 

[cwbullet]

I looked at the Pratt Hybrid box a while back but it seems to be out of supply for quite a few months. Hypertek control systems are no longer produced.

 

[ephantom1]

So it appears that the only currently available options for GSE are Black Dog and Contrail although I couldn't the price for the Black Dog GSE on their price list, I only saw the price for the solenoid assemblies. Do they not offer it anymore?

Elijah

 

[legranddudu]

Chuck,

to my knowledge Doug only produces on orders. May take a while you are right but he is one of these suppliers we can be proud to have in the rocketry. I uses his box in the full specs version for large hybrids. Only critic was the hose I changed for a big fat panzer-style german one The rest is out of the box since 3 years with zero problems and..many hybridz starts so far...

denis

 

[legranddudu]

Elijah, I would really doubt the Sanders @ contrail are having GSE's on stocks. My last discussion on the topic with Thomas was a negative feedback but hey, I maybe wrong. Give them and Doug Pratt a call. So easy. Great guys to work with..and they are alive and continue to produce.
D.

 

[MCS]

Ebay is a source for Nitrous tanks. Search for "Nitrous bottle." I would buy cheapest new bottle at 10 pounds capacity or more. Used bottles aren't worth the hassle.

Realistically, a 20lb bottle (45 lbs weight when full) is the largest bottle you want to carry around at a launch site. If you get a 35 lb or K cylinder you will need a cart, if this matters.

I own a 20lb bottle from Cold Fusion:
https://coldfusionnitrous.com/nitrous-systems/category/83-high-flow-nitrous-bottles.aspx

Pay attention to the fittings.

Nitrous bottles are offered with two fittings: CGA-326 and CGA-660. Opinions differ, but I recommend buying a bottle with CGA-660, which is the automotive standard. The auto guys can only fill CGA-660 fitted tanks. Adapters can be cobbled together, so it's not a deal killer either way.

Availability of Nitrous varies in different cities. Around here, the industrial suppliers only deal with corporate entities. Hot Rod Nitrous is the only option.. which sorta defines my GSE. I don't know if the auto guys can fill a bottle larger than 20lb.

I would use Doug Pratt's Nitrous manifold as a template for the necessary fittings. If you buy his system, I think Doug will customize it to the rest of your setup. DIY is pretty simple too.

Quick and dirty pic below

From the manifold to the rocket a hose 10-20 feet in length is needed. I use cheap Nylon tube from McMaster with Prestolok fittings. No need to buy high dollar braided stainless.

On the electronics side you will need a system capable of delivering current through three separate wires: fill, purge, and ignitor. I simply use 3 ignitor leads from whomever is sponsoring the launch. I don't use a hybrid specific control box.

-->MCS

(real rockets have tanks)

.




EDIT: comment, if you DIY a system, I would look into using all AN fittings. AN fittings are a pleasure compared to crappy pipe threads.

 

[MCS]

Any idea what a Catalina tank costs?? Sizes??

-->MCS

.

 

[bobkrech]

https://www.catalinacylinders.com/products.html is the listing for Catalina Cylinders. You want a DOT 3-AL tank which is rated for 1800 psi.

Any tank rated for CO2 is rated for N2O. Both gases have the same molecular weight and have virtually the same vapor pressure curves. CO2 tanks are rated by fill weight and a 20 pound CO2 tank is rated to hold 20 pounds of N2O. Pick out the size you want and google the part number.

As was stated earlier you will need a CGA 660 cylinder valve with rupture disk to make the tank legal to fill. B20. B22, B35 and B50 are 8" diameter tanks that ill hold 20, 22, 35 and 50 pounds of Nitrous. (Don't forget the full tank weighs approximately 2 x the tank rating so tanks larger than B22 weigh more than 50 pounds.) Hybrids require liquid nitrous so you need to order a tank with a dip tube so that you do not have to invert the tank to deliver liquid nitrous.

Tanks are date stamped and have a limited lifespan until they have to be hydrotested so don't by a tank more than 2 years old.

Nitrous oxide is an oxidizer and any grease or oil in contact with high pressure nitrous can burn or detonate. New tanks and components are cleaned and sealed at the factory. Never use any oil or combustible sealants on the tank or valve threads. Only use Teflon tape on the pipe threads.

Bob

 

[G_T]

Bob,

My ignorance here, but Teflon is combustible in N2O. Is it safe for that application?

Gerald

 

[bobkrech]

Bob,

My ignorance here, but Teflon is combustible in N2O. Is it safe for that application?

Gerald

CGA 660 fittings for Nitrous use a PTFE gasket...... and PTFE tape is use on the pipe threads of the cylinder valves..... so PTFE is not reactive with nitrous under storage conditions.

As a personal point of reference, in graduate school I coated quartz flow tubes with fused PTFE to prevent surface recombination of atomic oxygen for my thesis work where I measured the kinetics of O + F2 --> OF + F reaction because PTFE doesn't react with O-atoms which is what you get when nitrous decomposes....

Bob

 

[Zeroignite]

CGA 660 fittings for Nitrous use a PTFE gasket...... and PTFE tape is use on the pipe threads of the cylinder valves..... so PTFE is not reactive with nitrous under storage conditions.

As a personal point of reference, in graduate school I coated quartz flow tubes with fused PTFE to prevent surface recombination of atomic oxygen for my thesis work where I measured the kinetics of O + F2 --> OF + F reaction because PTFE doesn't react with O-atoms which is what you get when nitrous decomposes....

Bob

Diatomic Fluorine... now that's on the list of Chemicals I Don't Want Near Me.

 

[cwbullet]

What sort of launch control system do you use for hybrids?


Sent from my iPad using Rocketry Forum

 

[G_T]

Nitrous Oxide is a self-pressurizing liquid/gas in its cylinder. It is dangerous because (1) pressure (2) very cold when it vents (3) it doesn't take too much to light it and it is a monopropellant in its own right (4) under some conditions it is explosive (5) at elevated temperatures it is an oxidizer (2(N20) at elevated temp -> 2(N2) + O2 + heat). Because of these things, one wants to handle it remotely. So one needs the ability to open or close a valve to fill the flight tank. If the launch is aborted for any reason, one needs the ability to dump the flight tank. One needs ignition, which can be similar to solid propellant launches. Or, it can be more complex with the addition of gaseous oxygen to pre-light the fuel grain to bring it up to temperature before nitrous is released. That would then require control of another valve on another tank.

If one uses a DOT approved tank for the flight tank, then the tank can be pre-filled and transported. This obviates the need for a nitrous fill tank at the launcher. However some sort of valve - pyro or other - is needed to initiate flow of nitrous from the flight tank. Plus ignition/preheat is still required in some form. But it can reduce to as simple at the launcher as launching a solid propellant motor.

In essense, what you need depends on what you are trying to do.

Gerald

 

[freddiejojo]

I want to remind everyone of Jim Cooper at Star Rocketry. I don't know what the numbers are of sales, but he absolutely has to be right up there or the top as he does a tremendous amount of sales overseas besides here in the states. His sales would be far higher if only the manufactures would keep items "on the shelf". Jim also has GSE units of several types. Beyond providing and flying the Hypertek products, both Jim and myself own and fly the RATT Tribrid motor which is a hoot to shoot that nothing, either composite or hybrid, can match.

Kent/GLR
chief bottle washer