Should I be thinking about Hybrid?

To give you even more food for thought, check out the yahoo group

hybridrocketmotors

A lot of those folks are doing stuff that is way over my head, but they are wellspring of advice and encouragement, and the archives are invaluable.

Kevin O

PS> If I were in your position (already L1), knowing what I know now, I'd probably start with the Contrail 38mm motor set. Motors from G100 to a 45% J800, reasonable hardware and reload cost, good performance. I used the

38mm set to certify L2.

Laura,

I've flown the Ratt I80 and the Ratt K240. Both nice motors. I also own(ed) and flew an AeroTech 54mm hybrid, but I sent the flight tank to Gary for repair about two weeks before the fire in Vegas. Bummer. Gary said he's going to get me a replacement, and that they're working on getting some reloads made, but there's a problem getting the little pyro pellet that they use for their pyro valve. All three of the motors I've flown use APCP grains that are < 62.5 grams, so no permits involved.

A word of warning... Don't use any of the accelerometer based electronics in a hybrid powered rocket. Use a baro altimeter. There's a problem with accelerometers detecting launch with hybrids. Has to do with the oscillation of the thrust. I'll be using a PerfectFlite MAWD with mine.

I don't have a clue what's up with Ratt Works. He does motors as a side thing to his machining business, so they may be busy with higher paying customers. But I'm pretty sure he's still in business down in Monterey.

The thing to keep in mind for the Ratt motors is "build light." They aren't the thrustiest motors around, but they are very kool, fun to use, and cheap to fly. Pretty sure Bob has them in stock at

Tell him I sent you. Bob's good people. He will know better than I about continued support for the Ratt motors. Ask him.

I have a bird in construction to use the I80 Ratt, and need to machine an adapter to fly the K240 in my Comp4 (the K240 is an odd size,

2.5" mmt required. Since the Comp4 has a 75mm mount, making an adapter will be a piece of cake.) That is coming. I have to concentrate on the M flight at Snow Ranch for the time being, but both hybrids will fly this season at the ranch. But I do need to get my Beeline GPS up and running before flying an M or any of the hybrids. I'm addicted to getting them back.

If you decide to go with the Hypertek motors, no problem. The AeroPAC trailer is at Richard's shop in Oakland, and I know he'll be more than happy to bring the GSE out to a launch for use, O2 and high tension included. So really, all you need is a motor and a bird in which to fly it.

Please let me know if I can be of any assistance in your travels through the world of rocketry. More than happy to help. Oh, and to answer your other question, the Ratt K240 would be a killer motor for an L2 cert. Build a bird, buy a reload, and I'll be happy to loan you the motor and the GSE. (Standard loaner agreement applies.) Build your bird with a 75mm mount and a Slimline retainer, and I'll throw in the adapter, too. That way, venting won't be a problem. My adapter will vent out the bottom. And be sure to make the booster section long enough (4 feet should do) for the motor. It's over 3 feet long.

James

Will,

Thanks for the link. Doug did a nice job with the video presentation. As he points out the key is using electrical tape to seal the end of the Pyrodex P canister. I've used 1/2 " PVC pipe and an end cap on one end. I cross the open end of the pipe with electrical tape making a cross on the open end. Then, I put layer around the perimeter of the open end to hold those two pieces more securely in place. For ignition I use a 1/2" to 3/4" long piece of 36 gauge NiCr wire. No coating on the wire, just plain. It is wrapped around the wire and inserted into the Pyrodex. I use a little wadding to hold the Pyrodex down in the base of the pipe by the end cap so the powder stays in contact with the NiCr wire. Works every time.

For homemade, motors with a delay and charge, I use Pyrodex P as well. Just seal the open end of the ejection charge opening the same way with electrical tape.

I don't know if it is necessary, but I also add an extra gram of Pyrodex P from what I would use if going with 4F black powder. I haven't used black powder in years and never had a problem in over a hundred flights.

John

Will Marchant wrote:

James,

I'd disagree with you on this one. I've used Gwiz LC & MC flight computers for every hybrid flight I've made (42 so far) and these are definitely accelerometer based units. They've worked perfectly every time. The specified launch detect is simply 2+G for 1/2 second. I like the Gwiz LC Basic (apogee only deployment) for smaller, low altitude birds, because no vent holes are required and you have a lot of freedom in mounting the device.

I understand there historically have been some problems with certain types of flight computers being affected by high frequency signals generated by the Hypertek ignition system's spark gap. That was, frankly, before my time, and obviously not pertinent to all hybrids.

Not a thing wrong with baro based computers-- the MAWD is an excellent device. Nothing wrong with accelerometer based units either.

Kevin OClassen

James, Thanks again for the generous help. I found a hybrid motor group:

asked the same question regarding the RATT website. the RATT website is being updated and a preview of the new site can be seen here. (I'm sure that link will only be valid for a short while.) I may take your advice on the K240 for L2 cert. I don't know if I'll pull it off for Snow Ranch, but in the mean time I'll look into the I class RATTs for the upcoming Snow Ranch launches. I'm not sure what the "standard loaner agreement" is, but I'm sure it's reasonable. Good luck on the M flight sounds exciting. Oh one more question. Are the grains for these hybrids unique or are they some what interchangeable? I'm only concerned with the availability of fuel in the future.

James L. Mar>Please let me know if I can be of any assistance in your travels

Kevin,

Glad to hear you're having success with the GWiz. I'm sure Rob and Larry would be happy to hear that also. Perhaps I'm a bit over cautious, but I crashed a bird with a K240 Ratt using an accelerometer. It wasn't a GWiz, but it didn't live long. It was an AcceloRocket accelerometer. Worked fine on the J415, but failed to detect on the K240. Talk about depressed. That was a nice rocket, right up until impact. 8^(

I'll be finding out how well the GWiz will work this winter. Going to mount the MAWD in the av bay of my Comp4 along side the (2) GWiz units that are already in there, and see what happens with the K240. (Plenty of room. I AM a big GWiz fan. Fly with Rob and Larry, the GWiz Partners. Currently beta testing the new LCX for them. Nice unit.)

James

Laura,

The "standard loaner agreement" is "you break or lose it, you bought it." Other than that, give it back clean, and no charge. 8^)

Yup, Ratt Works is still there. I don't think there will be a problem getting grains for any of their motors for the foreseeable future. You could always make grains for them, but that would invalidate the certification for the motor, and classify it as Ex. Hybrids will burn just about anything as a fuel grain.

And of course there's no rush to get to L2. Plenty to learn and lots of fun to be had flying L1, that's for sure.

Looking forward to seeing you at the ranch. Come on rain! Get that ranch green!

James

James,

Please allow me to correct myself - there *is* apparently a problem with some accelerometers and hybrid engines, having to do with sampling rates and motor 'frequency'. I asked about it over in the yahoo group hybridrockets and got an excellent explanation, complete with links to more information.

I love this learning curve, and one of these days I'll learn to ask the questions first.

Kevin O

PS> Thanks for mentioning the LCX. I hadn't visited the GWiz site in a while, and had not heard of this computer. I have been considering a second dual-deploy flight computer, and had almost settled on a RocketMotion Mission Control. The LCX, while not quite as full featured is at a very attractive price, and GWiz have been very reliable for me, with great product support. Now I have to try to decide.... :)

Any idea when this will hit the market?

Liz (may I call you, Liz?),

I don't know that you could possibly wear out your welcome here by asking the questions you are asking.

I, for one, am following your project with interest as I am also looking at hybrids. If you and the previous respondents don't mind, I would encourage you to continue on rmr.

But, if you are uncomfortable with how it is going here, please let us know how things are going as you proceed.

Best wishes and clear skies,

Kevin,

Not sure when it will hit the market, as we're still in the testing phase. Really, it shouldn't be too far off. But I can say that I like it, and so far, it has worked quite well. I like being able to program the low altitude event, and the timer function allowed me to use it as a back-up unit in my ARLISS M rocket.

James

No problem, Laura. Reach me directly at jmarino1 (at) sbcglobal (dot) net.

Contrail looks like it has some pretty good numbers for it's motors. But... Are they CSFM certified for use in Kalifornia? I don't know... But I'll see what I can find out.

James

Gary, Thanks for the encouragement. This thread could get pretty long, but if others are interested I am all for it.

young and dynamic area of rocketry. It's br> lizardqueen wrote:

Laura,

The GSE for Contrail motors is the same as RATT or any other monotube hybrid. The only odd requirement is for a 24V ignition source, since the Contrail motors use a carbon film resistor to initiate their motors, rather than an igniter or ematch. Most folks swap the resistor out and use an ematch in its place.

Kevin O

Laura,

All of the monotube motors will use the same GSE as the Ratt. Just have to be sure we have the right connector to fit the fill tube. And I have access to many types and sizes of brass fittings for this. So, if the Contrails are CSFM certified, we're there. 8^)

James

's still back under construction, but their links work to the different motors and pricing if you click on "Products" at the top.. Their domain expired earlier this year and someone snatched the name out from under them before they could renew so they lost their primary website.. The above site is what they're working on to rebuild it.. They're not going anywhere.. I just picked up the H70/I80 casings as well as the L600/M900 set and they've still got reloads for all of them.. Dave is a good guy, but this is not their primary business.. They're a very old machine shop (Monterey Machine Products) doing aerospace parts since the 50's so don't expect them to be picking up and going anywhere anytime soon..

Laura,

The Contrail motor hardware "combinations" can be confusing. Just FYI, the I307 and the I333 use the same hardware, just a different reload kit. In fact, that hardware can be used to make 4 motor combos:

I-307 573NS I-333 556NS I-400 432NS I-290 Sparky 488NS

The I307 is a great motor. A poor-quality video of that motor in a 10lb rocket can be found at

Kevin O