Hybrids For 2016

Thanks for checking it out. Guess I need a slightly smaller drill bit, since they tend to cut a bit on the high side.. There is little material to remove, it might be easier to to get a reamer and just do it by hand.

So, I've been working on getting a rocket ready for my SRS 54mm motor. Figured it might be worth sharing the design, even though I'm a bit of an OR noob. I just wanted a basic sim to make sure I wasn't getting too heavy etc.. Hope it's useful.

View attachment Test BT Hybrid.ork

ttabbal said:

So, I've been working on getting a rocket ready for my SRS 54mm motor. Figured it might be worth sharing the design, even though I'm a bit of an OR noob. I just wanted a basic sim to make sure I wasn't getting too heavy etc.. Hope it's useful.

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So how is this build coming? And what 54mm size are you building for?

Just need to finish the av-bay. The booster section is complete. The only 54mm hybrid I have is the long K motor. I have the full 38mm set, but still need to build a rocket for those. With winter coming on, it might not fly till next year. The next research launch locally is in November, so it just depends on how the weather goes.

ttabbal said:

Just need to finish the av-bay. The booster section is complete. The only 54mm hybrid I have is the long K motor. I have the full 38mm set, but still need to build a rocket for those. With winter coming on, it might not fly till next year. The next research launch locally is in November, so it just depends on how the weather goes.

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The SkyRipper motors are still certified by the NAR, and are legal to fly at regular launches, no need to wait for a research launch. Here is the latest NAR certified motor list (May 31, 2016):

https://www.nar.org/SandT/pdf/CombinedMotorsByImpulse.pdf

EDIT: I backed up a couple posts and saw that you are making your own loads... but still good info to have if you run across some of the old SRS loads

Oh, well then... I thought they fell off the list a while back. I do have some of the real loads for both 38 and 54 motors, so I may have to try to bring it out to the October NAR launch. Should still be warm enough for the N2O.

For research loads I'm still tinkering with ideas. I think 3D printed ABS grains will work fine in a standard 54mm liner, the dimensions are really close. I can make them pretty cheap, but even with thick layers a set of 3 takes about 4 hours to print. Another option for liners is 1.5" PVC pipe. I keep forgetting to measure the dimensions for the O-Ring seal areas though. I found an older post where someone was saying they nested 1.25 pipe inside the 1.5 for a fuel grain. I'm trying to find a way to do it that doesn't require a lathe, but at these sizes the little Harbor Freight metal lathe could manage, and as a bonus I could make nozzles etc...

Took a minute to measure and compare the instructions... The sealing surfaces on the 38 and 54 are the same size. They both use -120 o-rings and measure the same. So 1" SCH40 PVC bored out, or even sanded a bit, on the ends will work fine, for sealing up. Obviously, without any support you would blow the PVC pretty fast. But 1.5" PVC OD is 1.9", which is what the stock liner measures out at. If you use Class200, that leaves a 1.7" ID. 1.25" specs a 1.660" OD, SCH40 1.380" ID. Then 1" lists a 1.315" OD. There is a bit of space between the sizes, but you could conceivably take that up with epoxy or solvent weld glue.

Of course, making those might take longer than printing them. And if I print, I can make finocyl grains, or other oddball geometry in there.

I wonder about making a new U/C valve and nozzle designed to seal against 1.5" SCH40 PVC, tightly so you would need to sand/drill it out a bit. Then cast HTPB into the PVC as the fuel. Maybe a spacer disk on either end with properly sized o-rings? Something like the Aerotech seal disk comes to mind... Might be easier to just do it once and skip trying to adapt the stock parts.

Our October launch has been called and I'll have to wait until May next year to fly it for a waiver. In the mean time I've been doing some testing on a 3" motor, as well as a 2.5" motor. I've also ran through about 5 pounds of various APCP formulations characterizing those for easy to fly rockets. I like to have a couple solid motors to fly each launch so that the hybrid isn't the main event every time.

I don't know where I will go after the 3" motor - it is the largest I can fly at my field with a 35k waiver. I'm thinking the next thing might be a 7.5" low and slow hybrid. Something that might give some coal rollers a run for their money.

Edward

I like the low and slow flights. I've been thinking of working up something really draggy for my SRS 38mm motors. I'm one of the weird ones at the local launches that flies oddrocks, uses a lot of AT Blackjack loads... And the hybrids of course.

I need to stop tinkering with my GSE or I'm not going to be flying the hybrids anytime soon. I'm almost done integrating a vent sensor, I'll probably stop after that and finish it up. The local club doesn't have hybrid gear, so I need to get mine wrapped up if I want to fly them.

I have everything for my GSE now except for the tank re-cert and fill. Also getting back into finishing the builds on my list.

Totally forgot about tank cert... I likely need to get mine done. Going to have to add that to the to-do list, since they will require it for filling.

Do you own a tank? I have/own a 20# tank, and the gas company is trying to get me to rent a larger tank. But since my flying record is non-existent for the last bunch of years, renting a K-cylinder was just not affordable.

Yes, I own a 20# as well. I fill it at a race shop rather than a gas supplier. I've been considering doing a K but it would probably just be for special events where I plan to use a lot of gas. It would be nice to have for testing as well. I might look into pricing over the winter.

I rented my K-Cylinder for $200 for 10 years. It costs $195 to swap it out. I have two 20 pound tanks, but both sit empty because I use the K Cylinder for filling and flight operations.

Edward

I know nothing about hybrids but want to learn. Is there a good reference to start with?

Lowpuller said:

I know nothing about hybrids but want to learn. Is there a good reference to start with?

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There are still some hybrid fliers on this forum that can answer most any question you have that is related to hobby. Otherwise, google is your friend, as there are still some references out there to be searched, although much has gone away. The owner of Alpha Hybrids, one of a number of hybrid mfg's from years past, regularly posts on here, and Thomas Sanders, the owner of Contrail, has been known to answer a question or two. Other than that, ask away, as the last two years have seen even the regular posters fade away from posting about hybrids.

You want to see what it was like "back-in-the-day"? Then search through the Rocketry Forum, as all of the history is archived there. You can still find release statements from the likes of Sky Ripper Systems when they were developing motors... they coined the phrase "Who Flew The First G-Hybrid" as they were the first to develope and market the first 29mm G-class hybrid motor. Here is one of the videos from that era:

[video=youtube;6iX4pKnWkL0]https://www.youtube.com/watch?v=6iX4pKnWkL0[/video]

[video=youtube;GFBZQJ-_4S4]https://www.youtube.com/watch?v=GFBZQJ-_4S4[/video]

Or the SkyRipper K launch in the snow...

[video=youtube;5CJzG_jJl7s]https://www.youtube.com/watch?v=5CJzG_jJl7s[/video]

Here is a HyperTEK video of my first Level 3 attempt back in 2005 I believe. Lovely motor, bad deployment!!

[video=youtube;ckohj0VVKZU]https://www.youtube.com/watch?v=ckohj0VVKZU[/video]

There are many many HyperTEK videos still available on youtube... look uo the RattWorks Tribrid... way cool motor!! Here is a slow motion launch of a K350 Tribrid:

[video=youtube;d5MmIpf0ki8]https://www.youtube.com/watch?v=d5MmIpf0ki8[/video]

Here is a yahoo group forum that is still semi-active, albeit less active than in years gone by. nevertheless, the archived discussions are still there in a month by month lsiting going back to 2003.

https://groups.yahoo.com/neo/groups/hybridrocketmotors/info

Search and destroy, there is still some good info out there.

So, took apart the SRS 38mm to check out some things and realized that the o-rings don't seal against the ID of the grain. They seal against the face. That explains some things I had messed up in my head.

Interestingly, 1" class 200 seats nicely with the o-rings on the ID. I suspect it's too thin to use alone in the 38mm motors though. I need to source some SCH80 to make exact match grains. SCH40 looks like it will work though.

On the up side, I figured out the ignition failure last time I tried to fire it. 2 igniters fired, neither lit the Preheater. Pffttt.... Much bigger and easier to fire preheaters going forward.

I may need to wait for the 2017 thread for flying. Weather is turning fast. Owell, better than rushing and making mistakes.

These seal because of the nitrous when you fill the motor compresses the mid-bulkhead against grain and nozzle. They do not seal in the traditional way o-rings do.

1" SCH 80 you can find at one of the big box stores.

Edward

The local Home Depot and Lowes don't stock it. I know a couple plumbing places that likely would though. When searching just now on HD's website, I found 1" SCH80 PVC conduit. Seems like that would work, but I didn't think to look in the electrical section for pipe...

That is the section where it is at - electrical. Plumbing places, even irrigation places typically don't stock SCH 80. You can on special order from electrical places get SCH 120.

I typically go to an electrical supply house for all the SCH 80 that I need.

Edward

I made some 38mm grains today. Used a 3D printed drill guide with a 1" forstner bit to open the ends out. Test fit with the nozzle in a case and it looks good. Everything lines up and seats nicely.

ROCstock - November 12-13th at Lucerne = HYBRIDS!

Im planning to launch the twin again, Cluster of 2 Ratt k's, plus the Contrail M, Aerotech Hybrid (yup got some of those too), plus maybe the RATT H or I.

Mike K

kramer714 said:

ROCstock - November 12-13th at Lucerne = HYBRIDS!

Im planning to launch the twin again, Cluster of 2 Ratt k's, plus the Contrail M, Aerotech Hybrid (yup got some of those too), plus maybe the RATT H or I.

Mike K

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Mike, can we buy fills from your tank?

CoyoteNumber2 said:

Mike, can we buy fills from your tank?

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What are you launching ? How much do you need?

Mike

kramer714 said:

What are you launching ? How much do you need?

Mike

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At most three RATT H70s. 0.2 pounds per fill.

im sure I can spare that, end your fill hose with an AN-4 connector and you can hook right up.

Mike K

kramer714 said:

im sure I can spare that, end your fill hose with an AN-4 connector and you can hook right up.

Mike K

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Awesome Mike, see you Saturday.

We want pics, and if possible, video! Looking forward to a launch report!

DRAGON64 said:

We want pics, and if possible, video! Looking forward to a launch report!

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I gotta get the boy to post his videos his pictures are at https://www.flickr.com/photos/paytonkramer/albums/72157676442340776 (the rocket on top of the Jeep is the big one)

On my flights,

Contrail M perfect flight, launched the 'big rocket' 16' x 8" diameter
Ratt K (2 motor cluster), good flight... both lit on the pad, one of them didn't kick out he flll tube until a few hundred feet up, Im thinking I get credit for an air start on that one.
Ratt H, low flight partial fill (had a leak on it)

James got 2 flights on a RATT H, very nice!
John flew a Contrail J, good flight (not so good landing)

Mike K

very nice launch....love that big round NC... obviously you had fun 😄 motivating inputs for me to retrieve excitment of hybridz...
But I wonder your rocket on the car roof. I would not drive 10 miles here in Bavaria LOL... and finish the day in a small and dark room with no views but a camera looking at me 😎