Q-Jet Clustering

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dpower

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I've been doing Q-Jet clustering for a few months now, 2, 3, 4 at a time of the same motor, and sometimes mixing with BP motors. Today is the first time I clustered 7, in a Semroc Hydra VII. Just for kicks, I mixed B4 and B6 motors to see if the slightly different thrust curves would present any issues, as the B4 gets up to pressure faster than the B6. So it flew on 4xB4 motors + 3 B6 motors, using the stock starters. All 7 lit nearly instantaneously with a 12v relay system, and it got up to 700-800' in a hurry, roughly the equivalent of an E34. I've had this model since 2006, usually fly it twice a year, so estimate it's burned nearly 300 18mm motors.

I also flew a Green Bay Packer themed Deuces Wild on a pair of Q-Jet B6-4s. It seemed to get off the pad a bit more slowly than a BP cluster of B6 motors, but I have no data to support that, other than my calibrated eyeballs. The twin smoke trails weren't as visible as I'm used to, so I'll stick with FJ propellant, or BP motors in the future.

These Q-Jets are fun, and cluster very well - while I'm not enamored with the thrust curve of the B motors (can we have a B8 or B10, please?), I'll continue to fly the C12/C18/D16/D20. I expect the D22/E26 motors will cluster equally well, and would be well suited to my upscale Hydra VII (7x24mm). A cluster of 7x D12 motors doesn't get it off the rail as quick as I'd like, so I usually add 1 or 2 CTI E31 motors. With the D22/E26, that shouldn't be necessary - and they're far less costly than the CTI E22/E31.

Nice work, Aerotech!
 

NOLA_BAR

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Yes, curious if you are using the supplied igniters. Also, I would not have expected the White Lightening Q-Jets motors to work as well as the Black Jack versions.
 

BEC

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NOLA_BAR

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My Estes Saturn V with 4 E26-7 Q-Jet motors, launched last weekend. I used the supplied stock igniters. I was surprised how well this went, considering how difficult 24mm AT White Lightning reloads are to ignite, and are notorious at chuffing. I would be curious if the Q-Jets use a different composition from the reload propellants?

P1030397_CROP.jpg
 

DigBaddy

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My Estes Saturn V with 4 E26-7 Q-Jet motors, launched last weekend. I used the supplied stock igniters. I was surprised how well this went, considering how difficult 24mm AT White Lightning reloads are to ignite, and are notorious at chuffing. I would be curious if the Q-Jets use a different composition from the reload propellants?

View attachment 513906

That is an awesome shot!!!

I've only done one Q-Jet cluster so far; but 3x D16-6 with stock igniters in my BT-80 scaled Big Daddy (carrot). Perfect flight. Will most definitely do this again.

 

AeroTech

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My Estes Saturn V with 4 E26-7 Q-Jet motors, launched last weekend. I used the supplied stock igniters. I was surprised how well this went, considering how difficult 24mm AT White Lightning reloads are to ignite, and are notorious at chuffing. I would be curious if the Q-Jets use a different composition from the reload propellants?

View attachment 513906
Very cool! Yes, the WL Q-Jets use a faster version of WL which is easier to ignite.
 

ShadowSpire48

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When clustering Qjets (or any composites really), would it be better to take the ejection out of one or two of them depending on the cluster size so the charge isn't as large? Thinking about 4 of them in a Boyce Nike Hercules but the separation might be a bit much with all 4 charges going off.
 
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neil_w

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When clustering Qjets, would it be better to take the ejection out of one or two of them depending on the cluster size so the charge isn't as large? Thinking about 4 of them in a Boyce Nike Hercules but the separation might be a bit much with all 4 charges going off.
You can also use longer delays on some of them so they'll fire (relatively) harmlessly after separation.
 

NOLA_BAR

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When clustering Qjets, would it be better to take the ejection out of one or two of them depending on the cluster size so the charge isn't as large? Thinking about 4 of them in a Boyce Nike Hercules but the separation might be a bit much with all 4 charges going off.
When I did the the Saturn V launch, even though they were all 7 second delay, the parachute was already out when 2 of the ejection charges went off. There was enough of a difference in motor ignition and delay. That said, for a Nike Hercules I would consider either removing 2, or reducing the charge by half in at least 2 motors. Maybe someone has done this?
 

Tractionengines

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That said, for a Nike Hercules I would consider either removing 2, or reducing the charge by half in at least 2 motors. Maybe someone has done this?
[ Get ready for the dispute about what is modification of a motor; and what is allowed; and what is allowed - IF manufacturer approved; ....and then what is "approval"... saying it's ok for people who understand the process and implications in email and public forums, vs an officiallly released instruction sheet ...]

In any case...after reviewing your situation, experience, lawyer, priest, and magic 8 ball....if you want to proceed: Stop at a pharmacy and get a dental pick. Wearing safety glasses. Use the pick to pull the plastic (rubber) plug from the Q-jet ejection charge well. Dump out the BP charge (Save BP for one that needs extra.) Then push the plug back in.

Notes. Do this only if you accept responsibility for your actions . If at a club launch get RSO approval. Do not pry to the side on the charge well. If you crack the charge well, or epoxy joint to motor body, it will CATO.

Remember YMMV.
 

Tractionengines

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The 18mm Q-Jets can be a little tricky to get ahold of the plug to pull it, just because of size. If you do it on 24mm or 29mm Single Use motors first you will get a feel for pulling it carefully.
 
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