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High count clusters

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KilroySmith

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A large shipping tube (~6 inch diameter and 4 feet long) fell into my lap at work, and I'd like to mount about 19 motors (18 C's and 1 E) in it. According to OpenRocket, it won't go very high (about 600 feet), but it should be entertaining for a $50 rocket.

Any great things to NOT do? I'm figuring a 3mm or 5mm plywood thrust plate for the fore ends of the motors with holes drilled for ejection charges, and a 3mm aft plate that'll be 90% empty space with all the 18mm holes drilled in it.

I'll use electronic deployment.

And, yes, I have a launcher capable of lighting 19 igniters. No worries on that front.

Thoughts?

/frank
 

rharshberger

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A large shipping tube (~6 inch diameter and 4 feet long) fell into my lap at work, and I'd like to mount about 19 motors (18 C's and 1 E) in it. According to OpenRocket, it won't go very high (about 600 feet), but it should be entertaining for a $50 rocket.

Any great things to NOT do? I'm figuring a 3mm or 5mm plywood thrust plate for the fore ends of the motors with holes drilled for ejection charges, and a 3mm aft plate that'll be 90% empty space with all the 18mm holes drilled in it.

I'll use electronic deployment.

And, yes, I have a launcher capable of lighting 19 igniters. No worries on that front.

Thoughts?

/frank

Good Luck, and build light.
 

Rex R

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you will need an FAA waiver to fly this beast (over 4.4 oz. propellant weight).
Rex
 

KennB

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Check out the Hellboy at this site. This is a very successful 19 motor cluster (the picture on the home page shows the two stage version with a booster; click on the Hellboy tab at the top).

You'll have about 190 total Ns in your cluster, equivalent to a small H-impulse motor, so HPR rules will apply.

Post pictures of your progress.
 

Micromeister

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As others have posted even using 18mm motors and a core E your cluster will be well over the 4.4oz of propellent limit requiring an HPR waiver from the FAA.

Large cluster flying isn't unheard of but the waiver requirment does throw another element into the mix.

Do keep in mind average igniters require about 2amps each so with 19 motors your going to need a power supply capable of suppling about 40amps.
Good luck and be sure to fly safe.
 

KilroySmith

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Thanks for the responses. I'd forgotten about the 4.4 oz limit, I'll have to go review those restrictions and modify my plans against that. I have an 8-site launcher that's capable of supplying about 10 amps per site, I've driven 50 amps through it in testing so I think I'm OK. I'd probably use Q2G2 igniters though, to keep the current down and ignition variability to a minimum.
 

75Grandville

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Search on "Boris Katan", user ID delta22

He regularly does all sorts of high count clusters. He has tutorials on making your own ignitors, dos and don'ts, etc. Would suggest that as some preliminary reading.

I've read some of his stuff with an eye to high-count clusters, but haven't had a chance to try yet.
 

KennB

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Search on "Boris Katan", user ID delta22

He regularly does all sorts of high count clusters. He has tutorials on making your own ignitors, dos and don'ts, etc. Would suggest that as some preliminary reading.

I've read some of his stuff with an eye to high-count clusters, but haven't had a chance to try yet.
The link in Post #5 above will bring you to Boris' site.
 

marcusSRG

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I'd do a flash pan instead of worrying about all of those igniters. Boris ignites his Hellboy with a variant of the flashpan...BP, quickmatch and lots of tape.
 
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