Cluster engine maiden question!

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Bill Gibson

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096.jpg Its a scratch built sorta BigBertha/sorta Ranger 3 engine cluster model....I didn't know if I should maiden it with A8-3 or A8-5 motors....the only experience I have with cluster rockets is with another scratch built rocket that uses 2 D engines called the Double D, and I noticed that with D12-5 motors it was still haulin ass when ejection occurred, so next time I think I will try D 12-7 motors....flew great otherwise! Any help would be greatly appreciated! THANKS!Haley! 011.jpg
 
Good lookin' birds, all of them. I like your color scheme.

Knowing the liftoff weight would help in choosing the best delay, but as a wild-hair guess I'd say the longer delay would be closer to ideal. Your earlier flight serves as an example of how a cluster can kind of 'overfly' shorter delays. Good luck!
 
a bbertha with 3.5 oz payload flies nicely on a D12-5, at a guess a -3 sec should work nicely.
Rex
 
Rex R said:
a bbertha with 3.5 oz payload flies nicely on a D12-5, at a guess a -3 sec should work nicely.
Rex
Click to expand...
I have a BB that flys on D engines and it DOES fly GREAT! I built the one in the pic for a 3 engine cluster as ive never tried this before! GREAT rocket design no matter whats powering it! Even single 18mm motors (the original intent) are fun!:)
 
Hi Bill!
I'd go with the two A8-5 engines.
Your work bench is WAY to organized!
 
I'm curious... What color and brand is that blue your using? The more I look at it, the more I like it :cool:!
 
with three A8s you're looking at 7.5Ns which is in the C impulse range, then you have to consider the added mass of the mount and engines, hence my suggestion of the 3 second delay. good luck with your flight,
Rex
 
Bill, have you tried simming it out in RockSim or OpenRocket? That's how I pick my initial delays for first flights.

Oh, and make sure you haven't accidentally put any spent motors in your box-o-motors, and then subsequently installed them in your rocket, as this may negatively impact your flight characteristics. Ask me how I know:facepalm:

Just a thought. I scratch-built something that looks a lot like your rocket, which I called "Spare Parts." Flew it on a pair of B6-4's, and it barely cleared the launch rod. Given the weight and the expected flight characteristics, the spent motor explanation is the only one I can come up with.
 
OR says that with a 28g payload, a Ranger should have an optimal delay of 3.48sec, sans payload 4.5sec. disclaimer I didn't do the design file so I don't know how it compares to real life(or your rocket).
Rex
 
hcmbanjo said:
Hi Bill!
I'd go with the two A8-5 engines.
Your work bench is WAY to organized!
Click to expand...

Thanks Chris! Nice to hear from you! Took a small break for a few months.. Back at it again, having a BALL! yeah......got a bit of the OCD thing, but I'm GOOD with it!
 
Last edited:
TangoJuliet said:
I'm curious... What color and brand is that blue your using? The more I look at it, the more I like it :cool:!
Click to expand...
Tango Juliet, it's standard Rustoluem rattle can enamel paint, and for the life of me, I can't remember what the color is called, BUT, I think I still have the can, and I will let you know ASAP! I do remember that it went on real nice!
 
75Grandville said:
Bill, have you tried simming it out in RockSim or OpenRocket? That's how I pick my initial delays for first flights.

Oh, and make sure you haven't accidentally put any spent motors in your box-o-motors, and then subsequently installed them in your rocket, as this may negatively impact your flight characteristics. Ask me how I know:facepalm:

Just a thought. I scratch-built something that looks a lot like your rocket, which I called "Spare Parts." Flew it on a pair of B6-4's, and it barely cleared the launch rod. Given the weight and the expected flight characteristics, the spent motor explanation is the only one I can come up with.
Click to expand...
Thanks for all the great info! I will keep it in mind when I get ready to launch!!
 
Rex R said:
OR says that with a 28g payload, a Ranger should have an optimal delay of 3.48sec, sans payload 4.5sec. disclaimer I didn't do the design file so I don't know how it compares to real life(or your rocket).
Rex
Click to expand...
Thanks much Rex for all the good info! You obviously know your stuff!! And I do appreciate it!
 
I used 3 A8-3s on my Ranger clone. It ejected about apogee. Three A8-5s would really raise the pucker factor. It is not going to get very high on A8 motors in any event. Remember, that according to S&T the Estes A8 motors are really A3s to A4s according to their test data. A true A8 would probably have a B6/C6 sized nozzle instead of the bigger 1/2A6/A8/B4 nozzle.
 
image.jpgimage.jpg
Bill Gibson said:
Tango Juliet, it's standard Rustoluem rattle can enamel paint, and for the life of me, I can't remember what the color is called, BUT, I think I still have the can, and I will let you know ASAP! I do remember that it went on real nice!
Click to expand...

Tango Juliet, Here ya go! It's called "Gloss Lagoon"...nice stuff
 
I agree with the others - I use A8-3s in my Ranger (modded from a Bertha kit) and it flies just fine. Likewise B6-4 and C6-5. The Bertha/Ranger is heaven and draggy, so the shorter delay works. BTW, the Quest A6-4 works fine too - and the Chinese motors are nice and smoky going up! ;)
 

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