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Need clustering advice on brand new scratch build with side tube fins

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cbwho

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I'll start a new thread to avoid confusion.

I am putting this sort of rocket together. The equal marks are tubes, angles are fins.

Side pod boosters will act as tube fins when not in use. To adjust the nose weight the body tube will be sectioned such that the top most body tube forms part of the nose cone. In which removable Play-doh can be installed for extra weight.

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My questions:
Is there a lot of planning needed to determine the size/delays of the side motors? All three motors be the same size? Or can I use lower power engines for the side and a more powerful longer lasting one in the middle? I plan on all 3 to be 18mm cases.
 

spigalau

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Personal experience is that not all delays are equal - we had a flight on 3 x 18mm C12-6 and one of the motors let loose after 2 seconds.


The other issue with have seen on the 18mm composite motors is that they can fail to ignite. The Black powder motors are far easier to ignite.

I would go with 18mm 'glider' (plugged) motors for the side pod boosters and just use the delay off the single central one.
 

teepot

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I use booster motors with zero delay in the side boosters. I also mix the power and size, ie, 1 F15-6 and 2 E12-0's or 1 G40-10 and 2 C6-0's etc.
 

cbwho

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Personal experience is that not all delays are equal - we had a flight on 3 x 18mm C12-6 and one of the motors let loose after 2 seconds.


The other issue with have seen on the 18mm composite motors is that they can fail to ignite. The Black powder motors are far easier to ignite.

I would go with 18mm 'glider' (plugged) motors for the side pod boosters and just use the delay off the single central one.
What an open launch site! I only get open launch sites on frozen lakes. Only a few more weeks left!
 

jqavins

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As the others have said, I'd use only the center engine for ejection, and one way or another "nullify" the side pods' engines for that purpose.

Using plugged engines is obviously the best way to do that, if there are plugged engines available that you want to use.

The discontinued Aerotech 18 mm SU engines had ejection charges under paper caps that could be removed; this was a vendor approved procedure, so it was allowed. I don't know if removing the charge is feasible or allowed with Q-Jets.

Otherwise, the conventional wisdom, as I understand it, says to vent the side pods' tubes just below their nose cone shoulders, and glue the cones in.

What some people do, which is against the safety code so I am not-recommending-it-even-though-it's-a-really-good-idea-but-no-I'm-really-not, is to plug the engines yourself by pouring some epoxy into the top. That's technically modifying the engine in a non vendor approved manner, so against the rules. So you definitely shouldn't do it, no matter how well it works. (Nudge nudge wink wink.)
 

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