Type of Body tube vs engine size

Jul 01, 2005 5 Replies
W

So, I have this giant (9" in diameter) plastic pig.



I was planning on putting a body tube up his... But after running some calculations, the finished rocket will be upwards of 10-15 oz. The pig itself is 5 oz. Add parts and clear plastic fins, and it really is... a pig.



Sounds like it will require an E+ engine to gain any sort of reasonable altitude. I was planning a standard Estes type BT-60 main tube, 24mm engine tube with rear ejection. Stop laughing.



Will a BT-60 handle an F? G? Should I go to a 29mm engine? How much power can I use and hope it won't shred? I could go to a .1" wall thickness, but that just adds more weight.



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S

Aerotech E30-4 or F21-4 are 24mm and will lift quite a bit.

BT-60 will do fine.

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J

The probelm is not the weight but the diameter. You will need more power to overcome that. When doing a sim, assume a hemispherical nose cone and a high drag coefficient, perhaps 0.85-1.

Jerry

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C

I've been talked into trying my Bt60 Patriot on a H128W for a L1 flight. I'm cheating & giving it a single layer of glass.... :-)

Clint.

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B

Good luck with the recovery.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

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R

Just remember -- you can always adapt down to a smaller motor, but there's no easy way to use a larger motor in too-small of a motor mount tube.

With a 9" diameter plastic pig, I'd probably look at using a 54mm motor mount, so I could use a J90 for a nice long burn.... But, that's just me :-)

Realistically, I'd suggest a 29mm mount. With the whole rocket weighing just under a pound, there are lots of motors in the F and G range that will work just fine to lift your pig, and you'd be able to adapt down if you wanted to use a 24mm motor. In fact, the F39 reload for the 24/40 casing would probably work great.

- Rick "Short delay, of course" Dickinson

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