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accooper

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I was talking to some rocket folks and I brought up the subject that I was building a rocket that would be using a full 18 inch length BT-60 body tube. I also mention it would be Estes D12 powered.

You would have thought they had seen a ghost! All of them claim that I would need an internal BT-50 because the D12 would not eject the chute because of all that empty space.

I don't believe them.

Am I wrong?

Andrew From Texas
 

sandman

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You are NOT wrong.

It will work just fine.

If it didn't the Estes Mean Machine (which uses 3 x 18" BT-60's)wouldn't eject it's chute.

It ejects it just fine.
 

tbzep

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I guess they've never heard of an Estes Mean Machine.

It will eject your chute as long as nothing is wrong with the motor.
 

tbzep

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You're too quick for me, Gordon. :p
 

powderburner

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I was talking to some rocket folks and I brought up the subject that I was building a rocket that would be using a full 18 inch length BT-60 body tube. I also mention it would be Estes D12 powered.

You would have thought they had seen a ghost! All of them claim that I would need an internal BT-50 because the D12 would not eject the chute because of all that empty space.
Back in the olden days, there was a design called the Big Bertha that had the same length of BT-60 but only had a single 18mm motor mount. It flew (and ejected) just fine. And Estes ejection charges have allegedly gotten more powerful since then, so much so that many people are having trouble with ejections that are too energetic.

Like these other guys have already said, you'll be fine.
 

sandman

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Back in the olden days, there was a design called the Big Bertha that had the same length of BT-60 but only had a single 18mm motor mount. It flew (and ejected) just fine. And Estes ejection charges have allegedly gotten more powerful since then, so much so that many people are having trouble with ejections that are too energetic.

Like these other guys have already said, you'll be fine.
Ya know I saw this really nice older gentlman fly one of those Berthas at NARAM this year.

It was pretty beat up but it still flew...

And it ejected it's chute too!

DSCF1750.jpg
 

Gillard

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if Estes carries on reissuing old popular kits then they will have to bring back the big bertha, it was a perfect small field flyer
 

powderburner

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The ejection charge from a D12 is pretty ferocious, as this video illustrates.
I had been kinda wondering if a modern/current Estes D12 (with the megaton ejection charges they are now using) would be too much for a BT60. It would be interesting to learn how many of those motors it would take to burn/blast through the walls of a BT60. I know that trying to route D12-0 blow-through gasses through unprotected BT20 tear it up pretty quickly.

Those are some really helpful videos to illustrate what's going on. Great legwork, MarkII
 

Micromeister

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I was talking to some rocket folks and I brought up the subject that I was building a rocket that would be using a full 18 inch length BT-60 body tube. I also mention it would be Estes D12 powered.

You would have thought they had seen a ghost! All of them claim that I would need an internal BT-50 because the D12 would not eject the chute because of all that empty space.

I don't believe them.

Am I wrong?

Andrew From Texas
Andrew:
Your not wrong, I completely agree with sandman. D12 ejection charges are plenty in BT-60's.
I use BT-60s as stuffer tubes in most of my BT-80 and Larger Upscale D12 clustered models. they are designed to have the laundry deployed with a single ejection charge. Some are full 36" long tubes. As shown in the pic below of my BT-80 Upscale OT. And don't let anyone tell you multi ejection charges make that much difference, While they may sometimes go at near the same time it's always[ the first charge the does the work. So your 18" stuffer tube is just fine.
 

spacecadet

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A D will pressurise a minimum-diameter rocket SEVEN FEET long. I've done it.
I only use stuffer tubes (which is what you're describing) for structural reasons, not to reduce the volume.
 

Pem Tech

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You will be fine....
We have been working on a 36" long BT-80 based kit with no stuffer tube and it ejects perfectly on a D12.
 

MarkII

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I had been kinda wondering if a modern/current Estes D12 (with the megaton ejection charges they are now using) would be too much for a BT60. It would be interesting to learn how many of those motors it would take to burn/blast through the walls of a BT60. I know that trying to route D12-0 blow-through gasses through unprotected BT20 tear it up pretty quickly.
Where it's feasible, I prefer to use ST-16 instead of BT-60, because it has a somewhat thicker wall. One can also line the first 2 or 3 inches of the body tube above the motor mount with a coupler to increase the durability.

Those are some really helpful videos to illustrate what's going on. Great legwork, MarkII
Well, the credit really belongs to Roger Smith (a k a jadebox) of Jonrocket.com, who posted the videos on his Payload Bay.com website.

MarkII
 

Nickc

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D's packed plenty of power. I used a single D in my rocket called 'BIGGUN', which was 54" long and it had no problems. I do use a simple piston that seems to capture the ejection charge gases better.

You can check it out on my site, http://www.mts.net/~nccard/rocketology/rocket.htm

PS. Look at the RIP image for the rocket 'ITCH', which also illustrates how much power there is, if it can't get out.

All the best.
 
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