BP Charge concerns

[rcktnut]

Also, when using the calculator, should I start measuring the BT length from the end of the MMT?

The distance between the MMT and the nose cone shoulder, in your case 70cm- 27 in. I see the concern in your case, it is close, it will pop the nose cone, but is it a big enough charge to get all the "laundry" out? Stuffer tube or more BP to be sure!!
I have a DD 4 in. rocket with both drogue and main compartments of around 12in to pressurize both with 20ft. shock cords and use 1.5 grams BP for both. That gets the shock cords, chutes out totally, but not so much as to overly do it.

 

[brentius]

The distance between the MMT and the nose cone shoulder, in your case 70cm- 27 in. I see the concern in your case, it is close, it will pop the nose cone, but is it a big enough charge to get all the "laundry" out? Stuffer tube or more BP to be sure!!
I have a DD 4 in. rocket with both drogue and main compartments of around 12in to pressurize both with 20ft. shock cords and use 1.5 grams BP for both. That gets the shock cords, chutes out totally, but not so much as to overly do it.

I've got the chute tied to a loop in the shock cord so the shock cord tugs it out.

 

[brentius]

Also, I can cut 1-2 inches off the BT. It's stable enough...

 

[rcktnut]

I've got the chute tied to a loop in the shock cord so the shock cord tugs it out.

Mine is that way also about 18" from the nose cone, as I guess most of us do it that way. If you don't have enough energy behind the nose cone to pull everything out, well it won't pull everything out! If your charge is only big enough to get the nose cone out an inch or so it won't do any good.
BTW: the rocket I mentioned does not have shear pins. Cutting that 1 or 2 in. off isn't going to help much.

 

[brentius]

Mine is that way also about 18" from the nose cone, as I guess most of us do it that way. If you don't have enough energy behind the nose cone to pull everything out, well it won't pull everything out! If your charge is only big enough to get the nose cone out an inch or so it won't do any good.
BTW: the rocket I mentioned does not have shear pins. Cutting that 1 or 2 in. off isn't going to help much.

Is the energy behind the nose cone proportional to the force on the NC? Because if so, I have enough (almost 100 lbs).

 

[NTP2]

Kind of funny, at the High School where my son went we got a call about a bomb scare, we had to come to school and pick him up. The scare was because a student had Estes engines in his locker.

What happened to the kid?

Ps I know what I’m doing next time I have a algebra test

 

[brentius]

The distance between the MMT and the nose cone shoulder, in your case 70cm- 27 in. I see the concern in your case, it is close, it will pop the nose cone, but is it a big enough charge to get all the "laundry" out? Stuffer tube or more BP to be sure!!
I have a DD 4 in. rocket with both drogue and main compartments of around 12in to pressurize both with 20ft. shock cords and use 1.5 grams BP for both. That gets the shock cords, chutes out totally, but not so much as to overly do it.

I see. What about my design for a stuffer tube (earlier on in this thread)? Will that work?

 

[Titan II]

I think you could possibly shorten the rocket by a good 10". Look at the specifications of the Little John, Tempo, Squat and Cowabunga on the Mad Cow site. They are all 4" and much shorter than yours. You appear to have large fins, pulling the CP back. Get out your sim and shorten the rocket to where you are comfortable with the motor popping the NC. If needed, add weight to the NC to get your 1 cal of stability.

 

[David Schwantz]

Don't remember if we ever heard about the after effect of it.

 

[rcktnut]

A stuffer tube would also work, if you eliminate the gap like in post #15. You could use a 54mm. stuffer tube with a 54-98mm. centering ring on top only. You won't get an aft centering ring past the coupler anyway. Get the aft end of the 54mm. tube over your 38mm. MMT and glue the forward centering ring in place.

 

[rcktnut]

Where are you intending to launch for your L1 certification attempt as it may be possible to obtain some additional ejection charge material? As has been mentioned BP is not illegal in the UK but requires an explosives licence.

Still the best option!!

 

[brentius]

A stuffer tube would also work, if you eliminate the gap like in post #15. You could use a 54mm. stuffer tube with a 54-98mm. centering ring on top only. You won't get an aft centering ring past the coupler anyway. Get the aft end of the 54mm. tube over your 38mm. MMT and glue the forward centering ring in place.

I'll probably use some leftover BT-70/BT-80 , then add a centering ring.

 

[brentius]

Still the best option!!

I understand, but I'm under 18 so I can't buy BP, and there is no way I can convince my parents to get me some BP.

 

[NTP2]

I understand, but I'm under 18 so I can't buy BP, and there is no way I can convince my parents to get me some BP.

Yup that’s the hardest part, I’m lucky as we have family in a very rural area and one of them was a gunsmith so he had contacts, got me a 1 pound can, for free.

Ps is it legal to make it? It’s a pretty simple mix.

 

[brentius]

Yup that’s the hardest part, I’m lucky as we have family in a very rural area and one of them was a gunsmith so he had contacts, got me a 1 pound can, for free.

Ps is it legal to make it? It’s a pretty simple mix.

No.

 

[NTP2]

No.

Ahh well it’s almost certainly fine without it.

 

[brentius]

OK, I've redesigned the rocket to separate into 2 halves. And I can stuff an altimeter into the bay above... Just one question: What do you use to secure the nose cone to the top section?

 

[brentius]

(this is going to take a LOT of cutting. Luckily I found LOC tubes on sale for $15, so I get another chance.)

 

[rcktnut]

Way to go!! Plastic rivets, small screws will do for the nose cone. I use 2 plastic rivets on a 4in. nose cone.

Also you must have a mentor right? If you are going to a sanctioned launch surely someone there would also be more than willing to fix you up with a little BP for free.

 

[Back_at_it]

Yup that’s the hardest part, I’m lucky as we have family in a very rural area and one of them was a gunsmith so he had contacts, got me a 1 pound can, for free.

Ps is it legal to make it? It’s a pretty simple mix.

Yes. Black powder produced for your own personal use is legal and not regulated. You just can't sell it or use it in a business setting. For instance, if you were in the demolition business, you couldn't make you own but the relatively small amounts needed for rocketry is completely legal.

 

[NTP2]

Way to go!! Plastic rivets, small screws will do for the nose cone. I use 2 plastic rivets on a 4in. nose cone.

Also you must have a mentor right? If you are going to a sanctioned launch surely someone there would also be more than willing to fix you up with a little BP for free.

I think the UK let’s kids get up too a L2, a. Better way I think.

Yes. Black powder produced for your own personal use is legal and not regulated. You just can't sell it or use it in a business setting. For instance, if you were in the demolition business, you couldn't make you own but the relatively small amounts needed for rocketry is completely legal.

I meant in the UK. I know that you can In the US.

 

[brentius]

Way to go!! Plastic rivets, small screws will do for the nose cone. I use 2 plastic rivets on a 4in. nose cone.

Also you must have a mentor right? If you are going to a sanctioned launch surely someone there would also be more than willing to fix you up with a little BP for free.

It's different here in the uk, we get to cert up to L2 when we're under 18. My mentor is at my school- he's doing his L2 cert at the same launch, and I ask him for advice. He isn't really official- you can do one without.

 

[Titan II]

I meant in the UK. I know that you can In the US.

https://letmegooglethat.com/?q=can+you+make+black+powder+in+the+united+kingdom

 

[rcktnut]

brentius
Do you have/ use any Estes motors at all?

 

[NTP2]

https://letmegooglethat.com/?q=can+you+make+black+powder+in+the+united+kingdom

Well I assumed that the OP knew more about UK law than me, or maybe he just meant that he couldn’t for non legal reasons.

 

[cbrarick]

work around: Go get some pyrodex. put it on top of the black powder and then use duck tape (or gaffer's tape) to tape it down securely. It's not a perfect soution but you can buy pyrodex powder in the UK. I'd put a little extra then what you'd use if you had black powder.

 

[brentius]

brentius
Do you have/ use any Estes motors at all?

A bunch of C6s, yes. But apart from that, I usually fly CTI for mid power (Estes mid power engines aren't certified.)