L2 TIME

[Warren B. MusselmanModerator]

Tim is the local rep for Giant Leap Rocketry. http://www.giantleaprocketry.com, currently the largest HPR dealer in the country.

Warren

[Anonymous]

The book recomends 4 to 5 grams of powder for a 3″ tube …… Any body have any coments fo powder charges????????????

Yes. Two words: “Ground Test”.

Also, you can bet your lunch that 5g of FFFF powder is way, way, way, way, way more than you need for a 3″ airframe 😯 I don’t think I have ever used more than 2g, and that is with serious shear pins in a vented airframe without a piston.

Of course it all comes down to how long the airframe is, how much stuff is in there, if it is shear pinned, are you using pistons, etc. All that said, if you are using 4F powder in a 3″ airframe, then 5g is almost positively (way) too much.

Your actual mileage may vary.

JW

[SCOTT EVANS]

The book recomends 4 to 5 grams of powder for a 3″ tube …… Any body have any coments fo powder charges????????????

Yes. Two words: “Ground Test”.

Also, you can bet your lunch that 5g of FFFF powder is way, way, way, way, way more than you need for a 3″ airframe 😯 I don’t think I have ever used more than 2g, and that is with serious shear pins in a vented airframe without a piston.

Of course it all comes down to how long the airframe is, how much stuff is in there, if it is shear pinned, are you using pistons, etc. All that said, if you are using 4F powder in a 3″ airframe, then 5g is almost positively (way) too much.

Your actual mileage may vary.

JW

Maybe Ill have to look at that book again! (maybe it was 5 grains, our 54 cal guns use to use 110 grains) If I ignite 5 grams, the next door niegbor lady might freak! She didnt like it when I was firing my gas powered machine guns (I built for my airplane) out the garage door. I know she wouldnt like it if she thought I was setting off explosives. I might be the next guy in the news 😉

scotte

[SCOTT EVANS]

OOPS
I guess it says 0.4 to 0.5 grams 😳

One and a half should have been enough 8)

[Bruce R. Schaefer]

For a 3″ tube, 1.3-2 grams should do it. Although I DID blow a phenolic tube up with 2 grams! Better a little more than not enough. But there are limits.

[SCOTT EVANS]

For a 3″ tube, 1.3-2 grams should do it. Although I DID blow a phenolic tube up with 2 grams! Better a little more than not enough. But there are limits.

I wonder if I blew the side out of the rocket?
It was fairly cold and the air frame was plastic.

Scotte

[Anonymous]

I wonder if I blew the side out of the rocket?
It was fairly cold and the air frame was plastic.

Scotte

If you used 4 or 5 grams of 4F black power in a Quantum Tube, you almost assuredly blew it up. I’d be concerned with using that much powder in a filament wound glass tube with Kevlar shock cords.

Ground test. Always. Keep notes. On smaller charges make note of which electric match you used, too – a 0.5g charge with match “a” may be altogether different than it is with match “b”. This surprised me, but it is true.

Good luck.

[slh56]

I think it also depends on how tightly you pack the bp. If the bp is loosely packed it will burn more slowly expending it’s force over a short duration of time. However if it is packed tightly maybe with some wadding on top it will burn with a sudden pop and release all of its force over a much shorter amount of time providing a greater push on your nose cone or coupler.

Although i might be wrong…this is just what i’ve observed.

By the way for those that don’t know who this is, I’m steve and a student at CU. I got my L2 at oktoberfest with a 4″ talon.

[Ken PlattnerParticipant]

Try using an ejection charge calculator for an initial estimate to ground test with:

http://www.info-central.org/recovery_powder.shtml

I had a 3″ rocket come in hard because there was not enough charge to push the laundry out even though is was the amount included in a standard reload. Turns out the volume of the airframe (sans the laundry) was right on the threshold for what 1.3 gms of powder would pressurize. The nose barely popped out even though it wasn’t in very tight.

Ken.

[SCOTT EVANS]

I wonder if I blew the side out of the rocket?
It was fairly cold and the air frame was plastic.

Scotte

If you used 4 or 5 grams of 4F black power in a Quantum Tube, you almost assuredly blew it up. I’d be concerned with using that much powder in a filament wound glass tube with Kevlar shock cords.

Ground test. Always. Keep notes. On smaller charges make note of which electric match you used, too – a 0.5g charge with match “a” may be altogether different than it is with match “b”. This surprised me, but it is true.

Good luck.

It wasnt 4 or 5 grams. I could not fit that much in. It was about 1.5 to1.75 grams. Thats all the cup would hold, thank goodness. That still think it might of been enough to do it in. I knew somthing wasnt making sense!
As Bruce was saying, he got in to big of a hurry. So did I. You learn way more from your mistakes. 🙂
Hey guys it was COLD. My feet were freezing. I was shaking so hard the decimal point moved in the book! It wasnt my fault! 🙁

[Author]

Posts