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

Warren

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

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

OOPS
I guess it says 0.4 to 0.5 grams 😳

One and a half should have been enough 8)

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.

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

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.

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.

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.

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! 🙁

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.

I wonder if thats the problem with that Arkus I have thats running on that G64. Chutes Popped only 1 out of 4 times. The first 2 failures it came in flat. The last time was balistic.

Scotte

8) Scott, you should ask Bruce to show you his ground test video 😳 As I recall he shot his nosecone thru a fence, nailed a cat, and ended up in a "82 Honda!! 😯 Or something like that. Truely a great video! 8) GOT YA BRUCE!

8) Scott, you should ask Bruce to show you his ground test video 😳 As I recall he shot his nosecone thru a fence, nailed a cat, and ended up in a "82 Honda!! 😯 Or something like that. Truely a great video! 8) GOT YA BRUCE!

I wanna see that!! 😆

Here is a link to a charge test that I did indoors. Nothing like impaling a car but it did scare the crap out of us. It's a large file, about 11M but it shows a 2.0 gm charge in a 6" rocket with piston.

http://www.rocketryphotography.com/rockets/FreezeFrame03.avi

Doug

Ha! I have it transfered to VHS, but I should still have it on the camera's tape. I also blew up a PVC rocket stand I made. Just 2 grams. Parts fly everywhere! Only time I ever singed a chute... so far. Still use that chute to ground test. The conversation Tim and I had for the longest time was... me: Tim? Tim: Whatta ya need now? Me: Well, I blew up... He always got me what I needed in time to make repairs and be ready for the next launch. Scott, get your Aeropoxy from Tim next time. He brings it right to you at the launch. 😉 Watch Doug's video, it is really cool!