RRC2 Mini is a 40k if I recall.

Most people will say 20k-30k is were you start to see real problems with BP and you need to start taking extra care in making your charges. Really as you go up it changes so the higher you go the more BP you may need but it will also depend on your type of charge. If you are packing your charge in surgical tubing, that seem to have the fewest issues for high altitude recovery but some people use PVC and other things, you just need to pack them tighter so that they stay together as the BP burns to insure it all burns to get the needed pressure to get your deployment. It is also a good idea to add more to the apogee charge to help with the same problem but that is based on experience and refined skills do to the variations in techniques and consistency in building charges. It also has a lot to do with what materials are used in construction to also determine the extra measure you use. FWFG tubing can take a lot more then paper or phenolic.

I will add that most of the guys flying over 15k-20k are using the surgical tubing and a lot of people are using it for all flights...

Since I've discovered the surgical tubing I've been using it exclusively. So easy to make the charges and they are in nice neat containers. For my 2 L3 attempts I've used them - worked great at 20k and 25k to deploy the laundry.

Edward

Are there different types (diameters/wall thicknesses)?

Thanks!

Yes, there are. I generally use 1/2" with 1/16 walls, and have gone up to 5/8 with 1/16" walls.

Edward

About a year ago I got some thick-walled tubing from McMaster and the ID was too small to get enough powder in there. Then a few days ago I bought some tubingg that Home Depot sells, thinner-walled stuff that has worked well in ground tests so far with Pyrodex. It's not quite as compact as potting the charges into cardboard tubes with epoxy, which is what I do for my usual tight volume applications, but it is easier.

I prefer the thicker walled surgical tubing. My way of thinking, the higher the bursting pressure, the longer is had (and higher pressure) to completely burn the powder. I get mine from McMaster and I typically use 3/8" ID 1/8" wall for charges of about 4 grams and 1/2" ID and 1/8" WT for up to 8 gram charges. Of course I use a plug at each end instead of just tying them off closed. Plus, I've gone away from the zip ties and use hose clamps. They're cheap and crimp on easier. Hope this helps,

Doug

I've switched over completely to the gum rubber hose method for charges. I have been using wire ties, but I like Doug Gerard's idea of hose clamps even better. I haven't flow anything else in 3 years now.

Warren

I just don't want to get hit by one of your hose clamps falling from 10,000 feet.

I'll stick with zip ties.

I just don't want to get hit by one of your hose clamps falling from 10,000 feet.

I'll be more worried about being hit by the rocket attached to the surgical tubing that was sealed with a tie wrap that gave way than a hose clamp. Haven't you seen the Mythbusters show on the falling penny? Terminal velocity would prevent any significant damage from being done from a hose clamp.

Doug

I don't do anything different under 20K. Above that, I use two zip ties at each end (4 ties total per charge) just in case one ruptures. I would worry a wee bit about a hose clamp cutting a tiny hole in the tubing and if that happened, there would be problems. I always use brand new zip ties, not the old brittle ones.

With regard to the thicker walled tubing - I hooked one of the thinner wall tubes up to a water hydrant recently and it expanded from 1/2" in diameter to perhas 6-8" in diameter without breaking... I was amazed. As such, I don't worry about the thinner stuff breaking, though it would be easier to cut with zip ties or hose clamps.

I'm with Ed on the falling hose clamps after I saw stuff from "Double Sixes" impacting the ground 😯 I sure don't want to get hit in the melon with anything...

I just don't want to get hit by one of your hose clamps falling from 10,000 feet.

I'll be more worried about being hit by the rocket attached to the surgical tubing that was sealed with a tie wrap that gave way than a hose clamp. Haven't you seen the Mythbusters show on the falling penny? Terminal velocity would prevent any significant damage from being done from a hose clamp.

Doug

A hose clamp has a hole in it. It would fall much faster than a penny. 😉

Scott,
Terminal velocity is based on the weight and drag. Something that weighs little will have less downward force on it from gravity, so, no biggie. Here's a cool NASA thread on it... http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

Adrian, what are the dimensions of the cardboard tubes are you using? Have you tried hot glue instead of epoxy?

I use the 1/4" launch lugs from Apogee for my charges. I make a 5-minute epoxy puddle on a piece of plastic, fold the wires of an ignitor 90 degrees and set the wires into the puddle with the head sticking straight up, and then put the cardboard tube around the ignitor into the puddle. Then when the 5-minute epoxy sets up, I fill the tubes with pyrodex and cap it off with more 5-minute epoxy. I haven't tried a glue gun. These have been very reliable charges for me, using easy-to-get pyrodex and motor ignitors (the Quest Q2G2 ignitors are sweet for this application). I'm going to see if I can fit one of these cardboard charges next to my surgical tube charge for the apogee deployment in my high-altitude Balls shot next week, and fire it as a backup using the 4th output from my new Raven altimeter.

The only advantage of the potted cardboard tube approach over the surgical tube is that it packages a little smaller. They're more of a pain to make. The size difference isn't a significant advantage for bigger birds, but it's helpful for 38mm and below.

Scott,
Terminal velocity is based on the weight and drag. Something that weighs little will have less downward force on it from gravity, so, no biggie. Here's a cool NASA thread on it... http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

Adrian, what are the dimensions of the cardboard tubes are you using? Have you tried hot glue instead of epoxy?

SO....... What are you saying? Because I wiegh more than you, I might fall faster? However, with my big stomach sticking out, there would be more drag and that I might actually fall slower than you? 🙂
Lets see? Wieght to third power times waist size, divided by hight and the sqaure route of your in seam = 123.682 mph.
HEY your right Greg!