At that weight, I'd be inclined to pop your main at 1000' or higher. You'll be coming in at a pretty zippy rate with that small drogue, which isn't a bad thing, but it will have some serious velocity. You want to make sure you give that main chute some time to open up. My 4" bird, about 14#, bounced from an 8000' flight with the main set at 800'. The chute came out, but didn't open fully before impact. It wasn't destroyed or anything, but it has taken a few bucks and a couple dozen hours to repair it properly.

Warren

Sounds similar to my BBX, which comes in on a 20" skyangle and pops a main at 800'. I would say you're probably fine at 800', but with that simmed velocity, I would probably go for 1000+, just to be safe.

For my part,, I think I've only used drogue chutes on perhaps 3 of my boosts (ever). I use streamers a lot, and I also just break the rocket and go w/o a chute or a streamer quite often. The fact that you are using Quantum tubing means you should probably slow things down a bunch, as QT will zipper.

I've seen absolutely enormous rockets brought down w/o a drogue of any type -- but you'd best have them constructed like tanks. At LDRS about five years ago I observed a crew that flew the same rocket five times the same day, and all the boosts were big M's. All the flights were flown without a drogue of any type, but it was a rocket that could have probably tumble recovered w/o damage :-O The rocket weighed perhaps 100# at burnout. It had a plastic coated steel cable as a shock cord. Yikes.

J

All you need to do is keep the tether (harness) of the two tethered ends up holding the thing level. As an example, my first L2 attempt, I didn't blow the main out but the two sections separated (was a GLR Vertical Assault), so it effectively came down without a drogue--or any chute recovery at all--of course, because of that, it was rightfully DQ'd. Very minor surface damaged, which is why I love that forgiving rocket. Last time I flew it--though it's been repaired and ready to go at our next launch, I obliterated the drogue, please don't ask. 🙂 My L3 at MHM will have a 24" drogue, only because I don't know how she'll free fall. Ideally, you want both sections to fly level and AWAY from each other. Which is why I have the WRC2 for the redundant charge, to fire if the primary doesn't, or, using Newton's 1st Law, to shoot the sections farther apart, if need be. In other words, you use the advice of those with more experience in high power, and your own experience... and PRAY!

Here is my two cents worth.

I have never flown a duel. I am just about done building a duel.

My first NCR launch. I watched a large rocket take off. Big motor, Big
rush. I was soooo impressed. The rocket finished its ascent and out came
the chute. The chute I thought was tangled. It was descending very
fast and I was hoping the chute would open at the last moment. I have
had tangled chutes and the result was messy. I was feeling sorry for the builder.
Suddenly there was another event. Out popped another chute, the whole assembly reversed position and it landed softly on the ground.

To me it was almost magical to watch.

http://www.putfile.com/pic.php?img=4962503

Drogue or No Drogue?

Motivation - Motivation

I am building my HyperLoc 300 to specs. and following the instructions
and see how it flys..

OK, I'm pretty set on using a drogue at this point, so if anyone has ideas or opinions on the best attachment point that would be awesome. Main focus is to keep the two parts from banging into each other and/or tangling.

OK, I'm pretty set on using a drogue at this point, so if anyone has ideas or opinions on the best attachment point that would be awesome. Main focus is to keep the two parts from banging into each other and/or tangling.

Batman, wait for JW's response on this, or Warren's, but using my Vertical Assault as an example, it is balanced in weight and length, so the drogue would be put in the middle of the harness. It just depends on how she flies in free fall. And you won't know that until you fly it. From the maiden flight, you'll know IF you need a drogue and what place on the harness to attach it. On my upcoming L3, I have NO IDEA how she'll fall in free flight, so I'm going center, since both sections are pretty close in weight, though aerodynamically different as night and day. I won't know how things will fall until I fly it. PLUS I'll be using a small drogue (24") and 60' of harness between the two sections. That's my 2 cents. 8)

I mount the drogue within 2' of the end of the booster section and the main 2/3 of the way to the nose. My booster shock cord is typically 2 or 3 times the total length of the rocket and my main shock cord is typically 3 to 5 times the total length of the rocket.

Warren

My booster shock cord is typically 2 or 3 times the total length of the rocket and my main shock cord is typically 3 to 5 times the total length of the rocket.

My booster separation will be at 60' separation, and my main at 40' for a 12 foot rocket (although I can lengthen the main separation after ground testing, if need be. I won't know until I do the ground testing.). You see, Batman, there are so many differing opnions--as you said when you posted this thread, and each original rocket is different. There are no right or wrong answers (well, there are, but only you will know that after a flight); it's you and your rocket that have to make the decisions. I have made some really stupid mistakes and learned from them, but as you move up, you can't afford to make as many as you did at L1 (well. maybe not you, but me 🙂 ). I tend to go long on harnesses. If you can cram them into an airframe and blast them out, you're okay and separated. The only failures I've had as far as harnesses is them being too shart. There really is no luck in this. If you're doing the wrong thing, it will catch up with you. The great thing about this club is that we are all on our own journeys in this, but we stick together and advise each other. Good thread. 😉

I like JW use alot of the same ways in recovery. Most of all my recovery has all been done without a drogue chute. Most times it was with a wide and long nylon custom built streamer. In fact when JW and I were some years back dueling for the K club alt record all I ever used was a streamer followed up by a main chute. worked great to about 15K with perfect recovery many times My choice for a drogue chute on my L3 project was within a weight consideration as well as the rockets over size and air drag. I felt that due to the size and weight and the amount of drag after separation that I wanted a little slower decent that was controlled the way it should so as not to botch up my main recovery. According to my data capture from my on board electronics I ended up while on a drogue chute at about 70 ft per second. About where it should be. I really think that there are more factors that go into choosing to drogue or Not to drogue then you are weighing out.

First off the weight of the rocket itself is fairly light. At a higher altitude a drogue will have more effects on drift and slow recovery. You don't want to have to much hang time way up high. A good rate of decent at apogee for any rocket like this is about 60 to 75 feet per second. I use shock cords made of either Kevlar or Tubular nylon. I prefer the Kevlar for the burn resistance and strength. Wider is better inside and direct outside the rocket body joint as it will aid in not zippering. Quantum tube is much more durable then most give it credit to. Ive had Quantum tube rockets before (not my personal favorite choice as im a composite guy But stronger then regular Phenolic and cardboard) Ive flown my 4" PML Endeavour That was Quantum tube on MANY motors. By the time of its retirement I bet close to 50 flights+. The smallest being my L1 cert flight with a H242 and then from every I and J motor in 38mm and 54mm I could throw at it from Kosdon to AT and even some AMW K motors on this very rocket past 2 miles in Altitude and most all flights were dual deply. So quantum is more durable then you think. The key is also how cold or warm it is makes a big difference as to how brittle it can be. The warmer the better. Anyhow. I would not use a drogue I would use a streamer Like I mentioned for your apogee deployment. Placement will vary from rocket to rocket based on weight and drag. Last thing you want is the Booster higher then the mains and have it come crashing though your main chute. I also believe that shock cords should be long. I normally use 3 to 5 times the length of the rocket for one event. On my rocket VDP I ad 25 to 30 ft on each end and on my L3 rocket Full Throttle I had roughly 35 to 40 ft on each event. I believe its better to also have a bit larger main and bing it down quite slow. With your rocket I would deploy the main at 800 to 1000 ft. But all the above is just my opinion and other may think differently.

Thanks Conway, Bruce, Warren, Mike, John and Chris (hope I didn't miss anyone) 😛 . As Conway mentioned, I KNOW for a fact that there are more factors involved than I am considering, since this is my first attempt to design a DD recovery. And as Bruce said, I realize that there is a certain amount of trial and error involved. I started out as a physics major in college, and have been flying airplanes most of my life, so I have alot of theoretical understanding of how things should work, but with rocketry, my real life experience is still pretty limited. I watch all you guys fly your big motors and complex recovery systems, that I'm sure you've refined over time, and I just wanted to sponge some of that experience. This club is truly awesome from that perspective, not only are people willing to help, but we have so many people that are really pretty extraordinary in their rocketry skills as well.

I'm gonna get down to building this thing and hopefully I can corral one or two of you at the april launch to look it over. I don't expect it to be perfect (is there such a thing?), but I do want to make sure that the design and construction are thought out and executed well enough to give me a good chance of success. Thanks again for the thoughts.