L2 Streamer for Drogue

[jpk]

Hey Folks,

Lurker posting for the first time. I'm planning on going for an L2 at some point in the near future and being a college student I'd like to do it on the Hi-Tech I used for my L1. The plan is to reinforce some fillets and weak points on the body (the added bonus of more weight means less walking right?) The thing is, I'd like most of the descent to be on a streamer since walking isn't on my hobby list.

As best I can tell, picking a streamer size is far from a perfect science, especially for a drogue, and I'll have to iterate a bunch in RS/OR with different sizes. I'd like to place an order while I'm doing the touch-ups on the rocket before I know what the final weight is going to be.

The short(ish) question: What's a good starting point guess for a drogue streamer size for a Hi-Tech (around 30 oz) going up on a J? Is there some other big issue associated with this build I'm probably forgetting?

 

[EeebeeE]

I suggest you download Open Rocket and try different streamer sizes and lengths. You can run sims against specific weather conditions and measure drift, landing velocity, etc. With a streamer you still need it to come in slow enough so that the impact with the ground will not cause any damage (no more than 30 MPH).

Your construction needs to be very solid. This rocket isn't designed for mach speeds and most J motors are going to push it there. I just downscaled an EZ-I65 sim I had to this rocket and it looks like that only a J94 will keep the flight below mach speeds. You will also need to apogee deploy with some sort of altimeter, and finally, you are going to need to use some sort of tracker to find this. This rocket will go about 8,000' up. You are not going to see it. You might see the delay charge burn, but as soon as you have your apogee event, the rocket is going to disappear. Remember that to cert, you have to recover it, and to recover it, you have to find it.

This is a pretty ballsy flight, but to each his own. I certified L2 on a Nuke Pro Maxx. The rocket hit 8,480' and drifted more than a mile away. Good thing I had a tracker.

 

[blackjack2564]

I would start with a Topflight 6in. x 60in. streamer

If that comes down too fast,I would add a 12in. drogue to top of streamer.
That should do it & save a long walk....LOL

Edit:
be sure to have vent holes in both fincan & payload, to prevent premature separation on the way up. Small 1/8 holes should do it.
You haven't mentioned if this is to be a dual de-ploy flight, I'm assuming it is.
If not you, must size recovery to land in one piece.

 

[jpk]

I suggest you download Open Rocket and try different streamer sizes and lengths. You can run sims against specific weather conditions and measure drift, landing velocity, etc. With a streamer you still need it to come in slow enough so that the impact with the ground will not cause any damage (no more than 30 MPH).

Thanks for the reply. Unfortunately I have a hard time running open rocket on my machine but I'll get to one that can tonight, I posted because my access time is limited. I guess I wasn't clear when I first posted. I intend to dual deploy so I'll have a streamer pop at apogee and then deploy a 28" chute at about 700'.

In terms of solid construction, I'll reinforce the body tube where there isn't already internal structure. With the fins already attached, do you think it's productive to try to airfoil them or is that not worth the risk of asymmetrical sanding?

I'm planning on using two stratologgers for my deployment charges and I wasn't planning on using a GPS but since you suggest it I have a hand-me-down eggfinder I can use.

 

[jpk]

I would start with a Topflight 6in. x 60in. streamer

If that comes down too fast,I would add a 12in. drogue to top of streamer.
That should do it & save a long walk....LOL

Thanks for the starter tip, I'm going to run some sims tonight or tomorrow and I'll let you know what I end up with.

Edit:
be sure to have vent holes in both fincan & payload, to prevent premature separation on the way up. Small 1/8 holes should do it.
You haven't mentioned if this is to be a dual de-ploy flight, I'm assuming it is.
If not you, must size recovery to land in one piece.

Vent holes are a great reminder, I'm starting to understand why the L2 test is necessary- lots of little tips like that. R/E dual deploy: yeah I wasn't clear on that. I plan to pop the streamer at apogee and then do the last few hundred feet on the 28" main. The streamer is just as much for practice, visibility, and not tearing the main as it is for otherwise controlling descent.

 

[claytonbirchenough]

I did my L1 and L2 on the Hi-Tech. I added a blue tube AV bay and an upper section for DD. Drogueless and then main at 700 ft. Probably landed 500 yards away and I was the only one to see it come down. I saw it about 100 ft off the ground and it landed in a tree. Barely saw it... It did not go over 5k. I used standard construction and had no problem. L2 was on a J94 and it was a little windy. Low thrust and higher winds led to the hard/farther recovery. If it's a nice and calmer clear day, shove a stratologger in it and let her rip!

 

[jpk]

That's great to hear. Congrats!

Do you know what your velocity was at main deployment? The sims I've been doing with a J340 have it staying under 5k ft but my descent speed is 60 mph at a minimum, even with a pretty big streamer, and I don't want the chute to shred. Also, how long were your shock cords? Thanks

 

[bobkrech]

That's great to hear. Congrats!

Do you know what your velocity was at main deployment? The sims I've been doing with a J340 have it staying under 5k ft but my descent speed is 60 mph at a minimum, even with a pretty big streamer, and I don't want the chute to shred. Also, how long were your shock cords? Thanks

That should not be a problem. It's equivalent of deploying a main chute 3 seconds from apogee.

IMO if your recovery system can not withstand a +/- 5 second deployment deviation from apogee, it's really not sufficient for a HPR.

YMMV.

 

[Oberon]

I've been flying my LOC IRIS - a somewhat larger 3" kit - on a 6x60" bright pink TopFlight streamer at apogee with a 36" chute deployed via a JL Chute Release. I haven't gone L2 yet, but I've been flying full I loads over 3000' and the streamer is a huge boost for visibility. It's basically just enough drag to keep everything falling straight. I haven't run an altimeter yet but the descent rate is pretty speedy without any evident stress on the LOC main chute.

I'm enough of a believer that I'm probably going to stick with streamers for rockets in this size range and a bit bigger. Drogueless works, but I don't like the flat spins that often seem to result, plus they are harder to see at apogee and confirm separation.

 

[Coop]

Hey Folks,

Lurker posting for the first time. I'm planning on going for an L2 at some point in the near future and being a college student I'd like to do it on the Hi-Tech I used for my L1. The plan is to reinforce some fillets and weak points on the body (the added bonus of more weight means less walking right?) The thing is, I'd like most of the descent to be on a streamer since walking isn't on my hobby list.

As best I can tell, picking a streamer size is far from a perfect science, especially for a drogue, and I'll have to iterate a bunch in RS/OR with different sizes. I'd like to place an order while I'm doing the touch-ups on the rocket before I know what the final weight is going to be.

The short(ish) question: What's a good starting point guess for a drogue streamer size for a Hi-Tech (around 30 oz) going up on a J? Is there some other big issue associated with this build I'm probably forgetting?

For that weight, I make a 9 x 9 streamer that puts you right around a 50 FPS descent rate. I'd recommend placing the streamer about 10' from end of shock cord so you deploy into clear air.


Later!

--Coop

 

[Coop]

I've been flying my LOC IRIS - a somewhat larger 3" kit - on a 6x60" bright pink TopFlight streamer at apogee with a 36" chute deployed via a JL Chute Release. I haven't gone L2 yet, but I've been flying full I loads over 3000' and the streamer is a huge boost for visibility. It's basically just enough drag to keep everything falling straight. I haven't run an altimeter yet but the descent rate is pretty speedy without any evident stress on the LOC main chute.

I'm enough of a believer that I'm probably going to stick with streamers for rockets in this size range and a bit bigger. Drogueless works, but I don't like the flat spins that often seem to result, plus they are harder to see at apogee and confirm separation.

Last weekend, I recovered a G-Force using a 30" x 30' streamer, and a king Kraken using a 36" x 36' streamer. I used a 24" x 24' on my level two cert flight, as well as one of the same dimensions on my level three flight.

Point is: you can go a lot bigger with streamers.

Later!

--Coop

 

[Igotnothing]

Or you can go with no streamer. Lots of folks go drogue-less, deploying light main chutes from fiberglass rockets that have been split open at apogee and falling in a flat spin. Doesn't seem to stress the chute.

 

[jpk]

Lots of good input here. What's the advantage to going drogue-less?