JLCR with Airframe/Nose Cone rocket...configuration opinions?

[MarsLander]

Rocket: 10.5lb, 56" Airframe/nose cone only rocket. Build thread in my signature (Viper). Designed for motor deploy with JLCR.

I saw two consistent themes of successful JLCR use. Going without drogue (avoids entanglement) and the use of a sled to avoid the rubber band fouling. I also used two loop 30' harness. Harness and chute attached to NC. Sled was firmly attached to harness, and length of harness, from sled to NC, was less than the exposed chute shroud lines length, to avoid any pull on the parachute (harness took all the shock). I *believe* this worked based on result.

Flew at LDRS 42 at Potter. In reviewing the video (in the build thread...video stops at apogee), the announcer say "not heading anywhere on-site." At that point in the flight , it was just north of the south side trees, the airframe was "flying" and heading towards the trees to the south, pulling the JLCR and nose cone. There was a change in direction of the airframe back to the north, then the main deployed as expected at 600. The winds then pushed it west. The fins on the viper are large, which create the flying platform...

The sled, I *believe* helped to avoid the rubber band fouling. However, with a 48" Fruity (packs small), and the large fins of the viper, there wasn't enough drag from the JLCR wad to overcome the weight of the flying airframe.

My thought on next flight is to keep the sled/chute config next to the NC, and put a loop about 1/3 down the harness and attach a 12-16" drogue. This would give an inverted V and enough space, 10', between the JLCR wad and the drogue to avoid entanglement.

Thoughts?

 

[teepot]

Rocket: 10.5lb, 56" Airframe/nose cone only rocket. Build thread in my signature (Viper). Designed for motor deploy with JLCR.

I saw two consistent themes of successful JLCR use. Going without drogue (avoids entanglement) and the use of a sled to avoid the rubber band fouling. I also used two loop 30' harness. Harness and chute attached to NC. Sled was firmly attached to harness, and length of harness, from sled to NC, was less than the exposed chute shroud lines length, to avoid any pull on the parachute (harness took all the shock). I *believe* this worked based on result.

Flew at LDRS 42 at Potter. In reviewing the video (in the build thread...video stops at apogee), the announcer say "not heading anywhere on-site." At that point in the flight , it was just north of the south side trees, the airframe was "flying" and heading towards the trees to the south, pulling the JLCR and nose cone. There was a change in direction of the airframe back to the north, then the main deployed as expected at 600. The winds then pushed it west. The fins on the viper are large, which create the flying platform...

The sled, I *believe* helped to avoid the rubber band fouling. However, with a 48" Fruity (packs small), and the large fins of the viper, there wasn't enough drag from the JLCR wad to overcome the weight of the flying airframe.

My thought on next flight is to keep the sled/chute config next to the NC, and put a loop about 1/3 down the harness and attach a 12-16" drogue. This would give an inverted V and enough space, 10', between the JLCR wad and the drogue to avoid entanglement.

Thoughts?

Where is your blanket? I put the JLCR around the chute only. The blanket is about a foot below the chute burrito. The chute is about three or four feet from the nose cone. The blanket flapping in the breeze adds drag and keeps the nose cone below the chute burrito. I would ditch the rubber band and use silicone bands instead. They won't break or weaken like a rubber band. I don't like the drogue idea because it will be above the main when it opens and could get tangled or be stopped from opening because the main hits the drogue and collapses. I'm sure there will be other opinions.

 

[MidOH]

I switched to Estes elastic on the JLCR.

The irony...

 

[MarsLander]

Where is your blanket? I put the JLCR around the chute only. The blanket is about a foot below the chute burrito. The chute is about three or four feet from the nose cone. The blanket flapping in the breeze adds drag and keeps the nose cone below the chute burrito. I would ditch the rubber band and use silicone bands instead. They won't break or weaken like a rubber band. I don't like the drogue idea because it will be above the main when it opens and could get tangled or be stopped from opening because the main hits the drogue and collapses. I'm sure there will be other opinions.

2-3 feet or so below the JLCR, however Teddy builds them. JLCR was inside the burrito. The fins on the viper are big enough to fly and pull the JLCR and the blanket sideways. I'm sure it would work if the fins were smaller.

 

[MarsLander]

Braden, (Rocket Vlogs) @UPscaler got a great video of the launch. Watch to the end and you can clearly see it "flying" toward the business end and pulling the blanket, JLCR bundle and the nose cone horizontal.

Like to figure out how to fly this bird without it flying away!

 

[MarsLander]

@John Beans Any ideas?

 

[John Beans]

I think you just need to spoil that balance somehow. You're right that smaller fins would do that, as would making the bundle more draggy to lift it up. (To some extent the excellently compact Fruity Chute may have contributed to the situation.)

I'm not a huge fan of drogues, though I would never knock someone who had a good working configuration that used one. To me they are just extra complication and sometimes extra drift, though I can't deny that it's sometimes nice to have a longer window for visual sighting, and drogues definitely can allow you to engineer a more organized, repeatable descent configuration.

Interestingly, your rocket would fall faster with a tiny drogue than it fell during that flight, because it would flip the fuselage vertical and lower its drag.

I personally prefer a tumble to a drogue. As some of you may have heard me say before, it's worth logging your flights with a recording altimeter to get familiar with tumble speeds and the terminal velocity of your rockets in your particular configuration. Tumbling isn't simulated well, It's often surprisingly slow.

Many people don't realize that rockets achieve terminal velocity and aren't speeding up after the first couple of seconds in free fall. They sometimes think they need to set their release high so that it will have time to slow down and won't continually speed up until it hits the ground. Though this of course varies by rocket size/weight and chute diameter, two rockets that reach 2000' and open their chutes at 700' and 300' will open their chutes AND hit the ground at the same speeds. The only difference is how long they are on main chute in the wind.

 

[MarsLander]

I think you just need to spoil that balance somehow

Yep, but the question is how. I've seen lots of posts WRT the use of a drogue and fouling.

Valkrie makes a drogue with a mesh design, intended to reduce fouling (I suspecting reduce fouling of the drogue, not fouling with the main).
https://www.valkyrierecoverysystems.com/store/p6/drogue-chute.html

The other thought that came to mind while reading your post, is to use a streamer. Anyone with experience using a streamer and JLCR?

 

[John Beans]

The other thought that came to mind while reading your post, is to use a streamer. Anyone with experience using a streamer and JLCR?

The only observation I would make is that while a streamer seems like it would be a low-drag solution, remember that it is like a big sideways sail with respect to the varying air masses it pierces and rides through. Falls pretty fast, but blows sideways surprisingly fast, too.

(I learned this the hard way.)

On the other hand, I can't think of anything that is more visible in bright sunlight than a reflective, waving streamer.

 

[MarsLander]

Well, then I don't know how to use the JLCR on this rocket. I built this rocket this way specifically for the JLCR as the deployment method. Ugh.

I'm out of ideas.

 

[jmasterj]

Parachute that packs bigger?

 

[John Beans]

Well, then I don't know how to use the JLCR on this rocket. I built this rocket this way specifically for the JLCR as the deployment method. Ugh.

I'm out of ideas.

Just add a small streamer, use a bigger blanket, add some small strakes near the front of the fuselage, add some weight near the tail—anything to break up the tumbling balance without losing flight stability. You have a number of options!

 

[jmasterj]

How many times have you flown it? Has the booster done the same flat coast thing every time?

 

[MarsLander]

How many times have you flown it?

Once. Given the design and the weight, I posited, with an 80% confidence interval, that this would happen...and it did.

I'm not flying it again, until I have a plan for some drag...or I have a REALLY big field...

OR, I'll fly on some I357s and just use nose deploy...