Bolt from the Blue, a Blue Tube, Tube Fin Level 2 certification rocket

[Neutronium95]

After an ill advised attempt to fill the voids with epoxy, I've been doing a bunch of sanding, removing a whole lot of laminating epoxy from the insides of the tubefins. I've also been rethinking the avionics bay, and I should be able to start work on that this week, along with finally finishing up the carbon on the tubefins.

 

[Neutronium95]

I tried out a new avbay concept that features swappable altimeter pods. Some of my material choices have made things a bit finicky and delicate, but I think that it's definitely worth developing an improved version.


I also did my first test flight with dual deploy. The main came out at apogee, mostly because I didn't install shear pins in the rocket originally. Everything else worked great, so I'm planning on doing one more test flight, and then going for my L2 certification with a K360. I'm also planning on doing an I1299 flight.

 

[Neutronium95]

Everything went according to plan. I got my L2 this weekend with a near perfect flight on a K360, only marred by getting a bit lost on the recovery walk. I also did a test flight on an I204, and I celebrated my certification with a flight on an I1299. Anyways, here are the pictures that I got.

Cert flight on a K360:

I1299 flight (I was more excited about this picture than I was about the cert):



That's all for now. I have a lot of improvements that I want to make to this rocket in the future, starting with getting a new nosecone that I can actually use shear pins with, since I've gotten the main at apogee on two of my five dual deploy flights. I also want to build a better version of the avionics bay that has things fit a bit better. I also need to start making more altimeter and tracker pods so that I can use them across the fleet. Finally, I need to figure out some sort of body tube extension, so that I can fly it on an L395. I might even get around to painting it someday.

 

[dhbarr]

Sim up the L395 hanging out the bottom a diameter or so, I think you might be surprised how forgiving these guys are.

 

[Neutronium95]

Sim up the L395 hanging out the bottom a diameter or so, I think you might be surprised how forgiving these guys are.

That might work. It sticks a long ways above the CG, and I've been meaning to think about doing single break dual deploy with a cable cutter, so I won't need space between the motor and the avbay on the drogue side.. My biggest concern is that this rocket has been exceeding the sims for every flight that I have data for, and the L395 sims to 15,000 feet, which doesn't leave a whole lot of room under our 18,000 foot waiver.

 

[Neutronium95]

Guess it's time to rebuild it again. It drag separated when I flew it on a K1103X. The parachute managed to escape from the zip tie that I was using for cable cutter dual deploy, and the shock caused some impressive damage. The unused upper parachute bay got ripped to shreds, the booster is zippered, the altimeter sled got snapped in half, and one of the fins got crushed on landing. All in all, nothing too difficult to fix, I should have it flying again in a month or so. This time with shear pins.

 

[Neutronium95]

The Blue Tuber has had an eventful month...

I ended up building a new booster section that will allow for longer motors in the future, and then flew it at the Hot Nozzle Summer event on a K400. Unfortunately I grabbed an untested cable cutter that I had prepped for a previous flight, and didn't do my due diligence. The cable cutter fired, but didn't cut the zip tie, leading to another hard landing.

I got the two broken fins replaced, and then headed out to LDRS. I flew it with just motor eject on a H550 on Thursday. Friday brought some amazing avbay parts courtesy of @Nairdasilver . The first flight with the new avbay was single deploy on an "I120" maggie EX motor from @Nairdasilver and @Maxwelljets that underperformed, but everything recovered fine. The final flight was on a K695, where it shredded again, this time the unused upper parachute bay failed, but the rest of the rocket recovered fine. I think that I'm going to change the design to eliminate that tube.

pictures by @Maxwelljets

Maggie Flight


K695 liftoff

The shred

 

[Neutronium95]

I finally fixed the shredding problem. The tubefin had a spectacular flight on a K2050 during the last round of daylight launches on Saturday at Rocstock. For some reason the parachute came loose from the zip tie at apogee, but I got crazy lucky, and the rocket drifted down to land about 100' from my car. The sims say that it should have hit around Mach 1.3, and the altimeter data clearly shows the weird supersonic effects, so I can definitively say that this is the fastest rocket I've flown to date.

Pad cam by Xander Pickard:

Launch photo by Xander:


Launch photos by @T34zac :



Photos by Lavie Ohana:

 

[boomtube-mk2]

With regards to "Tube-Fins".
Is there a min/max length beyond which tube-fins become ineffective?

For instance, you're building a BT-60 based tube-fin rocket that will be 36" in length. If you use tubes 12" in length for the "Fins" will they work and if not, why?
Conversely, if you use tubes that are only 2" in length will that be insufficient to insure stability?
Would the 2" length work on a rocket that is only 18" in length?

Basically, is there an optimal tube-fin length to overall rocket length and can the "Fins" be either too long or too short?

 

[Neutronium95]

With regards to "Tube-Fins".
Is there a min/max length beyond which tube-fins become ineffective?

For instance, you're building a BT-60 based tube-fin rocket that will be 36" in length. If you use tubes 12" in length for the "Fins" will they work and if not, why?
Conversely, if you use tubes that are only 2" in length will that be insufficient to insure stability?
Would the 2" length work on a rocket that is only 18" in length?

Basically, is there an optimal tube-fin length to overall rocket length and can the "Fins" be either too long or too short?

I generally tend to use tubes that are roughly the same length as their diameter. I'm not sure about what weird effects would show up with significantly longer or shorter tubes. Openrocket can simulate tubefins, and it's been generally accurate with this rocket, so I'd suggest just playing around with that.

 

[mtnmanak]

With regards to "Tube-Fins".
Is there a min/max length beyond which tube-fins become ineffective?

For instance, you're building a BT-60 based tube-fin rocket that will be 36" in length. If you use tubes 12" in length for the "Fins" will they work and if not, why?
Conversely, if you use tubes that are only 2" in length will that be insufficient to insure stability?
Would the 2" length work on a rocket that is only 18" in length?

Basically, is there an optimal tube-fin length to overall rocket length and can the "Fins" be either too long or too short?

Discussed in this Apogee newsletter: https://apogeerockets.com/education/downloads/Newsletter335.pdf

When I build tube fin rockets, I just play with the length in Rocksim until I get the optimal balance between performance and drag. If you make them too long, they just add huge amounts of drag to the rocket. So I adjust the length to get the CP where I want it and then do some sim flights to see where the altitude is going to be. Then repeat that process until I get to a point where I am happy with the CP location and am also getting good altitude on the flights.

 

[dhbarr]

At about 3:1 subsonic they're more cylinders than they are tubes. At about 0.8:1 they don't seem to choke no matter how fast you go.

Congrats on a machbreaking toober! Folks often think it can't be done, so counterexamples are always appreciated.

 

[Neutronium95]

Congrats on a machbreaking toober! Folks often think it can't be done, so counterexamples are always appreciated.

Thanks. After reading the Bluefin Tuba threads, I came to the conclusion that most people that have shredded tubefins were using cardboard tubes. You wouldn't make normal fins out of cardboard and expect them to survive supersonic flight, why would you expect anything different from tubefins?

I still kind of want to see how fast I can push this rocket before the tubefins will either come apart or tear off. I am still kind of surprised that the airframe failed before the tubefins.

 

[roytyson]

My Tubefin (see the second post in this thread) fins are nearly 3 times dia. Not sure how accurate rocksim is with tube fins but I spend hours playing with different fin lengths. What I found in tube fins, is there was a stability issue with the shorter fins, so I extended them as long as I could, which fixed the stability of flight, until the point at which the fin length started to degrade the overall altitude height of the flight. All I can tell you is it flies straight as an arrow and is a show pleaser on a J540.

 

[dhbarr]

My Tubefin (see the second post in this thread) fins are nearly 3 times dia. Not sure how accurate rocksim is with tube fins but I spend hours playing with different fin lengths. What I found in tube fins, is there was a stability issue with the shorter fins, so I extended them as long as I could, which fixed the stability of flight, until the point at which the fin length started to degrade the overall altitude height of the flight. All I can tell you is it flies straight as an arrow and is a show pleaser on a J540.

That's a good looking bird, and I bet it makes for a great show no matter how much wind there might be. Rocksim and OpenRocket both have challenges WRT simulating tubefins, but they're extremely forgiving. The only thing long toobers won't do very well is jump above high transonic without blowing apart no matter how hard we kick them in the pants.

 

[Rocketjunkie]

A word of caution. Tube fin rockets DO NOT weathercock. Found out on a windy day and a J90.

 

[Orien]

The Blue Tuber has had an eventful month...

I ended up building a new booster section that will allow for longer motors in the future, and then flew it at the Hot Nozzle Summer event on a K400. Unfortunately I grabbed an untested cable cutter that I had prepped for a previous flight, and didn't do my due diligence. The cable cutter fired, but didn't cut the zip tie, leading to another hard landing.

I got the two broken fins replaced, and then headed out to LDRS. I flew it with just motor eject on a H550 on Thursday. Friday brought some amazing avbay parts courtesy of @Nairdasilver . The first flight with the new avbay was single deploy on an "I120" maggie EX motor from @Nairdasilver and @Maxwelljets that underperformed, but everything recovered fine. The final flight was on a K695, where it shredded again, this time the unused upper parachute bay failed, but the rest of the rocket recovered fine. I think that I'm going to change the design to eliminate that tube.

pictures by @Maxwelljets
View attachment 476479
Maggie Flight

View attachment 476481
K695 liftoff
View attachment 476482
The shred

Please don't take my "like" reaction as an insult. Truth is, it's the highest of compliments. NOT because it shredded, but WHY it shredded and how epically it shredded. You're pushing the envelope. You're taking risks. And I can relate. I recently had an ambitious launch turn into a disaster. But between what I've learned from it and the support of the community that encouraged me to make adjustments and press on, it was almost worth the loss of the rocket to advance to where I am now. What I see in this pic is a man saying, "I'm all in. Come what may." F*** yeah. (that booster still burning and fleeing the scene... LMFAO)

 

[Neutronium95]

@UPscaler got a good shot of my flight on the J275 on Friday.