Bluefin Tuba 3"

Awesome Ari!

I will admit that that is very cool. When people suggest a model that will accomplish L1, L2, and L3 the discussion is usually centered around a LOC Bruiser. A half Bruiser will fly on a high average thrust I motor with motor deployment, followed by a mid range J or K with a payload, then a long burn M for the finale.

This changes that up entirely. I expect that people could easily recreate your design and accomplish this feat.

Also, you could have gone for 8 classes with an F240 as noted eariler...and with an accelerometer like the Raven an E75 MAY be possible, albeit marginal.

I will have to try this at some point. Really, really great design, thanks for the inspiration.

patelldp said:

I will admit that that is very cool. When people suggest a model that will accomplish L1, L2, and L3 the discussion is usually centered around a LOC Bruiser. A half Bruiser will fly on a high average thrust I motor with motor deployment, followed by a mid range J or K with a payload, then a long burn M for the finale.

This changes that up entirely. I expect that people could easily recreate your design and accomplish this feat.

Also, you could have gone for 8 classes with an F240 as noted eariler...and with an accelerometer like the Raven an E75 MAY be possible, albeit marginal.

Click to expand...

A looooooong rail would be very important for the E flight.

CarVac said:

A looooooong rail would be very important for the E flight.

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As stated, it would be marginal, but feasible if it flew on a G80. I doubt it'd get high enough for the Stratologger to arm.

Well done, Ari!

You have indeed become the TubeFather of TRF.

Wow... those flight photos look fantastic, great job on a real nice rocket.

What max speed did it hit on the M?

Hey iter what was the length of the air frame . I'm trying to get proportions right on a few of my 4" tube fin rockets thanks Chris

patelldp said:

When people suggest a model that will accomplish L1, L2, and L3 the discussion is usually centered around a LOC Bruiser. A half Bruiser will fly on a high average thrust I motor with motor deployment, followed by a mid range J or K with a payload, then a long burn M for the finale.

This changes that up entirely. I expect that people could easily recreate your design and accomplish this feat.

Click to expand...

It is my goal in designing a simple rocket and documenting its construction to make it easy for others to replicate my results.

CarVac said:

A looooooong rail would be very important for the E flight.

Click to expand...

About 130'-long rail would do nicely.

o1d_dude said:

You have indeed become the TubeFather of TRF.

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Now now Kit. It will take me a long time to surpass you. I'm really looking forward to seeing you at a launch soon.

Salvage-1 said:

What max speed did it hit on the M?

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It may be hard to tell with transonic noise. I have posted both graphs and raw altimeter data along with photos of each flight though, so you know as much as I do.

chris m said:

Hey iter what was the length of the air frame . I'm trying to get proportions right on a few of my 4" tube fin rockets thanks Chris

Click to expand...

The fuselage is one uncut length of 3" blue tube. It comes in 48" lengths, so that's how long the fuselage is. Simple and easy to replicate :=)

Ari.

A fantastic achievement, Ari! Very, very well done!

Later!

--Coop

Looking at this it seems around 1775ft/sec, or 1200ish mph. That could be the fastest tube fin so far, and may knock the 500mph limit completely in the head. From throwing together the design in Rocksim, it seems to sim around 1200ft/sec, still damn quick!

Again, major kudos and congrats.

Ok thanks so I'm thinking a 60" airframe is very doable in 4" . Thinking just the tube fin length was the flaw in my super evil minion

For those who are asking--here's my OR file.

I'd like to hear more opinions on the actual top speed from baro data. I hear all kinds of noise happens around Mach that makes it hard to read graphs. I have very little experience with supersonic baro graphs and don't know what to make of the wiggles. before and after max velocity. The highest number in the file itself is 1760.

Ari.

View attachment bluefin-tuba-3.ork

the file looks good . didn't know if you put the profile of the tube fin to get it to work . was thinking each fin would to be three fins in a sim to shown cd . also why are they 6" tall thanks chris

iter said:

Thank you for your encouragement Kit.My approach to landing damage control is right-sizing chutes :=)

As far as Mach, I doubt a tube fin can punch though. OTOH, it's unclear to me that one must disintegrate when it gets close. The 1.5" BFT survived a J510 which simmed to Mach 1.33.

Ari.

Click to expand...

A tube fin could totally punch through Mach. As many have surmised, however, the highest drag is at transonic where there exists a normal shockwave at or just inside the inlet to the tube fin. After you hit a certain critical Mach number, the tube fin will "swallow" the shock and you will be left with a less draggy oblique shock at the inlet. The trick is that you need to hit it with a very high thrust motor to punch through. Maybe try an altimeter with an accelerometer the next time you fly on an M?

iter said:

For those who are asking--here's my OR file.

I'd like to hear more opinions on the actual top speed from baro data. I hear all kinds of noise happens around Mach that makes it hard to read graphs. I have very little experience with supersonic baro graphs and don't know what to make of the wiggles. before and after max velocity. The highest number in the file itself is 1760.

Ari.

Click to expand...

From the data, it seems clear that the rocket accelerated through mach about 2.5 seconds into the flight and then decelerated back through the transonic regime (roughly mach 0.8 to mach 1.2) sometime >6.5 seconds into the flight. That would certainly explain the two very large dips in velocity that were picked up by the baro sensor.

This is pretty cool, because it means that a Bluetube fin of approx 1.3 length diameter ratio seems to be able to withstand the transition.

I would recommend flying the Tuba with a Raven3, or if John ever brings it into production try an Altimeter3. You are likely to get better speed from integrating accelerometer readings in the early stages of flight and particularly through mach than you are by taking the derivative of barometrically-measured altitude, although as time progresses the integration becomes subject to some drift.

This rocket gets cooler every time I read about it.

chris m said:

didn't know if you put the profile of the tube fin to get it to work . was thinking each fin would to be three fins in a sim to shown cd . also why are they 6" tall thanks chris

Click to expand...

Fin edges are square. I made no effort to reduce drag. BFT3 has very thick rail guide standoffs and an atrocious retainer. Retainer is a full 3/4" wider than the fuselage. BFT3, as it stands, optimizes for versatility, durability and quick turnarounds--Aeropack retainers are great for that. To optimize for performance, I'd airfoil the fins, remove rail guides and use a tail cone closure on the motor. This would require a bulkhead in the fuselage and would make it harder to use smaller motors (still possible, just extra fixture and extra time to turn around). I'd make up a kind of tower with 6 cantilever square tubes that would each go through a fin and hug the fuselage.

Size of fins is very approximate in my OR file. I try to get the cross-section area about right, but beyond that getting them close makes little difference. I know the rocket is going to be stable, and when I'm far enough along in the build, I override mass and CG. I try to get drag and total weight right--these are important in simulations. They are 6" tall as an approximation between Pi*3" "unrolled" area and 3" "projected" area. Their equivalent stabilizing area is somewhere between these two numbers.

TheAviator said:

A tube fin could totally punch through Mach.

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I love how quickly accepted wisdom changes. A week ago the consensus was opposite.

wfcook said:

This rocket gets cooler every time I read about it.

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That's pretty much my feeling, too :=)

Here are a couple of final photos, now that I cleaned everything up from that trip.

Ari.

Ari flew Bluefin-Tuba on a G80 blue, H115 sparky, I350 black, J316 pink, K695 red, L645 green, M650 white
at Aeronaut 2014 in Black Rock last weekend. He did it all in one day (7 hours (10 am to 5 pm))

That ~ 2 orders of magnitude difference between the total impulse of the smallest and largest motors.

(order of magnitude Log10(10,000/80) ~ 2.1)

Here's the "Documented Proof" :surprised:
G80 blue:
View attachment 180529

H115 sparky:
View attachment 180530

I350 black
View attachment 180531

J316 pink:
View attachment 180532

K695 red:
View attachment 180533

L645 green:
View attachment 180534

650 white:
View attachment 180535

Peter "Cardboard, it not just for breakfast anymore" Hackett

iter said:

I love how quickly accepted wisdom changes.

Ari.

Click to expand...

Unfortunately, I didn't see this thread until recently. I said you could do it, but it takes some serious brute force. No finesse here.

This is amazing. Did you use adapters until the minimum diameter L and M?

I am sure that there are some esoteric numbers associated with this BlueFin Tuba. Correct size of fins, right length ratio, etc. I for one can't see those numbers, but these flights will most probably lead to some of us tubefinatics to play around and send more of these beasts through Mach (or shred trying).

Everything about this rocket is cool. Everything.


Sent from my iPhone using Rocketry Forum

SCrocketfan said:

This is amazing. Did you use adapters until the minimum diameter L and M?

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Yes. I made my own 75-to-38mm adapter to save weight for lower-letter flights and to add a recovery attachment point.

BFT3 uses an Aeropack retainer. I have allAeropack adapters down to 29mm and they all nest. You can use this Russian Doll arrangement on BFT is you either add a hardpoint in the fuselage, or use threaded closures on all your motors.

BFT has no hardpoints for attaching a shock cord. Instead, I use eye-bolts in forward closures and attach shock cord directly to the heaviest part of the rocket--the motor. Now some of the smaller motors I use have no provision for threading the forward closure. AT single-use motors and CTI 38mm motors are equally problematic in this respect. My home-made adapter solves this problem. It's piece of 38mm MMT with two 75mm OD CRs, a 38mm Aeropack retainer on the bottom and an anchor point on the top. With this, I can use any 38mm motors or 29mm (with Aeropack adapter) regardless of threading. I can also use motor deploy with these motors, or motor backup as I did in last week's flights.

Wtih 54mm motors, I use a standard Aeropack adapter, as the K695 in the last photo (5th from left) demonstrates.

Ari.

Thanks. One more question, how long are the fins? I think I might try building one of these.

Well done, Ari.
The project as a whole, the planning and logistics, the rocket itself, the flights!!, and the excellent documentation in this thread.
Very well done.

thank you for sharing it with us.
s6

SCrocketfan said:

Thanks. One more question, how long are the fins? I think I might try building one of these.

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Fins are 3.5" long.

Ari.

Great job! I told my buddy about your rocket & he had a hard time believing what you did with it.

Ari -

I have video of your Bluefin Tuba cluster launch at Moffett on the 18th. I'm not sure if it's any better than the video you posted to youtube already. I'll can send it your way if you want it.

-RB

Please do Robert. I'm pretty sure what happened, but I like another point of view regardless.

I put a 7-motor BP cluster in BFT on Saturday (6xD12 + 1xF15) and one of the Ds CATOed. It looks pretty bad. There's thermal damage inside the fuselage. I'm unclear on how much weaker the airframe is now. In a way, this rocket has already accomplished what it set out to do. In a different way, I was looking forward to having this as my "go to" rocket at club launches.

Ironically, all 7 motors lit properly and simultaneously. One of them just lit too well. In the photo sequence you can see the rocket actually going up on 6 motors until it overtakes its own ejected nosecone. I'm sad.

[video=youtube;cf0Fc2RGqRs]https://www.youtube.com/watch?v=cf0Fc2RGqRs[/video]
www.youtube.com/watch?v=cf0Fc2RGqRs

Ari.

iter said:

Please do Robert. I'm pretty sure what happened, but I like another point of view regardless.

I put a 7-motor BP cluster in BFT on Saturday (6xD12 + 1xF15) and one of the Ds CATOed. It looks pretty bad. There's thermal damage inside the fuselage. I'm unclear on how much weaker the airframe is now. In a way, this rocket has already accomplished what it set out to do. In a different way, I was looking forward to having this as my "go to" rocket at club launches.

Ironically, all 7 motors lit properly and simultaneously. One of them just lit too well. In the photo sequence you can see the rocket actually going up on 6 motors until it overtakes its own ejected nosecone. I'm sad.

[video=youtube;cf0Fc2RGqRs]https://www.youtube.com/watch?v=cf0Fc2RGqRs[/video]
www.youtube.com/watch?v=cf0Fc2RGqRs

Ari.

Click to expand...

A tragic end(?) to an inspiring rocket.