Bluefin Tuba

Plenty of room on all we have used it on. Since the smaller nosecones can use smaller thread it will work.

iter said:

BFT flew today on an F50-4, I'd say about 800'-900'. Ejection timing is near-perfect. Sadly, all I have is a post-flight photo, but I like it nonetheless :=) Ari.

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How big of a chute is that, it looks quite large? Is that because of the terrain this launch was at? Looks like an airfield ( lots of asphalt)? Did you go with a lower lug or use your thru the tube fin idea?

Too late for first launch--today's mail brings SticketShock vinyl. Leah helps me apply it.

Rrwjr said:

How big of a chute is that, it looks quite large? Is that because of the terrain this launch was at? Looks like an airfield ( lots of asphalt)? Did you go with a lower lug or use your thru the tube fin idea?

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We fly at KNUQ/Moffet field. It's all concrete. A design goal for BFT is to be indifferent to this surface. I have nice rockets I refuse to take to Moffett. Concrete is like 3-grit paper. Does terrible things to finishes. The chute is from a Mega Red Max kit (I think 30" nominal). MDRM is one rocket I absolutely cannot take to Moffett. Leah and I put too much effort into finishing it (in pink) to drag it over concrete.

Ari.

P.S. I see pink MDRM snuck into the last photo. That's the parachute donor (it has a 36" black chute).

Very nice Ari and Leah!

Very nice work, and your little girl is adorable.

iter said:

Now I've seen an M2200 (or M3000?) shred the fins off a 6" Kraken. This is significantly more thrust per much thinner fin. 6" BT is about as thick as 38mm, but with 4 times the circumference. Kraken has 4 fins, meaning each has a single connection point to fuselage--unlike the 6-pack arrangement where each fin supports the two next to it. Again, no predictions, just trying to convince myself I'm sane.Ari.

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Cool looking rocket.

I think your right about both those points. Looking back on the 6" Kraken, I'm sure the wall thickness to tubing diameter along with the Kraken having freestanding tube fins was never going too handle a M2020 . I didnt really take that into account after launching a 3" BlueTube Kraken on a bunch of K's with no problem

In reading over the thread, I see you mention using the upper rail button mount to hold the recovery train. From the picture of Leah at Moffett it looks like you used paracord for the shockcord. How did you attach it inside the body tube?

I ask because...who doesn't need another tube fin rocket, right?

I use an 8-32x2.5" machine screw that goes all the way through the body tube and screws into a blind t-nut on the other side from the rail button (t-nut is on the outside of the rocket). To this screw I tie a loop of kevlar shock cord which in turn quick links to the parachute and NC. The rail button is far enough from top of rocket to make it difficult to use a normal nut inside the BT, and I want to keep it low enough to let the entire laundry to sit above it lest the laundry hangs up on the bolt.

Does this description make any sense? I'll try to photograph this arrangement when I get home.

Ari.

Iter I have a question about tap plastics isp weld on and hdpe . But your in box is full

chris m said:

Iter I have a question about tap plastics isp weld on and hdpe . But your in box is full

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Hah, so it is. Thank you for pointing it out. It now has room for new messages.

You may wish to ask your question in the sewer pipe rocket thread: https://www.rocketryforum.com/showthread.php?58482-Ari-s-6-quot-PVC-sewer-pipe-tube-fin-L3-rocket

Ari.

iter said:

I use an 8-32x2.5" machine screw that goes all the way through the body tube and screws into a blind t-nut on the other side from the rail button (t-nut is on the outside of the rocket). To this screw I tie a loop of kevlar shock cord which in turn quick links to the parachute and NC. The rail button is far enough from top of rocket to make it difficult to use a normal nut inside the BT, and I want to keep it low enough to let the entire laundry to sit above it lest the laundry hangs up on the bolt.

Does this description make any sense? I'll try to photograph this arrangement when I get home.

Ari.

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That makes sense and goes along with what I thought...didn't think of the blind nut on the other side, tho.

I imagine fitting the laundry into the 38mm tube is a bit tedious.

BFT flew on Estes BP E15-4 last Saturday. The delay is a tad long, but the flight is a success nonetheless.

This positively establishes the lower bound for motor classes BFT can fly on. Waiting for a Snow Ranch to test upper bound. Even a G puts BFT above Moffett's 1,000' ceiling. Looking for J.

Ari.

Great range of motors on your build . Great job , love not doing the norm

Flew BTF on an I140 today at Snow Ranch. Excellent flight but I almost gave up on it landing in our field. J270 is going to have to wait until I add DD to BFT. It just drifts too far when you put it over 2,500'. Ultimately, landing distance on an I is manageable as the photo shows, but the nail-biting trying to keep visual track of a small rocket is uncomfortable.

Ari.

I see my truck in behind the port-o-lets in the second picture. LOL!

That was a long hike to retrieve your bird.

Sad we were in such a hurry yesterday and didn't stop to talk. Did you get any flying done Kit?

Ari.

BFT flew and safely recovered on a J270 DMS today at Snow Ranch. This rocket has now flown on motors from E to J.

Ari.

How high? How fast?

Also, wow. 6 motor classes...

CarVac said:

How high? How fast?

Also, wow. 6 motor classes...

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No idea. No electronics. OR sims to 3,750, M.99 and 32G.

Ari.

The video I took of it today only shows the smoke trail, I280 simmed to 30 Gs and 3,200'. FrSky telemetry, if I trust it, says it broke 5,000'. If that's true, it probably left the pad faster than 30 Gs as well.

Graph is in meters (I don't know how to switch it to feet). RSSI drops dramatically at launch, then shows weaker but consistent inverse correspondence with altitude.

Photo shows telemetry display with last reading of 88' before the rocket went behind a hill and a maximum alt reader of 5,056' (I know how to switch the TX to feet).

Ari.

BFT had 2 nice flights at MudRoc, a demo DMS H45 and a J510.

J510 is significant in being the largest accessible certified 38mm motor. This is physically the most impulse that can fit in this rocket. Bluefin Tuba can now officially take anything I throw at it.

Ari.

Is that asphalt your club is launching on? Wow and I thought the dry lake bed was rough.

Some of the earlier flights are at Moffett, where we fly on a concrete taxiway. This weekend's flights (for which the forum won't let me post photos) are at Black Rock. Lake beds are only a little softer than concrete.

Ari.

So it most likely exceeded Mach?

CarVac said:

So it most likely exceeded Mach?

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Hard to say. The sim says it did (M1.4), but the sim has a hard time with tube fins. I hear that shockwaves reflect off open cylinders and make them act as closed ones in terms of drag. If that's true, the rocket spent much of the burn butting up against M1.0; in any case, it survived impressive aerodynamic loads with just yellow wood glue.

Ari.

I build one of these and flew it on a 38mm G something. It went like stink but the way I mounted my shock cord wasn't as robust as yours and broke clean into. The body fell gently back but the Pinnacle nose cone and chute drifted away never to be seen. The only other change I made was the glue, I used epoxy because that's what I had. I will rebuild it soon, it was a fun flight. It's nice to have a rocket that I have very little time invested into, it's almost expendable.

Now the image upload seems to work again, here are the photos from Black Rock. H45 and J510.

Ari.

CarVac said:

How high? How fast?

Also, wow. 6 motor classes...

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Wow, yeah; a 6 motor impulse range in one rocket. Impressive.

Would you be willing to post your OR file? I'm very intrigued by this rocket and it's ability to take an y motor you can put in it.

Sure, here it is. OpenRocket can't do tube fins. I simulate them with long, thick straight fins so that total cross-section is roughly equivalent. This is only a coarse approximation of course, and completely unreliable as you approach compressibility.

Ari.

View attachment bluefin.ork