Parallax Terror: Tubes galore!

Today I started a small rocket for 29mm (and maybe 38mm, depending on the retention situation) motors. It's made up of 38mm Blue Tube, and it has tube fins.

A lot of tube fins.









I plan to have two complete rows around, with gaps in place of two of the standard six for launch rail clearance (and symmetry).

Unlike most of my builds, this one is going to be by the seat of my pants. I have thought about it a lot, but nothing concrete has gone into simulation yet and so I'll be making it up as I go along. I'm probably going to use a 38-29 Slimline Tailcone retainer, because they look really sweet, but if I can come up with a good way to make it removable I might use it as an adapter rather than as a permanent feature.

Very cool I will be following this

Welcome to the tube side.

Ari.

Another t00b d00d joins our little club! Everybody cheer!!

Release the Kraken..... whoops.... release the Tubie!!!

Watching this !

Yeah, tube fins are addictive, watch out! I have now been convinced (didn't take much) to do my L3 on a BDR4.0 tubie.

Salvage-1 said:

Release the Kraken..... whoops.... release the Tubie!!!

Watching this !

Yeah, tube fins are addictive, watch out! I have now been convinced (didn't take much) to do my L3 on a BDR4.0 tubie.

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Yes I'm thinking a 8-12" tube fin for my L3 should be cool

I originally was surprised that nobody (to my knowledge) has made a two row tube fin rocket, but when (hand-) miter sawing all sixteen tubes I realized why. It takes a lot of tubes. And it will be hard to align. That is why I am taking it slow and only doing a few at a time.

Larry brand did a few of them . Don't remember how they did ,will re-read his paper

I just added the two opposing tubes.

I just posted my plans for my L3 build 10" 10.5' tall

I did this yesterday. Next I will do 4 at a time.

OK, now I understand your idea of double rows. This looks cool. I wonder if you expect any particular benefit out of this configuration, or just doing it for aesthetics.

Ari.

iter said:

OK, now I understand your idea of double rows. This looks cool. I wonder if you expect any particular benefit out of this configuration, or just doing it for aesthetics.

Ari.

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Pretty much only aesthetics. It will be like a honeycomb grid fin on the back of the rocket.

CarVac said:

It will be like a honeycomb grid fin on the back of the rocket.

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Now that the build is taking shape, I see your intention.

Looking forward the the flight report!

I wonder how this grid fin is going to take bending moments. Your grid is relatively wide and thin, I wonder if drag can bend the whole grid back at high Q. So far I have been unable to break a Blue Tube fin with aerodynamic forces.

Thank you for experimenting and increasing our body of knowledge Carlo. I'm looking forward to your experimental results.

Ari.

iter said:

Now that the build is taking shape, I see your intention.

Looking forward the the flight report!

I wonder how this grid fin is going to take bending moments. Your grid is relatively wide and thin, I wonder if drag can bend the whole grid back at high Q. So far I have been unable to break a Blue Tube fin with aerodynamic forces.

Thank you for experimenting and increasing our body of knowledge Carlo. I'm looking forward to your experimental results.

Ari.

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I don't anticipate sticking a J in it, so it probably won't ever see supersonic speeds. I have only a 5k foot waiver at my main field, after all. Depending on how intensely draggy it is, I might try an I though.

You can always go for the H999 :=)

Ari.

iter said:

Welcome to the tube side.

Ari.

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Everyone must make a personal choice --- Tooby, or not tooby? That is the question.

CarVac said:

I originally was surprised that nobody (to my knowledge) has made a two row tube fin rocket, but when (hand-) miter sawing all sixteen tubes I realized why. It takes a lot of tubes. And it will be hard to align. That is why I am taking it slow and only doing a few at a time.

Click to expand...

I can relate. I'm building a variation of Ari's 38mm bluefin tuba, but I decided to mitre the leading edge if the tube fins at 30 degrees.

Yikes! They have to be EXACTLY the same and they have to be aligned perfectly. Otherwise it looks very obviously wrong!


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wfcook said:

I can relate. I'm building a variation of Ari's 38mm bluefin tuba, but I decided to mitre the leading edge if the tube fins at 30 degrees.

Yikes! They have to be EXACTLY the same and they have to be aligned perfectly. Otherwise it looks very obviously wrong!

Click to expand...

My secret to perfectly aligning tube fins is out!

Looking forward to your build. Is there a thread?

Ari.

iter said:

My secret to perfectly aligning tube fins is out!

Looking forward to your build. Is there a thread?

Ari.

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Not yet, but I suppose I can do one. It'll be sloooooooooowwwww...


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iter said:

My secret to perfectly aligning tube fins is out!

Looking forward to your build. Is there a thread?

Ari.

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I might stick a few posts at the end of your BFT thread if you don't have objection. I'm not sure there is enough complexity in the build of this rocket to merit an entirely separate thread, and it is certainly going to be a derivative work.

This time I had to use clothespins.

Clamps ,rubber bands and tape is your friend with tube fins .

CarVac said:

This time I had to use clothespins.

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I wish I had thought of this. I like it.


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Looking good!

Clothespins are in just about every one of my build threads.

Ari.

As I mentioned, this is done by the seat of my pants. Thus, I just now made a measurement and determined that a Loki 38/1200 will fit. Somehow I think that would be a bad idea though...

I also decided that I can retain the motors using shock cord and a knot just in front of a removable forward bulkhead. This will require plugged closures in 38mm, but in exchange I don't have to glue anything into the center of the tube and I won't have to deal with a set of variable length extenders, just retying a knot each flight. I think this idea has come to me before, but not while making a minimum diameter rocket of applicable size. (and optimized for minimum size around one motor)

Or you can omit the bulkhead altogether, as I did on BFT3. You can use tape to retain the motor and tie recovery straight to the forward closure as you're saying. The worst that can happen is rear ejection--motor flies out, drags chute with it. You just need to make sure there's enough shock cord above the chute so it can come out of the tube from either end.

Ari.

You should probably consider a large parachute to keep your descent speed slower than normal.

Tube fins (the fins themselves not the rockets) tend to be susceptible to angular impacts with the ground and they will shear off or shatter. Having an outside band of tube fins as you're building will probably make that tendency a bit more problematic.

OTOH, go for it. Maybe well all learn something from the experiment.

o1d_dude said:

You should probably consider a large parachute to keep your descent speed slower than normal.

Tube fins (the fins themselves not the rockets) tend to be susceptible to angular impacts with the ground and they will shear off or shatter. Having an outside band of tube fins as you're building will probably make that tendency a bit more problematic.

OTOH, go for it. Maybe well all learn something from the experiment.

Click to expand...

I have a 30 inch that should be generous for a soft east coast farm landing, I hope. I am going to offset the less strongly attached ones forward to protect them from landing damage: these will be the corner pieces that are over the missing tubes.