Neil_W's half-baked design thread

neil_w said:

Great minds apparently think alike;

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Whenever I said that, my friend in college would say: "Well, yeah, and so do ours."

mbeels said:

A design change you could consider is rear eject, that would bring it down nose first. And also let you have a seamless front end.

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Hmmmmmm. @BABAR would approve. I would have to ditch the tail cone, but that wouldn't be a major loss.

I'm just so darned squeamish about rear eject, feel like I should be using it only when absolutely necessary. Probably because I haven't used it before.

I think I am leaning towards attempting slots in the pods as discussed, and just making them Strong.

mbeels said:

Whenever I said that, my friend in college would say: "Well, yeah, and so do ours."

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LOL.

neil_w said:

Hmmmmmm. @BABAR would approve. I would have to ditch the tail cone, but that wouldn't be a major loss.

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You could keep the tail cone, it would become the thrust ring that transferred the thrust from the motor tube to the main body tube. So there would be one seam between the main fins and the tail cone.

I've done rear eject twice, my second attempt worked much better than my first attempt. Done right, it can do a decent job isolating the parachute from the heat of the ejection gasses.

My first attempt had the recovery gear too close to the motor, and the heat of the motor melted things. My second attempt had a long motor tube so the parachute sat well above the motor, but below the top of the motor tube. I'll see if I can come up with a drawing....

Well, one downside is that rear eject eliminates the possibility of doing through the wall fins. But perhaps the fins don't need to be as strong. Egh, tradeoffs....

Everything red would pop out the back.



EDIT: NOT REMOTELY TO SCALE

Notching the nose cone shoulders then cutting the BT-5 is a method of what I was going to suggest, which is mortising the pod. Another method, which I would use, is to remove most of the material with a drill the clean up then sides with a #18 X-Acto blade, all after gluing the pod up. But then I have a drill press for the first part.

mbeels said:

Whenever I said that, my friend in college would say: "Well, yeah, and so do ours."

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My standard reply with my wife is "and fools come in pairs."

neil_w said:

Hmmmmmm. @BABAR would approve. I would have to ditch the tail cone, but that wouldn't be a major loss.

I'm just so darned squeamish about rear eject, feel like I should be using it only when absolutely necessary. Probably because I haven't used it before.

I think I am leaning towards attempting slots in the pods as discussed, and just making them Strong.

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Another alternative is to put the break just forward of the motor mount and have a long shock cord with the chute attached near the fin can end. Then the fin can hits after the nose cone/upper body and is moving slower. This takes some more care with packing the chute.

boatgeek said:

Another alternative is to put the break just forward of the motor mount and have a long shock cord with the chute attached near the fin can end. Then the fin can hits after the nose cone/upper body and is moving slower. This takes some more care with packing the chute.

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That's an interesting idea. So if I understand this correctly, the 'chute is not blown out of a tube, but instead pulled out of the top section?

boatgeek said:

My standard reply with my wife is "and fools come in pairs."

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Heh! My wife usually says: "No! Great minds think for themselves."

mbeels said:

Well, one downside is that rear eject eliminates the possibility of doing through the wall fins. But perhaps the fins don't need to be as strong. Egh, tradeoffs....

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If you have the pop pod in an intermediary tube, and center that in the main body tube, you can have TTW fins connecting to the intermediary tube with rear ejection. Best of both worlds. Cons are that most rear ejection layouts limit the space for the recovery device, so best suited for larger diameter rockets.

kuririn said:

If you have the pop pod in an intermediary tube, and center that in the main body tube, you can have TTW fins connecting to the intermediary tube with rear ejection. Best of both worlds. Cons are that most rear ejection layouts limit the space for the recovery device, so best suited for larger diameter rockets.

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Yeah, not enough room for the intermediate tube here. However, if it weren't coming down tail first it wouldn't need TTW.

In this case I think I'd rather try to make it strong than to make it rear-eject. I'm quite nervous about slotting the nose cone shoulders but will give it a try (when I get to it).

I bet that those pods, on those fins, being through the wall, will survive a landing in grass. Perhaps with a generously sized parachute.

I just checked and even with basswood fins I'll have plenty of stability. So: 3/32" TTW Basswood fins, slotted into the pods. Sounds good.

Now back to seeing what I can do with the pod paint scheme...

Ditching the color on the tips and going all black wouldn't be bad, but I do see why you like them. Matching the grey or silver of the tubes could work. Or whatever color you've got on hand that contrasts with the yellow in the decals is better that not quite matching. Alcbierre Red would look good, for example.

Edit: I should never never skip proofreading when I'm posting from my phone or tablet.

Also, I was thinking about your hesitancy about rear ejection due to never having done it. You should dive in; make a simple 3FNC with rear eject out of spare parts, just to give it a try. (I confess to 1: being a pot, and 2: calling a kettle black until I make a card stock transition.) It may not be the answer here anyway.

neil_w said:

Yeah, not enough room for the intermediate tube here. However, if it weren't coming down tail first it wouldn't need TTW.

In this case I think I'd rather try to make it strong than to make it rear-eject. I'm quite nervous about slotting the nose cone shoulders but will give it a try (when I get to it).

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There is some middle ground here.
I don’t have time at the moment to do a drawing, so I will try to describe.

Start with @mbeels post 994 (btw, we are over 1000 posts here!)
Take the chute out and leave the motor mount exactly where he puts it, except.....

Glue both the current centering rings to the mount AND the fin can body tube segment.

Extend the motor mount tubing ALL the way to the FRONT OF THE ROCKET. and I MEAN all the way. Cut the base of of the nose cone if it’s plastic, glue nose cone in place, put some JB Weld on the inside tip of the cone to protect it. Better yet, put a baffle far forward in the extended mount tubing. Now you can glue a shock cord into the inside tip of the nose cone. Baffle will protect shock cord nose section attachment from blast.

Add a centering ring around the motor mount just aft of the glued in nose cone, glued ONLY to the mount.

Here’s the fun part. “Where is the split/separation point?” , you ask. Thank you for asking.

Just in front of the fins.

Here’s how it works.

Cut the tube just in front of the fins.

Put a coupler in the forward part of the fin unit, glued TO the fin unit, the fin unit/motor mount are a single unit that will slide into (and out of) the main body tube/nose cone unit.

You now have a VERY long compartment between the current GLUED IN motor mount forward centering ring and the far forward centering ring, should give you plenty of room for a chute, loosely packed (bonus— no wadding needed!)

Attachment points

Nose cone section is inside the nose cone through the forward sliding centering ring. This section is LIGHT, ONLY THE WEIGHT OF THE NOSE CONE AND BODY TUBE.
Second is through the forward glued centering ring, so CG with the forward weight makes this dangle forward end down, fin unit up. Initial impact is tube, not fins. Would be a good candidate for that heavy duty tubing I think Odd’l rockets is selling (?? @hcmbanjo ??)


Here’s the beauty of it.

If you need nose weight, put it on the front of the motor mount, forward of the centering ring, at launch this is inside the hollow cone.

At launch, load up your motor.

daisy Chain nose section shock cord and drop it in body tube/nose section.

Slide motor mount half way, and the slide parachute in between mount tube and outer body tube/nose section.
Then daisy chain second shock cord in between sections.

Now fully insert mount with coupler.

Launch rocket.

At ejection, gas is ducted forward, cooled by baffle, shove the fin can motor mount out the back.

Chute deploys (hopefully.)

Motor mount and fin can dangle from chute. CG is FORWARD so descends forward end first

Body tube/nose cone dangle from front of motor mount. Mass is less, so impact on cone tip (one downside of rear eject) is lessened.

Favor to ask: how does the model with two small oval sold white “”eye spots” on on each side just at the base of the cone?

BABAR said:

Would be a good candidate for that heavy duty tubing I think Odd’l rockets is selling (?? @hcmbanjo ??)

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The Heavy Wall BT-20 tubing is only available from JonRocket.com
https://jonrocket.com/index.php?mai...result&search_in_description=1&keyword=BT-20H

Some vendors were concerned about confusion between the regular BT-20 and the heavier walled BT-20.
It only takes a little peel of the inside of a centering ring or sanding the inside of a larger flat ring for a perfect fit.
After you've used the heavier tubing (for sport flying and the Q-Jet C and D motors), you won't want to go back to the thinner tubes.

BABAR said:

(btw, we are over 1000 posts here!)

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I don't know whether to be pleased, embarrassed, or full-on horrified.

I think I see what you're proposing. Sort of a pop-pod that starts in front of the fin can.

Favor to ask: how does the model with two small oval sold white “”eye spots” on on each side just at the base of the cone?

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I'll get that for you later. It just occurred to me that the chevron design is almost sort of fish-scale-like... except they're pointing the wrong way. If I turned them around and rounded them it could definitely be suggestive of scales. I'll try that too when I get a chance.

hcmbanjo said:

After you've used the heavier tubing (for sport flying and the Q-Jet C and D motors), you won't want to go back to the thinner tubes.

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I've completely switched over to heavy-walled BT50, don't build 18mm mounts too often so I haven't had a chance to try the heavy BT20 yet.

neil_w said:

I don't know whether to be pleased, embarrassed, or full-on horrified.

I think I see what you're proposing. Sort of a pop-pod that starts in front of the fin can.


I'll get that for you later. It just occurred to me that the chevron design is almost sort of fish-scale-like... except they're pointing the wrong way. If I turned them around and rounded them it could definitely be suggestive of scales. I'll try that too when I get a chance.


I've completely switched over to heavy-walled BT50, don't build 18mm mounts too often so I haven't had a chance to try the heavy BT20 yet.

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Here's a trick for rear ejection recovery models.

The major PROBLEM with rear eject versus standard forward eject is SPACE. Specifically, often there is not that much space between the inner motor mount tube and the outer body tube to pack a chute , except for Fat rockets. Too tight and it's a PITB to pack, and may not successfully eject. Packed correctly, it should almost fall out by itself just when you hold the rocket by the outer body tube pointy side up.

You can however "downsize" the forward end of the internal tube, so say you have a 24mm motor mount BT-50. You can use a SINGLE centering ring to downsize this to BT-20 (if you have room, do this around 6 inches above the forward end of the engine, otherwise the ejection blast will burn the smaller diameter smaller tube. If you DON'T have room, stick it just in front of the engine and roll up a piece of aluminum from a can inside the BT-20----- yes, I know aluminum burns, but it doesn't catch fire in the short time it is exposed to the ejection charge and WILL protect the smaller diameter tube.) Since this is all internal and not exposed to airflow, you don't need any smoothing outer transition.

You will still need a second FORWARD centering ring (inside smaller tube to outside BODY tube, not motor mount), glued to the inside tube but NOT the outside tube, both to keep the tube centered at it's forward end AND to protect the chute from ejection charge "back blast", the hot gases blowing back from the nose cone (which are what will push your motor mount/extended tube rig out the back of the rocket.)

You can (IOW, I HAVE) even go down to BT-5.

The above GREATLY increases the available space for parachutes and streamers in rear eject models.

The DOWN side of downsizing the tubes is the (standard) smaller tubes aren't as strong, and particularly if you put extra weight on the forward end (which is inside the nose cone in launch/ascent configuration, a great way to improve CG on boost gliders during boost and completely take the weight out at deployment) may fold up on you over time. SO this is where @hcmbanjo 's tubing might help you out.

https://jonrocket.com/index.php?mai...result&search_in_description=1&keyword=BT-20H

Regarding fish scales, it's your rocket. The "blackfish" actual refers to Orca/Killer whale. So eye spots wouldn't work (at least from an animal classification standpoint) with scales.

BABAR said:

Regarding fish scales, it's your rocket. The "blackfish" actual refers to Orca/Killer whale. So eye spots wouldn't work (at least from an animal classification standpoint) with scales.

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Whoops, didn't realize that, even though you mentioned it way back when. Certainly the current design is not Orca-like, but I'll see if I can find some Orca-eyes to put on front as a test.

Oh, you were asking for the eye spots. Damn I need to learn how to read.

(Need to get this back to orange)

Not sure if the eye spots go with the rest... Actually I hadn't realized that the word "Blackfish" was almost exclusively tied to SeaWorld and that movie... makes me wonder if the whole thing shouldn't be more Orca-ish... but I really like this design. I guess the name doesn't have to be literally tied to the paint scheme. Hrmph.

The Stan Rogers song "Free in the Harbor" states "The blackfish are sporting again... untroubled by comings and goings of men who once did pursue them as oil from the sea..." Stan was generally a reliable source, through his songs, on the subjects he chose to sing about. And yet, according to Wikipedia, Orcas provide very little oil and were not widely hunted.

Therefore, we must conclude, that "blackfish" refers to a different species of whale. Any Google search for blackfish yields results dominated by stuff about the (widely discredited) movie, so I haven't been able to determine what whale species. I suspect the North Pacific Right Whale, as it was indeed very widely hunted, and specifically for its oil.

Hmm, maybe. However the rocket is currently not whale themed *at all*. Do I care? Not sure. I like the name and the design, only question is whether they belong together.

As I stated it is your rocket. Put scales on it. Put spikes on it. Put a thagomizer on it. No matter what you do we're going to like it. Surprisingly the word thagomizer actually was recognized by my voice recognition system

BABAR said:

Surprisingly the word thagomizer actually was recognized by my voice recognition system

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Now that is the weirdest thing I’ve heard today.

neil_w said:

Now that is the weirdest thing I’ve heard today.

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The Far Side is a part of our culture. Gary Larson is brilliant!

BABAR said:

As I stated it is your rocket. Put scales on it. Put spikes on it. Put a thagomizer on it. No matter what you do we're going to like it. Surprisingly the word thagomizer actually was recognized by my voice recognition system

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Hey, man the thagomizer is on my rocket! Stop encouraging Neil to steal my brand--he'll only make me look bad by comparison!

According to the dictionary, blackfish is either a dark-colored fish or a small toothed whale such as a pilot whale though Wikipedia says that the term applies to all large members of the dolphin family, of which orcas are a member. I always thought of term as applying to orcas, but also sort of generally as a large hunting whale/dolphin. That goes pretty well with the design and paint scheme as you have it.

This has been a post by Captain Technicality. You're welcome.

This started it all.

boatgeek said:

Hey, man the thagomizer is on my rocket! Stop encouraging Neil to steal my brand--he'll only make me look bad by comparison!

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I was going to mention that the thagomizer was going to be on Stage-a-saurus but I couldn't remember whose rocket that was and was too lazy to go look.

I think if Blackfish at least refers to some creatures other than Orcas (other cetaceans, fish, or whatever), then I'm ok where I am. But if Blackfish were specifically a nickname for an Orca than I be reluctant to go with the given paint scheme.

boatgeek said:

Hey, man the thagomizer is on my rocket! Stop encouraging Neil to steal my brand--he'll only make me look bad by comparison!

According to the dictionary, blackfish is either a dark-colored fish or a small toothed whale such as a pilot whale though Wikipedia says that the term applies to all large members of the dolphin family, of which orcas are a member. I always thought of term as applying to orcas, but also sort of generally as a large hunting whale/dolphin. That goes pretty well with the design and paint scheme as you have it.

This has been a post by Captain Technicality. You're welcome.

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Mea culpa, actually I knew someone recently had referred to the Thagomizer in a recent build, I should have looked it up and credited you accordingly. Hope your full two stage flight goes well!

neil_w said:

I was going to mention that the thagomizer was going to be on Stage-a-saurus but I couldn't remember whose rocket that was and was too lazy to go look.

I think if Blackfish at least refers to some creatures other than Orcas (other cetaceans, fish, or whatever), then I'm ok where I am. But if Blackfish were specifically a nickname for an Orca than I be reluctant to go with the given paint scheme.

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I thought your original design looked a bit like an Orca, and thought of the name from the documentary on captive Killer Whales, Called “Blackfish”. It is a disturbing movie, but I do recommend it, just keep an open mind.

neil_w said:

I think if Blackfish at least refers to some creatures other than Orcas (other cetaceans, fish, or whatever), then I'm ok where I am. But if Blackfish were specifically a nickname for an Orca than I be reluctant to go with the given paint scheme.

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I did not have an association of any kind of animal or mammal with the name "Blackfish" when I first saw your rocket design. Rather, it seemed like some kind of covert operation code name, or something like that. Certainly a bit sinister. But my daily world is pretty far removed from any aquatic wildlife.

mbeels said:

I did not have an association of any kind of animal or mammal with the name "Blackfish" when I first saw your rocket design. Rather, it seemed like some kind of covert operation code name, or something like that. Certainly a bit sinister. But my daily world is pretty far removed from any aquatic wildlife.

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That was exactly my thought as well.

In any case, that’s enough about Blackfish for now. We can talk more in the build thread (later this year).