More Half-Baked Designs Thread

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BigMacDaddy

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Is your test pilot skilled in such experimental odd roc flights? ;) It looks cool up there skywriting... not so cool if you were in the line of fire though I bet.

You could always retrofit some rear tubes... that would make it fly straight. It's the perfect design for that.

Please excuse my amateur photo hack..

View attachment 492641

Thanks, yes I am contemplating rear features I can add to this model to make it more stable. I also maybe should have recessed the motor and put some slots in the sides so that I could use GDS to help stabilize. I am probably beyond my amateur rocketry aerodynamic capabilities at this point...

My co-pilot was warned that this one was the most likely to be unstable but the rocket took an inconvenient turn and wound up between us on the ground so that was more disconcerting than other unsuccessful test flights... Maybe I need to bring goggles and helmets if I will test this one again...

It will look good as a shelf display in the meantime.
 

jqavins

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I think I need to go up to a D12-3 Engine as well as use some other tricks.
Ah, but that would move the CG back too. If more thrust is the answer then you'd be better off going to composites (Q-Jets).

You could always retrofit some rear tubes... that would make it fly straight. It's the perfect design for that.

Please excuse my amateur photo hack..
View attachment 492641
Would that help? The usual reason that lengthening a rocket helps with stability is that the CG is moved forward more than the CP, since the fins remain at the aft end. In this case, since the fins are up at the top, it's like having canards with no "regular" fins. Am I missing something?
 

BigMacDaddy

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Ah, but that would move the CG back too. If more thrust is the answer then you'd be better off going to composites (Q-Jets).

Yeah, I played around with some simulations and I would need to go to an E engine recessed into the body with like 6 oz of weight in nose to get to 1 cal of stability w/ base drag being considered. Does not seem worth it and too risky. More likely adding a ring tail or something would work well but would change the look of design substantially.

Would that help? The usual reason that lengthening a rocket helps with stability is that the CG is moved forward more than the CP, since the fins remain at the aft end. In this case, since the fins are up at the top, it's like having canards with no "regular" fins. Am I missing something?

I think maybe an assumption is that if there were some add-on body tubes that they could have fins far in the back as well.
 
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lakeroadster

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Would that help? The usual reason that lengthening a rocket helps with stability is that the CG is moved forward more than the CP, since the fins remain at the aft end. In this case, since the fins are up at the top, it's like having canards with no "regular" fins. Am I missing something?

Sure. Pull up a rocket in Open Rocket or RockSim. Add some tube fins that hang off the rear of the rocket. It pulls the CP back.

How much, and how it affects CG is of course based on the size of the rocket vs the size of what you have added.
 
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Dotini

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Sure. Pull up a rocket in Open Rocket or RockSim. Add some tube fins thtahang . It pulls the CP back.

How much, and how it affects CG is of course based on the size of the rocket vs the size of what you have added.
FWIW, in my limited empirical experience with ring fins (built 12, flown 8 extensively) the area of the ring counts for about the same stability as the equivalent area of fins - but has more drag. In my one tube fin build, I feel the tubes counted for less stability than a ring of equivalent area.
 

BigMacDaddy

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I saw someone post about Space 1999 Eagle. I had also been thinking about this model. There are 3D designs out there that could be modified. Question becomes -- how difficult would it be to make stable? I do not want to attach a huge body tube and fins behind the model (like the Estes version) so would like a less significant modifications.
  • Do you think if I take the front pods off and attach some fins to the rear pods that this would be sufficient?
  • I can fit 4 mini engines in the model without totally destroying the look of the engines.
  • A very rough approximation shows 3D printing these parts would be around 130grams so not impossible weight wise.
  • I would likely smooth out the details and/or glue clear plastic inserts inside to reduce drag some.
1640659958183.png

Here is the original model (minus a couple of minor parts).

1640660775677.png
 

Daddyisabar

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I flew mine horizontally and it worked fine. Thread in oddroc section. Design was rejected and banned at local club so had to go launch with the Top Men. Flew twice. Required cutting down the casing on a C11 0...a true abomination!
Major problem was getting the tightly packed plastic chute to fully deploy before impact.

Would be awesome to do a horizontal take off cluster for maximum scale points. Looked at the new larger plastic model. A little pricey. If I were a rich man!
 

Daddyisabar

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I saw someone post about Space 1999 Eagle. I had also been thinking about this model. There are 3D designs out there that could be modified. Question becomes -- how difficult would it be to make stable? I do not want to attach a huge body tube and fins behind the model (like the Estes version) so would like a less significant modifications.
  • Do you think if I take the front pods off and attach some fins to the rear pods that this would be sufficient?
  • I can fit 4 mini engines in the model without totally destroying the look of the engines.
  • A very rough approximation shows 3D printing these parts would be around 130grams so not impossible weight wise.
  • I would likely smooth out the details and/or glue clear plastic inserts inside to reduce drag some.
View attachment 496834

Here is the original model (minus a couple of minor parts).

View attachment 496837
YOU DON'T NEED NO STINKING FINS!
 

BigMacDaddy

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I flew mine horizontally and it worked fine. Thread in oddroc section. Design was rejected and banned at local club so had to go launch with the Top Men. Flew twice. Required cutting down the casing on a C11 0...a true abomination!
Major problem was getting the tightly packed plastic chute to fully deploy before impact.

Would be awesome to do a horizontal take off cluster for maximum scale points. Looked at the new larger plastic model. A little pricey. If I were a rich man!

Thanks - I tracked down your thread -- https://www.rocketryforum.com/threads/space-1999-eagle-pmc.139828/ -- Awesome launch!!!

You also proved a point that you can use streamers out behind a rocket to keep it stable... Does that make it a traction engine launch?
 

Daddyisabar

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Thanks - I tracked down your thread -- https://www.rocketryforum.com/threads/space-1999-eagle-pmc.139828/ -- Awesome launch!!!

You also proved a point that you can use streamers out behind a rocket to keep it stable... Does that make it a traction engine launch?
Yes! A traction engine launch! I will use that term because it really sounds good! Will make me look smart and like I have done some book learnin'. Hopefully I will not run into anyone affiliated with the Anti-traction League.

I never shorted or eliminated the streamers. From what I saw they might not be needed. Ran out of C11 0s to chop and gave into the mind killer...fear.
 

BigMacDaddy

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@jqavins - So do you have some ideas for making spring out fins / wings? I keep running into the issue that they get in the way of the motor or otherwise take up too much room inside the rocket when folded.

I was thinking about making a Von Braun Ferry Rocket and it would be great if the large third/final stage fins/wings could be folded in against the body (especially for second stage flight). I was also thinking about some spring out top & bottom fins on the second stage portion to help make that stage more stable. Easier to mess around with elements on a fictional rocket than on the N-1 (and those massive rear fins make the first stage of this rocket quite stable (I think).

1643419499284.png
1643419536734.jpeg 1643419652531.jpeg 1643419687522.jpeg

EDIT: My mind sim totally failed on this one... not stable even with the large rear fins...
1643465591205.png
Definitely better (i.e., less nose weight needed) with them folded in...
1643465769882.png
 

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jqavins

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So far I only have a notion, not an idea that's even close to half baked. The notion is to print or make a pivot arrangement with a round inner end of the fin, a rubber band to swivel the fin out, and an anchor for the rubber band attached to the inside of the body tube a little up. Keep the fin radius around the pivot as small as practical, then make the body diameter as large as needed to get the whole thing out of the exhaust stream. Oh, and there's no need for a mechanism to restrain and release the fins, as I'm thinking of this for use in a tube launch; the tube hold them in and they spring out immediately once the rocket exits the tube.
 

BigMacDaddy

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So far I only have a notion, not an idea that's even close to half baked. The notion is to print or make a pivot arrangement with a round inner end of the fin, a rubber band to swivel the fin out, and an anchor for the rubber band attached to the inside of the body tube a little up. Keep the fin radius around the pivot as small as practical, then make the body diameter as large as needed to get the whole thing out of the exhaust stream. Oh, and there's no need for a mechanism to restrain and release the fins, as I'm thinking of this for use in a tube launch; the tube hold them in and they spring out immediately once the rocket exits the tube.

You have probably seen this but just in case -- https://www.apogeerockets.com/education/downloads/Newsletter313.pdf
 

jqavins

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I have, now that you mention it. And flipping "sideways" rather than "down" has also crossed my mind, but I hadn't remembered that article.
 

boatgeek

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Trying to use my time a little more productively than arguing foreign policy and military strategy...

I want to build a spool-ish rocket to replace the dear, departed Drag Queen. I'm backing off a little bit from her cluster insanity--I'd like it to fly on a single D12-0 or up to a cluster of 3 24mm motors. After noodling ideas around, I happened upon a sail-type with moving booms. The rocket would launch with booms laid back in a sort of shuttlecock look:
1646193843067.png

At burnout, the -0 motor would cut a burn thread holding the booms down and rubber bands would pull the booms out horizontal:
1646193866931.png

With any luck, the rotational asymmetry of the sails would encourage spin on the way up and down. Many, many details yet to be developed. I'm thinking a 3-D printed body, ripstop sails, and carbon fiber rod booms. Notional sizes are 12" booms and 5" OD body. I might also need a "nose cone" to have a spot to hang the rubber bands from.
 

jqavins

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  1. Ooh, cool! I'd say it's more like a saucer design than a spool or shuttlecock. I like saucers.
  2. I assume that this is an artefact of the CAD.
    1646227378218.png
  3. Not seen is a frame to hold the sails in the right shape. I suppose something that would form a funny looking P with the boom and frame?
    1646227758458.png
  4. Why a nose cone to anchor the rubber bands? The bands need to pull the interior boom ends down, not up.
 

Aslansmonkey

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I'm liking this design idea. I'd use a sliding motor rig instead of cutting threads at burn out, though. Something where the motor retains the booms at an angle until the ejection charge slides it back allowing them to release. I confess I haven't fully thought through how I'd do that for a build like this but I've done something similar before.
 

boatgeek

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  1. Ooh, cool! I'd say it's more like a saucer design than a spool or shuttlecock. I like saucers.
  2. I assume that this is an artefact of the CAD.
    View attachment 507264
  3. Not seen is a frame to hold the sails in the right shape. I suppose something that would form a funny looking P with the boom and frame?
    View attachment 507265
  4. Why a nose cone to anchor the rubber bands? The bands need to pull the interior boom ends down, not up.
1. I'm not sure I know the difference between spools, saucers, and shuttlecocks, but I'll take it!
2. That is a CAD artefact, though there will be some kind of control line there (see below)
3. Rather than adding weight, complexity, and stuff to break with a frame, I'd like to use strings like control lines (aka sheets) on a sail. Not clear yet is how that works with the changing geometry. The shape is mostly as you describe, though the top and bottom edges that you drew are parallel.
4. I spent a couple of "woke up at 4" mornings thinking about this. The approach that you describe is where I started. It requires a hinge where the booms leave the body tube. I was having real trouble figuring out how to build that light and easy and also have reasonably positive boom retention. I settled on this approach with the booms hinging at their heels. The rubber bands from above attach to the boom outside of the body tube and pull the boom into the heel socket as well as up, so they're retained. The booms rotate in a slot, which keeps them from moving side to side. I think this will also have less friction when the booms shift position.
 

boatgeek

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I'm liking this design idea. I'd use a sliding motor rig instead of cutting threads at burn out, though. Something where the motor retains the booms at an angle until the ejection charge slides it back allowing them to release. I confess I haven't fully thought through how I'd do that for a build like this but I've done something similar before.
Thank you! If you have photos of what you've done before, I'd much appreciate seeing them. I've never worked with a sliding rig before so this seemed simpler. He says pointing at four control items on each sail. :D
 

Sooner Boomer

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  1. Ooh, cool! I'd say it's more like a saucer design than a spool or shuttlecock. I like saucers.
  2. I assume that this is an artefact of the CAD.
    View attachment 507264
  3. Not seen is a frame to hold the sails in the right shape. I suppose something that would form a funny looking P with the boom and frame?
    View attachment 507265
  4. Why a nose cone to anchor the rubber bands? The bands need to pull the interior boom ends down, not up.

This is a great idea. I had tried to explain to @DAllen how his frisbee goal could recover using something like this - don't think I was very successful. If the booms are tubes, and fit over another rod that does the up/down pivoting, the sails could rotate, giving the rocket spin (burning up more energy on the way down, slowing it). I built something a looong time ago, with foam fins (sails) glued onto soda straws. I think it got crushed in a hurry-up-and-load-I-want-to-get-home. I'll see if I can find parts.
 

dhbarr

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Trying to use my time a little more productively than arguing foreign policy and military strategy...

I want to build a spool-ish rocket to replace the dear, departed Drag Queen. I'm backing off a little bit from her cluster insanity--I'd like it to fly on a single D12-0 or up to a cluster of 3 24mm motors. After noodling ideas around, I happened upon a sail-type with moving booms. The rocket would launch with booms laid back in a sort of shuttlecock look:
View attachment 507230

At burnout, the -0 motor would cut a burn thread holding the booms down and rubber bands would pull the booms out horizontal:
View attachment 507231

With any luck, the rotational asymmetry of the sails would encourage spin on the way up and down. Many, many details yet to be developed. I'm thinking a 3-D printed body, ripstop sails, and carbon fiber rod booms. Notional sizes are 12" booms and 5" OD body. I might also need a "nose cone" to have a spot to hang the rubber bands from.
Wind Mill = No
Mend Wheel = Yes
 
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