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.
 

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