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  #1  
Old 05-12-2020, 11:06 PM
RobVG RobVG is offline
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Default Too much nose weight?

If I add 3.5 oz to the nose of a current configuration I get a stability of just over 1cal. Total weight- 10.4 oz.

Is this a reasonable amount of nose weight?
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Old 05-13-2020, 12:15 AM
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That must be a pretty odd configuration....what does it look like?
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Old 05-13-2020, 12:25 AM
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Quote:
Originally Posted by BEC
That must be a pretty odd configuration....what does it look like?


Space x Starship, without booster. Short and fat. BT 80 tube, just over 18" tal

Last edited by Ltvscout : 05-13-2020 at 11:27 AM.
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Old 05-13-2020, 12:31 AM
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Just the Starship, or on the Super Heavy stack?

That still seems a bit much though Starship's fins aren't very big in its current iteration, I guess.

But those forward fins....that's the issue, isn't it?
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Old 05-13-2020, 06:53 AM
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Yeah,

Bernard's right. The forward fins make that a totally believable amount of weight. Pictures would help.
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Old 05-13-2020, 11:42 AM
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I want to model just the Starship. Thought it might fly like somewhat like a Big Bertha. I had it scaled but had to add 3" to the tube and increase the fin size by 20%. It still resembles the real thing.

The super heavy doesn't really have fins and adding it would put the Starship's fins pretty far forword and move the CG rearward. Not sure if it's doable? As suggested earlier, adding a second set of clear fins helps. Rather not do that if possible.

Haven't yet figured out how to add the forwad fin set . To make it look right they need to be placed on the nose cone.

According to Openrocket simulations it'll fly. There was one warning when playing around with a few parameters just for fun.

No pics yet, only have the nose and tube. Parts are hard to find and shipping costs a fortune right now.

Last edited by RobVG : 05-13-2020 at 12:03 PM.
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Old 05-13-2020, 12:34 PM
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Well,

I checked on-line and there are a bunch of different iterations of the Starship but if the specific one you're modeling has forward fins and you've added 20% to the tail fins, then I suggest you reduce the forward fins by 20%.

I feel your pain. I struggled with forward fins on a Spartan, Nike-Zeus and the worst, a Wasserfall/Aries. The Aries nose ended up weighing more than the whole rest of the rocket. But they flew.

You're doing it right. At some point though, you gotta start the paper and glue stuff.
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Old 05-13-2020, 12:35 PM
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Just for context, a stock Big Bertha (without a motor)—the whole model—weighs less than your proposed nose weight. The Estes BT-80 V2, which of course has larger-than-scale fins weighs about 6 1/2 ounces (well, mine does). This has a 24mm motor mount and doesn't go very far at all on a C11-3. It likes D12-5s or more.

So with a 10 ounce plus weight, you're looking at composite motors, I expect. You're basically looking at something not unlike a dual egg lofter, with lots of momentum at the end of the shock cord....
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Old 05-13-2020, 01:03 PM
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Quote:
Originally Posted by MarkB.
Well,

I checked on-line and there are a bunch of different iterations of the Starship but if the specific one you're modeling has forward fins and you've added 20% to the tail fins, then I suggest you reduce the forward fins by 20%.

I feel your pain. I struggled with forward fins on a Spartan, Nike-Zeus and the worst, a Wasserfall/Aries. The Aries nose ended up weighing more than the whole rocket


I couldn't find an example. Any chance you could post a link?

It's good to know you had a similar situation with your Aries and still got it to fly. Thanks

Last edited by RobVG : 05-13-2020 at 03:38 PM.
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Old 05-13-2020, 01:08 PM
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Quote:
Originally Posted by BEC

So with a 10 ounce plus weight, you're looking at composite motors, I expect. You're basically looking at something not unlike a dual egg lofter, with lots of momentum at the end of the shock cord....


Simulations show an apogee of 100' with a C11 and 330' with a D12. This is fine with me because I don't have any large fields around. E30 = 900'

Edit: Oh, and the weight of the rocket icluded the D12--- Correction- did not include engine.

Last edited by RobVG : 05-13-2020 at 10:37 PM.
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