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  #31  
Old 11-21-2019, 12:37 PM
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LeeR LeeR is offline
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The BNC-55AO balsa nose cone is available from eRockets:

http://www.erockets.biz/semroc-bals...l-sem-bnc-55ao/
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  #32  
Old 11-21-2019, 02:38 PM
Rocketcrab Rocketcrab is offline
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Quote:
Originally Posted by A Fish Named Wallyum
BNC-55AO


Thanks. Color me embarrassed. Just after I posted my question, I noticed another Goblin thread that contained the answer. I even dug in to my stash of SEMROC parts and discovered at BNC-55AO! Now, another question - if I swap out the plastic cone for the balsa, will nose weight be needed?
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  #33  
Old 11-21-2019, 08:00 PM
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erik442 erik442 is offline
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I have an original from the early 70's and it doesn't have any nose weight added. I think it would depend on what type of streamer you use. Mine is crepe paper and maybe 7ft long. When coiled it has some substance. If I was going to use a shorter, plastic streamer I would most likely put a washer under the screw eye.
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  #34  
Old 11-21-2019, 09:54 PM
Rocketcrab Rocketcrab is offline
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Quote:
Originally Posted by erik442
I have an original from the early 70's and it doesn't have any nose weight added. I think it would depend on what type of streamer you use. Mine is crepe paper and maybe 7ft long. When coiled it has some substance. If I was going to use a shorter, plastic streamer I would most likely put a washer under the screw eye.


Thanks, sounds good! Might have to try the old string stability method . I can see it now. Our neighbors wondering why their 63 year old neighbor is whipping a rocket around his head!
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  #35  
Old 11-22-2019, 08:14 PM
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Earl Earl is offline
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I would suspect the stock Goblin is a very, very stable design. Those are some pretty big fins, and I would almost conjecture that it might be stable with just three fins (mounted in a standard three fin 120 degree configuration).

But, checking via a swing test or some CP/CG calculations won’t hurt. The quickie ‘cardboard cutout’ CP test would be easy on this one.

Earl
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  #36  
Old 11-22-2019, 09:34 PM
TigerHawk TigerHawk is offline
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Quote:
Originally Posted by LeeR
The BNC-55AO balsa nose cone is available from eRockets:

http://www.erockets.biz/semroc-bals...l-sem-bnc-55ao/



www.jonrocket.com has the BNC-55AO in stock at a good price.
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  #37  
Old 11-22-2019, 09:50 PM
Rocketcrab Rocketcrab is offline
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Quote:
Originally Posted by Earl
I would suspect the stock Goblin is a very, very stable design. Those are some pretty big fins, and I would almost conjecture that it might be stable with just three fins (mounted in a standard three fin 120 degree configuration).

But, checking via a swing test or some CP/CG calculations won’t hurt. The quickie ‘cardboard cutout’ CP test would be easy on this one.

Earl


Thanks! I dug up a copy of the original Estes kit instructions, and there is no nose weight listed in the parts list. So I'll still check the stability but I think we're good.
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  #38  
Old 11-22-2019, 11:51 PM
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ghrocketman ghrocketman is offline
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Guaranteed that a properly filled/sealed/sanded/painted BNC-55AO weighs more than a PNC-55AO.
You will not have any stability issues with the balsa cone.
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  #39  
Old 11-23-2019, 09:13 AM
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PaulK PaulK is offline
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The Semroc version doesn't have nose weight either, and it flies fine on D12-7s. I tried an E12, but it went KABOOM on the pad. Entertaining, in any case!
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  #40  
Old 11-23-2019, 10:07 PM
Rocketcrab Rocketcrab is offline
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Quote:
Originally Posted by ghrocketman
Guaranteed that a properly filled/sealed/sanded/painted BNC-55AO weighs more than a PNC-55AO.
You will not have any stability issues with the balsa cone.


Thanks!
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