#281
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New Design: Thunder Strike
This is another design that is not what I actually intended. Its rather a happy accident. I played around with the motor choice and have achieved an Deployment velocity of 1.10 with the Quest C6-5 and the Estes was a Dv of 5.23. Kind of interesting.
Thanks and Enjoy, JP James Pierson NAR #77907 |
#282
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Quote:
There is a difference in the power and formulation of those motors. They're not the same, just in the same range. Notice the big difference in the Estes B6-4 and the Quest B6-4 in your other runs? The Estes had a 30 FPS Dv, while the Quest only has an 18 FPS Dv. I haven't taken the time to study the differences in the RocSim motor files, but it's clear there is a difference in the power numbers.
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Craig McGraw BARCLONE Rocketry -- http://barclone.rocketshoppe.com BARCLONE Blogsite -- http://barclone.wordpress.com BARCLONE Forum -- BARCLONE Forum BARs helping BARs SAM 0044 AMA 352635 Last edited by CPMcGraw : 04-03-2006 at 09:56 PM. Reason: Looked again at the file... |
#283
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New Plan -- Scrappy
James noticed an interesting way to work with inside tubes with his Thunder Strike design, and it may be better than the cut-and-paste method for simulating tubes that are partially hidden and partially exposed.
I had to try his method out, and here's what I came up with. Another "Schoolyard Sounder"... Length: 18.3" Diameter: 0.759" (ST-7) Fin Span: 4" Weight: 0.6 oz 1/2A3-4T.....235'.....19 FPS A3-4T........565'.....20 FPS Although the Dv is high for both motors, they're within limits. Just reef the chute and you should be safe. As with some previous designs, the fin shape makes a big difference in the stability numbers. Adding that step in the leading edge can raise the margin while reducing the fin area as a bonus. Also, pulling the fin tip back at an angle is having a positive effect on the margin, while also reducing the total fin area. Enjoy!
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Craig McGraw BARCLONE Rocketry -- http://barclone.rocketshoppe.com BARCLONE Blogsite -- http://barclone.wordpress.com BARCLONE Forum -- BARCLONE Forum BARs helping BARs SAM 0044 AMA 352635 |
#284
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Quote:
Reminds me of a certain Prometheus........... (Sorry if I butchered that spelling. I'm too lazy to go back and check.)
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Bill Eichelberger NAR 79563 http://wallyum.blogspot.com/ I miss being SAM 0058 Build floor: Estes - Low Boom SST Semroc - Marauder, Shrike, SST Shuttle In paint: Canaroc Starfighter Scorpion Centuri Mini Dactyl Estes F-22 Air Superiority Fighter, Multi-Roc, Solar Sailer II, Xarconian Cruiser Semroc Cyber III Ready to fly: Estes - Solar Sailer II Semroc - Earmark |
#285
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"That's one scrappy Prometheus!"
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--Seriously, guys, wouldn't having a tiny body tube like that BT-3 (with 6 of its 8" length exposed) contribute to a serious case of the "bends?" (Nothing personal, Craig, but as a klutz, I seem to instinctively understand the laws of physics, and at this particular scale -- especially given Estes' currently "Thermonuclear" ejection charges -- I'm just a little concerned for this design. ) Of course, you *could* do an SLS ~2.5OX upscale with Semroc's thick-walled "LT" tubes (LT-085, -125), but then you'd probably have to cluster it for the additional weight. Hmmm... And now, for those of you who may have missed the Prometheus: http://forums.rocketshoppe.com/show...60&postcount=48 http://forums.rocketshoppe.com/show...71&postcount=12 But yeah, Bill, you got the spelling write... er, "right." (You should *see* some of the news copy that comes over the TelePrompter. The folks who get Closed Captioning complain every once in a while. ) Cheers, --Jay |
#286
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"The Shape of Things to Come"
Quote:
Cheers, --Jay |
#287
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Quote:
The thought did manage to inch its way across my brain as I worked up the design. If this were being done for 18mm A-C motors, I'd agree completely. The smallest tube I would have used in that configuration would have been an ST-5 or BT-5. But since this design uses the 13mm motors instead, I felt it should be safe, even with those T-Nuke deployment charges. In reality, though, I think the model will suffer less from actual flying and more from "hangar rash"...
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Craig McGraw BARCLONE Rocketry -- http://barclone.rocketshoppe.com BARCLONE Blogsite -- http://barclone.wordpress.com BARCLONE Forum -- BARCLONE Forum BARs helping BARs SAM 0044 AMA 352635 |
#288
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Quote:
I'll probably be using some variation of the shape in future projects. I'm still curious as to why the shape has so much of an effect, as opposed to an increase of fin area. It's like that issue we beat to death about the Hi Flyer fins: A smaller fin with this step in the LE greatly improved that model's margin.
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Craig McGraw BARCLONE Rocketry -- http://barclone.rocketshoppe.com BARCLONE Blogsite -- http://barclone.wordpress.com BARCLONE Forum -- BARCLONE Forum BARs helping BARs SAM 0044 AMA 352635 |
#289
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Quote:
Having that step in the leading edge moves the center of area, and therefore the center of pressure, for the fins further back than it would be with fins having a plain triangular shape. That moves the CP for the rocket further back. I'll see if I can figure out where the CP for the two styles of fins are, and I may follow this up with an edit or another post if I do.
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John Thro, NAR #84553 SR I was too old when I started! Now I'll *never* become a BAR! |
#290
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Quote:
Thanks, JRT. That makes sense, it's just the degree of change that caught my attention. You wouldn't happen to know of a text on the subject that we could pull up and read, would you?
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Craig McGraw BARCLONE Rocketry -- http://barclone.rocketshoppe.com BARCLONE Blogsite -- http://barclone.wordpress.com BARCLONE Forum -- BARCLONE Forum BARs helping BARs SAM 0044 AMA 352635 |
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