#11
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Thanks all for your comments. I've been thinking about this design all day (I was bored don't you know) and I'm seriously considering taking it down to 18mm engines. They're cheaper and I'm not ready to try certification yet.
Also, I've written to three rocket companies about the rocket. So far two have responded. Once I get the design solidified I'll post an update. Thanks again! |
#12
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No update on the Six-Shooter (I'm redesigning) but I do have something else I'm currently building.
I call it the "Sky Breaker" - terrible name I know - but it's essentially a double-length Sunward SkyBender. It'll be about 70" tall and will fly on three D12-5s. I've run it in Rocksim and it says "overstable" and flies to almost 1000 ft. As soon as I get it built and flown I'll post pictures. I'd appreciate any thoughts. |
#13
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Stability?!?
I consider whirling loops of death part of the design process... |
#14
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Quote:
Feyd, I'm looking the "Sky Breaker" design over, and I've altered the file a bit based on what your 2D line drawing indicated. I hope I'm reading this right - The model is supposed to have the three engine tubes exposed between the forward and aft sections, similar to the Custom Landviper. However, RockSim wasn't behaving properly and was showing a solid tube where it should have been just a "filler". The new drawing rectifies the problem with a pod for the aft section, and three continuous 36.5" BT-50's for the engine tubes. I included a pair of couplers in each tube to trim out the weight (see the new file). Either you're a time-tested expert in rocket design and just keeping it a secret, or you're one of the luckiest guesstimators I've seen yet! This new design hits the ULTIMATE SWEET SPOTS for each of the engine combinations in a way I've never experienced by ANY design before. Also, I trimmed out some mass from the nose cone by reducing the wall thickness down to 0.05", which seems more likely than having it 0.125" thick. This brought the calculated weight down to just under your 'user override' weight. It's still a thick-skinned nose cone. Specs: Length: 70.15" Diameter: 2.6" (BT-80) Weight: 3.74 oz (empty) Fin Span: 10.60" (3) A8-3.........193'......Dv <2 FPS......28" launch guide required (3) B6-4.........396'......Dv <3 FPS......25" launch guide required (3) C6-5.........759'......Dv <3 FPS......25" launch guide required (3) D12-5.......1120'......Dv <1 FPS......26" launch guide required (3) E9-6........1697'......Dv <1 FPS......31" launch guide required (3) E15W-7......2087'......Dv <3 FPS......13" launch guide required (3) F21W-8......2391'......Dv <1 FPS......10" launch guide required Keep tossing up ideas like this, and you'll get recognized very quickly!
__________________
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 |
#15
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Well I've been dreaming up rocket ideas for quite a long time and even entered the Estes contests a *really long time ago* (never won anything) but I wouldn't call myself anything like time-tested :-)
Essentially I took the Sunward Skybender and doubled everything so I had a really good base to start with. My Skybender has flown a couple of times and I really like it alot. I've built most of the new rocket already, just need to finish the top and cut out the fins. Then paint. I do have a question though.... how far does an ejection charge travel? The rocket is about 5' 8" tall. Since there are several regular model rockets out there that are much taller, I assume I won't have a problem with the ejection charge ejecting the parachute. I was thinking of putting a BT-80 baffle in there, but wasn't sure if it was necessary. Thanks! |
#16
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Quote:
If you were trying to get by on just one charge, you might be in trouble. But you have three charges going off in this design. It ***should*** be enough to pressurize the tube and toss the laundry. Also, since the model has such a low Dv, the aerodynamic resistance to the ejection is much less. This is one of the important reasons we stress keeping the Dv (Velocity at Deployment) as low as possible. You did good, Feyd! All of these combinations are less than 5 FPS at deployment, meaning it's just barely moving when it blows. Little to no resistance at all. Baffles have their place, but so does a good handful of dog barf (shredded newspaper insulation)... Keep up the design work!
__________________
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 |
#17
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Thanks.
One final problem / request. I need to put 5 fins on the BT-80 at the base of the Sky Breaker. Does anyone have a template/wrap I can use? Maybe a location where such things are kept? Almost ready for paint!
__________________
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Dale Marshall, San Antonio Texas NAR #90990 Semroc SAM #083 BAR Since 2008 Enjoying model rocketry since 1977. The Spotted Dragon -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- |
#18
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Quote:
I draw up my own patterns for each model using Corel Draw. What I like are patterns that allow me to hold the fin in place while the glue dries. These patterns have a slot for the fin to fit inside, and it takes two to keep the fin aligned correctly. The general arrangement is a circle with fin slots radiating outward...
__________________
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 |
#19
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Feyd,
Would you mind if I posted this design in our "official" BARCLONE lineup?
__________________
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 |
#20
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Sure, no problem. Thanks!
I'm hoping to finish the fins at least this week (out of town right now) and hopefully fly it soon. I'm really looking forward to seeing if it'll fly like it's supposed to.
__________________
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Dale Marshall, San Antonio Texas NAR #90990 Semroc SAM #083 BAR Since 2008 Enjoying model rocketry since 1977. The Spotted Dragon -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- |
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