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#231
03-10-2006, 01:07 PM
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...And here are the 3D images for Mini Jet #1... One "tweak" to this model -- the original design used a 1/4 oz ballast of clay in the nose cone. The model will perform a little better, with lower deployment Vs, if this is reduced to 1/8 oz (half of the original amount). The heaviest motor in the simulation list -- the Apogee B7-6 -- can still be balanced out with the 1/8 oz ballast, with the model retaining a 1.7 margin. Additionally, this should improve the low-impact speed on landing using the streamer. For most flying, and to keep the model within visual range, use the 1/2A3-4T instead of the full A3-4T. The 1/2A will get over 300', and deploys at the lowest V -- below 10 FPS. The full A3 will get over 650', which would be BVR for a model this size. The 1/4A will still provide a flight to 130', which might be a good first-flight motor.
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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 : 03-10-2006 at 01:19 PM. 
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#232
03-10-2006, 01:12 PM
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James, I like these small park flyer models, mostly because the field I fly in - a schoolyard - is small and is surrounded by residential buildings on three sides (with a graveyard on the north boundary... Some of the best neighbors, actually. They don't complain about the noise and smoke...  )...This is one for my own "build pile"... Thanks!
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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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#233
03-10-2006, 01:28 PM
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More For Built Pile
Add more to your build pile Craig. Last year when I came up with this design style I came up with a few more just by changing the main wings. Here is one more, Mini Jet #2. Only 15 more to go.
PS. I also have launch field problem as I live in the middle of a stinking rain forest here in WA. surrounder by rocket eating TREES.  James Pierson NAR #77907
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#234
03-10-2006, 01:46 PM
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Your weather has been getting as much national attention as ours down here... . Our "windy & rainy season" is just about to start...Similar tweaking for this one, you can reduce the ballast in the nose to 0.15 oz, which is a hairsbreath above 1/8 oz. This provides a margin of 1.26, which is more than enough. Don't reduce it below this weight, though, as the balance is a bit critical for this bird. James has balanced his model with a large stability margin, which is good and doesn't compromise much on performance. I trimmed out the extra weight to find the "optimal" margin, and this gave me as much as 60' of extra altitude using the A3-4T. Keep this in mind -- an altitude of 740' versus 680' doesn't change the fact that you still can't see the model reaching apogee... Use the 1/2A3-4T for most flying, as this keeps the model below 350', which is just at the edge of visual range.
__________________
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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#235
03-10-2006, 02:16 PM
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Numbers ???
Craig, I really appreciate all your input and please help me in these designs get a few numbers figured out.
 Acceptable streamer decent rate? Acceptable paprchute decent rate? Accetable static margin size? Acceptable deployment velocity parachute and streamer? Does Ricsim account for Fin sheer? Any other important numbers I am not thimking of? Thanks, for all the tweaking, James Pierson NAR #77907
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#236
03-10-2006, 10:54 PM
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James, Can the designs you're making go up on the BARCLONE site at the next update? If so, Craig, please upload the files for his designs along with the pics to your ftp area. Also, if you would please rip James' descriptions from the forums and put them in a text file for me to use on the site. Thanks, guys.
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Scott D. Hansen Ye Olde Rocket Shoppe - Your One Stop BAR Shoppe! Ye Olde Rocket Plans - OOP Rocket Plans From 38 Companies! Ye Olde Rocket Forum WOOSH NAR Section #558
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#237
03-10-2006, 11:03 PM
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Craig and Scott, I would be honored if you would post these designs at Barclone. Also please include any and or all changes that help improve the designs.
Thanks Again, JP James Pierson NAR #77907
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#238
03-10-2006, 11:09 PM
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OOP's
I meant to add this one to the last post but forgot. I need alot of help tweaking this one Craig. I still dont like the velocity at ejection, but motor choices are limited.
I call it the Master Blaster. Kind of a retro/vintage/ Galactic Pirates spinoff. I think that the Sandman might appreciate this one the most. Enjoy. James Pierson NAR #77907
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#239
03-10-2006, 11:33 PM
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You're welcome, James. Quote:
Of these data points, only the margin and the Dv tend to get my attention. For the static margin, or margin of stability, the magic number is 1.00. You will also see this called the "calibre" of the rocket, and it represents an ideal distance of one body tube diameter separating the center of gravity from the center of pressure. Any margin value above 1.00 (greater than one body tube diameter) will fly without chasing its tail. Below this number, and the model is (generally) unstable. A negative number is out of the question. Having said that, you can "tweak" a design to fly when the initial margin is less than 1.00. What you have to account for is the amount of weight that is burned off in the motor between ignition and when the rocket exits the rod. The margin can actually change (increase) in that short distance from unstable to stable, and if you're designing a very high performance model, you can take advantage of this. I try to get my designs to be anywhere from 1.00 to 1.20 when using the C6 motors (in 18mm designs). The drawback to having higher margins than 1.20 is the tendency to weathercock significantly when the rocket exits the rod. The greater the margin, the greater the reaction to the fins' correcting force. For lack of a better way of putting it, when the margin is 1.00, the amount of correcting force applied by the fins is equal to the amount of opposing force applied to take the rocket away from its straight-line path. You can generally use this value as a multiplier to the opposition force to get the correction force. Note, though, too much of a good thing is not always a good thing. In winds that are in the upper limits of safe flying, the rocket may shift into a near horizontal path and not gain very much altitude. I've seen a Big Bertha do this on a B6 coming off a 36" rod. It was like watching a ground-to-ground missile aiming for its target. For deployment velocities, try to get below 20 FPS for either parachute or streamer models, though you can sneak this up a bit with streamer models that are very lightweight. A Dv below 10 FPS is an excellent gentle deployment and you generally will not shread the lines. Dv's below 5 FPS are better still, and if you can get below 2 FPS, the model is just barely ticking over the top -- almost standing still. Above 20 FPS for parachutes, however, is not a good thing. The parachute typically "explodes" open with a loud, audible "pop" that you can often hear on the ground. That's a lot of shock and stress on the lines and the plastic sheet used in most of our models. They won't survive too many such openings. As for descent rates, this is a function of parachute (or streamer) size and is useful only if your goal is to design an optimized parachute diameter, or streamer length. From my POV, you have very limited options short of cutting your own. SEMROC's 12" and Estes' 12", 18", or 24" parachutes are my "usual suspects"; for streamers, you can get the material at Lowes and Home Depot. Just follow the basic pattern of 10:1 length-to-width. Use multiple streamers if you need to slow it down a bit more. Quote:
Watch the acceleration at liftoff. Some motors can rip a model apart from the stresses of having too much power. With our A-E motors, this is not that big of a problem, but when you start talking about "mach busting" in MPR and HPR, these forces can destroy a model that may not be constructed to withstand such forces. This is what usually results in "fin shear", or causing a model to attain "the speed of balsa" -- accelerating to a point where the balsa fails. Be careful when using the A10-3T, for example, in some very small and light models. It is a very powerful motor with the capability of accelerating a small model past a safe limit. If this was a booster, it would be a better motor... Quote:
__________________
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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#240
03-10-2006, 11:34 PM
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Scott, they're already in the FTP area. I just need to do the blurbs. I'll try to get them done this weekend.
__________________
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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