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5" rocket weights

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Neil

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Could anyof you tell me how much a 5" diameter by 75" long bird should weigh? I am designingone like that and I am trying to decide if it is practical or not. sims show it at abou t25OZ (stupid material database....), whichI know isnot right. I put it up to 100 OZ, but I am still not sure if it is enough. Thanks guys. -Neil
 

Ryan S.

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depends on alot of things. Is it glassed? What is the nosecone made of? What are the fins made of? Is there nosweight? What size motor tube? How thich are the centering rings? Does it have electronics? etc etc etc
 

Neil

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Will most likely be glassed with 6 OZ fiberglass, will have a glassed foam cone, 75MM motor mount, just so it can handle Ks when the time comes, I am thinking quarter inch or half inch aircraft plywood, and there will proabably be a 2 pound noseweight, but less once I tweak the design to make the thing more stable.
 

rocwizard

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If built adequately, I am guessing about 15-20 pounds dry
 

Neil

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OK. Thanks. I just set it to #20, and it is recalculating all simulations asI write. Thanks. -neil
 

Neil

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I was pretty darn close on my first predictions. I set it up to #20 (added about #4.5), and it still flies on a J350. Only too 700', but hey. J420s are no better. only 600'. But hey... If K550s or K670s are readily availible.... Or, if my rocket doesent weighthe full #20.... I set itat that just so I can make sure its ok. It looks like I am going to take a shot at this, once i make some money. I wish I had a job.... Pretty much any thing besides a wallmart greeter. Well, actually, if a wallmart greeter gets paid $10 an hour.........
 

havoc821

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Um........I'm kinda confused? You said it will have a 75mm MMT which is 3 inch diamter and you were saying something like:

"75MM motor mount, just so it can handle Ks when the time comes"

Well, as far as I know, Ks don't come in 75mm. 75mm is full Ls and baby Ms. Maybe you goofed and ment to say 54mm because I think you made a mistake because something isn't right. A 75mm K would be one heck of a K!!!:D
 

Neil

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OOOOOK... Ooooook.... "L777WW" is what I meant to say.... But thats "just in case I feel likeit when I am older". I saw that motor a few months ago for the first time and thought: "someday I wanna have a flight like that...". But thats nothappenin any time soon. I just want a 75MM motor mount just for the heck of it. I want it to be able to handle a lot when the time comes. Besides. I just like it. it gives me more options in future, if it survives untill then.

If I put a 54MM motor mount in it, I might find myself at age 18 wishing I had put a bigger mount in because I just bought a big motor. Just makes me feel better. And I already have a good tube that will work. I could just yadda yadda yadda about this forever, but I think you got the picture.... Also, there might be a K Hybrid motor. I think I saw one on the Pratt Hobbies website for 75 bucks. thats a dollar a millemeter, there!
 

rocwizard

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there are 75mm Ks. There is the AT K560W and K780R. THey are both full Ks. AMW also has the 1700 ns K450 BB, and the K470 ST. Then there are the full Ks which are the K600 WT and the L (more like a K) 700 BB. Personally though, I dont recommend any of them simply cause the loads are more expensive that 54mm Ks of the same impulse. But that's just me.;)

Higher thrusts are alos found in 54mm Ks sinde there is a greater burn surface area. lets compare. 54mm K700W or 75mm K560W. 54mm K1275R or 75mm K780R. Which would you choose?:D
 

daveyfire

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Originally posted by rocwizard
54mm K700W or 75mm K560W. 54mm K1275R or 75mm K780R. Which would you choose?
How bout a 54mm Vulcan K2000? I miss those motors! :D
 

rocwizard

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Ok, you got me on that one. But i'll bet we can make something better!:D

K4000 anyone?
 

Ryan S.

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Originally posted by rocwizard
54mm K1275R or 75mm K780R. Which would you choose?:D

K1275 ;) I am saving for it now
 

DPatell

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Neil - the 75mm K Hybrid on Pratt? Did you mean 64mm, which is the RATT, or the 75mm L made my Hypertek?. I own the K240 RATT, and it is maxed out at about 16# loaded on the pad. Slow liftoffs, but cool!

I bet a Hypertek L would, but remember the hardware is not cheap, and if you borrow it and crash it, it's still not cheap to replace!
 

Neil

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Yeah, thats what I meant. Whoops. I just wanted to prove I wasnt stupid saying there were 75MM Ks....
 

Neil

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THERE! I wasnt wrong! Yay!:p :( ;) :D :kill:
 

havoc821

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Ok, my bad. You got off on this one Neil. :D ;) :p Well, I never researched the really big motors nefore because I'm not interested inanything above a J right now, so I was wrong. I always thought that Ks went as big as 54mm. Guess I was wrong. Neil, putting a 75mm MMT for the future is a good idea. I did the same for my rocket, so that in the future I can put this thing out of sight....literaly!:D Well, gotta go.
 

Neil

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HEHE. Yay. I guess.... Not that I am going to fly a 75MM K if there are 54MM Ks that do the same thing. The 54MMs are so much cheaper. With the possible exeption of those new AMW Blue Baboon motors. 75MM Ks, and they only cost about $75!
 

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