Rocket length?

Discussion in 'Beginners & Educational Programs' started by Rex R, Apr 21, 2010.

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  1. Apr 21, 2010 #1

    Rex R

    Rex R

    Rex R

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    Hi. was wondering if there is a rule of thumb for a 'good' length for a rocket? in the 'distant' past my rockets(low power) were mostly kits...now I find myself wanting to scratch build a D-powered bird (34mm dia) any suggestions on how long it should be? thanks.
    rex
     
  2. Apr 21, 2010 #2

    cjl

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    "Typical" rockets tend to be 10-15x their diameter. You can make it as long or as stubby as you want though.
     
  3. Apr 21, 2010 #3

    dedleytedley

    dedleytedley

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    I suggest you get the free download of Rocksim from Apogee. You'll be able to design rockets of different lengths and compare the performance before building. Ted
     
  4. Apr 21, 2010 #4

    Rex R

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    ah, so somewhere between 13-20", that works :). I've found all sorts of info on fin and chute sizes...but overall length must have slipped by me. thanks for the info and quick response.
    rex
     
  5. Apr 22, 2010 #5

    RimfireJim

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    And also the books "Handbook of Model Rocketry" by G. Harry Stine, and "Model Rocket Design and Construction" by Tim Van Milligan.
     
  6. Apr 22, 2010 #6

    Rex R

    Rex R

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    gee my hand book is only the 7th edition :) (got it a few years back when I was playing with aero-ammo for spudguns :)(yes they work, no I'd best not go into details...someplaces frown on anything other than spuds). down loaded rock sim will 'play' with it later. thanks for the suggestions. did build a shuttlecock rocket totherday thats fun to pla/\/\er launch.
     
  7. Apr 22, 2010 #7

    MarkII

    MarkII

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    The 7th edition of The Handbook of Model Rocketry is the current one.

    [​IMG]

    MK
     
  8. Apr 27, 2010 #8

    bobkrech

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    RockSim is a powerfully analysis tool but it can't design your rocket. I think us old timers would suggest that a novice get Stine's book, read it, and build their first rockets without a computer program. This way the novice will learn model rocket construction techniques and how to design a model rocket. Once you learn how to design and build a model rocket, tools like RockSim are wonderful to analyze the design and refine it to optimize performance.

    My two cents.

    Bob
     
  9. Apr 27, 2010 #9

    Rex R

    Rex R

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    decided to go with; 18" bt-55, 3 clipped delta fins, a more or less parabolic nose(as determined by the mk1s :)), and a baffle. also a 'trash bag 'chute'. I'm probably as 'old school' as they come for designing stuff, rather reach for the paper and pencil(or just start bending tin), than the computer... just dug out my 1974 edition estes catalog(that brought back some memories) and glanced up at my original version sissor wing transport hanging from the celing :). I agree that the 'handbook of model rocketry' ought to be required reading...(haven't quite reached the point of rummaging through the old astoundings looking for G.H. Stine's science article on model rocketry yet for another read)
     
  10. Apr 27, 2010 #10

    Micromeister

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    Two of my favorite D12 powered models from "the Golden Age" LOL are the Goblin, and another outstanding performer the Cherokee-D. Both are BT-55 (1.325" diameter) models, the Cherokee is a 3 fin design the Goblin-4. Either are nearly always out of sight flights on D12-5's.

    Your 18" model should fall right in that range. Hope you have a Good size flying field and use a long streamer (2" x 120" in the Goblin) or 12" X-form chute for recovery.

    As a couple others have mentioned 10-15x the diameter is usually the normal rule of thumb for mod-roc length.
    Welcome to the forum and Good Flying; Hope ya get her back.
     

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