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  1. #1
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    Difuminar: 9400 feet and Mach 1.6 on a CTI G150

    Hi all,

    This is a build thread for my 24 mm MD (called "difuminar" spanish for blur). It is essentially designed to get the most possible altitude out of a non-HPR motor. It consists of a Polystyrene 8.7:1 Von Karman nose cone resting on top of a CF body tube with 4 CF fins.

    The design of this rocket depended heavily on the reduction of drag which was a key factor in gaining altitude. Openrocket was used mostly to test out different configurations.


    Attachment 316139


    Nose Cone

    As the body tube was designed to be as short as possible, most of the electronics were transferred to the nose cone as to cut down on unnecessary length. The electronics are mounted on top of a 3D printed sled and secured inside the nose cone with another 3D printed bulkhead/deployment charge. Stability was ensured throughout the rocket by implanting 30 grams of tungsten powder with epoxy in the tip of the nose cone.

    3D printed polystyrene was chosen for the material for the nose cone due to its low price and easy machinability. Fiberglass and Carbon Fiber were originally considered as materials for the nose cone due to their high strength to weight ratio but they were more expensive and not as easy to machine.

    For the Nose cone, a Von Karman shape was optimum for the speeds achieved by the rocket. A number of different lengths were experimented with and in the end a 8.8:1 ratio was ideal for achieving maximum altitude and also for storing the electronics, including the telemini's 6.5 inch antenna.

    Body Tube

    The material chosen for the body tube was Carbon fiber. Fiberglass is cheaper but due to the small size of the rocket the cost was not substantial.

    The main source of the drag was the body tube which caused more than 50% of the drag on the rocket. Compressing the components in the payload section allowed the length to be shortened a good deal and therefore cut down on the drag.
    m
    Fins

    Carbon fiber was found to be the best material for the fins due to its high strength to weight ratio. Most other materials were found to either be too heavy or too weak. Fiberglass possesses similar characteristics to carbon fiber but carbon fiber has an edge over fiberglass in strength and weight and so CF was chosen to be the final material.

    The design of the fins was also crucial to get the maximum possible altitude out of the rocket and went through over 50 different configurations before the final design was implemented. From the start, it was obvious that a three-pointed fin had a significant advantage over a delta fin performance-wise. For the three-pointed fin, three different designs were considered. Swept fins are more efficient when tilted back a long distance but they become structurally weak after and prone to fin flutter after a certain extent. They also do not offer an advantage over a short distance and so were disregarded as an option. Clipped fins cause too much drag and although they are more structurally sound, the 1/32" mm thick CF plate provides more than enough structural integrity. A balance was found between the two by making fin halfway between clipped and swept (a 90-degree triangle). This provided a good deal of strength while also keeping drag to a minimum.

    Another challenge was finding the perfect balance between the Tungsten weight in the nose cone and the size of the fins. Increasing the weight in the nose cone and decreasing the fin size ultimately ended up with a higher altitude in the simulation but in real life an insufficient fin size would have resulted in weather cocking soon after leaving the rail. To lessen this effect, the fin size was increased to a sufficient amount (enough to ward off the effects of weather cocking) and the weight in the nose was lowered to 30 grams.

    A four fin design allows the span of the four fins to be reduced to return to around the same stability margin with a three finned rocket. Although this may seem to have no real advantages, lowering the span means the fin itself will be stiffer and less prone to flutter. The fins themselves will weigh more, but since the rocket is about as close to optimal weight as you can get, adding ~1 gram of weight does not provide a real impact on the flight.

    The fins will be tacked on with BSI 5 minute epoxy and filleted with JB weld.

    Avionics

    The model will be tracked with a Telemini altimeter, which also will enable deployment and measurement of the rocketís final altitude.

    Propulsion

    Out of the Pro24 6 grain motors the G150 was picked to be the propulsion system for this rocket. Most other motors in the Pro24 6G case offered less impulse than the G150 except for the G117 and G65. The G65 offered a longer burn time as well as more impulse but the offset core produces stability issues and weathercocking. The G117 has a longer burn time and just 1 less newton/sec of impulse than the G150 but the G150 has more ISP and less weight and so produces better
    performance.


    So anyway, there is the introduction. build should start in a month or so while I get the parts. So far the RASAero and Openrocket results are similar (about 9,500 ft AGL) so I'm pretty confident that the rocket will reach the expected altitude.



    Openrocket file
    Attachment 316140

    3D File in Openrocket
    Attachment 316141

    RASAero file
    Attachment 316143

    Project Writeup
    Attachment 316142


    Last edited by TRFfan; 2nd March 2017 at 07:18 PM.
    trffan has been retired

  2. #2
    Join Date
    7th August 2014
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    298
    Looks great so far.

    BuiltFromTrash
    First RMS Flight: June-17 2015
    Pringles Can Rocket
    G53-FJ-7 (29-40/120) 92 Newton-Seconds
    ~1300 Ft

  3. #3
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    7th July 2013
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    Good luck in your goals, sounds like you have done a lot of research up to this point, I hope it pays off.
    Michael Pitfield
    TRA 14579 L2
    NAPAS BoD
    URRG
    MARS
    CRC

  4. #4
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    Do you have enough delay to get to 9K with the G150?

    Love the name and good luck with the project.

  5. #5
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    Quote Originally Posted by Threemorewishes View Post
    Do you have enough delay to get to 9K with the G150?

    Love the name and good luck with the project.
    He's using electronic deployment so no delay is needed.
    Rich

    NAR# 99154

    L3-4x upscale Estes Cherokee-D- AT M1297W 5/28/2016 http://www.rocketryforum.com/showthr...r-rharshberger

    TriCities Rocketeers NAR section# 736 http://www.tricitiesrocketeers.org/

  6. #6
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    Quote Originally Posted by Threemorewishes View Post
    Do you have enough delay to get to 9K with the G150?

    Love the name and good luck with the project.
    Yes a telemini will be used in the deployment.
    trffan has been retired

  7. #7
    Join Date
    27th December 2015
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    Hailey, ID
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    NAR Member
    Class D water rocket world record 417 feet 130 mph.
    Machbuster #8 Mach 1.71 on a G80 5260 feet.

  8. #8
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    Quote Originally Posted by mpitfield View Post
    Good luck in your goals, sounds like you have done a lot of research up to this point, I hope it pays off.
    Quote Originally Posted by BuiltFromTrash View Post
    Looks great so far.
    Quote Originally Posted by retortec View Post
    Thanks!
    trffan has been retired

  9. #9
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    I hate to be a wet blanket, but is a G150 technically MPR? Its average thrust is 146N, which is over the 80N NFPA limit. But regardless, it looks like a fun and exciting project!
    NAR 91107, Level 2

    I really, really hate bugs.

  10. #10
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    He's from Canadia. Their rules are more polite.

  11. #11
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    Quote Originally Posted by qquake2k View Post
    I hate to be a wet blanket, but is a G150 technically MPR? Its average thrust is 146N, which is over the 80N NFPA limit. But regardless, it looks like a fun and exciting project!
    Quote Originally Posted by Nytrunner View Post
    He's from Canadia. Their rules are more polite.
    Yes in canada you can fly any motor regardless of thrust as long as it's under 160 newton/sec total impulse.
    trffan has been retired

  12. #12
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    Quote Originally Posted by TRFfan View Post
    Yes in canada you can fly any motor regardless of thrust as long as it's under 160 newton/sec total impulse.
    Ah, I did not know that.
    NAR 91107, Level 2

    I really, really hate bugs.

  13. #13
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    Quote Originally Posted by TRFfan View Post
    Yes a telemini will be used in the deployment.
    I did reference having a HAM license in another of your threads, now I'm going to specifically ask.

    Do you have an amateur radio license? If so what is your call sign?
    If you do have a license, congratulations and welcome to the wonderful world of amateur radio!

    If you don't have a license you can't legally transmit using the telemini as it is in the 70 cm band. Since the launch you are planning to fly at is on a Canadian Forces Military base, legally transmitting is a requirement. Actually it is a requirement everywhere.

    Not trying to be critical or judgmental, only trying let you know the rules we all have to live by must be followed by all participants!
    I want you to succeed in your goal and not arrive at the launch and be refused your flight because your not in compliance of the launch rules.

    If you are licensed, I can help you out by lending a receiver and 7 element or three element yagi for your recovery adventure, if you need them?

    Please feel free to PM me if you have any questions or need clarification of launch regulations.

    Greg
    TRA 10756 L3
    CAR S922 L4, RSO
    VE1GCG

  14. #14
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    Quote Originally Posted by rms View Post
    I did reference having a HAM license in another of your threads, now I'm going to specifically ask.

    Do you have an amateur radio license? If so what is your call sign?
    If you do have a license, congratulations and welcome to the wonderful world of amateur radio!

    If you don't have a license you can't legally transmit using the telemini as it is in the 70 cm band. Since the launch you are planning to fly at is on a Canadian Forces Military base, legally transmitting is a requirement. Actually it is a requirement everywhere.

    Not trying to be critical or judgmental, only trying let you know the rules we all have to live by must be followed by all participants!
    I want you to succeed in your goal and not arrive at the launch and be refused your flight because your not in compliance of the launch rules.
    I don't currently have a HAM license but i was planning to research into that field. Right now I'm just dealing with getting all of the parts and building the rocket and after I was going to research into the radio issues. Does


    Quote Originally Posted by rms View Post
    If you are licensed, I can help you out by lending a receiver and 7 element or three element yagi for your recovery adventure, if you need them?

    Please feel free to PM me if you have any questions or need clarification of launch regulations.

    Greg
    And yes, that would be awesome. Can you track the telemini using that reciever?
    trffan has been retired

  15. #15
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    And yes, that would be awesome. Can you track the telemini using that reciever?[/QUOTE]

    Yes you can, this is the receiver setup I use for radio direction finding.
    Getting your ham ticket really isn't that hard, glad to hear your looking into it.
    Greg
    TRA 10756 L3
    CAR S922 L4, RSO
    VE1GCG

  16. #16
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    Quote Originally Posted by rms View Post
    Yes you can, this is the receiver setup I use for radio direction finding.
    Getting your ham ticket really isn't that hard, glad to hear your looking into it.
    Greg
    Ok thanks. Do you know any site which i could start researching the basics of radio operating?
    trffan has been retired

  17. #17
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  18. #18
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    Quote Originally Posted by timbucktoo View Post
    Thanks.
    trffan has been retired

  19. #19
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    If you have a local ham club, contact them. I willing to bet that they would be very happy to assist a 14 year old obtain his ticket!
    TRA 10756 L3
    CAR S922 L4, RSO
    VE1GCG

  20. #20
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    Quote Originally Posted by rms View Post
    If you have a local ham club, contact them. I willing to bet that they would be very happy to assist a 14 year old obtain his ticket!
    Thanks! Will check.
    trffan has been retired

  21. #21
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    Subscribed!

    If there is anything I can help with just let me know! I look forward to seeing this fly!

    (If you want to test fly on some smaller motors first, you could come check out a launch Petitcodiac in the spring or summer)
    CAR S 1096 Level 3 | My YouTube channel
    NB Rocketry.
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  22. #22
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    Quote Originally Posted by rocketgeek101 View Post
    Subscribed!

    If there is anything I can help with just let me know! I look forward to seeing this fly!

    (If you want to test fly on some smaller motors first, you could come check out a launch Petitcodiac in the spring or summer)
    Thanks! Maybe after i finish the rocket, i could come there and fly it on a estes D12 motor to test out the systems. I'm planning to ground test the electronics and deployment but a actual flight should do much better.
    Last edited by TRFfan; 16th February 2017 at 03:58 PM.
    trffan has been retired

  23. #23
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    Quote Originally Posted by rms View Post
    Yes you can, this is the receiver setup I use for radio direction finding.
    Getting your ham ticket really isn't that hard, glad to hear your looking into it.
    Greg
    And also, do you need a teledongle too to track the telemini?
    trffan has been retired

  24. #24
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    Quote Originally Posted by TRFfan View Post
    And also, do you need a teledongle too to track the telemini?
    You need either a ham radio which is capable of recieving APRS packets or the teledongle or the teleGPS. All require ham license.
    Tim
    L3 NAR 98225

  25. #25
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    Quote Originally Posted by timbucktoo View Post
    You need either a ham radio which is capable of recieving APRS packets or the teledongle or the teleGPS. All require ham license.
    Ok thanks for clarifying.
    trffan has been retired

  26. #26
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    Quote Originally Posted by timbucktoo View Post
    You need either a ham radio which is capable of recieving APRS packets or the teledongle or the teleGPS. All require ham license.
    Except for the ham license part this statement is wrong Tim.

    The telemini is a dual deployment altimeter and rf beacon only and does not send aprs packets therefore no decoding is needed, just a 70cm receiver capable of attaching a yagi antenna for radio direction finding.

    Greg
    TRA 10756 L3
    CAR S922 L4, RSO
    VE1GCG

  27. #27
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    Quote Originally Posted by rms View Post
    The telemini is a dual deployment altimeter and rf beacon only and does not send aprs packets therefore no decoding is needed, just a 70cm receiver capable of attaching a yagi antenna for radio direction finding.

    Greg
    You are correct that it doesn't transmit APRS packets (no GPS) but it will transmit telemetry data that can be recieved by the Teledongle or TeleBT (confirmed by Keith Packard).
    Last edited by timbucktoo; 16th February 2017 at 10:05 PM. Reason: typo
    Tim
    L3 NAR 98225

  28. #28
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    Good luck with it!

  29. #29
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    Quote Originally Posted by GrouchoDuke View Post
    Good luck with it!
    Thanks!
    trffan has been retired

  30. #30
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    I'm so following this thread. Had something similar in my fleet a while back.

    For what it's worth....the Telemini is THE avionics package for something like this. AFAIK, nothing else on the market comes close to providing deployment and tracking needed for something like this (taking into account available space and mass allowance). And yes, it is RF only, which is plenty good enough....while it is true that GPS has become much more the norm these days it seems, there is a long history of rocket tracking via RF before GPS was so affordable and available to the masses. Get some advice from folks with experience in RF tracking - it will serve you well.

    Can't wait for more, and hopefully some successful flight reports,
    good luck,
    s6

    - Yes, I did a search before posting. -

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