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  1. #31
    Join Date
    5th August 2015
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    1,207
    Pro24 case gone.

    trffan has been retired

  2. #32
    Join Date
    5th August 2015
    Posts
    1,207
    Reloads, launch pad, electric wire paint, masking tape, and spray adhesive are still available.

    trffan has been retired

  3. #33
    Join Date
    5th August 2015
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    1,207
    Quote Originally Posted by TRFfan View Post
    If anyone lives in the maritimes then if you are interested in these reloads you could pick them up or i could drop them off to you if you are close enough. PM me for pricing. Reloads are a Pro24 G150, Pro24 G117, and a Pro38 G50.

    Attachment 342763
    Does anyone who lives in the maritimes be interested in these?
    trffan has been retired

  4. #34
    Join Date
    13th June 2014
    Location
    Cocoa Beach, FL
    Posts
    3,708
    Hey are you selling the Difumar rocket?


    Sent from my iPhone using Rocketry Forum
    Tim
    L3 NAR 98225

  5. #35
    Join Date
    5th August 2015
    Posts
    1,207
    If anyone wants it.
    trffan has been retired

  6. #36
    Join Date
    21st September 2017
    Location
    NY/NJ
    Posts
    337
    Quote Originally Posted by TRFfan View Post
    If anyone wants it.
    OK, I've got to ask - what is Difumar rocket?


    __
    Radrocketeers.org NAR L2

  7. #37
    Join Date
    23rd July 2011
    Location
    Butte, MT
    Posts
    2,566
    Quote Originally Posted by afadeev View Post
    OK, I've got to ask - what is Difumar rocket?


    Quote Originally Posted by TRFfan View Post
    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




    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  8. #38
    Join Date
    13th June 2014
    Location
    Cocoa Beach, FL
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    3,708
    Quote Originally Posted by TRFfan View Post
    If anyone wants it.
    Pics? Price?
    Tim
    L3 NAR 98225

  9. #39
    Join Date
    5th August 2015
    Posts
    1,207
    Quote Originally Posted by timbucktoo View Post
    Pics? Price?
    Price is 40 cad. If anyone is interested I'll put pictures up here.
    trffan has been retired

  10. #40
    Join Date
    21st September 2017
    Location
    NY/NJ
    Posts
    337
    I will take it!

    PM sent.

    a
    __
    Radrocketeers.org NAR L2

  11. #41
    Join Date
    13th June 2014
    Location
    Cocoa Beach, FL
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    3,708
    Quote Originally Posted by afadeev View Post
    I will take it!

    PM sent.

    a
    Cool! Hope to see this thing fly!

  12. #42
    Join Date
    21st September 2017
    Location
    NY/NJ
    Posts
    337
    Quote Originally Posted by timbucktoo View Post
    Cool! Hope to see this thing fly!
    That's the plan.
    I might even take it to the NSL, if my schedule continues to cooperate.

    a
    __
    Radrocketeers.org NAR L2

  13. #43
    Join Date
    5th August 2015
    Posts
    1,207
    Sold
    trffan has been retired

  14. #44
    Join Date
    5th August 2015
    Posts
    1,207
    Will you be doing a build thread?
    trffan has been retired

  15. #45
    Join Date
    13th June 2014
    Location
    Cocoa Beach, FL
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    3,708
    Quote Originally Posted by TRFfan View Post
    Will you be doing a build thread?
    I thought you built that rocket but only needed tracker?
    Tim
    L3 NAR 98225

  16. #46
    Join Date
    21st September 2017
    Location
    NY/NJ
    Posts
    337
    Quote Originally Posted by TRFfan View Post
    Will you be doing a build thread?
    Sure!

    Quote Originally Posted by timbucktoo View Post
    I thought you built that rocket but only needed tracker?
    Just the tube and fins so far.
    The rest is yet to come, starting with the nose cone, electronics, and a lot of sanding...

    a
    __
    Radrocketeers.org NAR L2

  17. #47
    Join Date
    8th October 2016
    Location
    Midwest
    Posts
    255
    Ooops, nm.


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