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  1. #1
    Join Date
    24th February 2009
    Location
    Pasco, WA
    Posts
    351

    Round tube fins vs Square tube fins?

    I have an extra 5.38" LOC nosecone and a short length of matching body tube. I would like to build a stubby tube rocket with them. I have lots of foam core that is easy to reinforce so I'm thinking of a square tube finned lower section that transitions to the 5.38" body tube.

    Any thoughts on the drag difference between these types of fins for simulation purposes?


    Derek McGuckin
    Tri-Cities Rocketeers
    NAR Level 2
    www.TriCitiesRocketeers.org

  2. #2
    Join Date
    24th February 2009
    Location
    Pasco, WA
    Posts
    351
    delete

    Derek McGuckin
    Tri-Cities Rocketeers
    NAR Level 2
    www.TriCitiesRocketeers.org

  3. #3
    Join Date
    30th January 2016
    Location
    US > OK > NE
    Posts
    3,844
    Flowing air doesn't like sharp edges. All of those corners are going to be even draggier than a regular tuber.

    I think it's a great variation on the classic. Any thought of a hexagon with three squares in?

  4. #4
    Join Date
    27th August 2011
    Location
    West Tennessee
    Posts
    2,825
    Suspect higher drag due to the triangular segments that make smaller tubes.

    That said, the tendency to weather cock will be less than for the tube fins due to less lateral surface area (I.e. BETTER THAN ROUND TUBES), and tube fins are already better than regular straight fins for weather cocking.

    Since you aren’t going for any altitude records (or you wouldn’t be messing with tube fins anyway) maybe build a small version of it with a BT20 body tube that you can swing test (or “eyeball” it and launch as a heads up flight, ideally when nobody is around to tease you if it sky writes). Once you get something you like, rescale it proportionately for your larger tube and adjust the CG proportionately as well.
    It is amazing what you can do when you don't have a choice.

    Smart people learn from their mistakes.
    REALLY SMART PEOPLE learn from OTHERS' mistakes.

  5. #5
    Join Date
    24th February 2009
    Location
    Pasco, WA
    Posts
    351
    Thanks for the thoughts. Yes, I plan on building a smaller version to work out kinks. I like rockets that stay low with big motors. Lots of noise and you can see the whole flight. This will fit the bill nicely I think. I'll start another build thread when the time is right.

    Derek McGuckin
    Tri-Cities Rocketeers
    NAR Level 2
    www.TriCitiesRocketeers.org

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