DeHavilland DH-88 Comet

Discussion in 'Gallery & Designs' started by jmueller, Mar 17, 2005.

  1. jmueller

    jmueller Member

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    Hi Folks,
    it's me again. I actually started what was announced in my sig. The famous, glorious and victorious DeHavilland DH-88 Comet. I just went to my workshop and took a picture of this wooden beauty. I will try to keep you informed on the progress I am making.
    What you see here is 6 hours work of tweaking, sclaing, resizing, doing over again...and still not all formers are correct.
    At this point I will also try to share some tips and tricks using RHINO which I stumble upon during the design process. Check out next post.

    Greetings
    Jan
  2. jmueller

    jmueller Member

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    A few Rhino tips

    Helpfull:
    Use a reference object. For me its a 1cm square in each view. This prevents you from fiddling round with parts at large zoom scale that end up being the size of the paper thickness.

    -Always work in the actual scale of your model from the beginning.

    Helpfull:
    Do not use the loft function for parts that are to be unrolled. Although options like "straight sections" and "developable" are provided, the better way is different. Use 'sweep two rails'. Connect the formers using a straight line at the point where you want the surface to be cut. That way you alway get a surface that can be unrolled and is cut at the position where you want it.
    I used the loft function at the beginning to get the shape of the fuselage. Then I put vertical planes at the position where I want the formers. These are then created by using 'intersect'.

    Thats it for now
    Jan
  3. jmueller

    jmueller Member

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    Maybe we need some pitcures to make it more clear.
    Here are two formers, connected by a straight line.
  4. jmueller

    jmueller Member

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    And this is what you end up with:
  5. Jimi

    Jimi Member

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    is the sweep two rails better than the loft command? i have to say, your work looks really neat!
  6. jmueller

    jmueller Member

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    I think the loft command uses the sweep funtion internally, but it sometimes gives strange results where you actually can see that the created surface does not correlate with the formers. Using sweep makes me more confident because I now exactly whats happening.

    Jan
  7. Jimi

    Jimi Member

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    oh ok.. thanks :)
  8. lunarhighway

    lunarhighway Member

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    great, i've been thinking of designing this model myself in paper too once.
    a long time ago i carved it from balse but never really finished it
    So 'im glad someone else decited to make a paper model of this beautyfull bird!

    looking forward to see the final result... so far it looks really great

    :D
  9. jmueller

    jmueller Member

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    porgress update

    Hi Folks,
    I just want to share some progress pictures.
    Have a look:
  10. jmueller

    jmueller Member

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    and the result of an evening, one beer and two commuting trips
  11. wunwinglow

    wunwinglow Active Member

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    With Rhino, the commands are ordered on each drop-down menu in order of 'complexity', and usually if the command is nearer the top of the list than an alternative, it is more likely to succeed. Often the results, such as a 2-rail and a loft give identical results given certain settings. In other cases, matching curvature of an adjacent surface for example, the results will be different. Then you have to choose which is better for your particular case. You might need to consider what you will be doing with the surface later on, perhaps. I try to work on the KISS principle ( Keep It Simple, Stupid!)

    The Comet looks good, by the way!

    Tim P
  12. jmueller

    jmueller Member

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    Progress of the comet

    Hi Folks,
    just wanted to show you some of the progress I made. The Comet now has its Tailfins and I finished most of the fuselage formers. Especially the center wing section is done. Note that I couldnt resist to make them a little Halinski style with mounting links. Next step to go are the engine nacelles.

    Hace a nice week
    Jan
  13. NOBI

    NOBI Active Member

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    Hi Jan,

    I wonder how u make a very smooth tail like that, what function u use to create that tail? sweep2rail or only loft.

    your Comet look real cool
  14. jmueller

    jmueller Member

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    Hey Nobi,
    nice to have you back!
    Actually, to be honest, the vertical stabilizer is not unrollable. It is just a surface from a few edge curves. I did that because the rudder is really thin and you can use the projection as the unrolled surface (with a little bit of tweaking to account for the thickness).
    But the horizontal stabilizer is unrollable. I used sweep2rails for the large surface. The tip (look at the picture) is done by dividing it in two surfaces and also using sweep2rails.

    Jan

    When did you change to using Rhino?
  15. NOBI

    NOBI Active Member

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    Hi Jan,

    thank you very much for your reply, sweep2rail is very cool command but weak point is result is unrollable surface, i used to use sweep2rail and then re-build it to make it unroll, some can unroll and some cant unroll so now i use loft command to do surface for me and it work well :)
  16. jmueller

    jmueller Member

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    Hi Nobi,
    hmm, I did it the other way round. For me loft sometimes gives strange results. So I always use sweep2rails with a straight line as cross-section. That way you should get a simple curvature (and therefore unrollable) surface by definition.
    When I use loft I always check that 'simplification' is turned of, because that reduces acurracy.

    Greetings
    Jan
  17. NOBI

    NOBI Active Member

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    Hi Jan,

    use straight line as cross-section? i never try that technic before. u mean u use straight as cross-section and use half of subject's cross-section as rail? i think i must try that technics :)

    i agree with u that loft function make model not accurate if u use it follow through cross-section what make feom blueprint :) that why i must try your technic

    another question...that wing's fillet can unroll?
  18. jmueller

    jmueller Member

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    It actually does. I used the same technique. First I constructed the rails using intersections of planes, so that they lie on the wings surface. Then I connected the ends with a straight line. Using sweep2rail gives you this result, which can be unrolled.
  19. NOBI

    NOBI Active Member

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    Hi Jan,

    That's real cool technic...thank you very much.

    oh! i forgot to answer your question that when i begin design in Rhino...u will see my Seafury, Ki-27 and Ouragan is come from Rhino :) and also with my next project too
  20. bfam4t6

    bfam4t6 Member

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    Jan,
    Your designing techniques are way above my head, but the plane does look very cool so far. You'll have to keep us posted.