Free Internet Rowing Model (FIRM)

Discussion in 'Software' started by Leo Lazauskas, Oct 30, 2014.

  1. Leo Lazauskas
    Joined: Jan 2002
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    Leo Lazauskas Senior Member

    A program for Windows-based computers that predicts hull resistance,
    velocity, acceleration, and yawing moments. FIRM contains offsets for
    a fleet of rowing shells, and many examples (including all Olympic
    classes) that can be used as templates for your own projects. A 150
    page manual is included.

    Version 2.2 (beta) can be downloaded from the FIRM page at:
    http://www.cyberiad.net/firm/firm.htm
    (20Mb is too big for boatdesign.net.)

    After downloading the file, unzip it into a convenient directory. The
    manual is in the man sub-directory. To uninstall, just delete the
    entire directory.

    If you want a quick demo of the program, double-click on one of the
    batch files in the main directory. I suggest one of the m8 or w8
    examples so you can see how much input is required for some cases!

    (Some versions of Windows report a "file has stopped working message"
    which disappears after a few seconds. This is a well-known Windows
    problem. Click on the X to dismiss the error message and FIRM will run.)

    The program takes a few seconds to initialise.
    Press r to run the model. (The items labelled "n/a" will be replaced
    with actual values.)
    Press m to see the Model Screen.
    Press Esc to go back to the Opening Screen.
    Press f to see the Forces Screen
    Press Esc to go back to the Opening Screen.
    Press Esc to exit FIRM.

    The graphics in FIRM are not interactive. They are really just a way of
    checking that input is reasonable. The arms in the animations will look
    unusual because of the 2D projection. If the stick figures make wild
    motions you have probably made an error in specifying the body angle
    regimes.

    NOTES
    1. Version 2.2 is a beta version. Updates will be announced here and
    on the FIRM page.

    2. I am still looking for a good "canonical" fixed-seat rowing hull to
    include as an example. See the M1x Fixed Seat example in the manual.
    The hull I have used is just a fattened up single scull. Does anyone
    have (Michlet-like) offsets and dimensions they are willing to share?

    3. In the present version, most of the manual comprises graphs that
    have very few comments. These are intended to help users (and some of
    my beta-testers) set up their own graphing packages such as Excel. It
    is pointless trying to set up your own projects if you can't reproduce
    the graphs in the examples from the enormous amount of output that
    FIRM produces.

    OTHER MODELS
    FIRM is a very difficult program that requires a lot of input. If it is
    beyond your capabilities or requirements, Bill Atkinson's model might
    be more suitable. His web pages also contain many valuable insights.
    See: http://www.atkinsopht.com/row/rowrpage.htm
     
  2. NoEyeDeer
    Joined: Jun 2010
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    NoEyeDeer Senior Member

    I'll take a look at it as soon as I get time. :)


    Re the fixed seat example: may I suggest using either (or both) of the Herreshoff/Gardner 17 footer, or an Adirondack guideboat. These seem to be the two often-referenced fixed seat boats when talking about performance. The offsets for both are available. I have a good approximation of both as Delftship models, and I'm sure someone else here would have the original offsets and could help with really accurate models if necessary. I'd even be keen to do the modelling myself if I could get the offsets for free.


    I've spoken to Bill Atkinson via email and he doesn't have any user notes for his model, although he has thought about making some.
     
  3. Leo Lazauskas
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    Leo Lazauskas Senior Member

    I have DelftShip, so I would happy to convert the offsets to Michlet format if
    you are willing to share them.
    Otherwise, the offsets required by FIRM are identical to those in Michlet.
    FIRM automatically calculates the required draft for the crew, equipment and
    boat weight so you don't have to stuff around with sinkage to get the
    correct displacement. Just make sure you use several waterlines above the
    static waterline to allow for larger crews. Like ships, some rowers
    accumulate weight around midships as they get older :)
     
    Last edited: Oct 30, 2014
  4. NoEyeDeer
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    NoEyeDeer Senior Member

    Ok, this is what I have at the moment. The file for the Herreshoff/Gardiner is done partially from memory (I used to see them every day), and partially from dimensions and drawings found online. The problem is with the latter, which everyone seems to have slightly different. Hey ho.

    If someone has the actual table of offsets for any versions of this boat (original Herreshoff, or modified by Gardiner) I'd be happy to model it, on the basis of a gentlemen's agreement that I wouldn't use said table of offsets to build a boat. I'm not actually interested in purchasing plans for the boat since I'll probably never build one anyway, and the close approximation is good enough for my interests.

    Same applies to the files for the Grant "Virginia" guideboat. I made two of these: one trimmed level and one trimmed aft one degree (guideboats are often rowed trimmed by the stern). The hull is only modeled to a height of 200 mm above the baseline, which is probably adequate. Can take it higher if necessary.

    I also have a file D Cockey exported from Rhino, for a Rushton Saranac Laker (another guideboat). I haven't included that because it needs fairing and I still haven't got around to doing this. I'll make an effort on it, since the Saranac Laker is the prototype for the modern guideboats produced by some builders, so is probably one people are likely to encounter outside the Adirondacks.

    Anyway, the other three are attached. No rights reserved. Do wotcha like. :)
     

    Attached Files:

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  5. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Thanks. You deserve a free version of FIRM and triple your money back!

    Do you have any idea of a reasonable hull weight to use for these boats?
     
  6. upchurchmr
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    upchurchmr Senior Member

    Leo,

    I have never used any of the programs you have provided, nor anyone else's.
    Do you think it would be possible to model this "row boat" in FIRM?

    Not most peoples cup of tea, but it works well for my wife's needs.

    [​IMG]
     
  7. Leo Lazauskas
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    Leo Lazauskas Senior Member

    No. FIRM is only for monohulls.
     
  8. NoEyeDeer
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    NoEyeDeer Senior Member

    Can vary quite a bit, depending on how they're built. If you just want an all-round ballpark baseline figure, I'd call it 35 kg for both of them. That's about in the middle of the likely range. Could go as low as 30-ish or as high as 40+.
     
  9. NoEyeDeer
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    NoEyeDeer Senior Member

    Hey I had a brainwave. All I have to do is download this sucker 100 times and I can get 300 times my money back. I'm gonna be stinking rich. :D
     
  10. NoEyeDeer
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    NoEyeDeer Senior Member

    Ok, I've been perusing the manual, and one item is befuddling me at the moment: your Fig 23 graph of air resistance, comparing non-feathered and feathered blades.

    The area under the curve is higher for feathered blades, which implies total air resistance over the course of a race will be higher if you feather. This seems odd, given that on the recovery the blade has a higher apparent wind acting on it that any other part of the whole shebang, and if not feathered will obviously have much greater area exposed to said apparent wind.

    What am I missing?
     
  11. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Thanks for pointing out my inadequate explanation of that figure.

    Most models, including my previous attempts, do not include the effect of
    feathering. They treat the oar as a long shaft of uniform diameter with the
    blade being parallel to the water for the time it is out of the water.
    I labelled that situation "No Feathering" in the graph.

    By "With Feathering" I meant that the model includes the effect of the
    oarblade not being parallel to the water near the start of the stroke and at
    the release. That's why the (green) curve in the figure for that case has
    those "blips" at the start of the stroke and at the release.
     
  12. NoEyeDeer
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    NoEyeDeer Senior Member

    Aha. That makes sense. Also leads to a question. How hard would it be to model actual "no feathering" rowing for higher freeboard boats? It's pretty common to not bother with feathering at all for fixed seat.

    From what I've seen so far the program looks detailed, but fairly straightforward and logically laid out.

    BTW, after a bit of looking around I managed to find a legit table of offsets for this boat: 1903-1906 Saranac Laker

    I'm going to whip up a full model for this one. The term "Saranac Laker" is a generic Rushton term which covers quite a range of guideboats over the years, with different lengths and beams. This seems like a good example to use.
     
  13. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Quite easy.
    FIRM uses a set of air drag coefficients in the airdrag_coeffs.csv file which is
    in the "globals" subdirectory.
    You could change the values of the coefficients for the oar and/or oarblade.


    Thanks. I'll be happy to consider it.
    (The last three you posted loaded Ok in version 6.27.259 of Delftship,
    but not in 5.06.186. )
     
  14. NoEyeDeer
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    NoEyeDeer Senior Member

    Cool. Thought so. I'd be curious to see how much not feathering at all slows things down.

    And yeah those were 6.27 files. I wouldn't expect them to load in an older version. Delftship is free, so I keep it up to date. :)
     

  15. Leo Lazauskas
    Joined: Jan 2002
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    Leo Lazauskas Senior Member

    It can add several seconds over 2000m in a head wind.
    Top class rowers start feathering as the blade leaves the water, but not
    everyone can do that as easily as they make it look.
     
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