Sailing Dinghy Design

Discussion in 'Sailboats' started by Tim B, Mar 12, 2003.

  1. SailDesign
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    SailDesign Old Phart! Stay upwind..

    MadEngineer (Can we just call you "Mad"? My fingers hurt...)

    Is it possible to export the Hullform files as an IGES file? I use Rhino and AutoShip, and neither of those will take a text file such as yours (unless someone else knows better)

    Steve
     
  2. Polarity
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    Polarity Senior Member

    Hi Steve
    Rhino will imort the point cloud. Go to import/merge and just select point file.
    Does not look like a boat much though!

    Paul
     
  3. Tim B
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    Tim B Senior Member

    http://www.hullform.com/
    for A Hullform 6s free download (which I use occasionally) also outlines the rest of the Hullform range.

    Polarity,
    The files posted shuold in fact be .hud files. Just change the filename in the save dialog box. These files will then read straight into hullform 6s. For an explanation of why they look strange when loaded into Rhino, download the free hullform 6s, then read the instructions. A file format is given.

    Mad Engineer,
    This stuff looks good. Personally like the winged version. I have a feeling that wings might be the way to go. The question is, can we keep the hull smooth at the same time. Personally, I'd like the loaded waterline to be a complete curve, just touching the transom (stern). I have to admit that the one hull I did check that out on (v3 I think) looked nice.

    I'll be back with TBI14v4p1 (for those using the image indexing system I suggested) after the weekend.

    Cheers,

    Tim B.
     
  4. Tim B
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    Tim B Senior Member

    It's Here. It's bigger, better and faster, and there's no bump in the waterline. Yeah!!

    Cheers,

    Tim B.
     

    Attached Files:

  5. mad engineer
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    mad engineer Junior Member

    Tim,

    talking about the waterline just touching the transom, I believe the norm with the skiffs is to design for some dymanic lift so that the static waterline is just kissing the transom at
    (Total Weight - X). On the 29er, Julian Bethwaite took X to be about 30Kg I believe. If we are looking at an all-up sailing weight including crew of about 225 to 230Kg, I make that a design displacement of say 200Kg for the boat floating "on its marks".

    Not sure how close to that I got - I think the transom still digs in by about 20mm or so.

    My trial and error on a smooth hull resulted in a much wider beam on the waterline because of the mid-length section control - also the chine is good for ensuring flow separation when planing which reduces the skin friction drag noticeably.

    I have also toyed with the idea of introducing a hollow between teh waterline and the chine to give a greater dynamic lift but this does mean that the boat would have to be sailed absolutely flat and it doesn't look all that pretty. Given most things in design, if it doesn't look pretty, it probably isn't fast - anyway it is attached for entertainment value.

    (By the way, the forum didn't like me attaching .hud files so I had to change them to .txt).
     

    Attached Files:

  6. Jeff
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    Jeff Moderator

    Sorry about that - I've now added .hud as an ok file extension so it should work for you next time without having to rename.
     
  7. Tim B
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    Tim B Senior Member

    Fantastic, Jeff, I'm sure that it's not only us who'll be pleased.

    Mad Engineer,

    I will have a look at you Hullform I14, sometime this week, not today though, and I'll post an opinion. I have to say, after a while of drawing various hull-shapes, I think we're getting close to something good.

    Cheers,

    Tim B.
     
  8. Tim B
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    Tim B Senior Member

    Mad Engineer,
    The design is great but I am concerned about the pitch as it heels, perhaps assuming a CG of 2.5 meters aft would help to solve the problem. I'll write it into Rhino and have a look if I have time. It does look nice though.

    Cheers,

    Tim B.
     
  9. b14maniac
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    b14maniac Junior Member

    Mad Engineer,

    Like the work, but it does have its problems. I've given it a quick (5 minute) fix-up and rendered it here... the sheerline is modified from your own... I'm not a big fan of how you did the decking work though... then again, the comes down to personal preference. Enjoy... tell me what you think.

    as geocities is a pain to use to display images on here, please put http://www.geocities.com/b14maniac/i14-rework.jpg into your address bar and then come back
    cheers
     
  10. mad engineer
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    mad engineer Junior Member

    B14maniac

    Its nice to know someone pays attention to detail!!

    I have had a second look at the lines since I posted them and you are absolutely right that the measurement bumps almost certainly don't measure!

    As far as I can tell from the rules the pan test on the measurement bumps is only used immediately at the measurement point, so if we widen up Section 6 and lower the chine line at section 6 too that should solve it.

    I was also a bit worried about the size of the hollow against the tight tape measurement but I think this one is OK.

    Attached is my tweaked version to pick up your points!

    Cheers.
     

    Attached Files:

  11. mad engineer
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    mad engineer Junior Member

    B14maniac

    Just had a look at the image - that red colour scheme is very sexy!

    I agree with you on the sheerline and decking but my hullform skills don't go as far as getting that bit right. Probably a case of over to those of you who have more skill and better software to do that bit.

    Tim B - yeah going nose down when it heels seems to be a problem with the weight in the right place for level trim with no heel. But as the boat goes faster you tend to move back in the boat which might help somewhat. Certainly at planing trim with the bow up in the air it is much less of a problem. Not sure we can do much about it though without totally changing the shape of the waterlines....
     
  12. b14maniac
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    b14maniac Junior Member

    Has anyone given the moth design any thought yet? The I-14 seems to be dominating the content in this discussion.... whilst the I14 may be a fun boat to play around with, there is not much new happening within that class to make this all worthwhile, as opposed to the Moths where hydrofoils are making sailing them unfair for those who can't fly, and several new hull designs are emerging this year, including one in france aimed at making the moth a comfortable boat to sail (if that were possible).

    I've done 2 or 3 1/2 decent moths in hullform, however none of them are particularly original (thats the big problem with designing the narrow ones... once something works, there is very little else that you can do!)... one looks a lot like an Aussie-Axeman (Lazich Mk II for those who really want to get technical), the other like a British Skippy2 with a super narrow pintail, the third was designed to accomodate new sailors in the moths (fat skiff hull but without those ugly old flares... kinda like a shrunken Bieker I14 with scaled-up wings). Will render/post images and lines if this post catches any positive attention... otherwise I'll try and throw together my own ideas of what an I14 should look like and show these off.
     
  13. Tim B
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    Tim B Senior Member

    Winning is worthwhile in itself... Being told we've all done it against the odds is just recognition.

    Good Night,

    Tim B.
     
  14. BrettM
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    BrettM Senior Member

    Moths have one huge problem that i hate - At close to 90kg I am simply putting myself out of the competitive weight range. I would love to race them but given most of the guys are about the size of a laser radial sailor it puts it out of reach. How about adding 2 feet to the wl and a monster amount of sail area then we can go sailing...
     

  15. tspeer
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    tspeer Senior Member

    That's what you need - a 14 ft, two-handed Moth.
     
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