Full Version: Lofting a boat hull.

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Seems a cool result!
Of course will be fine if you can explain your method used with moi in a decicated thread!

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The trouble -- or part of it -- is that I'm doing this by the traditional method, i.e. a "lines-drawing". I think one needs a few years of work on this method, with paper and pencil, before adapting the process to MOI. If you don't know how to make a lines-drawing, you have nothing to go from, or to. If you do a google: "yacht lines drawing", you will find some examples of these. I looked and couldn't find what I though was a good example, so I'm not offering anything here. But basically, you design the hull entirely in two dimensions, with sections corresponding to 'x', 'y', and 'z' planes. As I said, the trick is that all the points which correspond to intersections -- in three dimensions -- must be coincident. Once you have all the sections in 2D, you can select, move, and assemble them into the 3D form. Then, 'Network' will add surfaces. BTW, you need those 2D sections in order to figure the displacement (which we usually do using 'Simpson's Rule'). And if anyone is really interested in this subject they should get a copy of 'Skene's Elements of Yacht Design'.

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Hi Tim,

It seemed to me the original poster was working from a line drawing of some type. Don't know if it is the same as what you are using though. One thing I did notice though is the issue of the curves not matching up. Moreover, they were off by quite a bit in some places. It looks like he digitally traced them and got some really funky results. In places where you would have a line, a radius, and another line, it was just one huge curve. You couldn't make it like that if you wanted to using normal tools. So I have to believe it was some sort of conversion. Other places where a fillet would be logical was not a fillet. But some sort of curve. That is why I was saying the profiles were not quite right and needed fixing. But other more advanced forum users where able to work with them.

I have to agree with you though, I can't imagine this is very accurate. I know with propellers I'm extremely accurate with the points and curves. To get the right aero performance. What you are saying makes me think you are doing the same to get the right marine performance. I'm not sure what the original poster's intent was. However, most of the people that post here aren't worried about engineering. There methods are advanced in terms of modeling technique but terrible from an engineering point of view. Burman brought this up years ago and got his head ripped off. He's since disappeared from here mostly, which is a shame.

I have found that most of the questions on the forum relate to a lack of understanding of the real world. If you use Rhino and MoI like you would build something in the real world, there isn't many questions you run into. Most of the people here are coming from Poly modeling though.

Anthony

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Hi Tim,
Your correct the method I mentioned is not accurate enough for an actual sea going vessel only a visual model.
The method you mentioned of producing curves in 2d and adjusting into a 3D curve using line drawings can be achieved in delftship, Freeship and Polycad softwares.
Cheers
Barry

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Thanks Tim. I am indeed very familiar with lines drawings. I'm a professional modelmaker and specialised in yacht models for various well known designers. I may be having to do a model of a tug and a barge for the owner who is having them restored to a luxury level. I was hoping to transfer those skills to MOI and set up the lines in exactly the same way as I would make a plank on frame model and then get it made on a CNC router. All is good until I discover you can't sand bits to shape very easily!

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HI, I'm developing often hulls and boats, and the lines plan are god for building and not for modelling, for a better result I use a few sections and a network surface, or a 2 rail sweep.

And other thing consider only an half boat when you make the model, is bit complex making the keel and hull both in one surfaces.






Here a simple Dinghy made with loft.. but in IGES, the Moi version has no more sections.

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Hey Anthony,
Still here!!! I got cancer which set me back a bit. but still around.

"Got his head bit off"

Well, mostly my own doing. You are touching on some of the points here. "Accuracy", "the real world"...

I found though that it starts to encroach on someone's process, and can feel offensive. So have been working at avoiding "philosophies".

Your prop was a fun project. You were open to changing your process to get a result. In the REAL WORLD, big Ship prop makers for instance, have a highly paid, experienced guy, with a GRINDER in his hand, working and balancing the part. after it is manufactured.... lol

Cant really do "Accuracy" from a 2d drawing, most likely downloaded from the internet. A REAL ship drawing would be far more intense. Filled with math.

So, here when we talk about accuracy, I believe we are talking about "How much time are we willing to put in"... REAL models can be YEARS in the making. Down to the PATCH, bolstered by mountains of math and supporting files for each patch...

Michael already posted a link to a thread where I discussed with a guy his ship model (Mark Brown). He ended up making some beautiful stuff. I think he worked on it for "MONTHS".... The idea that a few curves and a loft to generate an entire hull, is reaching.

My suggestion in his approach would be the same here. Model your curves as "Waterline" instead of station. In a real world ship build, the stations are just a means to create the waterlines, which ARE the design of the ship....

But I would have to tell the OP to scrap all his work, start over and work for months to generate the design... So just gracefully getting across Michael and Barry's points and methods, are good. Being stuck on "The accuracy and this drawing", is a no win.... Allowing in "Loose loft" methods, and adjusting for that, really goes a long way.....

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Hi Burrman,

Damn, really sorry to hear about getting cancer. That's terrible. I hope you are able to beat it.

Yeah, the mountains of math is the hard part. I'm still finding bugs with PROP_DESIGN. I started with a code called PROPSY, thinking I could scan it it and it would just work. Damn, was I wrong. 10+ years latter and still pounding on it. You helped a lot with figuring out the leading edge was an ellipse. That was not clear at all from the NACA definition.

At various times, I asked if a script could be made to automate the geometry creation process. Some progress was made but don't think a finished product was posted. However, that helped me find some important bugs as well. So it was helpful.

Yeah, I hear you about forum posts regarding accuracy. A lot of the work flows that seem to be popular aren't something I could use. Even a loose loft is not an option. So I just kind of shut up as well. Just easier that way I guess. Plus I saw what happened to you. I couldn't stand that guy either. Naming lofting after himself. The arrogance was unbelievable. Yet he was a popular user. So that left me pretty dumbfounded.

I started with a 2 rail sweep using 1 profile. I ended up finding out Rhino was screwing up the geometry. Even small deviations had big impacts on stress and vibration. You would be surprised what a small deviation can do. Eventually I figured out lofting with multiple profiles was the best way to go in my case. That ensures the aero and structural performance.

Anthony

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Hi Burr, that really sucks about the cancer. I sure hope that you'll get rid of it.

- Michael

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Hi Michael and Anthony,
Yeah, an out of the blue punch in the gut....

But, it seems to be gone for now!

The treatment was brutal though.
Lucky i didnt post while on morphine!!!! Lol

Making my comeback now. See you in the funny papers

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Hi Burr, sounds like a rough time but I'm glad you're on the upswing now.

- Michael

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Thanks again Michael!!

Really appreciate your forum and community...

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that's great news, except for the horrible treatment. you reminded me of the beginning of the movie shallow hal. the kid goes to talk to his father who's high on morphine. tells him a bunch of crazy but true sh** that changes his life.

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Hi Burr!

Some minutes ago I read your posts:

"Still here!!! I got cancer which set me back a bit. but still around."

"The treatment was brutal though.
Lucky i didnt post while on morphine!!!! Lol"


It's really sad to hear these really bad news!
So sad...

But I understand from your words that you're a "fighter" :)
This is a very good thing for you!

I hope all the best for you and your life.

Have a blessed day!

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Hi Marco,
Thanks for the nice words! On the upside now, so back to it....

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Gord had a nice thread going here...

Didnt really mean to derail it...

Onward!

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Hi Burr.

I'm sorry...but English is not my native language :)

I tried to translate your last post, but I couldn't do it:

"Gord had a nice thread going here...
Didnt really mean to derail it..."

Is it figure of speech in English/US?
What does it mean?

Thanks :)

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Hi Marco,
I dont want to change Gord's post "lofting a boat hull" into "Burr got sick" post....

And also, "Thanks for the kind words"....

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Ah...ok!
I should have known by myself...

Thank you very much for the clarification.

And...Have a blessed day Burr!

Ciao :)

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Burrman the return of the new year ... always pertinent! ;)

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