Making an accurate hull

[Chikokishi]

I am trying to build a hull that is 5′ exactly across at the widest point. so i set the point to 2.5 feet and when the program models it, it appears to be less than 2.5 feet. What do i do about this?

Attachments:

• Hull.JPG

[Martin Sch�¶�¶n]

The control point is not on the hull surface. Regard them as attached to the hull surface by means of springs.

I just pull at them until I get what I am after. There may be better ways.

/Martin

[Chikokishi]

I restarted the model and did just that. My new model is much better than the original. Thanks for the assurance. 🙂

[giorgio zuppin]

hello to everybody, Hy Mr. C. I think you have had a good answer by Martin, I’m here to expand a bit the matter.
Some time ago I answered a post about creating a model vessel by points, e.g.: points achieved by linesplan.
My answer was YES, with an explanation of the procedure ( one among the many ).
What I missed, taken it for granted, was that, by the nature of the program, when you have a grid to work on, try to imagine a tent or a tissue in space, hold by a tensile structure assembled like a 3D grid – your DS grid in effect – moving the knots of your structure you’ll modify the aspect of the tissue; that of course has to be tweaked to cope with the desired surface
You can see clearly in wirefram wiew, with the interior edges on.
You can see the distortion and the changing shape of the surfaces.
Thus adding appropriate control points – more knots on yor grid – you get an approach to the desired shape.
It’s all about that: surface control.
Keep it on.
Jurgen.

[giorgio zuppin]

P.S.: As a footnote, what you’llhave had learnt up to now:
The grid is NOT the surface
It’s like the poles of your tent.
So hold them tightly, you won’t sleep in the rain!

Cheerio, Jurgen.

[Chikokishi]

Hah, you guys are great. Whats the purpose of being able to specify point locations to the 3rd decimal place if the boat isnt even touching them? Also, heres a screenie of what i have so far…

[giorgio zuppin]

Thank you Sir, I’ll appreciate.
Anyway, in a technical environment you have to stuck to the fifth decimal almost.
It’s a current practice And useful.
For ex.: when I start a fresh design, I draw a scale down model, 1:3 or 1:10 it depends on the final size.
Why? Because is easier to manage, of course and you can hold small changes on the grid better.
That’s why you need a three digit precision.
Furthermore, more detail management means more tools you get… so more defined models, full stop
Nice the pic, well streamlined and detailed, but strange the choice of a beam so large.
Anyway wish you enjoy the program And this bunch of Silly forum’s hosts.
Jurgen.

[Chikokishi]

Im designing a sailboat for senior design. the purpose for the width is to allow it to have a large righting force when heeling over. Im limited to the length, and if i make her thinner shell capsize easier. So i went for a wider boat to minimize this. It also allows a good bit of legroom for two people. the boat is only 11.5feet long. trying to stay below the legal licensing requirement

[giorgio zuppin]

You can try to blend it with this one, I’ve kept lenght on 11’6″ but if speed is not the matter this hullform allows more room on the cockpit and easier developement of surfaces on the workshop:

To be completed with a removable – ? – ballast fin keel for transport.
Jurgen.

[giorgio zuppin]

Sorry, it was a long harsh day…
what I ment was a mobile fin to act as moving ballast. business as usual on small boats, to be raised of course fo’ transport.
To be on the posh side you can raise the knuckle towards the stern thus gently round it.
Skin a bit the waterline beam mantaining the clearance on freeboard and so the height. you do NOT want have a drawning bum…
It’s all fo’ now, call me out, goin’ to sleep.
Jurgen.

[Chikokishi]

Thats a cool design, is the hull all fibreglass? Mine that im working on will hopefully be strip planked then have a layer of fibreglass on top. trying to go for a classic shape a bit to keep speed up.

[giorgio zuppin]

I’ve done as a sketch to cope with your parameters: lenght 11’6″ and a wide hull to accomodate a crew of two.
Comfort slow cruising instead of speed, with this size a performer hull would be like a 49er or a 470 both are 3′ bigger and of course arranged solely for racing.
An alternative could be old designs of centreboard Dinghy still they are no more than a tender sloop, with no room for cruise.
After a bit of refinement as I said it appears like:

Still a bit fat but more attractive.
Also it would be easier to build it as you have said: grp cover on a plywood core: the lines are in the developable range.
Have a glimpse how this technique is wisely used at: http://www.enavigo.hr/en/
Bye, Jurgen.

[Chikokishi]

How did you make a closed hull in your design? I am trying to close mine up and i cant figure it out all too well.

[Jamie]

Hah, you guys are great. Whats the purpose of being able to specify point locations to the 3rd decimal place if the boat isnt even touching them? Also, heres a screenie of what i have so far…

i think this question was answered somewhat but have a second reason.

i draw and build 3m long hard chined planing hulls specifically for jetboating so i am using the crease tool alot. when i am using the crease tool the boat is almost always touching the points

[giorgio zuppin]

All right, give away time: two answers one post. C’mon Ladies & Gents!
First one, Mr.C. – specify please what do you mean for closing a hull, if the question is clear I am glad to answer.
Second – hard chines – for a boat like that it’s quit a compulsory choice, surfaces developed by a flat sheet and sharp
edges. you can still draw it with normal edges but a long, long time is needed and for that size, it’s not the case.
I try to avoid chines but it’s a personal choice, something related to a real life approach where true edges does not
exist and all CAD programs have a tool to set the appropriate radius.
Furthermore I find the rendering more… sexy? – if I can say – with this approach.
Btw it gives a flexible option to smoothen or sharpen corners, cavities and the general aspect of the mesh.
The dark side comes when you try to draw the steps or redan of an offshore racer: mission impossible (quite) with DS.
For that task you go on another program: to any job the proper tool.
And with that bombshell ( ? ) I’ll leave.
Bye, Jurgen.

[giorgio zuppin]

to Mr.C.: if you refer on how to achieve a closed – fully decked – hull, within a continuum of the grid, well the answer is easy but demanding – yuo need practice – it’s a matter of extruding edges following the bluebrint, the one in your mind or a real one, no difference.
Have a glimpse at the grid in the sample I’ve done, and appreciate THE MIGHTY TEAPOT in her’s full glory:

To make my answer more clear to Mr.H. it’s true when you set points on a hard chine and creat a surface to another hard chine, it will stay closer to the design’s set, closer, not coincident it’s still a 3D curve…
Nice dreams.
Jurgen.

[Chikokishi]

So basically, i take the top of my boat and continue it around until the hull is fully closed? Thats seems simple enough. what about on the back where the transom and the out and top and inner walls create points that have multiple faces touching them? I know freeship had a problem with this, does delft ship?

Thanks a lot

[giorgio zuppin]

Nay, you can avoid multiple points and double edges, the program will help you in detecting the fails, it’s a matter of use all the available features.
In the “face” section on the upper string there are two magical buttons: “create a face” – from selected points – always remember selection must be done in a appropriate order; and “close hole” – fills the gap between highligted edges – you have to complete the face with a suitable serie of new edges.
In the edge section you can use “extrude curved” – carefully – the choice of the edges to extrude may cause a messy result.
In case you are guessing “how to?” separation between parts of the drawing could be done easily assigning different parts to a proper layer, a quick way is – in hull display section – toggle on “interior edges”, now you can select parts of the mesh by left click or entire zones by shift/click.
Other features I recommend you are in the “tools” string – “offset surface” as modelling tool and of course “move”,”rotate”,”scale” in the transform section.
Stop for now, there are more useful tricks just ask if you need.
Bye, Jurgen.

[giorgio zuppin]

About transoms, here’s a sample; all done by continuosly extruding edges, assigning new layers, creating holes, re-extrudig edges, and so on.

To semplify you can leave all edges as hard chines and decide later what edge to smoother or not, it’s a personal choice and it depends by the final use of your job.
Bye,Jurgen.

[Chikokishi]

I rebuild the hull, this is the newer model. Also, if youd like to chime into other chats, i have a couple of posts on sailnet. Head over there and search for chikokishi. Ill come back here time to time to upate you on the progress too if you dont come. =)

Thanks for the help!

[giorgio zuppin]

Hy Mr.C, well done!
Pardon me I have had a glimpse at sailnet to your posts.
Rolly Polly, you need this:
Have a look at the forum, in hull modelling>>search “show me your ship” at the last page…
For construction details on gaff rigging, I can’t help directly but try to explore websites of the old continent, small shipbuiders in France, Holland, Italy, Greece, museums and preservation societies, Classical ship’s events photo galleries and so on.
Best wishes, Jurgen.

P.S..before wearing a NBC suite for sail in your premises, have you ever considered horse-riding as an alternative?

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