modeling full keel hulls in rhino

[Kirk Hill]

Hi,
I am trying to determine the best approach to modeling a full keel
hull (alberg design) with Rhino. The stern part of the hull cantilevers over the rudder below.
I have tried lofting and network srf for the full hull and keel and cutting out
the portion at the rudder. This works pretty well but it seems somewhat difficult to control the smoothness.
I later tried to separate the keel from the hull in the lofting process and this seemed to work better. More control over the
smoothness. The problem with the second concept is I have to
either join or merge the keel and the hull. If I am only able to use join I cannot tweek or rebuild the surface Even with that issue it seems to work better. Any of you pros have any thoughts? Keep in mind I am doing this for graphics not to mold
or design a boat.
Thanks

Hi, My aproach will be to model the boat just pulling vertex to shape the hull and keel, will be a single surface clean and smooth, model it even with the rudder (if the rudder its going to follow the shape of keel and skeg) once you model that, then you cut the rudder form the model, that way you will have the surface for the rudder teh way it has to be and following the shape of keel and hull.

maybe a surface with 8 columns by 5 rows will do for the half hull.

IF you are tracing a set of plans and creating a new version of this hull or similar.

DO NOT bug down yourself trying to match 100% inch by inch the hull, shape it nicely, the NURB surfacing it wont guarantee the smoothness of wethever shape you ar doing...but if you practice you will find out that you can get really smooth shapes....Let it Flow.

Good luck

[Kirk Hill]

Here is a shot of how I did the model by separating the hull from
the keel. After joining it seems to work ok except I cannot tweek
the points.

[Polarity]

How about projecting station lines on to the hull once you have it how you like it, delete the surfaces, make sure the projected lines are in one piece and loft (or sweep 2 rails) the lot. This has the advantage that you can tweak the lines plan to your hearts content.

Paul

[Kirk Hill]

I've tried several times models that sound close to what you are
suggesting but with no or little success. It seems like the results
are more predictable to separate the hull part of the shape from
the keel. I keep wondering how professional yacht designers approach this problem. Maybe full keel hulls are no longer in
demand.

Thanks anyway for your input.

[SailDesign]

Kirk,
I have not tried this myself (full keel hulls, that is) but you might want to try making a surface that looks perfect, except that the keel at the aft end is extremely skinny, and goes all the way to the transom. Then go in afterwards and trim off the part of the keel that "isn't" there with a transverse surface, and join/blend the centreline aft.
Steve

[Tad]

Kirk;

Actually Steve's solution above may be one of the better ones. If you go to the Design Articles section on this site you can find a piece by Steve Hollister called "The Dirty Little Secrets of Computer Design" (I think!). He covers full keels in a couple of ways, one is to insert a bunch of control points at the tuck, (where the top of the rudder meets the counter. The other method is to end the hull at the top of the rudder and make the counter a separate piece. (this sounds very difficult, perhaps impossible, to me)

You are correct that there is no demand for full keel boats, in the traditional sense. There is a demand for full keel hull designs, but the keel is very much an add-on appendage, rather than a fully-faired extension. This is for hydrodynamic reasons, the appendage type keel can retain a modern foil section shape all the way up to the canoe body. This means more salient keel for a given draft, thus better performance, all other things being equal. These appendage full keels have a small, tight radius at the hull, similar to a fin keel.

Then again it may just be the capability of available software driving yacht design again


Tad

[Kirk Hill]

Thanks Steve,

Here is a quick attempt at first modeling the hull without the keel
and then the keel and joining the two (hull/keel) together.
I then trimmed the back (transom/back of Keel) off. This attempt
was very crude but could be made to look better. The tricky part
is like you said about the keel getting thinner at the rudder. It seems like this should be easier with Rhino. It sounds like you do
boat modeling for a living. If so do you use rhino or another modeler? I happen to be a sailor who has a background in Architecture and not to much experience in modeling organic shapes. Generally buildings are blocky shapes.

Thanks

[CGN]

Hi this is an example of what i may do its really smooth transition it may not be perfect but it will be inside tolerance.

[CGN]

sorry about that

here is the file:

RhinoV2

[CGN]

i create a patch surface between the skeg and the hull.

[SailDesign]

Kirk,
Yes, I use Rhino a LOT. All of the renderings and models in my gallery are Rhino productions.
http://www.boatdesign.net/gallery/sh...er=909&cat=500
Steve

[Kirk Hill]

Tried it with network srf and it's coming along pretty good.
Here is one attempt. I still have not trimmed out the area for the
rudder. Thanks for everyone's help.

Kirk