I’m having a really hard time trying to get my head around lofting ship hulls… I’ve watched a few tutorials and I’ve spent a good few hours on different files trying to make this hull but it’s driving me round the twist!
lofting seems to be OK but then I can’t seem to fathom how to model the bow. I’ve tried rebuilding the surface but then it makes it uneven from the side view… Trimming and cutting makes a mess of the surface edge, nothing seems square and if I turn on the points to manipulate the surface they look square even though the surface is all over the place.
I’ve tried shrinking the surface etc.
Any pointers, please? Or tutorials that I may have missed and would help?
(I’m aware that I’ll probably have to use curvature analysis on the sections to get the flow correct.)
Have you tried the rapid hull methodology from rhinocentre.nl? This will explain how to loft a hull form from one surface with strategically placed curves.
2D, you are on the right track with your hull from lofted curves. Turn on history when creating the loft from the curves and then you edit the curve points and the hull surface loft will update. The key thing at the bow is to rotate its curve 90 degrees and then project it to the midship longitudinal plane. Once you get your hull surf close then make a copy of it and hide the original surf and its curves so as to not break the history on the surf. Hide them and then you can point edit the copied surface for fine tuning. If it gets too goofy then you can ditch it and turn the history enabled original back on and get a fresh hull half for another try.
A nice trick is to make a series of station planes and intersect them with the hull surf with history turned on. Hide the station planes and turn the intersecting curves to a contrasting color and use them to watch the results of your curve or surface point editing. The surface isocurves can be misleading if they get skewed too much and it is better to have true planar station intersection curves to judge your shape. Zebra stripes are a big help too!
Good luck!
Thank you both, I’m on the right track now the rapid hull methodology helped; thanks Matthijs, I couldn’t see the wood for the trees! It would seem that rebuilding the curves to have the same number of points makes a much cleaner loft.
I can see there is pretty much all the information I could ask for in that drawing from 1979!
You’re right about point editing Jody, thanks for the tip, I guess I wanted to avoid a lot of curvature analysis, smoothing and fairing etc but it should come right with a few tweaks.
Always getting tripped up with too many curves to drive the shape!
What jodyc111 stated regarding the surface history is essential for edditing/fairing the hull form. Also keep the control points of the curves and also the curves to a minimum.
This is what I made in over 5 minutes as an example to start with: Ship of the line 03.3dm (147.1 KB)
I think I’ve sussed it now, it was mainly rotating the curve for the bow… Don’t know why I didn’t see that - network curves is what i was trying to build it with.
I’m fairly happy with the shape, it needs a little tinkering but it’s almost there for joining and detailing.
Matthijs has nailed it!! The rapid hull methodology from rhinocentre.nl is the (only) way to go if you want to get a really clean hull from an exsisting lineplan.
So I’ve nearly cracked this - I’ve rebuilt it so many times… This part is holding me back, I’m confident with the rest of the model but I hate not being able to explain something or iron it out as invariably it comes back to haunt you later on if you skip things early on.
I’ve used the loft options as per our earlier discussions but I can’t seem to loft the bow without creating a nasty kink/pinch point.
I’ve tried connecting the curves but that only leaves me with a straight section loft option.
If I make the end curve shorter I still have the pinch point…
looks great so far! please analyse the rhino file in my earlier post. If you take a look at the curves, you will know. the problem is that you have a connection between the curves (as far as i can tell by the picture) which creates a kink. It is important that no the curves are not touching.
Furthermore, I would also recommend adding a second bow curve(just as in my file) to get the waterlines right. I know from experience that this kind of hull type has broad shoulders(waterlines) in the front. To get such a curve I recommend the ‘shear’ function in rhino on the bow curve. I believe there are tutorials on this function somewhere. If not? let me know and I will make a short 101 on Monday when I have access to rhino.
Good luck finishing this beautifull hull from around the 1800’s, I guess;-)
The pinch point is a point where the surface is degenerate. It’s a good idea to avoid degenerate surfaces because they tend to cause lots of commands to fail.
For instance, if you want to offset the surface to create thickness that will likely produce a bad result.
The best approach to avoiding the pinch point is to make the loft extend past the bow and then the bow is created by trimming back to the centerline. In the enclosed file I used only half your curves to keep it simple and then edited the control points at the bow to match the intersection of the bow and centerline plane to
your bow curve.
Thanks for the tips, sometimes It’s easy to get trapped by curves when modelling something from a plan - a good lesson to tweak and play around with things. I’d actually done something similar by the time you’d posted but using Setpt and moving the edge and trimming etc.
Each time I hit a wall like that I keep thinking I should be learning T-Splines but there’s always a work around and then I think - no, I should be trying to learn Rhino
Thanks again for both taking the time to answer with a solid example!
