Help with a loft

Still relatively new to Rhino. I am trying to model a rather unusual early boat and am having problems finding a way to create the front of the hull. The boat had a unusual bulge at the front. I am trying to use the loft command but keep getting the twist at the front, its quite obvious in the model.

Can anyone please advise how I get a smooth outline at this location? I would like to understand how it is done.

Many thanks, Paul

Fuse loft test.3dm (384.0 KB)

Hi Paul - I’d loft up to the last curve but one and then work on the bulgey part as a separate surface. You can get a cleaner loft from the curves you have by choosing the ‘Rebuild’ option in loft with maybe 12-18 points or so.
Do you have an image of the bulgey part? What is the shape you’re trying to match?


Thank you as always for the assistance. I will be working on this today.

I have attached a photo of the ‘boat’. There are no plans remaining, just a few photos. The bow is very unusual to sat the least.

Thanks for any other suggestions!


Hi Paul,

that boat has a beautiful shape!
I felt like giving this a shot…

check out the “NetworkSrf” command it has some advantages over the Loft.

You can input U and V curves which gives better control of the resulting shape.

I just traced the outlines and moved the control points into space with softmove/gumball.
You would probably need 1-2 additional cross sections to pin down the shape in the midsection of the hull but it is already getting there.

you can use symmetry to mirror the section curves into closed ones in order to create the entire hull in one shot.
NetworkSrf is history enabled, so you can still tweak the U/V curves after generating the surface.

hull.3dm (1.8 MB)

Hi ‘dk2017’

Many thanks for the help, it has taught me a lot. Looking at how you created the model has allowed me to improve my techniques.

I am amazed at the craftsmanship of the carpenters who build these boats, absolutely incredible skills.

you are welcome.
always interesting to work with beautiful geometry, it is really a piece of art how they are blending the sharp edges into the round tail.

looking at it again it might be worth, depending on what your exact objective in modelling this is, to set the cross sections up so that they align with the direction of the wood cladding of the shell and so mimicking the material properties of the wood. this would also make it easy to texture(for rendering) the hull because the surface mapping would be set up in a realistic way… that is probably shooting over the goal,
but would be a good opportunity to get into grasshopper :wink:


NetworkSrf produces surfaces which have curvature continuity, even when the input curves are kinked. To capture the sharp “chines” along the forward, top portion of the hull the area between the chines needs to be modeled separately.

On the model which dk2079 supplied, what is the advantage of the front transverse curve not being vertical, does this help control the shape? (I have seen this is a few ship hull models.)



That is what I have done, David.

This model might be a bit ambitious for my level of skill, but I am getting there!

it is more a choice for getting more “relaxed” alignment of the isucurves closer to the sharp edge along the bottom of the hull.

if the transverse curve hits that edge in a 90° alignment it appeared to me that the resulting surface has a better distribution of control points/isocurves which flow better along the generating curves of the shape pictured on the photo.