topic Re: creating a boat hull - Loft or Patch? in Fusion Design, Validate & Document Forum

creating a boat hull - Loft or Patch?

rprovideo — Sun, 25 Jan 2026 23:14:42 GMT

Hi
I have a top view and a side view of my boat, and I am trying to do a 3d model to print it. I also have a pretty bad 3d scan of the hull from my phone.

I tried creating several horizontal planes, and trace the 3d scan to a sketch on each level. I also traced the side profile and made those sorta match. I then tried to create a loft between the hull lines. That sorta worked, but the transom ending is strange. I am trying to have the loft match onto a closing curve I draw. I also made the transom with some 3d sketched, but I am having problems with closing that.

Since the deck is not flat, I created a plane 15 degree tilted - I would have loved a way to make a curved surface, but I can live with the tilted plane. I traced the outside of the deck and the cabin, but I cannot, even on the 2d plane, close the sketch. I tried to close the lines with Patch, but it wouldnt do anything- the OK button is grey. I was only able to close one part of the transom. For some reason, the other part, the sketch lines meet in the sketch view, but in 3d view, they dont.

Can I have some help with this? I want to make this for our wedding, and I have about a week to finish it.

Here is a pic of an Oceanis 411:

(I have first made the side view only and tried a flat, extruded version thats still in there, ignore that)

Thank you

Re: creating a boat hull - Loft or Patch?

TrippyLighting — Mon, 26 Jan 2026 13:36:03 GMT

Loft! The Patch tool is a tool of last resort, or in cases where geometry cannot be broken down into quadrilateral geometry.

Use as few splint points as you can get away with. Rather than adding spline points, work with the tangent handles to get the shape you are looking for.

Or work with Control point splines. Use a control spline with 1 more point than the degree. A 3-degree control point spline should have 4 points.

Use as few rails and profiles as you can get away with. No more than three of each for a given surface.

All of that will usually yield somewhat acceptable results.

Your time estimate is way too low, so you'll have to make compromises in quality and fidelity!

Re: creating a boat hull - Loft or Patch?

TrippyLighting — Mon, 26 Jan 2026 16:07:05 GMT

A modeling technique that is underappreciated is T-Splines.

Assuming this doesn't need to be a 100% accurate remodel of existing geometry, hardly possible with "that" scan, for this purpose T-Splines make this quick work:

Re: creating a boat hull - Loft or Patch?

rprovideo — Mon, 26 Jan 2026 21:47:39 GMT

Wow that is amazing. If you wouldnt mind, can you share a little bit of the process? I am very happy with the result, but would love to learn the way to do this. I tried to use sculpting, but never got a result anywhere near yours.

Re: creating a boat hull - Loft or Patch?

TrippyLighting — Mon, 26 Jan 2026 23:02:01 GMT

Yep. Here's a screencast.

@adam.helps , why is Fusion "swallowing" that T-Spline point ( at 11:15 into the video) when I repair the body?

Re: creating a boat hull - Loft or Patch?

MichaelT_123 — Tue, 27 Jan 2026 00:04:36 GMT

... and the next "overlay" in the Design Space!

Regards

MichaelT

Re: creating a boat hull - Loft or Patch?

rprovideo — Wed, 28 Jan 2026 15:54:47 GMT

Hi Trippy,

thank you very much! That was really informative! I am making some good strides Here. However, there are some things I cannot deal with, so may I ask some more questions?

What is the easiest way to create a 'bent' Form?

I have created a new deck, and I am probably printing it separately (so the hull can be upside down to print). I have created the deck parts on top of this. Strangely, some parts I created in Form have a different icon (the classic grey cilinder of a Solid) even though I created them in the Form menu. I am not sure what causes one item to stay on the yellow surface icon and what causes another to became a solid right away, but this causes some problems for me as I wanted to weld some of these together. I created these in the same Form step, and they are purple when I edit the Form, but then become different (with different names) after I Finish Form. Does it make a difference that one started as a Cylinder and one as a Box?

Update: yes, it does. A cylinder ends up orange and a box ends up grey. Seems a bit counterintuitive for me. I have now tried to redo the whole thing with a box (its amazing how many errors you realize just by trying to type a forum post), But the way You have created the face (and I used on the cylinder) alt+pulling a shape fails on the Box. And this whole thing is a bit of a mess, since a box, ending as a solid, is much easier to manipulate. The way to convert a cylinder (by thicken) fails a lot of the times, for example by the rudder I did. However, the alt+pulling method is much simpler to work on.

Oh, and very frequently (in this case I created a New Form in Surface window, and then clicked Undo I get into this situation where the bodies are all go missing from the browser, even though they are on the screen: Moving back and forth in the Timeline fixed this.

Re: creating a boat hull - Loft or Patch?

TrippyLighting — Wed, 28 Jan 2026 18:09:01 GMT

Forms that are closed "watertight" convert into a solid body, which is the grey cylinder icon.

Forms that are open like the T-Spline cylinder convert into a surface body, which is the orange cylinder icon.

If you re-attach the updated model I can take another look at it.

Don't click "undo" after creating an empty form. This is a bug, that has been reported recently and will take some while to get fixed.

Simply delete the empty Form if you don't need it.

A Modify->Compute all is likely also going to fix that behavior and generally is a good idea 😉