Lofting with guides that cannot pass through all profiles

tony_459

I'm modeling the hull of a boat. For that I'm using a loft, starting from the deck of the boat and moving down through horizontal slices all the way to the keel. The shape of the boat has to be precise, so I created guides from vertical slices of the boat, taken at various points along the length axis.

...Trouble is, some of the vertical slices, and therefore some of the guides, do not pass through all of the horizontal slices (for example, because they are close to the tip of the boat and therefore hit the keel after only a few horizontal slices).

If I use those guides, I get a warning that all guides must intersect all profiles. In other words, the guides I created near the shallower ends of the boat seem invalid.

Are there any loft experts with a quick pointer on what I could try to get this loft right? The loft has to pass through the shallow guides or the results isn't usable. Thanks in advance!

lemon1324

Perhaps try using several fill surfaces to create a surface representation of the hull, and then a thicken or enclose to get a solid body?

tony_459

Can't! No option to match curvature between fill surfaces, so the result is lots of kinks between them—no good whatsoever. 

I've sliced and diced and sliced and diced and sliced and diced all day and no go. My god. If I didn't care so much about this project I would have quit days ago. 

I've had to touch and retouch and retouch sketches. Split lofts galore. A loft won't do for the corners? OK, let's do a fill surface and an enclose feature. Or not! OnShape gets picky, and what works for one slice of the hull will break mysteriously for the next. And when something works, it works only partially—you'll get your loft, but you can't join it to the other lofts, no matter how hard you try—not even with a boolean operation.

I'm going on four days just trying to get a decent hull, and still nothing. Jesus. A loft should be only so complicated.

owen_sparks

Personally I'd loft along the hull horizontally, not down it.

O.S.

tony_459

That was my first approach too, but as the length is greater than the depth, you get far more slices, and you run into other issues. I struggled to complete a single loft, as there would be *something* about a slice that wouldn't jive with the loft tool.

I also didn't like that with so many more slices—all based on eye drawings from boat plans—the loft would be wigglier and more likely to show any errors due my limited precision. There must be a better way to do this. I've been doing CAD for years, but I've never struggled like this. Boy!

owen_sparks

If you post a link to your document I'd imagine someone will help you out

Brian_McVeigh

owen_sparks said:

Personally I'd loft along the hull horizontally, not down it.

O.S.

Pretty sure this is the typical approach for this.  If you're running into issues achieving a loft with this approach I'd share your document and someone will be able to point out where you're going wrong.

michał_1

@tony_soares459 Hi Tony, you're asking for troubles. There are reasons for why we don't use loft trough series of sections.

I'm dealing with a similar problem on Fusion 360 forum (be worn, I do act a bit dic**sh in that thread), below you will see links to my two reasonable post:

https://forums.autodesk.com/t5/fusion-360-design-validate/sketch-constraints-coincident-or-colinear-to-origin-plane/m-p/8329963/highlight/true#M171637

https://forums.autodesk.com/t5/fusion-360-design-validate/sketch-constraints-coincident-or-colinear-to-origin-plane/m-p/8337341/highlight/true#M172035

For Onshape users designing hulls I would propose to use Freeship:

https://sourceforge.net/projects/freeship/

You can export IGES file and use it in Onshape

If you looking for a specific workflow in Freeship this tutorial should do:

https://modelshipworld.com/index.php?/topic/2657-modelling-a-ships-hull-with-delftship/

It's done for Delftship, but that's actually "older brother" of freeship.

You can use tools from Onshape also but this will work only for certain shapes of a hull.

tony_459

Thank you. My issue is not so much with getting a hull, though. I will need to do many lofts in the future, and it's a problem if I can't get this one right. I see this as a learning experience—I thought I knew lofts, but... clearly I don't. I'll keep FreeShip in mind. Is 2006 really the date of the last update on that software?