Compound Twisting Curves - Boat Hull

So I’m trying to model a boat and have no idea how to make the hull sides smooth. I have modeled the overall boat and just filled in the faces using triangles. I then tried to unwrap and flatten the faces so I could transfer the shape to a piece of plywood for tracing and cutting. The unwrap and flatten extension did not work for me. The hull sides are curve around the front of the boat and also twist under the boat. Can someone direct me on what I need to do or what I need to search for to create a smooth hull side and then flatten it to transfer to wood? Thank you!
miniboat 2a.skp (283.5 KB)

You’re trying to do this in the free web version?

You would need to do it manually with the Rotate tool. No extensions available for the web versions.

With Unwrap and Flatten Faces extension

It might be worth your while to try the free 30 day trial of SU Pro. (Your profile says SketchUp Free, which is web based, but you may mean the free trial of Pro, since you say you have tried the Unwrap and Flatten extension.)

Pro would allow you to use Extensions or Plugins. The free Web version does not. .

The (not free) Curviloft extension from the SketchUcation Plug-in Store would do a good job of skinning the lines of the hill. I believe there is a trial version free for about 15 days

It is possible to flatten a curved surface manually, but difficult and slow. Though if you are making the hull out of plywood, it can’t be too hard,

PS. I see @DaveR and @mihai.s have got there while I was typing.

Sorry about that. I’m using the trial version on my desktop. I got the plug in to install but could not get it to work like the person in the video above. That’s exactly what I need to do. Can you give me a step by step on how you did that? Thank you!

As in how did you even get that hull piece separated and cleaned up without all my triangle lines showing?

Please correct your profile to show you are using SketchUp Pro. That information helps us help you.

Thanks, done. I selected pro even though I’m just on trial version.

Even though you’re using the trial version it is Pro not SketchUp Free which is web based. also add the graphics card.

The first thing you need to do is correct the face orientation. You have some reversed faces and some not reversed.

Right click on one of the white faces and choose Orient Faces.
Screenshot - 8_23_2023 , 9_58_15 AM

Then select all of the model, right click, and choose Soften/Smooth Edges. There will be one left you can erase. Then select the surface (I made a copy of it first) and use Unwrap and Flatten.

BTW, you would get a nicer looking surface if you used Curviloft to generate it from the edges. And the more segments you use in the curves at the sheer and chine, the closer the flattened shape will be to what you need to cut out of the plywood.

Note that to be made from a sheet of plywood, a surface must be “developable”, meaning it only curves along one axis at a time. More complicated surfaces can’t be flattened to a plane without stretching or tearing. The plug-in will try to find the flattening that needs the least amount of tearing, but there is no guarantee there won’t be some.

It is possible to “torture” plywood to bend in more than one direction at least a little. I had to do that on the sailboat I built.

@derf9h I was thinking that you should hunt up a copy of the free Hulls program. You could put the offsets for your boat into it and let it sort out the developable panels. It’ll also do some of the hydrodynamic calculations if you need them.

Yeah, I had to resort to some torture of the garboard strake at the wineglass transom on the boat I built. I heated it up to soften the glue a bit and then clamped it between cauls to force the plies to creep. The boat designer told me “oh, I just usually put in a bunch of screws and then epoxy it when it cracks”.

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There is a recently introduced new type of plywood especially meant for forming with heat.

Did a little checking. Evidently Hulls won’t run on Windows 10 or 11 but there’s a free version of DELFTShip that does. I just downloaded the latest version and will see what I can get from the offsets on your boat. Is it really supposed to be only about 69-3/4" long?

This will actually be the second boat I’ve built. Just trying my hand at making my own plans. First boat was a Glen-L TNT.

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Might be a good idea to use a proper boat design application. Especially for a tiny little boat like yours.