concave sections in between chine points

[Eric Bailey]

Hello all,

I have imported and refined a hard chine hull for a 28 foot sailboat. The problem is the hull in section is concave in between the chine points… these would be (plywood) and should be convex. At the moment my only option seems to be to finish the lines manually on the drawing board.

Any suggestion for using DelftSHIP? Is this even possible in this software?

thanks

[Eric Bailey]

Hello… anyone with DELFTship have any comments?

thanks,

Eric

[Marven]

Concave sections are not uncommon in chine boats. Actually it is a wide spread misunderstanding that the sections should be straight. I can show a lot of examples… However it can also be the case that you’re using faces with more than 4 points in which case you get a lot of twist in the surface. Can you post an example image showing the control net and the sections?

[Eric Bailey]

True, it was very common when, for example, they used to design a hard chine boat for traditional plank construction to use straight or concave lines in section eg. Seabird.

Of course the point of this is to design the sailboat I want for construction in plywood. This would mean using conic projection or a variation on it – which as I understand it would always result in hull sections with some degree of convex curve between the chines.

In other words a developable hull.

I have attached an early version of my design – as you can see the sections are concave between chines. I have spent a fair bit of time trying to find a work-around… nothing I have tried will allow easy addition of these curves where I want them in section. Mainly in the bow of course – although a small convex curve is usual throughout the remaining sections.

DELFTship

thanks,

Eric

Attachments:

• DRAFT-CHINES-006c.fbm

[Eric Bailey]

Hello anyone from DELFTship… how about a different take… my original questions.

Any suggestion for using DelftSHIP? Is this even possible in this software?

I have attached a sample of my design… refer to post above.

thanks,

Eric

[Marven]

Hi Eric,

If you look at the image below you will see that the bow area of the bottom is displayed in red, and therefore actually not developable. Your bottom panel has a lot of curvature and at the bow also twist which makes it impossible to flatten the surface without torturing it.
Designing a chined hull is fairly easy, but trying to maintain the surface developable is an art form which takes a lot of practice.

The concave sections can be easily straightened out by inserting a row of points and edges all the way back to front in your bottom panel and then adjust these new points so the sections will be straight.

[Author]

Posts