Lofting developable boat side panels to a curved bow cross-section?

Hi, I develop boat designs in the usual way …create curves in plan and profile, the use Curve From 2 Views to create (what I call) construction lines in 3D space. From there, I loft (or Sweep 2 Rails) to create developable panels that can be unrolled and used to produce the actual boat. Note: I always fair and rebuild plan and profile lines to be 2nd degree with minimized number of control points (usually 5). When creating side panels (between chine and sheer lines), I have had trouble figuring out how to make the panels meet in a way that lets me have a curved bow …and for MY work, I have always defaulted to a straight stem between chines and bow point …easier and it works. But right now, I’m doing some work for someone else and they want a bow that is curved (when viewed in profile). Using my usual method, above, I don’t know how to produce developable panels that meet on a curve bow without introducing a gap (a slim, vertical ‘football’ gap when the panels are viewed from the front of the boat …after cutting the panels with a curved bow shape). You can, in ‘real life’, usually force the wood to do what you want, but in this case, the largest point in the gap is over an inch and too big to just be ignored… Is there info online, or can someone here explain, how to produce developable boat side panels that meet on a curved bow? I can provide pix if you like …Wife’s calling me for dinner right no :smile:

Thx, Brian

Hi Brian,

I’m no boat guy and not sure if I can help, but if you could indeed send some pictures, it would help anyone over here to have an instant view of what you are facing.
Had a nice dinner? :slight_smile:


I use to
build a NURB surface from the 4 curves using just 3 points for bow and stern curves
then develop with
UnrollSrf (if within tolerance)
Squish with PreserveBoundary=Yes Deformation=Free Material=Rigid
The Squished surface is unusable (just a lot of segments), so I rebuild the contour and recreate the surface.

Then I check the length of all borders and sections and compare to original and side squished planks.

I think, here you can find useful tutorial which might help you out.

Good Luck with your project


Thanks Guys… I just spoke to the guy that I’m doing the work for and discussed the issues with the curved bow and have a mixed answer - yes, the curved bow profile is mandatory, but yes …I can modify other curves a little if necessary. I suspect that if I let the upper end of the side panels ‘open up’ at the top of the bow, that the resulting ‘look’ from the front would actually be acceptable, e.g. look like a tall ‘V’. Allowing that, using a little less curvature in the bow profile, and giving the side panels a little straighter run to the stem, should in combination alleviate the issues ‘enough’. I’m going to iterate a little on this and see what I can come up with …and will post pix (!) and questions here if I’m running into corners… The guy already ran into these same issues with another CAD guy and gave up on him …so now he’s softened up a bit and allowing me more flexibility than the last guy …it’s good to be PAID to fight issues regardless!

More later…


PS: Yes …I’m also ‘BrazosBrian’, the original poster …but couldn’t remember the login info so registered again :slight_smile: