Here a speed one about the above method

a little difficulty with your own object :it's very thin...
but you can with a bigger thin for understand the process to take the bottom curve (or any trimed curve) ;)

Project any curves from Top
erase the second bottom projection

Extrude the projected curves
Copy Move it out the volume for better view

Take the bottom Side line of your original Surf
maybe you must join its different part for have a unic curve
Rebuild it for have less points (select a curve Press Tab write Rebuild and enter your number of points)
movup a little in side view for drawing a cool triminng curve

Move some points to the extremities of the "any curves lines"
Extrude it for have a perpendicular plane
maybe Blend the Bottom curves for the background
and make some Boolean Diff of all that :)
Sorry for the masking pannel at the end, i am not in a comfortable place...for work!



All is here in 3 D view but of course change view (Left) for drawing or modify curves!

Hi Gord,

re:
> That looks to work for some reason.

The reason is what I wrote earlier - the top of that new one is not skimming right along the same surface area as the top of the other object so it doesn't have to try and resolve a complex intersection between 2 surfaces that are overlapping over top of each other.


re:
> However, I can't reproduce that over the whole surface. How can a flat object be 'bent to fit'?

The Transform > Deform > Flow command can be used to map a flat object onto a curved surface:
http://moi3d.com/3.0/docs/moi_command_reference8.htm#flow

So for your case you would probably want to build a surface that is not pinched together at the ends, something like a sweep like this:



Then with a set of flat objects you can put a base plane around them like this:



And the Transform > Deform > Flow command can map them from the base plane onto the curved sweep surface:



- Michael

After struggling with projecting lines from the planks, and extruding groves, I think that flow is a better/easier solution, adding the planks to the top of the curved deck.

The scale of the grooves should maybe be greater than a physical model, to reduce the size differential? Current planks look good.

The current deck might be drawn as single surface, with the edges smoother?

- Brian

Ah funny...never thought that was for a boat!:)
I had believed that will be for engrave something with letters!
So i will start for build an inversed boat's hull for have any form of engraving! :)

A boat floor deck is totally other thing!
I am not sure that the deck is longitudinally curvated!
It's generally flat! Flat inclined or domed laterally for evacuate water! ;)

Watching teak deck maintenance, repair and replacement is interesting.
The narrow teak planks are spaced with deliberate gaps. The gaps are filled with various materials, to prevent leaks. Oakum/pitch historically, with screws and bungs. Special caulk has been used. More recently, 9mm teak veneer, epoxy bonded, no screws nor bungs, with black epoxy filling the gaps. Steam bending.
- Brian