Flattening hull panels with CAD etc...

[baeckmo]

Originally Posted by Rampager

I'm not gonna ask how old you are

....no problem, with age comes experience said the lady in red.....!

Anyway, attached please find the sediments from the cave. The classical way to do the rollout was a graphical triangulation done manually; took an hour or two for a set of hull panels. The arithmetic approach, based on the same triangulation is a matter of minutes, so here was the quantum leap! In fact, we still use it for the odd panel to be cut now and then, its so easy to take a few coordinates from whatever is beeing built, and off you go.

I think it could be done within a CAD module, as a macro, or the CAD coordinates may be sent to an Excel sheet working with the "3D Pythagoras". The output is the triangle legs for each sector, or "field", C, D, E and F. Don't bother to convert to a 90 deg coordinate profile, just use the measuring-tape to work your way from transom and fwds. If you want the "real" outline, a spline along the edges will do it for a cutter.

Or just laugh at our ancient efforts......!

[johngilpin]

Hi All

Is what you wish?

We made lots of changes along the way - this is quite rough.

Kind Regards

John

[Joe Petrich]

Rhino has a Developable Surface Creation plug in http://en.wiki.mcneel.com/default.as...el/DevSrf.html. Would this work for you? We have used Rhino with Solidworks successfully in the past.

[pamarine]

I have been browsing the forums reading posts about flattening panels with SW and keep see SurfaceWorks come up. Right now, I manually loft each curved surface to a flat drawing to export to our CNC router, and it is a pain and prone to slight errors. Will SurfaceWorks take a curved surface and flatten it for CNC cutting? Is this what "Developable" means?

I am complete self-taught about CAD and Boat design so I'm quite a bit behing the curve on this type of stuff.

[alidesigner]

Surface works is their surface modelling plug in. To flatten you need to buy their flattener module as well.

[Raggi_Thor]

I think the boat in John's picture can be flattened by plain Rhino.

[nordvindcrew]

My Pro Surf program allows you to develop panels and print then out. I have done a few models in small scale, and it seems to work. Like the rhino program, if you see red it's not developable.

[boat fan]

So in the " real world " what would happen if you built this boat full size.

The small red area ....how would it actually look on the boat , and rather

more importantly , how do you decide its a " go " and build it or its

rejected.I realize all this is highly subjective , but I`m interested how people here would evaluate this.I have some hulls developed similar to this with " minor " areas showing up like this.

Enough to be hesitant , yet not significant enough to be rejected . Just interested in other people`s views on this.

[boat fan]

Can a " constant camber " or " cylinder molded " hull be developed the same way with this software?


Would you set out to develop this hull like any tortured or compounded plywood design and ignore the preformed molded curvature in the panels ?


I have often pondered this , seems that such an approach requires reversing the process ? Interesting.

[alidesigner]

I would personally fix the hull shape but you could build it and just accept that there will be some trimming of internal parts and bogging before painting.

If a surface is conical or cylindrical then it can be developed. Constant camber is just a part of a cylinder. If you take a sheet of paper you can form a cylinder or a cone, but you cant form a sphere. So a cylinder or cone can be developed, a sphere cant. So yes you can do it with the software. How fast and how easily depends on which software you use.

[boat fan]

Originally Posted by alidesigner

I would personally fix the hull shape but you could build it and just accept that there will be some trimming of internal parts and bogging before painting.

If a surface is conical or cylindrical then it can be developed. Constant camber is just a part of a cylinder. If you take a sheet of paper you can form a cylinder or a cone, but you cant form a sphere. So a cylinder or cone can be developed, a sphere cant. So yes you can do it with the software. How fast and how easily depends on which software you use.

Thanks for your reply.
I agree with everything you said above , but , do you ignore the " preshape " or panel curve and develop like a flat panel or some other method ?

[alidesigner]

I use Maxsurf & Workshop so I use the tools in Maxsurf to check for developability and then use Workshop to flatten it. Then in Workshop I check the strain plot and if that's all ok I export for cutting, otherwise I tweak the surface in Maxsurf and flatten again. I always use curved panels and true lengths etc are all worked out by the software.

[boat fan]

O K thanks .....looks like its something for high end software.

[Raggi_Thor]

There are many tricks used in plywood building, se for example,
http://www.dixdesign.com/ch21notes.htm

7 ~ BOTTOM SKIN IN BOW

There is a lot of twist to the bow bottom panels in the forefoot area. Don't try to skin this in full length plywood sheets. Break it into 2 or 3 lengths to reduce the strain in the plywood. If building with okoume plywood, 2 lengths will do it. If building with meranti or mahogany plywood, 3 lengths will be needed because of the greater stiffness of the sheet.

Builders in UK have had no problems fitting these panels, without breaking them down into shorter lengths. They are using okoume plywood, which makes a big difference. They also soften the plywood with water to help it. One builder used a steam wallpaper stripper to steam the sheets during fitting, which proved very effective.

I have seen some pictures of plywood with many cuts half way (or more) through to make it easier to bend.