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How are kits made with pre-spiled planking?


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Just out of curiosity, I was wondering how kit makers are able to provide pre-spiled planking. I have just received one such Russian kit for a longboat in card, and have seen others (such as Chuck's longboat) with laser-cut pre-spiled planks.

 

Is this done with some computer software, or is it that when making a pre-production model the spiled planks are carefully traced, or that paper is laid on the frames or shell to achieve the same outlines?

 

Tony

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Thanks, Welfalck. I suspected it was through software. I realise that 3D CAD can show the spiled planks in their fully fitted form. Can it work out the shapes when flat, before bending to the curvature of the hull. I can't see how to do that with my 3D TurboCAD (though admittedly I am only really conversant with it in its 2D form).

 

Tony

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You may have to post this question in the digital modelling section of this forum. In order to show a geometrically correct projection of the spiled planks onto a 2-D-plane, your program would need to be able to calculate the distances between e.g. the frames and the angle at which the spline-curve of the outside shape intersects with the frames. TurboCAD does not have such functions. You would need a specialised CAD-package for that, but I don't know which one would do it.

I gather one could do it the 'pedestrian' way in TurboCad too. You would need to measure the lengths (in 3D space) of the upper and lower edge of the planks between each frame and the height of each of the intersecting points above a reference plane. You then can draw the respective sections of the edges, starting from the middle, in the right orientation as projected onto a 2D surface. Not sure though, that you would be able to achieve sufficient precision that way. 

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Even though you can probably get there about 90 percent with CAD, Each plank still needs adjusting and tweaking for a really good fit.  At least with me, i like to adjust each plank for real life issues the computer would never pick up like the kerf of the laser cutter or adding a little extra width to compensate for creep and bevel.

 

In fact, all of my pre spiled planks for the longboat were done without a computer at all.  I used the method described in my build log for it.  They were spiled the old fashioned way.  Then it was scanned and traced into a vector program. Then i tweaked each one as described above.

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Hi Tony

You got to divide the hull surface into longitudinal sections, first. They represent the plank strakes. Each strake is a sub-surface on it`s own.

Then you apply the develop or flatten command in your CAD application. This command doesn`t just project the selected entity on a plane. Rather than that it straightens the entity. Be aware, that the thickness has to be taken into account.  By default surfaces don`t have thickness in virtual modeling.

The development command may only work, if the surfaces (plank strakes) are straight or flat across their length. So the station lines should be polylines rather than arcs or curves. Development works best on stations, that have knuckles and straight portions.

I`ve never done it myself, but I know that Rhino 3d, the CAD I use, provides this feature.

I can hardly await to see more pics of your Chaloupe built.

 

Michael

 

 

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On ‎3‎/‎31‎/‎2019 at 5:05 AM, Chuck said:

In fact, all of my pre spiled planks for the longboat were done without a computer at all.  I used the method described in my build log for it.  They were spiled the old fashioned way.  Then it was scanned and traced into a vector program. Then i tweaked each one as described above.

Whew! That was welcome news and not at all surprising. I'm only theoretically conversant with CAD. I know how it works and what it's limitations are, but I don't use it for a variety of reasons, not least of which are exactly the reasons Chuck mentions. I do my drafting "on the board" and I hang plank "on the boat" as in full-size practice. For my purposes, (okay, at my age...) I find that faster (and less expensive) than buying the really good software necessary and taking the classes to learn how to use it. (As chance has it, Autodesk's world headquarters are just down the road from my office.)

 

 

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In modeling software this is a primary use case, as 3d objects have to be texture mapped with 2d graphics. Therefore the modeling software has to be able to project all of the surfaces onto a 2d plane, it's called unwrapping UVWs, UVW being the XYZ axes of the texture space. So if I made a model in 3DS MAX with all the planks, it would then be very easy to output all of the plank shapes into a 2D file that could be used to drive a laser.

 

But most people will use CAD, where as described above the process is a little different, but the result is the same. So the answer is that 3D CAD/modeling applications have built in functions for several reasons that are able to take 3D shapes and project them into 2d.

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