Flatten/develop plank shapes from lofted offsets

[Dale Rogers]

Hi folks, is there a 'paper' way to develop the 'flat' plank shapes from offsets and lofted lines?

[brucein...@nowhere.org]

On Mon, 7 Sep 2015 17:34:11 -0700 (PDT), Dale Rogers
<da...@madethings.com.au> wrote:

>Hi folks, is there a 'paper' way to develop the 'flat' plank shapes from offsets and lofted lines?

Certainly there is. It is called "spiling". Try
http://tinyurl.com/p4qymfk
and click on the first entry - Planking a Carvel planked boat
which should get you a PDF from the Pennsylvania State University
or
http://www.boat-building.org/learn-skills/index.php/en/wood/making-plank-templates/
which has a video and instructions.

there are several other sited on the same page that cover things

In rough terms, you simply divide the length of each timber (rib) by
the number of planks you will use and that gives you the width of the
plank at that station.

That is not an exact measurement as you likely will have to allow for
the outgage and perhaps for having to hollow the back of the plank to
fit a timber.
--
Cheers,

Bruce

[Wayne.B]

===

Good links Bruce, thanks. I would argue however that creating cutting
templates on the framing is not quite the same thing as lofting
dimensions from the plans. There may be a way to do it with computer
design systems, at least for larger pieces of steel, aluminum or
tortured plywood.

[Mark Reuten]

On Monday, 7 September 2015 17:34:13 UTC-7, Dale Rogers wrote:
> Hi folks, is there a 'paper' way to develop the 'flat' plank shapes from offsets and lofted lines?

There is but it may not always be perfectly successful. It's referred to as an expansion. it works best on panels that do not have much twist to them or in which you can determine a common point or plane in which the twist occurs. It is best done from a full scale lofting. It's pretty strait forward in the case of a curved transom for instance but becomes trickier when you get into planking.
Howard Chapelle covers it in "Boatbuilding" in his portion on lofting and also in which he applies the plank expansion technique to a grand banks dory lines. For plywood panels, John Teal covers "conical expansions" in his book "Designing Small Craft".
Paul Gartside also discusses conical expansions in a Watercraft Magazine article and explains his builders method which utilizes a simple station mould scale half model.

[brucein...@nowhere.org]

Well, you did say "plank" which does infer the exterior covering of a
hull :-)

If you are building a smallish plywood boat then it is possible to
developer planking straight from the design, and in fact I had a
simple boat design application that would do it automatically. That
application was called "Hulls" and was a freebe. I used it to make sew
and glue small boats and it certainly worked well on small - 12 - 20
ft. dinghy sort of things, where if it doesn't quite fit you just glob
a bunch of epoxy in the hole.

But if you are talking about doing it on a larger boat than I think I
would be a bit apprehensive about cutting planking directly from a,
say 3 ft x 3 ft. drawing and expect them to fit perfectly on a, say 35
ft. boat. And if you are talking about "tortured" planking then it
adds the element of how much you are torturing them :-)

Again, if you have a hull design application it is certainly possible
for the software to accomplish the job, but that also means that every
thing you cut to shape and fit has to be exact also. If, for example,
you pre-cut your planking to exactly fit on a specific curve and than
cut one of the formers, ribs, etc. a tiny bit over size, or get the
curve a tiny bit wrong... the plank doesn't fit.
--
Cheers,

Bruce