I have used this for a couple of years for my students in an Intro to Nav
Arch class. They use it to develop a 3-view (plan, profile, body plan)
drawing, as well as small models. My observation is that the unwrapping is
based on a geodesic approach (i.e., attached triangles), not a developable
surface (i.e., unwrapped conic sections). As you get more curvature, the
geodesic can underpredict the real unwrapped length of the surface. Having
said that, I've never seen more than a small gap at the stem. We usually
plot these via the DXF - have you tried comparing plots from the nesting and
DXF through a CAD program? The DXF/CAD approach has the benefit of showing
the BHEAD locations on the CHINE and DECK plots. This is very valuable with
the proper alignment of pieces.

One other FYI - the DXF format exported by this program is not compatible
with all CAD programs. I've had good success with TurboCAD, Rhino and the
Voloview Express viewer. I'm sure there are others.


Regards,

Don

Donald M. MacPherson
VP Technical Director
HydroComp, Inc.
http://www.hydrocompinc.com

[2004 Propeller Seminar - January 16th in Tampa, Florida.]


"William R. Watt" wrote in message
...
Has anyone sucessfully built a boat out of unfolded panels from this hard
chine design program?

I set up stations and made a cardboard scale model of a boat by wrapping
the cardboard around some frames, marking, unfolding, and cutting. Then I
put the offsets into the Carlson program and used the "Patterns/Nesting"
feature to arrange the panels on sheets of plywood and print out points
for hand plotting. I plotted and cut the panels from cardboard, same scale
as the model, and taped the cutouts togehter sticth-and-tape style. The
result isn't the same as the model. There is a big gap at the stem, the
topside panels are 25% wider, and the it just doesn't fit the frames.

(I've been back seeing if I can alter the offests to get a better fit and
find the auto spline makign S-curves in the keel at the stem. Very
strange.)

Am wondering if others have got good unfolded panels from the program.

(The boat is the 15ft solo cruiser design I've been documenting under
"Boats" on my website.)


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"D MacPherson" ) writes:

..My observation is that the unwrapping is
based on a geodesic approach (i.e., attached triangles), not a developable
surface (i.e., unwrapped conic sections).

yes, I made a silly mistake in my first attempt at this boat of having the
lowest point midships adn the widest point somewhat further aft, a shape
to which plywood would not confrom. Neither the BluePeter nor the Carlson
program complained. I knew better but was not thinking. So then I made the
carboard model the old fashioned way to check before keying the offsets
into the two programs to do the calculations and get the unfolded plotting
points for the panels.

I know designers use computers to calculate the shape of unfolded plywood
panels and transfer the points to a computer controlled cutting board.
I've seen advertisments on the Internet from companies like Chesepeak(?)
Ligth Craft who sell kayak kits made this way. Since Greg Carlson sells
cutter/plotters and his program produces a file for his cutter/plotters
then I figure there should be some way I can get the program to produce
accurate plotting points.


Having
said that, I've never seen more than a small gap at the stem.

I've given myself the challenge of attempting a constant bevel which is
making the stem a bit tricky on the small scale drawing on the computer
screen.

We usually
plot these via the DXF - have you tried comparing plots from the nesting and
DXF through a CAD program?

oh no, I have to learn how to use anoother computer program?

BHW: I've found it easier to use the Patterns/Nesting output because all
the files have negative values for plotting points which I haven't been
able to figure out.

One other FYI - the DXF format exported by this program is not compatible
with all CAD programs. I've had good success with TurboCAD, Rhino and the
Voloview Express viewer. I'm sure there are others.

I can display the DXF images with the program that came with the flat bed
scanner I use. They look okay, just like the images displayed by the
program itself. Havent' figured out yet how those images relate to the
problems I've had with the plotting points.

I tried again last night producign a new file of plotting points, drawign
and cutting the panels, and taping them together. I still have more work
to do on this. I could use teh old fashioned way but am determined to
learn how to do it on the computer.

BTW2: I make the panels pretty quickly by taping 2 letter sized sheets of
paper together which gives 16" for the 16' of two sheets of plywood,
plotting and joing the points (straight lines with a ruler is okay for
this), putting duct tape over the back of ach panel outline for some
stiffness, then cutting out the panel with scissors, and taping
teh panels together on the duct tape side with small pieces of cello tape.
The duct tape makes it easier to move the cello tape, no tearing of paper.

Thanks to everyone for the advice.
I'll keep at it.
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Try printing onto trimmed manila folders. They give enough stiffness and
bend nicely. It helps to have a straight-feed printer, though. (The students
use a Laserjet for this.)

Regards,

Don

Donald M. MacPherson
VP Technical Director
HydroComp, Inc.
http://www.hydrocompinc.com
tel (603)868-3344
fax (603)868-3366

2004 Propeller Seminar - January 16th in Tampa, Florida.
http://www.hydrocompinc.com/support/...lerSeminar.htm



"William R. Watt" wrote in message
...
"D MacPherson" ) writes:

snip...


BTW2: I make the panels pretty quickly by taping 2 letter sized sheets of
paper together which gives 16" for the 16' of two sheets of plywood

Card stock is a lot cheaper to buy and has the stiffness that is easy to
work with.

Brian

The Carlson program develops panels correctly but that doesn't mean that
those panels are developable.
Let's explain: the development method is simple, the program divides a panel
in a bunch of parallelograms and then unroll them BUT that doesn't mean that
the surface is developable.
A developable surface must fulfill some conditions: a cone is developable, a
panel made of cones is developable but the Carlson program does not check
that.
There is another program with that flaw, Plyboats.

Good programs like Rhino, Prolines, the old Nautilus and many others will
create a developable surface that fills some conditions and can be developed
within certain limits. All the ones I know are based on the Kilgore
algorithm. Through an iteration process they check for ruling lines:
straight lines that are included on that surface and run from one edge to
the other without intersecting. There is more to it but that is the basic
problem. You must create a developable surface first. It is a much more
complicated task than to develop the panel.
A test is to design a hull with some nice curvature at the bow then cut
stations through it. If the sections close to the bow show stations with
straight sides, then the program does not do a proper job because that part
of the panels should be generated by cones.
Over the years I wrote about that in this group several times: the Carlson
program is good if you start with a hull that is developable. It is a valid
tool to scale up and down an existing boat, create patterns etc. It can even
be used to design a very simple developable hull like one with cylindrical
panels, "a la Bolger", all station sides parallel.
Who said you get what you pay for?

--
Jacques
http://www.bateau.com



"William R. Watt" wrote in message
...
Has anyone sucessfully built a boat out of unfolded panels from this hard
chine design program?

I set up stations and made a cardboard scale model of a boat by wrapping
the cardboard around some frames, marking, unfolding, and cutting. Then I
put the offsets into the Carlson program and used the "Patterns/Nesting"
feature to arrange the panels on sheets of plywood and print out points
for hand plotting. I plotted and cut the panels from cardboard, same scale
as the model, and taped the cutouts togehter sticth-and-tape style. The
result isn't the same as the model. There is a big gap at the stem, the
topside panels are 25% wider, and the it just doesn't fit the frames.

(I've been back seeing if I can alter the offests to get a better fit and
find the auto spline makign S-curves in the keel at the stem. Very
strange.)

Am wondering if others have got good unfolded panels from the program.

(The boat is the 15ft solo cruiser design I've been documenting under
"Boats" on my website.)


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"Jacques Mertens" ) writes:
The Carlson program develops panels correctly but that doesn't mean that
those panels are developable.

I've seen the paper and pencil method of looking for the apex of curvature
in a couple of boatbuilding books, TF Jones for example. For the design
I'm working with constant bevels restrict the bend to one plane. As you
mentioned below I eyeball the pictures displayed on the computer screen to
make sure the station lines are parallel (no twist). Avoiding twist in the
panels at the stem shortens the waterline length but that's a (small)
price I pay for simplicity in design and construction. All I have to worry
about is that the radius of curvature is not to tight for the thickness of
the plywood to bend to. Admittedly I haven't done any radius calcutations.
With a bow half angle of 32 deg I think its okay. One more thing to put on
the "todo" list.

All the ones I know are based on the Kilgore
algorithm. Through an iteration process they check for ruling lines:
straight lines that are included on that surface and run from one edge to
the other without intersecting. There is more to it but that is the basic
problem.

Thanks. I've written down the name and will look for more info as I would
like to learn how it's done.

Over the years I wrote about that in this group several times: the Carlson
program is good if you start with a hull that is developable. It is a valid
tool to scale up and down an existing boat, create patterns etc.

Yes, all I want from the Carlson program are the plotting points for the
plywood panels on the sheets of plywood. I used the Blue Peter program
initially to flesh out the hull with stations (the program rounds the
chines as you ask it to insert more stations) and to do the design
calculations, then printed out the offsets and typed them into the Carslon
program. I naively expected to get accurate plotting points with a couple
of clicks of the mouse.


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How about trying the free version of Rhino: rhino3d.com.
You can't save but you'll see what it does.
The command to create developable surfaces is in /surfaces/loft/developable.
Maybe it will accept to import your current model, that way you can see
where the problem is.


--
Jacques
http://www.bateau.com

"William R. Watt" wrote in message
...
"Jacques Mertens" ) writes:
The Carlson program develops panels correctly but that doesn't mean that
those panels are developable.

I've seen the paper and pencil method of looking for the apex of curvature
in a couple of boatbuilding books, TF Jones for example. For the design
I'm working with constant bevels restrict the bend to one plane. As you
mentioned below I eyeball the pictures displayed on the computer screen to
make sure the station lines are parallel (no twist). Avoiding twist in the
panels at the stem shortens the waterline length but that's a (small)
price I pay for simplicity in design and construction. All I have to worry
about is that the radius of curvature is not to tight for the thickness of
the plywood to bend to. Admittedly I haven't done any radius calcutations.
With a bow half angle of 32 deg I think its okay. One more thing to put on
the "todo" list.

All the ones I know are based on the Kilgore
algorithm. Through an iteration process they check for ruling lines:
straight lines that are included on that surface and run from one edge
to
the other without intersecting. There is more to it but that is the
basic
problem.

Thanks. I've written down the name and will look for more info as I would
like to learn how it's done.

Over the years I wrote about that in this group several times: the
Carlson
program is good if you start with a hull that is developable. It is a
valid
tool to scale up and down an existing boat, create patterns etc.

Yes, all I want from the Carlson program are the plotting points for the
plywood panels on the sheets of plywood. I used the Blue Peter program
initially to flesh out the hull with stations (the program rounds the
chines as you ask it to insert more stations) and to do the design
calculations, then printed out the offsets and typed them into the Carslon
program. I naively expected to get accurate plotting points with a couple
of clicks of the mouse.


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