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## Re: [bolger] Re: Design With Plywood - arcs

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• Chris, I ve had some pretty interesting results using arcs or arches. Arcs can be manipulated geometrically because their explicit mathematical expression is
Message 1 of 19 , May 4, 2006
Chris,
I've had some pretty interesting results using arcs or arches. Arcs can
be manipulated geometrically because their explicit mathematical
expression is relatively simple compared to NURBS. Arcs are simple to
loft. All you need to know is the radius of curvature and the
vertual center of radius. Using a compass or a string, you can draw

I started using arcs as a means of analyzing other designers' work. For
example, looking at Phil Bolger's Tortis and Brick in the profile and
using the waterline as the chord, you see an approximate arc with a
camber of about 10% of the chord below the water line. I reduced this
arc to a single number, expressed as the arc Tan ( Camber/ (1/2
chord)). By looking at several designs, I found that an arc of about 10
degrees in the profile of the canoe body is characteristic of a
relatively slow boat capable of carrying a large load.

If chord is 10.7639 units in length, camber is 1.0, then I would call
this a 10.5258 degree arc. By naming it in degrees it is easier to
visuallize, since the angle is close to the entry angle.

These arcs' geometry can be easily manipulated with a calculator - Easy
to design with and loft in cardstock or plywood. I use a spreadsheet
and a caculator for complex designs. The camber of an arc in a plywood
pannel can be established from the arc in the profile and the angle of
the pannel from the vertical. For example, say you choose the arc for
the profile view, yet the topside is flared out 6 degrees. The profile
arc can then be rotated through 6 degrees using triginometry to find the
camber of the arc required on the plywood pannel. Now, you need to
know the chord for the arc in the plywood pannel.

Say you have a plan view with an arch for the side of a scow. This
waterline arc effects the same pannel we were just discussing. This
time we rotate the plan view arc until it's camber is perpendicular to
the camber of the arc we just rotated from the profile. The length of
the perimeter of the plan view arch rotated will give you the length of
the chord you would need to loft the pannel for the topside.

Sorry if this is confusing. It seems a bit complex to be describing by
text. Hopefully it gives you some idea about the concept of designing
with arcs. I'll try answering questions about the technique if you have
any.

Michael Collins

>

[Non-text portions of this message have been removed]
• Chris, I ve had some pretty interesting results using arcs or arches. Arcs can be manipulated geometrically because their explicit mathematical expression is
Message 2 of 19 , May 5, 2006
Chris,
I've had some pretty interesting results using arcs or arches. Arcs can
be manipulated geometrically because their explicit mathematical
expression is relatively simple compared to NURBS. Arcs are simple to
loft. All you need to know is the radius of curvature and the
vertual center of radius. Using a compass or a string, you can draw

I started using arcs as a means of analyzing other designers' work. For
example, looking at Phil Bolger's Tortis and Brick in the profile and
using the waterline as the chord, you see an approximate arc with a
camber of about 10% of the chord below the water line. I reduced this
arc to a single number, expressed as the arc Tan ( Camber/ (1/2
chord)). By looking at several designs, I found that an arc of about 10
degrees in the profile of the canoe body is characteristic of a
relatively slow boat capable of carrying a large load.

If chord is 10.7639 units in length, camber is 1.0, then I would call
this a 10.5258 degree arc. By naming it in degrees it is easier to
visuallize, since the angle is close to the entry angle.

These arcs' geometry can be easily manipulated with a calculator - Easy
to design with and loft in cardstock or plywood. I use a spreadsheet
and a caculator for complex designs. The camber of an arc in a plywood
pannel can be established from the arc in the profile and the angle of
the pannel from the vertical. For example, say you choose the arc for
the profile view, yet the topside is flared out 6 degrees. The profile
arc can then be rotated through 6 degrees using triginometry to find the
camber of the arc required on the plywood pannel. Now, you need to
know the chord for the arc in the plywood pannel.

Say you have a plan view with an arch for the side of a scow. This
waterline arc effects the same pannel we were just discussing. This
time we rotate the plan view arc until it's camber is perpendicular to
the camber of the arc we just rotated from the profile. The length of
the perimeter of the plan view arch rotated will give you the length of
the chord you would need to loft the pannel for the topside.

Sorry if this is confusing. It seems a bit complex to be describing by
text. Hopefully it gives you some idea about the concept of designing
with arcs. I'll try answering questions about the technique if you have
any.

Michael Collins

Christopher C. Wetherill wrote:

> I am looking for ways to do it with pencil and paper. I have been playing
> with hull.exe for a while and it's nice, but I like being able to do
> things
> the non-electric way.
>
> -----Original Message-----
> From: bolger@yahoogroups.com [mailto:bolger@yahoogroups.com]On Behalf Of
> Bruce Hallman
> Sent: Wednesday, May 03, 2006 3:51 PM
> To: bolger@yahoogroups.com
> Subject: Re: RE: [bolger] Re: Design With Plywood
>
>
> > From: "Christopher C. Wetherill" <wetherillc@...>
> > Subject: RE: [bolger] Re: Design With Plywood
>
> There are two issues,
>
> (1) the strength/durability of plywood materials, and
> (2) the topology of developed shapes / the curvature of plywood.
>
> For (2), the development of curved shapes by bending flat sheets,
> you can skip the book theory altogether and experiment directly
> with computer programs that automatically take care of the mathatics
> of bending flat plates.
>
> I especially like the opensource software FreeShip.
> [Also, I like the Hulls.exe software.] Both of these
> allow you to easily experiment with the bending of flat plates
> into curved surfaces.
>
> My personal favorite is to print the experimental hulls onto
> thin cardboard, and use sissors and tape to make models.
>
> After just a little practice you can get from an idea in your head
> to a 3D scale model in about one hour.
>
> http://www.flickr.com/photos/hallman/71601266/
>
>
> Bolger rules!!!
> - NO "GO AWAY SPAMMER!" posts!!! Please!
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> horses
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> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax:
> (978) 282-1349
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> - Open discussion: bolger_coffee_lounge-subscribe@yahoogroups.com
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
> Bolger rules!!!
> - NO "GO AWAY SPAMMER!" posts!!! Please!
> - no cursing, flaming, trolling, spamming, respamming, or flogging
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - Pls add your comments at the TOP, SIGN your posts, and snip away
> - Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930,
> Fax: (978) 282-1349
> - Unsubscribe: bolger-unsubscribe@yahoogroups.com
> - Open discussion: bolger_coffee_lounge-subscribe@yahoogroups.com
>
>
>
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• Hello Everybody, I have tried several of the DXF viewers and could not get any to work. They all seemed to be teasers for paid products. The best results I ve
Message 3 of 19 , May 6, 2006
Hello Everybody,

I have tried several of the DXF viewers and could not get any to
work. They all seemed to be teasers for paid products. The best
results I've had so far is with OpenOffice Draw available free from
www.OpenOffice.Org I need to work with it more. Started working with
Plyboats and then FreeShip.

Somehow I was able to make Plyboats work in XPpro and print to a
parallel laser printer. Even have an icon on the desktop that works.

From and Plyboats Email to Ray Clark:

I had some problems with the DEMO not accepting mouse and cursor
movement when I tried to run the program from the XP command promp.
I extracted the ZIP some other way in XP, maybe using XP's extractor
and an icon was placed on the desktop and the program now works.
This may help if someone else has the same problem

Plyboats running in whatever mysterious way actually takes much
more time to execute calculations than FreeShip.

Roger Van Arnam
Micanopy Beach Florida

--- In bolger@yahoogroups.com, "adventures_in_astrophotography"
<jon@...> wrote:
>
> Hi Bruce,
>
> ...snip...
> > I also agree that hull.exe is nice. Though, FreeShip
> > has hull.exe beat ten times over when it comes to modeling and
> > visualization, key features when prototyping.
>
> Several years ago I used Plyboats, but it never ported quite right
to
> W2K, and since it has a lot of limitations (only two chines, among
> others), I gave up on it. I've just downloaded Free!ship and look
> forward to giving it a try. One question for you, though, is how
> expanded panel dimensions are output from the program. Do I need
> some other application that can read .dxf files, or can I just
print
> out the panel dimensions from Free!ship? Will it translate
> locations onto the panels?
>
> I was thinking of starting with the offsets for Cartoon 40, scaling
> the length at 125% per PCB's suggestion, and getting panel shapes
and
> dimensions from the application. Think this will work? If it
does,
> it would allow me to assemble the sides and bulkheads, then use a
jig
> to hold everything square, rather than making critical measurements
> on the jig, erecting the bulkheads, then spiling the panel shapes.
>
> > I have the personal theory that to get a boat design 'right' you
> > need to go through many many itierations by trial and error.
> ...snip...
>
> I agree, and think it's true even using the software tools
> available. Using Plyboats, I made many cardboard models of
different
> hull shapes, including a lot of sharpies and box-keel designs. It
> was always interesting to see just how bad a model could look when
> the wire-frame in the software looked so good. Slab-side sharpies
in
> particular can look fine on the screen, but not so great in "the
> flesh." Part of the problem was Plyboats' limitation of fixing the
> lowest point of the sheer at the point of maximum beam.
>
> Jon Kolb