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Shinchan
04-16-2011, 05:14 PM
Aloha all,

anyone know of a program that can design boats/canoes using tortured/compounded plywood? I've read the Gougeon Brothers book on boat construction chapter dealing with that and it suggests trial and error method. I was just wondering if there was an easier way to do it than to use a bunch of material. Any other books on the subject? Any help is appreciated.
Mahalo,
Randy

Lewisboater
04-16-2011, 06:28 PM
Freeship/delftship will do it but it won't tell you when you cross the line too much. It shows stuff that is purportedly not developable in red under developability check but the program was originally written for steel plate and ship building. I have had some success with it for tortured areas or areas that it thinks wouldn't be doable in ply. The main factor is keeping the #s in the plate development to .02 total and .00x edge or below (error that is). My usual margin for error is .125 inch +/- so the epoxy I use will fill any unintended gaps. You will also probably get that kind of error in layout and cutting of the panels too if you don't CNC.

Cuyahoga Chuck
04-16-2011, 07:09 PM
A decade ago I built a tortured plywood kayak design by Chris Kulczicki. The design is called "Yare". Before Kulczicki sold Chesapeake Light Craft he used to visit their web site. One day he got on the process of designing Yare. It started with a boat called "Skua". By the time he got to Yare he had a stack of unused tortured hulls in his back yard. The torturing process seemed to defy building exactly what was on the plans. The only way to know what you had built was to get in and see how it worked. In the end he got a boat that worked fairly well but it never drew a following and faded away over time.
I still remember reading Kulczicki's book over and over and not realizing I didn't understand the building process until it came time to glue everything up. Like a dummy I even altered the design slightly which nearly made it impossible to attach the front deck.
http://gallery.bateau2.com/displayimage.php?album=lastup&cat=10905&pos=1
I wonder how many of these oldies are still out there.

flo-mo
04-17-2011, 06:53 AM
I made two compounded plywood designs using New Wave Systems' ProSurf3 (http://www.newavesys.com/sname.htm) for developing the panels.

A few years ago I started this build which I have not finished yet: http://flo-mo.weebly.com/compounded-plywood-kayak.html

http://flo-mo.weebly.com/uploads/6/0/6/0/6060415/9862018_orig.jpg

It is a compounded plywood kayak made of 3mm poplar ply. It is similar to Chris Kulczycki's Yare kayak which again is similar to Dennis Davis' DK 13 kayak. In Chris Kulczycki's book "The Kayak Shop" there are plans for two compounded plywood kayaks: The Yare (16'3" x 2'0") and the Pocomoke (19'10" x 2'4"). Dennis Davis' DK 13 kayak is covered in WoodenBoat issue #70 (http://www.woodenboatstore.com/WoodenBoat-Issue-70/productinfo/200-070/). Another interesting compounded plywood design is Dave Kuperstein's Long Lake (http://www.sageboats.com/stock/longlake.html).

My second compounded plywood design is this rowboat. There only exists a scale model of this design.

http://flo-mo.weebly.com/uploads/6/0/6/0/6060415/3809222_orig.jpg

A little more information about this design can be found here: http://www.boatdesign.net/forums/boat-design/designing-fast-rowboat-14250-61.html

Here is a quote by Chris Kulczycki from his book "Stitch and glue boatbuilding" which may help to understand what compounded-plywood boatbuilding is about:



Compounded Plywood

....The plywood would have been forced to bend in two directions at once, which, by the way, many traditional woodworkers will tell you is impossible. This process stresses the wood - and perhaps the builder - to the limit; hence, tortured plywood.

Compounded-plywood boatbuilding is, for the most part, limited to long, narrow hulls such as kayaks, multihull sailboats, rowing shells, and a few canoes. Designing compounded-plywood boats is both fascinating and frustrating; the results are often not as you had hoped. And building these boats is an inexact science. The most minor variation in stiffness of individual sheets of plywood can result in hulls that have differences in shape even though they were built to the same design.

So why bother? Because compounded-plywood boats can be beautiful, efficient, and sleek, and it is thrilling to see them take shape.

wizbang 13
04-17-2011, 10:11 AM
http://farm6.static.flickr.com/5133/5419965319_efe7cf93b9_z_d.jpghttp://farm5.static.flickr.com/4065/5126056716_f1aeac4771_z_d.jpghttp://farm5.static.flickr.com/4122/4819140124_61763af07c_z_d.jpghttp://farm5.static.flickr.com/4046/4658800088_2df0d147a9_z_d.jpg I've built about 30 torture ply boats, from 4' long to 18'. Most have been short n fat, not long n lean. None have seen a computer, but 2" to 1' cardboard scale models. It IS very inexact .

Terry Haines
04-17-2011, 08:42 PM
Freeship/delftship will do it but it won't tell you when you cross the line too much. It shows stuff that is purportedly not developable in red under developability check but the program was originally written for steel plate and ship building. I have had some success with it for tortured areas or areas that it thinks wouldn't be doable in ply. The main factor is keeping the #s in the plate development to .02 total and .00x edge or below (error that is). My usual margin for error is .125 inch +/- so the epoxy I use will fill any unintended gaps. You will also probably get that kind of error in layout and cutting of the panels too if you don't CNC.

FreeShip does a reasonable job of developing planks. I adapted Rushton's Wee Lassie lines (Dillion's version) from lapstrake/clinker to create a FreeShip design, but I noticed the garboard and first bilge plank could be blended to form a single plank as they were parallel everywhere; huge mistake! I ignored the distortion numbers that FreeShip reported and was able to bend the resulting double-width plywood garboard but the bottom shape was horrible. I changed back and things went back to normal. The lesson here was, if the plank developments start to look weird or are difficult to bend then maybe you should reduce the plank width; long skinny planks will conform much more readily than short wide ones of the same thickness. This approach works with either lapstrake/clinker or S&G construction. For a new design with developed planks that get twisted severely, I like to cut templates from cheap ply and check to see how those bend first before I let my saw sink it's teeth into good quality wood.

Shinchan
04-19-2011, 06:11 PM
Mahalo for all the info, I have much to read and study... hopefully when I'm done I'll post pics in the outrigger and proa thread.