Location: Milwaukee, WI Tortured plywood designs When I first heard about tortured plywood it seemed like a great idea.
Location: Alliston, Ontario, Canada Depends what you mean by tortured ply, I suppose. Location: Tasmania,Australia With the low quality, high price of ply - it probably is just too hard.
If you need something to hold wet fibreglass off the floor while it dries, marine foam does a better job easier. Location: Duluth, Minnesota Tortured ply is only suitable for long skinny hulls such as multihulls and kayaks etc,Malcolm Tennant had a very nice cat design called Red Shift available and also a coupleof designs dating back to the late 60s i think,also hard to argue with the success of Meade Gougeons 2400lb 35ft 40yr old tri Adagio, rates something like negative 60s under PHRF on lake huron. Originally Posted by rwatson With the low quality, high price of ply - it probably is just too hard.
Location: Alliston, Ontario, Canada The Carene software is very quick for creating cosntant camber designs. Location: Milwaukee, WI I was thinking about modifying the constant camber to change it in the ends of the hull. Originally Posted by gonzo I was thinking about modifying the constant camber to change it in the ends of the hull. Location: Alliston, Ontario, Canada It is no longer available from the original source.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. I suspect that they both use metallic bevel gears and it looks like the gears are completely enclosed to protect from corrosion. The HPV guys use a twisted chain drive (similar to the chain on a bicycle) to solve the same problem. You might be able to locate nonmetalic or stainless pulleys - try the commercial food processing equipment industry. Location: Sydney, Australia The biggest problem is the right angle change to the axis of rotation from the pedal axis (across the boat) to the propulsion axis (for and aft).
I have never see examples of a toothed belt being twisted the way chain drives can be twisted.
Location: Juneau, Alaska Haven't heard of it, but seems that it'd be more efficient than twisting a chain which causes a lot of friction within the chain links. I've had this idea of a drive system for a catamaran that uses a ribbed belt like a snowmobile drive belt running lengthwise down the tunnel between the two hulls, on the water surface. More explanation: Another value behind my efforts is to do it lighter than is currently available. I am keen to use all the techniques (and tortured ply is one of them) that are available to reduce the total weight. The last company has many other options in all stainless, different reductions if you want a worm drive etc.
Location: Eugene, OR The simple way to design tortured plywood hulls, at least for me, is to build a model.
Location: Coastal Georgia What kind of car is that in the background center of the photo in post #6? Location: Port Orchard, Washington, USA I've got a photostat of Lindsay Lord's conic development booklet (at least that how I recall it right now) buried in a box somewhere at home.
A vessel is nothing but a bunch of opinions and compromises held together by the faith of the builders and engineers that they did it correctly. Originally Posted by jehardiman FWIW, sheet panels take a curve that minimizes the total stored flexural energy, so a lot of the shape depends on how you restrain the edges. For some reason I cannot remember, I thought that the resulting minimum-energy curve is a 3th-degree polynomial passing through given control points.
Originally Posted by SamSam What kind of car is that in the background center of the photo in post #6? Location: Gold Coast Australia For those that use Rhino and other surface modellers you can also use curvature matching techniques vs radii for the construction curves. As others answered before, I think that Rhinoceros with the option of building developable surfaces is a great aid in designing boats to be built in plywood, whether stitch & glue or not. What I learnt a few years ago, and I wrote somewhere that I can not find at the moment, was to use the curvature feature in Rhino, to point all the areas with a radio of curvature bigger than a value given in Gudgeon's book that relates the thickness with the radii of curvature the plywood can be easily bent to. Also, and trying to answer the original question, now I am just starting to peep at the wonderful world of Grasshoper for Rhino, and I think that it could offer the tools to simulate how plywood can bend, in an easier way that FEM can do it, that for some of us is still very far away and obscure.
Originally Posted by lohring The simple way to design tortured plywood hulls, at least for me, is to build a model. I'm trying to reproduce the patterns of Tornado almost primitive way and using software such as Corel Draw and Sketshup (see attachments). I did not know the GVT Cat, I was impressed with its smooth lines, but I'm not finding anything about it on the web. Location: Michigan If the axis of the bend is not perpendicular to the center line of the boat, the cross sections will show a curve.


Originally Posted by valter.f I'm trying to reproduce the patterns of Tornado almost primitive way and using software such as Corel Draw and Sketshup (see attachments). Originally Posted by johnhazel If the axis of the bend is not perpendicular to the center line of the boat, the cross sections will show a curve. Location: UK The reply from Mr Watson misses the point in that the shoe size limitation does not arise from the deck shape which is just curved in one direction, but rather from the limitations imposed by using only two sheets of ply for building the kayak.
The point raised with regard to Uffa Fox, Mosquito aircraft & cold moulded construction are all different to compounded (tortured) ply construction which critically depends upon a curved keel line being forced to conform to a straight line on the keelson, or a fibre reinforced seam. Uffa designs, notably the Firefly & Albacore, were originally built by Fairy Marine using hot moulded construction cured in an autoclave.
Location: Cancun Mexico Compounding is bending on the 2 directions of the plane (in the geometric meaning) a flat sheet to obtain a spheric surface. The monohull Kriter V has been built in that way; complete sheets of plywood when possible instead of strips have been compounded on the mold, joined, and layered.
Classic cold moulded wood uses narrow strips to minimize the problems of compounding veneers, you obtain a faceted surface you have to fair.
Location: auckland nz The Mirror dinghy was tensioned ply and that was an early 1950s design.
Aside from the stressed plyTornados in this country, the earliest in this technique would be Malcolm Tennants Bamboo Bombers; two were built in Auckland back in the late 1970s. Hot and cold moulded boats were also done here in Auckland at a very early stage and Jim Young's 1957 swinging keel boat was cold moulded with glues and fastenings, the first in this country to use this technique. Here is tensioned ply 32 foot Bamboo Bomber Supplejack being launched from Little Shoal Bay in 1977. At that time I did not know of Dennis Davis' kayaks which are very similar but were created about three decades earlier than the ones by Kulczycki. But because the shape of the hull resulting by the use of this method is not exactly predictable I stopped bothering. Compounded-plywood boatbuilding is, for the most part, limited to long, narrow hulls such as kayaks, multihull sailboats, rowing shells, and a few canoes.
Right now I keep myself busy with another method which also contains compounded plywood and allows a little more control of the hull shape but there are still some issues to deal with. Location: UK Thanks for the replies - seems to have hit a nail with this topic.
Location: Cancun Mexico The Mirror (70000 made!!!) was designed on 1962, I checked it. Attitude has a flavor of 1970 cat type like the Tennant ones, I do not know the actual underwater shapes and volumes repartition, I guess there are some differences with 1970 ones. For those afraid by a 4mm ply with glass and minimal framing, this system is very similar to the Lord one for fast boats. Unhappily compounded plywood on multis needs a zen state of mind, a good eye and some self confidence of your capacity. 5- A steam generator for cleaning carpets or a simple steamer for taking out the wall paper make miracles if well used.
Location: Cancun Mexico Flo-mo your canoes are sweet, the last one on the grass is a beauty. Location: Vienna, Austria For the prove of concept build of my Gorewood 14 Canoe I used 3 mm Poplar plywood because that is the only 3 mm plywood I could get in my area. Luckily the build was successful but the only plywood I recommend for this endeavor is 3 mm marine grade Okoume plywood. As you are in Vienna, I guess you employed a plywood coming from Italy where there are several manufacturers.
Originally Posted by dddesigns The reply from Mr Watson misses the point in that the shoe size limitation does not arise from the deck shape which is just curved in one direction, but rather from the limitations imposed by using only two sheets of ply for building the kayak. I suppose a size nine shoe size seems insignificant to a size eight builder, but then designers who dont cater for realistic client sizes have plenty of competition out there who can supply a realistic design.
Originally Posted by Ilan Voyager What do you reproach to the poplar compared to okoume ? So my only chance to get my prove of concept build done was to use the readily available 3 mm interior grade poplar plywood (thin face veneer, poor quality of face and core veneer, no waterproof glue) and hope for the best.
In the end, with the exception of some minor problems, everything worked out fine (maybe it was just luck) but I think with top quality marine grade okoume plywood the build would have been easier.
Location: Arlington, WA-USA here are some free plans for a plywood cat, easy to build from local materials. In one case I have made J-hooks in another I laminated clamps from glass, carbon fibers and kevlar. Location: denmark ha ha ha, of course it would never talk, it was made in china.
Location: Pacific NW North America Fiberglass with resin weighs about 96lbs a cubic foot. My canoes have some twist in the garboards, quite a lot on one of them, and I have done some experiments on a new design with bottom planks that will each have a 85 deg twist from midships to the stems.


While you are correct in principle, dividing the hull into a greater number of planks would reduce the stress. Is there anyway to use CAD tools to get even a first cut at the flat shapes that need to be cut?
He has developed a propeller drive system for human powered boats that is simple, powerful, uses a twisted chain to turn the rotational forces 90 degrees and is easy to incorporate in the design of a new boat. In reality it seems that the resulting curve of minimum energy is the one with linearily-varying curvature along the axis of symmetry of the curve, for a simple symmetrical case. In this way, Rhino would show, for example in red colour, complicated areas, and I could check the areas where I could have problems and take some action if the value of the curvature in there was very deviated from the ratio I knew we could bend the wood. It is also slightly tongue in cheek since only one builder has ever mentioned this to me & many have been built.
And of course even earlier, in larger multihull sizes, like over 25 odd feet, the early 1970s Gougeons' Adagio has to be either the first, or close to it.
This process stresses the wood - and perhaps the builder - to the limit; hence, tortured plywood. Designing compounded-plywood boats is both fascinating and frustrating; the results are often not as you had hoped. Because compounded-plywood boats can be beautiful, efficient, and sleek, and it is thrilling to see them take shape. Take the best quality marine plywood: no voids, excellent gluing, good faces, regular bends. It also means that it was mandatory to completely sheath the hull with glass no matter what. If they had a show where you could sit in bleachers eating hot dogs and nachos and watch a bunch of boats like that doing wheelies and crushing smaller boats by running over them. 2 panels are joined on a keel profile and the sides are bent in a cylindrical curve as the stem and stern are fastened adding a curve in the for and aft direction. I have been experimenting with cutting the seam bevels before bending the planks, since they are also constant. The complex non-symmetric curves can imo be divided into smaller symmetrical sub-regions and the above result would be locally valid for each region. The Mosquito was certainly moulded, I believe by the hot process possibly utilising an autoclave to cure the glue, but don't post to tell me I'm wrong - I may well be. The advantage is to suppress a lot of joints and also to cut radically down the amount of work of sanding. Canoes do not like rowing, as the movements of the body of the rower make them balance on the longitudinal axis. Then again in Austria boat building is not popular at all so it is even more difficult to get marine grade okoume plywood in small quantities for an acceptable price. And then a big crane barge would come out with a crane attachment that looked like the neck and head of a plesiosaurus which would pick up the crushed boats and completely demolish them.
A outside deck jig is put over the sheer to determine and hold the shape while building.The Gougeon book on boat construction has building and designing information for this fast, light build technique. The exact shape of the curve, as you pointed out, will depend on the restraints at its ends, but also along the curve.
It's interesting that the result equates directly to a parametric cubic spline using the arc length as the parameter. 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.
Bend the hull ends up and the middle down so that the end have the final angle (strip ends are tight).
If you curvature match the curves then there is no tangencial intersection but the curvature of the curves is the same at both sides of the intersection so the intersection is much smoother then if a tangent is used.
A very close approximation for most purposes is a parametric cubic spline using chord length between supports as the parameter.
Large boats can be built this way, the Gougeons are still winning races with a trimaran they built in the 1970's. If you take a 450g strand mat with resin you add nearly 1kg (avoid it if you can) per square meter.
I like the idea of using foam for bulkheads, although I don't think that's what RW was referring to.
I use insulating foam as a table top, makes cutting ply with a power panel saw a snap, and I assemble small boats on the foam as well.



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Comments to “Tortured plywood boat building”

  1. Boy_213  writes:
    The concrete box patterns of wood.
  2. quneslinec  writes:
    Routes are predefined and you have the assist of other from a plan.
  3. 027  writes:
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