Veneer Building
- Thread starter JEM
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Todd Bradshaw
Sailmaker
If you're talking about "Cold Molding" (laminated layers of veneer set in epoxy with the grain running different directions) one good place to start is the book "The Gougeon Brothers on Boat Construction". It documents several methods and the materials used. Another one that is supposed to be excellent, though I haven't seen it is "The Laminated Wood Boatbuilder" by Hub Miller.
I have The Gougeon Brothers. I'll look into the other.
I was hoping there was one directed more toward canoes. Glen L has a set of plans like this but the weight of the finsihed hull listed seem pretty high.
I'm going to be trying this technique out except with a new twist. Going to attempt to use 1/8" plywood, 2 layers, in alternating direction. There's easier ways to build a canoe, but I want to give this way a go. If it tunrs out well, I might use it for a plug for a fiberglass mold.
I was hoping there was one directed more toward canoes. Glen L has a set of plans like this but the weight of the finsihed hull listed seem pretty high.
I'm going to be trying this technique out except with a new twist. Going to attempt to use 1/8" plywood, 2 layers, in alternating direction. There's easier ways to build a canoe, but I want to give this way a go. If it tunrs out well, I might use it for a plug for a fiberglass mold.
Todd Bradshaw
Sailmaker
But isn't plywood heavier than cedar? Judging by the scantlings for cold-molded dinghies, two layers of 1/8" cedar veneer should have enough strength and rigidity across the bottom to do the job (though a layer of six-ounce cloth on the outside for abrasion isn't such a bad idea). In any case, you do pay a bit of a penalty by not being able to thin the hull out above the waterline to save weight (just as you would on a wood/canvas boat and unlike most composite constructions). There used to be a company that made cold-molded canoes from cedar veneer and epoxy and they were pretty nice looking boats. It's been a long time since I saw one of their ads though, so I presume they may have gone out of business. Here is one of their ads from the May/June 1979 issue of WoodenBoat.
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Blue Viking
Wooden Canoe Maniac
Didnt the Stephenson Canoe Company of Canada use 2 layers of Sassafras wood with a waterproofed mesh in between to make canoes prior to switching over to canvas when that became the popular way to make canoes?...Think I read that somewhere!.... I just got a piece of sassafras to make a paddle and got a reply to a post from the former owner of Shaw and Tenney saying that way back he tried to find a source for that kind of wood as it is light,flexible and rot resistant....Just throwing in a couple of pennies worth!
Blue Viking said:
No. What you are thinking of is the Herald Patent canoe, which was two layers of cedar, one transverse, one longtidunal, with a layer of white lead-saturated linen between. The cedar would not be thin enough to really be called veneer.
There was no "Stephenson Canoe Company". J.S. Stephenson patented the cedar strip and cedar plank canoe construction techniques, and sold the rights to J.Z. Rogers of Ontario Canoe Company.
JEM said:
Are you talking about cold-molding, or trying to recreate something like a Haskell or Plycraft?
What I'm thinking is along the lines of what American Traders produces:
Looks like a canvas style canoe except using fiberglass on the outside instead of canvas.
I'm thinking more like what you said about Herald Patent's method. The inside wouldn't be ribs. It would be strips going 90 degrees from the strips on the outside. The boat I have sketched has about 65 square feet of surface area.
I did some rough cost esitmates based on what I can get locally.
Cedar
Figuring in waste, if I want to cut 1/8" x about 1.25" strips from cedar, it would cost me around $1.50 per strip. Total wood cost about $230 or so for the wood.
I figured the density of a hypothetical sheet of cedar 4' x 8' x 1/8" would weigh 7.3 pounds.
Okoume Plywood
If it I did the strips from 1/8" Okoume, it would cost about $1.10 per strip or $170 for the wood.
The weight of a 1/8" sheet of Okoume is 10 pounds.
So total weight of the wood (not including gunwales and such) in the boat with cedar would weigh 30 pounds. Using marine Okoume wood weight would be 40 pounds. That's a big difference for a canoe!
$60 differnece is significant, but not a whole lot when saving 10 pounds. It would be more work cutting the cedar. But not too bad. Easier to handle than a 4x8 sheet of plywood.
I've played with some 1/8" ply and it will bend in the cross sectional "hoop" shape with no trouble. No steaming or anything needed.
So the question is: will a 1/8" strip of cedar bend in that hoop shape without cracking? Or would it need some steaming? I haven't played with cedar that thin.
Looks like a canvas style canoe except using fiberglass on the outside instead of canvas.
I'm thinking more like what you said about Herald Patent's method. The inside wouldn't be ribs. It would be strips going 90 degrees from the strips on the outside. The boat I have sketched has about 65 square feet of surface area.
I did some rough cost esitmates based on what I can get locally.
Cedar
Figuring in waste, if I want to cut 1/8" x about 1.25" strips from cedar, it would cost me around $1.50 per strip. Total wood cost about $230 or so for the wood.
I figured the density of a hypothetical sheet of cedar 4' x 8' x 1/8" would weigh 7.3 pounds.
Okoume Plywood
If it I did the strips from 1/8" Okoume, it would cost about $1.10 per strip or $170 for the wood.
The weight of a 1/8" sheet of Okoume is 10 pounds.
So total weight of the wood (not including gunwales and such) in the boat with cedar would weigh 30 pounds. Using marine Okoume wood weight would be 40 pounds. That's a big difference for a canoe!
$60 differnece is significant, but not a whole lot when saving 10 pounds. It would be more work cutting the cedar. But not too bad. Easier to handle than a 4x8 sheet of plywood.
I've played with some 1/8" ply and it will bend in the cross sectional "hoop" shape with no trouble. No steaming or anything needed.
So the question is: will a 1/8" strip of cedar bend in that hoop shape without cracking? Or would it need some steaming? I haven't played with cedar that thin.
Todd Bradshaw
Sailmaker
Some 1/8" sawn strips will make that bend dry and some won't. Grain run-out is generally the determining factor. Some bend OK, some break immediately, others break after a few hours. It's a real pain to close up the shop for the night while the glue is drying and come back the next morning to find a strip which shattered and has now glued itself into some unacceptable position.
At this point though, you have a bigger problem. A two-layer boat from 1/8" cedar with strips running lengthwise and crosswise is a really weak construction. The lengthwise strips will be contributing next to nothing when it comes to hull strength, impact resistance or hull stiffness. This is why two-layer cold-molded boats are virtually always planked with the layers running diagonally to the keel and crossing each other at an angle. Both layers contribute to the strength of the boat and they work to reinforce each other. They do it well enough that as far as a strength-to-weight ratio, you would likely need to go to a carbon fiber construction to improve upon it. A lot of people will then add a layer of fiberglass to the outside of the hull for increased abrasion resistance, but it isn't really contributing much at all structuraly and the boat could certainly be used without it as long as you watch out for rocks. On the other hand, assuming you're not planning on the wood part forming just a core for a stripper-type, inside/outside fiberglassing job, a canoe built from just a layer of 1/8" crosswise strips and one of 1/8" lengthwise strips would be weak enough that you run a certain amount of danger of stepping right through the hull.
The diagonal strips are also considerable easier to bend into a hull and under less stress once they're bent into position since the curves are less dramatic. I'd suggest getting out your copy of the Gougeon book and reading up on what they call "the mold method" for planking up a cold-molded boat. For a light, strong, two-layer, frameless construction, it's going to be extremely difficult to do better, whether you're using thin strips or wider hunks of veneer or plywood.
At this point though, you have a bigger problem. A two-layer boat from 1/8" cedar with strips running lengthwise and crosswise is a really weak construction. The lengthwise strips will be contributing next to nothing when it comes to hull strength, impact resistance or hull stiffness. This is why two-layer cold-molded boats are virtually always planked with the layers running diagonally to the keel and crossing each other at an angle. Both layers contribute to the strength of the boat and they work to reinforce each other. They do it well enough that as far as a strength-to-weight ratio, you would likely need to go to a carbon fiber construction to improve upon it. A lot of people will then add a layer of fiberglass to the outside of the hull for increased abrasion resistance, but it isn't really contributing much at all structuraly and the boat could certainly be used without it as long as you watch out for rocks. On the other hand, assuming you're not planning on the wood part forming just a core for a stripper-type, inside/outside fiberglassing job, a canoe built from just a layer of 1/8" crosswise strips and one of 1/8" lengthwise strips would be weak enough that you run a certain amount of danger of stepping right through the hull.
The diagonal strips are also considerable easier to bend into a hull and under less stress once they're bent into position since the curves are less dramatic. I'd suggest getting out your copy of the Gougeon book and reading up on what they call "the mold method" for planking up a cold-molded boat. For a light, strong, two-layer, frameless construction, it's going to be extremely difficult to do better, whether you're using thin strips or wider hunks of veneer or plywood.
Well I did some experimenting on this project. Went to Lowes and got a nice piece of cedar. Mostly clear. Set up my tablesaw to cut a 1/8" strip.
I gave it the test and bent it. It held a radius about far tighter than what I need. So I think I'm going to switch to using cedar strips instead of plywood strips. I'll set up my tablesaw with a featherboard and be able to rip strips to a consistent size.
Also looking into buy a band saw but to get a good one I need to drop about $300 minimum or find a used one.
I gave it the test and bent it. It held a radius about far tighter than what I need. So I think I'm going to switch to using cedar strips instead of plywood strips. I'll set up my tablesaw with a featherboard and be able to rip strips to a consistent size.
Also looking into buy a band saw but to get a good one I need to drop about $300 minimum or find a used one.
We used bothe Okoume and Sapele in building my last boat. I had ordered some veneer from the U.K. as I liked the grain....we then laminated the veneer to the Okoume plywood in Thailand. I did have need for several additional sheets of ply to finish the interior....and we found some Russian made stuff with the veneer already applied (Russian Ash, a better figured wood than American Ash), it was considerably cheaper, so I bought it and did the boil test, etc.....it passed with flying colors....and when clear varnished, was lighter than Butternut and didn't take on the yellowish color of spruce....
