Lightweight Canoe

Bluegoose; I chose the foam & ply build as I am familiar with these materials and did not want to research or to try something new like skin on frame. Just wanted to build it and use it.
The benefits of thick light foam bottom is built in buoyancy, two skins to puncture, very stiff and can have large radius chines so easy to glass. I wanted to use the extruded 35kg styrofoam but could not get it localy. I used 600gsm glass on the inside as I thought the 25kg styrofoam was pushing the limits and could be bruised easily by heels or shoes. I think 400gsm would be sufficient and saves a bit of weight. At worst case could add another 200gsm in the area where you step in and or stand.
This is the first canoe we have used and at this stage prefer more stability so I have built a full lenght pvc pipe outrigger. This works great and is easy to attach with 4 bolts and wingnuts. Not very heavy but if you are on your own you would carry each to the water and then bolt together. If I was to build another then I think would go with 750mm wide bottom.

 

skin-on-frame can be built in any shape and any size, even large flat bottomed hulls. If I had the time and money I would like to build a 24 ft pocket cruising sailboat with a cabin, just to show it can be done. I will likely build a 16 ft folding picket cruser sailboat in the near future some time (much faster and less costly to build a small one).

Here are some good websites, including an on-line builders manual:

http://www.yostwerks.com/WoodSOFFrameMenu.html

http://www.kudzucraft.com/designs/FreeB/

http://www.instructables.com/id/Build-a-Greenland-Kayak/

I have built small sailboats, skifds and kayaks and canoes using the method, no reason it could not be used on a skiff pram type fishing boat. simplest method would be use plywood frames with stringers. I have used fiberglass cotton duck, nylon pack cloth, and polester fabric for the skin material. I have use dough fir, cedar, aluminum, hemlock and fiberglass rods as frame material. It is a construction method that can be adapted to a lot of shapes and uses, fast and easy to build, light weight and inexpensive. And it can be very tough and druable.

The only disadvantages are you have to have hard chines (though you can approximate round hull shapes with lots of stringers, this is the same disadvantage with stitch and glue), it is difficult to get hollows in the hull shape but for most designs this is not a major disadvantage, and there is somewhat less interior room because of the frame as compared to a hollow stitch and glue hull. And it is not practical for having varnished wood exterior finish. But certainly the frame and coming can be varnished wood.

good luck.

 

So Bluegoose,

What's the plan ?

 

I think you should skip the foam core approach, mostly because of the amount of laminate effort and materials. Having thought about this, A couple of courses of Spectra, followed by localized reinforcement and another course of spectra will produce a 20 - 25 pound canoe. No expensive fabrics or materials, maybe some foam ribs and bottom stiffeners, if you like, though hollow ones will work too.

 

PAR - thanks for the input, but you've lost me here. I'm not familiar with Spectra, but from what I could find from a quick internet search it sounds like an expensive, difficult to use, exotic material. Am I missing something?

Can you please give me a few more details of the type of construction you're envisioning. Are you saying there's no need for a foam core material when you use Specta? You just bond a few layers together (with epoxy?), and voila, you have a hull? Would this be more like a skin-on frame approach? Build a wooden frame and stretch the Spectra across it? Sorry, but I'm just not clear on what you're suggesting.

Thanks.

 

Spectra isn't very costly, particularly compared to Kevlar or carbon. My idea would be to build a Kevlar canoe, but with Spectra instead.

 

I rear that epoxy does bond to spectra very well, is that outdated info?

 

Finishing Spectra is an issue, but properly produced fabrics bond well. Early fabrics did have trouble.

 

I dont know why anyone would try a strange, non suitable exotic fabric and ignore the thousands of kayaks being successfully made with ballistic nylon.

 

There's nothing strange about Spectra and it's been around for a half a century, in a few different forms. The hard part until the early '90's was weaving and more importantly finishing it, so it's suitable with resin systems. Weaving took some doing, but it's a commonly used material, particularly in garment strapping and camping gear. Recently, new finishing processes have made it possible in sail cloth and ballistic armor, as well as other laminations.