: I'm building a Cunningham SOF, cedar frame, oak ribs. Everyone
: seems to use a hardwood masik, so I made one out of mahogany I
: had laying around the shop. Just wondering, why couldn't the
: masik be cedar? Are the stresses / loads on it too much for
: softwood?

You can make it out of softwood: pine, spruce, cedar, fir, etc.; just be sure to make the size of the wood big enough to hold whatever stress you think you might subject the boat to. Usually that means a "softwood" piece will be larger than a part made from hardwood. Just lumping wood into those two broad categories is not too useful. For example, balsa is a hardwood, and so is oak. Size for size, though, oak is much stronger than balsa.

In softwoods, sitka spruce has been prized for aviation use because it has great strength for its weight. Cedar is much lighter, but not as strong. Spruce, pine and fir are used for common construction because they are cheap and (in appropriate sizes) very strong. A row of 2x4's is probably holding up the roof on a house near you right now. Fortunately, you don't need anything that large for a masik that just has to support one paddler.

For a long and detailed introduction to the strength of wood, check out: http://www.fpl.fs.fed.us/documnts/pdf2001/green01d.pdf
It compares the specs on 5 wood species: Sitka spruce, loblolly pine, balsa, poplar and red oak. That's a good range and mix of hard and soft woods which are easy to find. Google some of the other items listed in the references section at the end of the article. US Forest Service out of Wisconsin has some good documents on wood strength, too.

If you go with softwoods, look for peces which are free of large, strength-wasting knots. If necessary, scarf several small pieces together, or laminate thin layers.

Some hardwoods are specified for particular parts because those parts need to be steam-bent, or cold bent, to achieve the necessary shape. Using a thicker piece of softwood may give you the same strength, but the piece may then be too thick to bend. In this case, laminating thin strips of your softwood lets you do all the bending you need, and build up a part with the desired size and strength.

If you are really worried about strength, put on an extra layer of glass cloth, or find a strip of carbon fiber cloth, or sandwich a piece of aluminum between two thin wood faces.

You have many options, and if you try something that doesn't work well, you can always rip it out and put in something else. That's the marvelous thing about building your own boat: you can tinker all you like :)

Good luck with your project.

PGJ