Build a Greenland kayak part 5

In this instructable you will be adding ribs to form the hull of your kayak. This involves bending wood with steam or hot water. Although this may sound like a daunting prospect, it isn't. There's a total of 24 ribs to bend. If you have no experience bending wood when you start, you will be quite good by the time you're done.

Step 1 Materials

Ribs are best made out of hardwoods like oak. Softwoods like pine or spruce don't bend nearly as well. Elm bends even better than oak, although you're not likely to find it at most lumberyards. Ash is also a good bending wood.

I like to get my oak boards in 3 inch widths, 5 to 8 foot long. I pick through the boards to find ones that have flat grain that runs straight for the whole length of the board. The longer the board, the less likely it is that its grain is going to be straight for the whole length of the board. The boards should also be free of any irregularities in the grain.

Ribs need to be about 8 inches longer than the width of the gunwales where they are being inserted. For estimation purposes figure an average of 24 inches per rib. Lets say you buy boards that are 5 feet long and 2-1/2 inches wide. Your ribs will be 1/4 inch thick, so you can get about 7 sticks out of each board assuming you lose 1/8 inch per cut. Each of those sticks will give you two ribs, so each board will give you 14 ribs. Allowing for breakage means that you will probably need three of those 5 foot boards to make all the ribs for your boat.

Comments

[j2gcarter]

In your description of the wood to be used you did not mention that the wood needs to be air dried and not kiln dried. The kiln drying process will harden the cellular stature and you will not be able to bend toe wood.

[KCB1]

I disagree ... green or air dried is better ... but kiln dried wood can be steam bent. That's what I used for my F1 and it bent just fine.

[nativewater]

Right. Wood for bending ideally comes directly from the mill and has never been dried at all. But you can work with kiln dried wood if you soak it first for a few days. But kiln dried wood even after soaking will not bend to as tight of a bend as wood that hasn't been kiln dried.

[cjohnson-417]

I used a PVC pipe we had laying around and an electric kettle for my steam. It's a little goofy, but it worked well.

[cjohnson-417]

I used a band saw with a fence. I was much more comfortable with bandsaw vs. table saw. There was also less waste from the blade.

[Boatdoc]

Hello...I've just clamped up all the ribs, and have a question about the hull stringers.  Do they lay on the 3/4'' edge or flat to the ribs?  Thanks, this has been alot of fun!

[nativewater]

they lay on the 3/4 edge.  The stringers support the skin and should provide at least half an inch of clearance between the skin and the ribs.  Remember the water pressure will push in the skin a little. Lay a stick between the stringer and the keelson to check clearance between skin and ribs.

[Boatdoc]

Thanks for the clarification on the stringers...and the advice on checking the clearance.

[KCB1]

I'm using kiln dried Red Oak for my ribs and I'm soaking them for over a week before steaming ... but they're coming out of the steamer pretty dry. How do I prevent the ribs from drying out too much in the steam box?

[nativewater]

wood drying out on the surface is normal because the steambox is hot. When you first put the ribs in the box, steam condenses on them and they end up looking wet, but once they heat up, they dry on the surface. If they have soaked in water for a week, they shouldn't need to be in the steambox for more than a few minutes, 5 max. If anything, leaving them in too long causes them to delaminate when you try to bend them. I generally soak the ribs for 3 days then steam them for two to 3 minutes. Actual time varies on the particular batch of ribs. Red oak is a generic term and can include any number of species of oak. Some bend more easily than others. They also vary in how much water they soak up.

[crasch48]

using Eucalyptus might not be a good idea. Eucalyptus was brought to America because it grows fast in arid areas for railroad ties. it was too soft and porous, also it rotted easily so it was abandoned as a building material.

[nativewater]

I wouldn't rule out eucalyptus saplings. But like you say, larger timbers have all kinds of problems. Given enough time, I would bend a sapling, set it into some kind of form and see what it looks like after sitting in a dry place for a month or two. I would check for shrinkage and warping. If these were tolerable, I would go ahead and use the wood. Resistance to rot is not a major issue for SOF boats since they do not stay in the water. Worst case, if your boat was hopelessly deformed after a year, take off the skin and put new ribs on it. This is not a huge project like replacing the hull of a conventional wooden boat.

[skuthorp]

What about green timber for the ribs? I have thickets of Eucalyptus saplings that will have to be cleared for fire prevention purposes and shaved somewhat will bend easily and I thought might do the job. Incidentally I have a half-finished S&G kayak in the shed which will be superseded by two of these beautiful craft. It's almost a pity to put a skin on them. Sku

[nativewater]

If the saplings are flexible enough you can use them. Ideally you can bend them green without steaming. I have used various kinds of wood in the past. For a kayak, pick saplings that are about 1/2 inch in diameter with the bark on. With the bark peeled, they should be about 3/8 inch in diameter. Space the ribs 4 inches apart - you can then drill circular mortises instead of cutting rectangular mortises for the flat ribs. For more details, go to
http://www.wolfgangbrinck.com/boats/boatbuilding/ribs/greenribs.html

[GorillazMiko]

wow, this is one of the best instructables i have ever seen. (im talking about all the steps)