Finding the wood for the gunwales may take some time, but the actual work on the gunwales takes less than a day.
Step 1: Materials
You will need a piece of wood 1-3/4 inches wide by 3/4 inches thick by 5 feet long. You will cut this up for risers that go at the ends of the gunwales.
You will need four each 1/4 inch dowels 36 inches long. Exact length doesn't matter as long as you have enough total length since you will be cutting these up. Four dowels is more than enough for working with the gunwales. You will be using the left over dowels for pegging the deckbeams to the gunwales.
You will need about a dozen 1-1/2 inch long finish nails. These are generally referred to as 4 penny nails. You will need more later on so buy at least 4 dozen of them.
Step 2: Tools
You will also need a pencil for marking and a tape measure and a combination square.
A pair of sawhorses will be handy for keeping the gunwales at a comfortable working height.
Step 3: Selecting Gunwale Lumber
If you want to avoid a lot of sawing, you can try to find boards that are 3-1/2 inches wide and 16 feet long. This will push the final weight of your boat up to about 45 pounds, but it will be a rugged boat. If light weight is important to you, you'll have to do some sawing to get the 2 inch wide boards.
The wood for your gunwales should be some kind of soft wood like pine, spruce, or douglas fir. The wood should be free of knots and have straight grain. Softwoods are preferred over hardwoods like oak because they are lighter and because hardwoods with straight grain are hard to find in 16 foot lengths. For best results and highest price, get wood of a grade called CVG, which stands for clear vertical grain. Vertical grain assures uniform flexibility throughout and is subjecct to the least amount of warping over time. Clear means no knots.
If you want to build your boat with the wider 3-1/2 inch boards, these can have some knots as long as they are tight and small, under 1/2 inch. Two inch wide gunwales should not have any knots in them at all.
When you select gunwale boards, also make sure that they have roughly the same amount of flex. You can check for equal flex by supporting both ends of the boards and seeing that they sag the same amount in the middle. If flex is mismatched, try flipping one of the boards over. Sometimes they have more flex in one direction than the other. Flex in the two gunwale boards does not have to be absolutely the same but if the difference is too great, it will make it harder to get a symetrically shaped deck.
Step 4: Nail the Gunwale Boards Face to Face
Put the gunwales face to face and nail them together leaving 1/4 inch of the nail heads sticking out so they can easily be pulled when we are done marking. Space nails roughly two feet apart.
When you nail the board together make sure that the sides with the same amount of flex face each other.
Also make sure that the ends of the boards line up exactly. If they don't you will be installing all your deck beams at an angle.
Step 5: Mark the Longitudinal Center of Your Gunwales
Run the center line around all 4 faces of the nailed together boards. Mark each face with a C for center.
Step 6: Mark Bow and Stern and Up
You generally want the better looking edge to be at the top.
Mark the bow and stern with arrows so you can keep track which is up and which is front. You will be marking deck beam positions on the top edge of the boards and rib mortise positions on the bottom edge of the boards.
Once you work on the boat with a bow facing a certain direction, always keep it facing the same way so you don't get confused over which end is which.
Step 7: Measure Your Body
Distance from your back to the back of your kneecaps. Your knee brace will be positioned right behind your kneecaps. Put a 1-1/2 inch wide board right behind your knee caps. Move it far enough back so that it doesn't feel uncomfortable when you press down on it.
Distance from your back to the balls of your feet. Sit with your heels together and the toes slightly outward.
Width across your feet at the balls of your feet. This measurement is mainly for people with feet larger than size 11. Greenland boats are fairly narrow so you have to make sure your boat will be wide enough at the foot brace for your feet to fit.
Height of your thighs behind your kneecaps. We need this measurement so we can make the knee brace high enough for your thighs to fit under.
Step 8: Transfer Body Measurments to the Top Edge of the Gunwales
Make a mark 17 inches back of the centerline you marked earlier. This will be the location of the front edge of your back rest. Make another mark 1-1/2 inches back of that. Your back will be 15 inches back of the boat's longitudinal center. The extra two inches will give you enough room to add some padding to the back brace or to install a back band to support your back while you're paddling.
Take your back to kneebrace measurement and add 2 inches to it. Measure from the backbrace front edge forward by this amount. This will be the front edge of your knee brace. Make another mark 1-1/2 inches back of that and label it knee brace.
Take the measurement from your back to the balls of your feet, add 2 inches and measure forward by that amount from the back brace mark. Make another mark 1-1/2 inches forward of that. Label this foot brace.
Step 9: Mark Positions of the Remaining Deck Beams
Make a mark 24 inches from the bow and another 24 inches from the stern. Make another mark 1-1/2 inches toward the center of the gunwales. This will be the position of deck beams 1 and 11. Label them on each gunwale.
Space deck beams 2 and 3 evenly between deck beams 1 and the footbrace which is deck beam 4.
Space deck beam 5 halfway between deck beams 4, the foot brace and deck beam 6, the knee brace.
Space deck beams 8, 9 and 10 evenly between deck beam 7, the back brace and deck beam 11.
Step 10: Mark Rib Mortise Positions on the Bottom Edge of the Deck Beams
Start by marking a rib mortise 2 inches back of the back edge of the foot brace. Mark all rib mortises on the bottom edge of the gunwales. Mark the next rib mortise 8 inches back of the front edge of the first rib mortise. The reason for starting here is that you want to position these ribs so they don't dig into the back of your heels (painful).
Space all the other rib mortises forward and backward of the first two mortises. Mortises should be spaced 6 inches on center. That't not 6 inches between rib mortises, that's 6 inches between their centers. Mark forward until the last rib mortise is 24 inches or less from the bow. Mark backward until the last rib mortise is 24 inches or less from the stern.
Step 11: Cut Bow and Stern Risers
Step 12: Dowel Bow and Stern Risers to the Gunwale Ends
Trim off any dowels sticking above the edge of the risers.
Step 13: Trim Gunwale Ends
These angles are the angles at which the stem and stern boards will be attached to the gunwales.
The stem slopes at a flatter angle than the stern.
Step 14: Shape Tops of the Risers
Step 15: Cut the Rib Mortises
Rib mortises are 1 inch long, 1/4 inch wide and 1/2 inch deep and are centered on the bottom edge of the gunwales. If you have a router and 1/4 inch bit, that is the fastest way to cut the mortises. If you don't, drill a 1/4 inch hole on either end of the mortise and remove the wood inbetween with a 1/4 inch chisel. Wear ear protection if you use a router.
Step 16: Mark the Ends of the Gunwales for Planing
Step 17: Separate the Gunwales
We need to do one more marking step once the nails are removed. See the photo below for how to do the marking.