Hull - The main part of a boat, sides and main structure.
Frame - Wooden vertical piece of structure, that holds the shape of the boat.
Kerf - A slit or cut in a piece of wood.
Sawhorse - Triangular support to hold lumber for sawing.
Awl, Table saw, Electric drill, electric sander, steam box, camp stove, old pipe, old tank, Gloves
"How to Build a Wooden Boat" - by David C McIntosh
I was trained as a shipwright at the Northwest School of Wooden Boatbuilding, and have worked on a variety of vessels, up to 90' long. This is a 32 foot sailboat that needs all new frames. This yacht was built in 1942, and as a result, most of the frames have rotted away. This instructable will cover some basics on how to replace steam bent oak frames in a sailboat. In a wooden sailboat, the skin of the boat is thin cedar planks, which are screwed to oak frames that hold the shape of the hull. There is a frame every foot along the interior of the boat. Each frame is green wood, that is steamed and then bent to shape, and allowed to dry. When dry it retains the shape it is bent to. This is complex work, but not outside the ability of the average carpenter.
Step 1: Determine Frames That Need to Be Replaced.
You are looking for cracks or rotten spots. The wood will be spongy, or powdery.
On this boat, you can see the deterioration from the steel nails in the oak frames. There is a chemical interaction once the zinc galvanized coating has worn off. The point here is to never use steel in oak - it does not last.
Step 2: Using an Awl, Pop the Plug Covering Each Screw in the Planking.
Step 3: Remove the Screws From the Frames With Your Electric Drill.
Step 4: Remove the Old Frames.
Step 5: Sand the Old Paint Off to Get a Clean Surface.
Step 6: Buy Your Lumber for Steam Bending.
This needs to be freshly cut, straight grained, white oak with no knots. Spend the money for good quality lumber, as it determines the success of the bending.
Step 7: Soak It in Salt Water.
This keeps it wet until you are ready to steam it. The saltwater helps preserve the wood.
Step 8: Lumber Preparation
- Measure your boats old frames. Using your table saw, cut your frames from your lumber.
- Once they are all cut square, cut down the middle of each one creating a “kerf” so that the wood will bend easier. Leave the last foot uncut, to hold the halves together.
Step 9: Build a Steam Box.
I built mine from leftover cedar fence boards. All you do is nail them at the corners, and plug one end.
Step 10: Boiler
For the water boiler I used an old propane tank. Cut a hole big enough for your pipe to fit into it, and drill a hole so you can add water. Put a cork in the small hole, to prevent steam from escaping.
Step 11: Drill Another Hole to Fit the Pipe on the Underside of Your Steam Box.
Step 12: Set Up to Steam
- Set up your propane camp stove, set the water boiler on it.
- Slide the pipe into the top, then wedge around it with a rag.
- Finally set the box up on sawhorses, with the pipe going into it.
- I then cover my box with heavy tarps and blankets, to help insulate it.
Step 13: Steaming
- Fill your water boiler and start your stove on high.
- Once steam is leaking out of your box (they always leak a little), then put your first frame in.
- Steam it for one hour for each inch of thickness ( Our frames our narrower because of the kerf, so only have to steam for an hour).
- Remember to replenish the water in your water boiler.
- I also put a frame in every 5 minutes, so I can pull them out in order, and install without leaving them too long.
Step 14: Installation
- Wearing your gloves, open your box, and pull out the frame.
- Move quickly to the hull, and slide it into place. Clamp every 6 inches. Repeat the process with the rest of your frames.
- Let them all cool for a day, and then drill and fasten with Silicon Bronze screws.