However, piling thick balsa boards can also do the trick and can get you with a minimal concept powered by a stirling engine.
The most expensive part of this project is the stirling engine. You can purchase that from eBay or make one yourself.
So, here are the steps:
1. Prepare the stirling engine
You can use an alpha-type stirling engine with a bore of 15mm and a stroke of 6mm, and use an alcohol lamp as a power (heat) source. Of course, one can can the creative juices flowing and use a solar concentrator, track the sun, etc. That would be more exotic.
2. Drawing the Plans
You’ll have to draw the top view, side view and sectional, on a 1:1 scale. You’ll have to think about where you’ll put the engine and balance the weight exactly. If you can’t do that on paper, you can always experiment afterwards. Also think of the thickness of the balsa boards.
3. Making Paper Patterns
In this case, you’ll be using nine balsa boards, just like in the picture. After you’ve made the real-life sketches of each layer, make a carbon copy to the boards, or see the next step.
4. Pasting Paper Patterns
This is sometimes more easy to do than carbon-copying the sketches to the boards. Paste the paper patterns to the balsa boards with double-sided tape, so they stay glued while you saw them.
5. Cutting Boards
Use a sawing machine to cut the balsa boards, while taking care for the paper not to fall off it, as this will help you in the next steps.
6. Glue the boards together
Use wood glue to fasten the boards together. This step is very important, as it will ensure the viability of the model and the strength of the stirling engine boat.
8. Finishing the boat
After you’ve glued the whole assembly together, finish it to make it smooth. Be creative at this step. You can shave the steps and then use sand paper to give it a final touch.
9. Waterproof the boat
This step is self-explanatory. Just paint the entire boat with clear lacquer, let it dry, apply another layer and so on. Paint about three to four layers of lacquer, so water doesn’t enter the balsa pores.
10. Give it life
Paint the stirling engine boat with a color of your choice. Attach a rudder mechanism to it. Then, fit the stirling engine and there you go, power it with renewable energy all day long!
You can download the entire CAD sketches from NMRI’s own website.
A quick note: because the balsa wood burns well, you’ll have to heat up the stirling engine near the water, to avoid potential trouble.
Paper pattern of the hull (Autodesk DWF format)
Additional parts of the boat, No.B1-B6(Autodesk DWF format)
Download of the whole CAD data including the hull and the engine (Autodesk AutoCAD 2000 DWG format)
Download of the whole CAD data including the hull and the engine (Autodesk AutoCAD 2000 DXF format)
MPEG Movie of the Model Boat (2 MB)
I originally found this tutorial on a Japanese website (NMRI). So all the thanks go to Koichi Hirata, the original maker of this tutorial. You can find his website at the end of the page. All of the pictures are (c) Koichi Hirata. I reshaped the tutorial a bit to give his project a bit more attention, because it looked interesting.
You can view the original instructions here: http://www.nmri.go.jp/eng/khirata/stirling/boat_design/index_e.html