Sailing Canoe Project
Our goal is to convert one of our canoes into a sailing canoe. At the moment, the only people working on this are students taking Foundations of Physical Science (SM144). Most of the students in this course want to be early childhood teachers (K-3), By keeping this project less than 10% of the entire course, it is very easy to ensure that we follow the established guidelines (“standards”). Topics incorporated include: measurement, units, error, density, and torque. Formulas and calculations used for the project but not part of the course standards will be stated without proof or explanation.
Here are three photos of a sailing canoe that resembles what I want to make: [photo] [photo] [photo]. I got these photos from Craig O’Donnell’s Cheap Pages
1/7/08 Today we brought one of our 2-person canoes into the classroom-lab and weighed to be 65 pounds. Two shipping scales were used. We all agreed that it was “obvious” that the sum of the scale readings is the canoe weight.
· Photos of students weighing the canoe [photo] [photo]
The next step is to examine an enlarged photo taken from Cheap Pages and obtain the dimensions of the outriggers. [PDF].
1/23/08 Today the physical science class used scaling on a photo to estimate the thickness of the outrigger. We also measured the beam of our canoe.
· Photo of students analyzing the photograph [photo]
· The students measured an ama thickness of 5.4 +/- 1.4 inches (based on my interpretation of the three group reports). This assumes that O’Donnell’s Coleman-15 has the same beam as our 35.5 inch Old Time Camper
· The students also decided to have this measurement double checked by me, the professor. I have decided to be absent during such deliberations because I want all important decision made by students. (I retain veto power which will be used only in the case of obvious bad decisions.) My analysis of the photo was done using Mathematica [code], and my conclusion is that the ama thickness is 5 inches with an uncertainty of perhaps a quarter inch.
2/2/08 I originally concluded that O’Donnell used sheets of 2 inch Dow Blue Board (closed cell Styrofoam) and about a half inch of plywood. I later read that the ama was made of luan and epoxy. From our local Carter’s I learned that 2 inch Dow Blue Board (4 x 8 ft) costs about $32. The class now has to make the following decisions:
· Should we stay with Dow Blue Board? If so, should we verify that Dow Blue Board does not appreciably soak up water? My original plan was to do this. Then recently, I Googled “blue board bailing canoe” and found something at http://www.kayakforum.com/cgi-bin/Building/index.cgi/noframes/read/107629
I did a water test on the Dow Blue Board a few months ago by weighing a ¾”x1’x1’piece on a gram scales, then submerged it underwater for 7 days and weighed it again. It picked up it’s weight in water, which was like adding a feather to it. I let it set for seven days and it lost any water it had absorbed. This piece of blue board had some utility knife cuts in it that I could tell did have water trapped in them because of the coloration. So it may be that this polystyrene’s absorption was nothing at all. I will have to glue slabs together and shape them carefully to fit the bow and stern which will take some time.
o If we use Dow Blue Board, what do we do for ultra-violet protection? (I was told that UV eventually destroys polystyrene. I do know that the white polystyrene floatation used in City Lights was useless after two unprotected years.)
o Should we build the ama now and deal with these and other questions later?
In my absence, the class decided to go with luan. I recommended polyurethane adhesive. The class also requested that I notify some local vendors and see if we can get some supplies donated to the university.
3/5/08 Held competition to design ama. Inspired by the winners I came up with the following dimensions and calculations.
· The plan uses about two sheets luan underlay at approximately $11 per sheet. I also bought eight 8-ft “2x1” (nominal inches) furring strips for framing. We have a large collection of “2x4” boards that are a bit over a foot long for more framing.
· The calculation (linked above) leads to a knowledge of the lwl and displacement as a function of draft. I also checked that we are not bending the plywood too much.
· Since students questioned whether the ama had sufficient buoyancy, and since we were doing torque at the time, I explained that we have more torque than we could possibly need from the ama. [photo]
Summer Construction:
Walter cutting paper to make the model
Walter building the model
Bertha and Steven lofting