Description
|
Measurment
|
Reason
|
Length
|
16’
|
Typical length for a 2 seat canoe. Long enough to keep straight, and will fit on my car.
|
Centre width
|
34”
|
Slightly
shorter than yoke length (36”), giving me a bit of play so the yoke
will fit, even if the canoe ends up a bit wider than anticipated
|
Depth
|
20"
|
Tested a good height for the seat, so leg room is comfortable, and I am sitting deep enough in the canoe
|
Formation of bottom
|
2 pieces
|
This will allow for a rocker to be made easily, and for better tracking than just a flat bottom
|
Rocker
|
3”
|
Not too big, as we will not be canoeing places that require careful steering
|
Number of tiles
|
6 (for now)
|
Enough to create a decently round hull profile. More might be decided on after the prototype.
|
Based
on these, I created some a smooth surface canoe that matches the canoe
that I am interested in, aesthetically. See pictures below.
Then I broke this surface into 6
surfaces that can be made from a sheet of material. This was done by
creating sheet metal surfaces. Solidworks assumes that sheet metal can
only be bent in one direction (you can create a cylinder type bend, but
not a double bend like a saddle). This will be the case even more so
with the wood. In Solidworks, sheet metal parts can be flattened, which
means I can see how the part should be cut before being bent. Because it
creates strange spline like curves, it is nearly impossible to
dimension the parts. As a result, I will have to have the drawings
printed out in full size, then cut.
I
have done some preliminary simulations in solidworks, to figure out how
much the hull profile will change the stability, and found that the
difference between extremes was minimal (less than 1mm more movement
when 200lbs was applied approx 8” away from the centre). For the
simulation, I made an approximated half cylinder (the approximations
being different hull profiles), and constrained the shape along the
centerline at the bottom. I gave the shape a weight, and applied gravity
to it. I then had a pressure applied upward along the bottom, up to
where the waterline would be. Then I applied a point force
eccentrically. The simulation was done with the shape as rigid, so it
would only move with itself (in this case, rock along the centerline). I
then took note of the maximum displacement (which occurred at the top
portion of both walls, as I had predicted). Since the results did not
indicate that the shape made a very big difference, even with incredibly
high weights (far more than the 200lbs), I will not continue to attempt
simulations, unless I can come up with a better way to model it. (I did these on another computer, and forgot to take screen shots. If I feel motivated to do the test again, I will post pictures.)
I
was also interested in finding some equations that would give me a good
idea of how far plywood can be bent, how much spring back it will have,
and basically any other information with regards to bending plywood.
All that I found was very vague, and meant more for smaller projects.
This surprised me, as making stitch and glue boats are not uncommon. I
decided that the best thing to do would be make a prototype. This would
be 4’ long and made out of cheap plywood. It would give me a good idea of how the
wood acts when it is bent. It also gives me a chance to practice my
cutting and gluing skills with cheaper material. The model will also
have the benefit of allowing me to test how stable the boat will be in
real life (I still need to figure out what this test will look like
though…).
I have two long weekends in a row coming up, so I am hoping for some decent weather, so I can cut and assemble the mini canoe!
Next Post: The Creation of a Prototype
