How can you arrange 6 toothpicks
to create exactly four congruent equilateral triangles?
Turn in textbooks
Questions about the final?
If we have time to kill: hovercraft, games, long exposure
What letter comes next in row 1, below?
1. A E F
H I K L M N
2. B C D
Turn in books by next class.
If you plan to contribute shrinkwrap money, but you haven't,
it's not too late. You can turn it in to me or put it in my
box in the main office. $9 per boat.
Final chance to ride the hovercraft
Play games or Long Exposure Photography (unless
the weather is really hot)
Check Jupiter Grades to see if you have to take the
final. I will try to remember to e-mail those who do not have an
The diagram below shows the cross-section of a glider
wing. The glider is pointing to the left. The "camber"
relates to the curved main part of the wing. The upward-tilting
section on the back is an "elevon."
What is camber, and what does it do?
Can you use Newton's 3rd Law (action/reaction) to
explain the force imparted by the elevon?
Questions about test on Friday?
Final Exam Info (for those who will not
have an A- for the semester or for the year, after Thursday's test):
Your exam will be a combination of material from the car test and
the pressure test. To see what you should study, go to
last quarter's stuff, and see
3/23/12 and 2/9/12. You should also review your returned
Lessons learned from Wednesday shrinkwrapping: 1) Don't
wrap the whole boat; fold over rails and tack down material to
sides. 2) Start shrinking in areas where plastic needs to be
concentrated; the last areas to be shrunk may be thinnest.
1. Some boats have "displacement hulls," while
other boats have "planing hulls." What is the difference?
2. A boat with a displacement hull has a "hull
speed" that is said to be the boat's maximum speed. This
limitation is imposed by the waves created by the boat as it travels
through the water. Would you guess that a longer or shorter boat
has a faster hull speed?
Discuss platform requirement (see last class, below)
Today will be the final day for water tank testing. Find
out what you need to know. Finalize your boat design.
Complete an inventor's log entry. Try to anticipate
problems that will arise when you try to make larger scale versions
of your boat.
Next Several Classes:
Wednesday (4/18): begin assembling full-size boat
"skeletons" (frames , seats, and platform supports) out of
wood strips and twine or cable ties. Log entry.
Friday (4/20): finish frame assembly. Experiment with
using an outdoor cooker as a shrink-wrap heat gun. Log entry.
Tuesday (after break May 1): Mr. Stapleton gone to Disney World.
Boat problem set / test review.
Thursday (5/3): Check out boats' condition. Has warping
occurred due to drying? If so deal with warping. Final
securing (probably gluing) of frame members. Log entry.
Monday (5/7): Final shrink wrapping, waterproofing, testing and
adjusting. Last log entry.
Wednesday (5/9): Final boat "contest" -- drag and
stability trials. Reflective writing assignment handed out.
Friday (5/11): Test review. Try out boats at North
Beach. If you have them, bring life vests, paddles, towels...
Tuesday (5/15): Test. Reflective writing and Inventor's
Complete an inventor's log entry (unless you already did this in
class). Don't forget to date your entry!
1. If your boat is not stable, you do not have
to build a new one. You can stabilize it with an outrigger.
What is an outrigger? You can even stabilize your boat by using
outriggers that do not add buoyant force to your boat. How?
2. During last class, the boats were pulled by a 22.5g
falling mass. How much falling mass should we use if we want to
know how the boats will function when they are powered by a human
Find your passenger's CM. How high will it be (above the
bottom of your boat). Design a seat and a way to support a
plywood platform in your boat. ***New parameter -- platform
for holding 150lb weight must be 30cm above the water line
(before your boat is loaded with the weight). The platform itself
will be approximately 3/4" thick plywood, 40cm wide and 60cm long.
This means your scale platform should be about 4cm from the bottom
of your boat, and it should be about 5cm wide by 7.5cm long.
Current rankings, based on fastest time with 22.5g falling mass...
Terminal Velocity (m/s)
Esmir, James, Jonas, Stephen
Aaron, Lauren, Michaela, Elena
Nell, Anna, Rachel, Tom
Hai, Julianna, Alaina
Erin, Nancy, Matt, Emma
Ian & Lucas
#4 on the front of the Boat Stuff page; #4-6 on the
back of the boat stuff page.
A cork won't float in the middle of a narrow glass of
water. It always floats to the side. Why? How can you
make it stay in the middle without touching it?
Boat work. Continue work from last time. Make and
test at least two prototypes.
Message to Block 1: maple sticks and shrink wrap stuff is
in the cabinet above the boats.
Message to Block 2: please drain and put away the tank. There is
a garden hose for siphoning water out the window. Pine boards
should be stored in the bunker (get help from Mr. Hoffman or Mr. Meyer,
in E104) or outside the classroom window.
To do Today: The main idea is to
perform water tank testing to see how your boat moves through the water.
Hopefully, you will be answering these questions: 1) Is it stable when
it's moving? 2)Does it have a lot of drag? 3) Does it
"track" straight? Record the answers to these questions and
show your work in your Log.
Here are some more detailed instructions...
Assess your boat's drag as it is
pulled across a water tank. I am envisioning a set-up like the
one pictured below. You will have to determine the best way to
attach the thread to the boat. If the falling weight isn't too
big, your boat should reach a terminal velocity before it reaches
the end of the tank. With the same falling weight, a more
"hydrodynamic" boat will have a lower terminal velocity. Two
pairs of photogates will you give you an idea of whether or not your
boat has reached terminal velocity by the time it reaches the first
set of gates. If it has not, reduce the falling mass. Find
a way to determine your boat's cross-sectional area (that is exposed
to the water) and use its terminal velocity and the drag equation to
calculate your boat's drag coefficient. Show your work in your
Log. Remember that, just because you have a low
drag coefficient, that doesn't necessarily mean you have low drag.
Experiment with your placement of
the 130g passenger; some locations may give you less drag.
Assess your boat's stability.
I plan to create a 130g "passenger" with Velcro on the bottom.
Make a platform that holds the center of the passenger at least 5cm
from the floor of your boat. You may want to attach some
complimentary Velcro to your platform.
Make adjustments to your boat, or
make a new one. There should be plenty of maple strips, hot
glue, and shrink wrap. Remember that this contest will be
based on low drag.
If you have time, test your boat's
ability to track ("coast" in a straight line) when it is not being
pulled. Rig up the pulley system so that the boat will be
pulled a short distance and then allowed to be carried only by its
momentum. You may want to add a keel or a rudder to improve
tracking. You may also find that this lowers your drag.
Organize your notes/work from class.
If you put a "cartesian diver" in a sealed plastic bottle of
water, and you squeeze the bottle, the diver dives. When you stop
squeezing, the diver rises back to the top. When you squeeze, what happens
to the diver's...
1. Density? 2. Volume?
Return tests and discuss
Find temperatures in class balloons
new project. Organize into groups of no more than 3