To:          Dr. Harvey Lipkin
From:        Stefanie Higgins, Joe Haemer, Daniel McCarthy, Chris
             Crecente, Kenneth Chastain
Subject:     Letter of Transmittal

     The following document is a summary of the canoe outrigger design project that our 
group completed this quarter.  This document describes the creation, building and success 
of our design for a canoe outrigger.  It includes an executive summary, an introduction, 
the design components, a conclusion, and appendices containing our engineering 
analysis, part and layout drawings, and color photos.

The Collapsible Canoe Outrigger

ME 4182

Team Members:

Stefanie Higgins
Joe Haemer
Chris Crecente
Daniel McCarthy
Kenneth Chastain

Executive Summary

Outriggers for canoes are currently very cumbersome. They are not collapsible or
adjustable. The person has to build it himself to fit his canoe. The purpose of this project
was to design and create a light, collapsible, portable and adjustable canoe outrigger.
While designing this our group kept in mind our customer’s needs and the constraints we
set in order for the design to succeed. It was important for the customer to have an
outrigger with a stable platform for activity, allows ease of paddling, ease of assembly,
and adjustable to different size canoes. The size, strength, weight and cost of the design
were our limiting factors. Our design was broken down into three major components:
the floats, the arms and the brackets. We generated five design concepts and using
selection analysis we finally chose the side by side sliding arms design.

The bracket was made out of poplar and attached to the gunwale and thwart of the
canoe. Two u-bolts connected the bracket to the thwart, while a lip on the edge of the
bracket allowed for easy mounting against the gunwale. The bottom of the bracket was
shaped to help prevent it from falling toward the front or back of the canoe. The arm was
made out of aluminum and rests in a clamp attached to the bracket. The arm is able to
pivot to allow for various levels of water. The arms rest inside the boat, resting under the
pivot when they are not needed. Once they are needed they can be extended out and
hooked into place with a pin. Floats made from polystyrene are attached at the end of the
arms. Four metal rods extended through the floats to help provide a rigid connection to
the arms.


As environmental conservation becomes a larger issue, restrictions on boats are
increasing. Florida, as well as other states, has established many water areas as "no wake
zones." This requires the use of a canoe or other similar non-motor boat. Often people
are trying to fly fish or hunt out of their canoes in these areas. Both of these activities can
require a lot of movement. Moving in a canoe can be very risky; it is not hard to tip a
canoe over. This creates the need for a device that will help guard against the canoe
tipping over. Such a device has been created called the outrigger. Some problems with
the outriggers people use today are that you usually have to build it yourself, it will only
fit your canoe, you have to drill a hole into the side of the canoe, they are usually only on
one side of the canoe and once the outrigger is attached to the canoe it cannot be retracted
back into the boat to allow for paddling from both sides of the canoe. The patented
designs we found were very primitive and one sided. The outrigger had to be assembled
and attached to the canoe before you launched the canoe, making it difficult to paddle.

We felt there was a need for a pre-made outrigger that was portable, adjustable,
collapsible, and did not affect your rowing. This outrigger would not only satisfy the
needs of avid hunters and fishers, but it would also be ideal for summer camps to use
with young or special needs children. There were four constraints we had to keep in
mind while designing our outrigger. Our outrigger had to be small enough to be
transported on a car with a canoe. It was very important for the members to be able to
withstand forces to resist yawing, so strength was vital in our design. The weight of the
outrigger had to be kept down to allow for ease of assembly and transport, as well as
floatation. The cost of the outrigger had to be competitive with the time and material for
a homemade outrigger.

Design Components

Overview of Design

The final design of our outrigger consists of a bracket, a float and an arm. There
is one design for the outrigger that can be used on both sides of the canoe, limiting the
number of parts needed. The bracket attaches to the gunwale and thwart of the canoe.
This bracket holds the arm which has the float attached at the end of it. The arm can
rotate on the bracket to be set at different angles to allow for various levels of water.
The brackets should be mounted onto the canoe before getting into the water. The
arms can be retracted in and resting under the pivot of the other bracket when they are not
in use. Then when the outrigger is needed the arms can be slid out and the pin placed
through the arm and bracket to hold it in place. (See Appendix B for all part and layout

Layout Drawing


At the end of the arm is a float. The float has four metal rods through the center
of it to provide a rigid connection to the arms. This foam block needed to be large
enough to provide stability. The block also needed to be made from a low-density
material. We used polystyrene foam for our floats.

Using engineering analysis, we looked at two important questions. First we
needed to know the load at the floats. This load was found to be 133.33 lb. Then we
needed to determine the optimum size to make our floats. We determined that we needed
to have a volume of 3704 in^3. This worked out to a float with the dimensions 12" x 12" x
25". We ended up using floats with the dimensions 16" x 12" x 30", which is larger than
we needed. (See Appendix A for all engineering analysis calculations, all calculations
used the worst loading conditions possible.)

Float Drawing


The bracket provides a rigid connection to the boat. The bracket also takes the
force load from the arm. The material needed to be light, while being able to withstand
the transmitted forces. Hard poplar was used since it is light and able to withstand the
bearing stresses. The trapezoidal shape of the bottom of the bracket prevents it from
falling toward the front or back of the canoe. The lip on the edge allows for easy
mounting against the gunwale (edge). Two u-bolts were used to keep the forces on the
arm from pulling the bracket off of the thwart (central support). Padding was added to
the bottom of the bracket and the u-bolts to help stabilize the connections and prevent
damage to the canoe. Multiple holes were drilled into the side of the bracket to allow for
the arm to be set at different angles to allow adjustment to various water levels.

Many questions had to be looked at to ensure that our design would be strong
enough to withstand the forces placed upon it. We first looked at the following forces:
the pivot would have a force of 800 lb. down on it; the locking pin would have a 666 lb.
force on it; the u-bolt closest to the edge of the canoe would have a force of 466 lb.; and
the other u-bolt will have a force of 600 lb. on it. The next step was to ensure that the
pivot would not shear. We found that if we used a ¼" diameter pin, we would have a
factor of safety of 4.6 for yielding. Then we found the minimum diameter needed for the
u-bolt closest to the edge of the canoe. Using a ¼" diameter u-bolt gave us a factor of
safety of 3.5. Next we determined the minimum width the wood needed to be to be able
to withstand the bearing stress at the pivot. If we were using southern pine we would
need to have in 2" thick for a safety factor of 2.5. But we ended up using poplar which is
a harder wood, so we only used a piece that was ¾" thick. Then we determined if there
was a need for extra large washers to keep the u-bolts from crushing the wood bracket.
We found that only an outside diameter of ½" was needed, so normal sized washers were
fine to use. The last area we needed to look at as far as the bracket was concerned was
whether or not the force from the two u-bolts would bend the thwart. We determined that
the load should not bend the thwart, with a factor of safety of 3.44.

Drawing of Bracket


It was important to make the arms of the outrigger a size that would not bend. We
needed them long enough to provide stability, yet shorter enough to fit completely inside
the canoe when they were retracted. The arms were made out of aluminum, which is
strong and light. The arms are able to slide in and out for easy deployment and stowing.
The design of the arms does not impede motion, so it is possible to row with the arms in
or out. The duplicate bracket pieces allow the arms to slide past each other. The arms
also store nicely under the pivot of the other bracket when they are retracted.
The one question that needed to be answered as far as the arms were concerned
was if they would bend. We found that we could use a tube with a diameter of 1.5" with
1/8" thick walls and we would still have a factor of safety of 1.7.

Drawing of Arm


Our group was able to build the collapsible, portable and adjustable canoe
outrigger we set out to design and build. We developed a robust and functional design
that was able to withstand the rigorous testing it underwent. The one part of our design
we would like to work on in the future would be to develop a more elegant connection to
the thwart. The cost of building the prototype came to a total of $92. While the cost of
materials to actually build an outrigger would be $41.

Appendix A - Engineering Analysis

The following areas have been identified as critical to the design of the outrigger, in
sizing components and preventing failure due to over-loading.

1. Loading on the outrigger - floats
2. Size of the floats - floats
3. Reaction forces at pins and fasteners - bracket
4. Shearing of pins at pivot - bracket
5. Failure of fasteners in tension - bracket
6. Bearings stress in bracket at pin holes - bracket
7. Stress on bracket at fasteners - bracket
8. Bending of thwart (central canoe support) - bracket
9. Bending of the outrigger arms - arms

The outrigger will be designed to keep a canoe from tipping while two men lean over the

Shigley and Mischke, Mechanical Engineering Design
Gere and Timoshenko, Mechanics of Materials
Dowling, Mechanical Behavior of Materials
are used as references

Engineering Analysis

Appendix B - Part and Layout Drawings

Layout Drawing

Part Drawings

Appendix C - Copies of Photographs

Photo 1

Photo 2

Photo 3

Photo 4

Photo 5