Comparison of Traditional Hawaiian and Modern Outrigger Canoe Manufacturing ­

Dept. of Mechanical Engineering University of Hawai'i at Mānoa

Students: Justin Dery Advisor: Dr. Jingjing Li, Ph. D. Jeffrey Ibara Mitch McLean

William Segall

Holm Smidt Joseph Valle

Abstract: In this report, we will compare ancient Hawaiian canoe building to the modern

production of canoes. Comparing the materials used, the methods of construction, and the tools at each builder’s disposal. It would be obvious to say that things have gotten better over time, but there are methods and components from ancient traditions that are still very much a part of how canoes are built today.

1. Introduction As engineering students in Hawaii, it is hard not to notice the engineering solutions

produced by ancient Hawaiians. In a remarkable feat of achievement not seen elsewhere until several hundred to thousands of years later, the ancient Hawaiians engineered, built, and navigated vessels capable of traversing the vast expanse of the Pacific Ocean without the benefit of metals[1].

In this paper, we aim to investigate the materials and manufacturing processes of the ancient Hawaiian people, as well as detailing what improvements and advancements have been made to canoe design, and how the modern design evolved from its traditional Hawaiian roots. 1.1 The Outrigger Canoe

A variety of canoe designs can be observed from Hawaiian culture ranging from double hulled voyaging canoes, called Wa'a kaulua; to small, single hulled outrigger canoes called Wa'a kaukahi. The single hulled outrigger canoe was considered in this study; it can be identified by the attached float (`ama) that adds to the vessel's buoyancy and increases the roll stability, shown in Figure 1. Without doubt, the outrigger technology is a remarkable solution to the problem of roll stability for dugout canoes that can still be observed in modern canoe designs.

Figure 1: Drawing of a Hawaiian style single outrigger canoe that identifies the main components of an outrigger canoe. 1.2 Objectives

The primary goal of our research was to identify the major differences and modifications between traditional and modern outrigger canoes. To do this, the following objectives needed to be accomplished:

Identify manufacturing processes, the materials used in the manufacturing of traditional Hawaiian canoe and indigenous knowledge in engineering;

Identify manufacturing processes and materials used in the manufacturing of modern style outrigger canoe;

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Comparison of traditional Hawaiian canoe and modern style outrigger canoe. 1.3 Overview

Chapter 2 focuses on the traditional Hawaiian canoe ­­ the materials used, the manufacturing processes and surface treatment. Chapter 3 then continues with a case study of the the materials and manufacturing processes used by a local canoe manufacturer. The results of the case study apply to modern canoe manufacturing in general. Chapter 4 makes a comparison between traditional and modern outrigger canoe manufacturing, followed by an overall conclusion.

2. Traditional Hawaiian Canoe 2.1 Background

The outrigger canoe was an essential part of ancient Hawaiian life. The large double hulled canoe (waʻa kaulua) helped polynesians navigate the arduous journey from Tahiti to Hawaii. Upon their arrival, they found an abundance of Koa trees. This discovery led to a new type of outrigger canoe.

The design of each canoe matched the purpose it would serve. Canoes were vital for fishing, transportation, war and recreation. The process by which they were made was done by specialists (kahuna kālai waʻa) that would dedicate their lives to the rituals and craftsmanship required to produce seaworthy vessels[2].

Figure 2: A small traditional Hawaiian canoe.

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2.2 Materials The materials used in the manufacturing of traditional Hawaiian canoes can be split into

two parts: the material for the hull and the components connected to the hull, and the joining material which bound them together. For the purposes of this document, the mechanical properties of the hull and adjoining parts connected to the hull are considered, of which all are usually made of Koa.

Koa (Acacia Koa) is a Hawaiian hardwood and considered Hawaii’s finest native tree. In modern times the supply of Koa is scarce, but in antiquity, Koa was plentiful. The hull of the traditional Hawaiian canoe was typically made from the trunk a Koa tree. The trunk selected was anywhere from 20 to 60 feet (6 to 18.3 m) in length and between 10 to 12 feet (3 to 3.7 m)in circumference. Spreaders, called Wae, were made of the same material and were placed inside the hull horizontally (in compression) to prevent the hull from collapsing on itself. Pieces were attached to the bow and stern of the ship to break the waves which were also made of Koa.

Koa is considered a hardwood and has similar mechanical properties to Black Walnut[3]. Acacia Koa behaves as a brittle material and has a variable density, making it difficult to machine or work by hand[3]. In woods, the modulus of rupture is used to compare species. The modulus of rupture is commonly known as the flexural or fracture strength. Woods are tested using a three point flexural test.

Table 1: Mechanical properties of Acacia Koa and Black Walnut

Density (kg/m3)

Specific Gravity

Modulus of rupture (kPa)

Modulus of elasticity (MPa)

Compression strength parallel to grain (kPa)

Black Walnut[5] (Green) 510* 0.51 66000 9800 29600

Black Walnut[5] (12% moisture

content) 550* 0.55 101000 11600 52300

Koa[4] (green) 529 0.53 87000 10370 48700

Koa[4] (12% moist) 545 0.61

Koa[3] (air dry) 608.7 0.55 ­ ­ ­

*Calculated values assuming a density of water of 1000 kg/m3

Despite its variable density, Koa’s average density is still around half the density of

saltwater, which allows it to float. In Table 1 it can be seen that the density of Koa appears to increase as its moisture content decreases.

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2.3 Manufacturing Processes When a suitable Koa tree is selected, it is carefully cut down using ancient adzes called

ko`i. The care taken in cutting down the tree is partly due to tradition, but it is also so as to not damage the trunk as it falls.

The Adze or Ko`i [6] was an invaluable tool used by canoe builders to not only cut down the Koa tree, but to shape the canoe as well. There were several types of Ko`i. Refer to Appendix A ­ Figure 1 for an illustration of several types of Ko`i. Each had its own function and name, but they all had the same basic components. The Tang, or the cutting blade, was made out of shaped basaltic stone. The Tang was lashed to a Haft or a handle which was usually made from branches of Hau (Hibiscus tiliaceus). The Lashing that bound the Tang to the Haft was made from the bark of the same Hau branches.

Vertical cuts or scarfs are cut into the base of the tree roughly one meter apart [2]. When the scarfs are deep enough, the wood between the scarfs is chipped away. The wood chips are cut with the grain of the wood. This helps prevent the wood from cracking vertically along the trunk.

Before the tree falls, a bed of fern, the Hapu`u (Cibotium Menziesii), is laid out on the forest floor to cushion the fall. With the tree safely on the ground, the branches and the bark at the top of the tree is ceremoniously removed to preserve the spirit of the wood. Then the rest of the branches and the bark are removed. Now the hewing can begin.

The Hewing is a rough shaping of the canoe. The bow, the stern, and the sides are cut out, and the beginnings of the interior also starts to take shape in this process. With the Ko`i, the wood is chipped away piece by piece. In this process, a large section of the bow is left uncut on the canoe. This neck is used to make transportation, usually downhill, possible. This is essential as the unfinished canoe often would weigh several hundred pounds. Rope is tied to the neck and a team of people supports the weight of the canoe as it slides down the hill. When the canoe makes it to the village down at the beach, it is housed in a shelter and allowed to cure for days, weeks, or even years, depending on the size of the canoe.

Other tools used to shape and finish the canoe were Stone Chisels called Pōhaku Pao. These chisels were used to punch holes into the hull of the canoe for Hau branch lashing and other components to pass through. When these holes were punched through with the chisels, seashells called Pūpū were used to smooth out the holes. For smaller holes in thinner parts of the canoe, a pump drill called Nao Wili was used. The Nao Wili is shown in Appendix A ­ Figure 2. After the wood has been given the chance to cure, it is now ready for final shaping. The neck is cut from the bow of the canoe, and the bottom is rounded off and smoothen out using stones called Pōhaku `Ānai. The final shaping of the interior is also done.

Next comes the installation of the outrigger or the ‘Ama [7]. The ‘ama was usually a smoothed out narrow long piece of Koa that was lashed to the main hull by two shafts called `iako. The `ama was smoothed out by the Pōhaku `Ānai and affixed to the left side of the hull (being that was usually the leeward side of the canoe). Now the canoe is ready for surface treatment and further curing.

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2.4 Surface Treatment After the polishing was done by the moʻo, it was time for waterproofing and painting.

Kukui nut oil was often used to waterproof the hull. However, the paint was usually the most effective treatment to seal the surface. A black paint (pā`ele) was made by first crushing buds from the `akoko shrub, flowers from the banana plant (mai`a), and the inner bark from kukui tree roots into a liquid. A charcoal powder from burnt wiliwili wood or lau hala leaves was added to the liquid, then strained through a mesh of `ahu`awa sedge. Finally, juice from ti plant root was added to the mixture to make the paint colorfast. This paint would be applied by coconut husk, hala root, or even bare hands[2].

3. Case Study of Modern Canoe Manufacturing 3.1 Background

With increasing popularity in outrigger canoe racing, modern outrigger canoe manufactures aim to design fast, light­weight, and versatile boats. MAXSURF, a marine vessel design and analysis software, SOLIDWORKS, and other computer software programs are used in the design process of modern canoes. These software programs provide the designer with tools for structural and strength analysis, stability analysis, and computational fluid dynamics.

Kamanu Composites is a local canoe manufacturer that builds superior and high­performance canoes. Kamanu Composites builds all of their canoes in­house from beginning to end while striving for "perfection within every step of the manufacturing process''[8]. A case study of materials and manufacturing used in the building of their canoes was performed; the results of the case study are as follows.

3.2 Materials

3.2.1 Carbon Fiber The manufacturer uses AS4 which is a 12x12, 3000 strand, Standard Modulus carbon

fiber weave with an epoxy resin to create a Carbon Fiber Reinforced Polymer in the build. Carbon Fiber typically has much higher strength in one direction than the other. AS4 is a weave of carbon fibers which can result in high strength in multiple directions.

Carbon fiber can be compared to fiberglass with respect to its flexibility and ease of use, but has the highest specific stiffness of any commercially available fiber and is considerably lighter than fiberglass. Carbon Fiber Reinforced Polymers have a high strength in tension and compression, and a high resistance to corrosion, creep, and fatigue. There are High and Ultra High Modulus Carbon Fibers available but the additional cost and high brittle characteristics of those materials make AS4 the clear choice for this particular manufacturer’s build.

The AS4 is both more flexible and affordable than other options and provides more than enough strength and rigidity for their needs. The results in the table shown in Appendix A ­ Table 1 were obtained from data which a popular carbon fiber manufacturer has provided[9].

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3.2.2 S­glass® S­glass is the trade name for a stronger version of standard fiberglass cloth (E­glass)

which was invented by Owens Corning Co. in the late 1990’s[10]. This is a type of cloth consisting of fine filaments of glass that are combined in yarn and embedded in resin to make a high strength structure. The canoe builder uses one of the lighter forms of this particular fiberglass which weighs in at roughly 2.5 grams per cubic centimeter. The flexibility of the pre­impregnated cloth is greater than that of the carbon fiber. The numbers in the table in Appendix A ­ Table 2 come directly from the Owens Corning website.

3.2.3 Divinycell® One of the key components in all ship building is buoyancy. Kamanu Composites

maximizes this in their builds by sandwiching a semi­rigid PVC foam between the laminate fibers called Divinycell H80[11]. This particular semi­rigid foam has a high strength to weight ratio, good properties for tensile and compressive strength, and is extremely light. Divinycell is widespread in the marine, transportation, and aerospace industries, and can be used in countless applications where strength, stiffness, and low weight are desired. The numbers in Appendix A ­ Table 3 come directly from the manufacturer of Divinycell.

3.2.4 Coremat® (2mm) Coremat is a flexible nonwoven material used where the bends as designed by the ship

builder have too small of a radius for the used of Divinycell. The use of the Coremat extends similar weight and resin saving properties of Divinycell while maintaining stiffness and rapid thickness build up of the core foam in the hand lay­up process. The numbers in in Appendix A ­ Table 4 come directly from the manufacturer of Coremat[12].

3.2.4 Epoxy Resin In a sandwich construction process all the components are important but perhaps none

more so than the choice of the resin. The resin is the literal glue that binds the layers of laminate and core foam together. Kamanu Composites uses a Proset Laminating Epoxy[13] in their builds. No specific data sheet for their product could be found so the numbers from a competitor ­ Westsystem[14] were used in Appendix A ­ Table 5.

3.3 Manufacturing Processes

A variety of manufacturing processes can be observed at Kamanu Composites as the entire canoe is manufactured in­house from beginning to end (except for the `iako ). While 1

Kamanu fabricates their own molds, rudders, seats, and fins, this paper focusses on the processes involved in the fabrication of the boat and the `ama. Both the boat and the `ama are fabricated in

1 Because the `iako is composed of 6061 Aluminum that needs to be anodized, in­house fabrication is unfeasible.

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two parts ­­ the hull and the deck ­­ which are then joined with a ½ in lap joint. The fabrication time of a canoe at Kamanu Composites is 60 man hours, and the goal is to complete one boat per day.

3.3.1 Vacuum Bagging Process The process starts by wiping down the mold with a wax based mold release formula. For

each boat design there are two deck and two hull molds, shown in Figure 3. Each part takes two days in the mold which allows the team to complete one boat per day. The next step is to apply a gel coat which protects the surface and the construction underneath while allowing a customer a choice in color and design. The boat is then allowed to rest overnight and is checked the following morning for defects.

Figure 3: Custom molds used for the deck and hull in the vacuum bagging process.

The layup follows the concept of sandwich construction, where either the divinycell or coremat is sandwiched between layers of carbon fiber or s­glass. The layup ­­ the combination of materials and type of materials ­­ can be varied to adjust strength, weight, and flexibility according to customer demands, which is illustrated by the following example.

The standard layup for the deck of the Pueo model consists of a 3.9 oz (110.6 g) carbon layer, a ⅛ in (3.1 mm) foam core, and a 4.8 oz (136.0 g) carbon layer on the inside. The layup of the hull, on the other hand, is composed of two layers of 4.0 S glass on the outside, a ⅛ in (3.1 mm) foam core, and a 4.8 oz (136.0 g) carbon layer on the inside, resulting in a total weight of 23 lbs (10.4 kg). In comparison, when manufactured with layers of 3.9 oz carbon on the interior of hull and deck, the weight is reduced to 22 lbs (9.9 kg); yet, the impact resistance and overall strength remain the same.

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If no repairs are needed after the gel coat process has been completed, the various layers of fabric and foam are carefully laid out in a sandwich design and the epoxy is applied. After the epoxy resin has been applied, a large plastic bag is fashioned and is then placed over the canoe and vacuum is applied. Vacuum bagging is a technique used to put pressure on a laminate during curing. Applying pressure to the laminate increases its strength by removing air trapped between layers and compacting the fibers of the laminate to ensure they resist shifting during the curing cycle. The vacuum also pulls out any trapped moisture in the air, circulates the resin through to saturate each piece of laminate to the core material, and most importantly, optimizes the fiber­to­resin ratio.

The canoe is then placed in an autoclave for a minimum of five hours. Neither the s­glass nor the carbon fiber have any particularly impressive strength when in their non­laminated state. The laminates are simple cloth before impregnation and the resin is extremely brittle if cured without reinforcement from the cloth. Any excess resin or dry laminate lowers the overall strength of the boat. It is the combination of these materials that makes the composite exhibit such impressive strength to weight properties. This creates a lightweight yet incredibly strong finished panel.

3.3.2 CNC Machining CNC machining plays a major role in the cutting of the foam (divinycell and coremat).

Accurate foam cut­outs are crucial in the fabrication of superior boats. Kamanu Composites uses industrial CNC machines to ensure accuracy and quality of the foam parts. Appendix A ­ Figure 3 shows the CNC machine used.

3.3.3 Finish and Quality Control After the hull, the deck and the `ama have cured in the autoclave, they are joined together

using epoxy adhesives. To finish the assembly of the canoe, `iako mounts and seats are installed. If the design has a rudder, foot pedals are also integrated.

Quality control is integrated into the manufacturing along each step in the manufacturing process; each part is analyzed for defects and fixed if necessary as quality is most important for Kamanu Composites. Finally, a surface finish is applied. 3.4 Surface Treatment

As described in Chapter 3.3.1, the surface of the boat is a gel coat that serves as a protective finish to the hull. The main purpose is to prevent damage from abrasions and the penetration of moisture. It is a polyester resin with a higher viscosity and hardness than a standard resin. This allows for both easy application and increases the structural integrity of the fiberglass material. These properties are due to the use of Isophthalic/Neopentyl Glycol (ISO/NPG) resin.

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The Coating is applied by a relatively simple process. First the surface is prepared by sanding any imperfections smooth, then cleaning any debris, oil, or paint that may inhibit adhesion. Next, the gelcoat, catalyst and tinting are mixed together and are now ready for application. This can be done either with a sprayer or roller. It is important to sand between layers as this allows for proper adhesion. The curing process takes between four and six hours before a final hardness is ready[15].

4. Comparison To make a comparison between ancient traditional Hawaiian canoes and modern canoes,

several factors must be taken into account and looked at both objectively and subjectively. On the surface, it is easy to say that modern canoes are far superior to ancient canoes, for that is indeed the goal of the evolution of manufacturing ­­ to improve upon a product. However, from an objective point of view, the factors that will be discussed and compared are materials, manufacturing methods, production time, performance, and expected canoe life. From a subjective point of view, artistic quality, value and use will be discussed.

The evolution of the materials used to construct racing canoes has resulted in lighter, stronger, and faster canoes. The weight­to­strength ratios are much higher with modern canoes. This is not to say that the ancient Hawaiian canoes were not strong, but they were much heavier. With modern methods of manufacturing, not only has the time to construct a canoe been drastically reduced, but the product consistency has increased. Ancient canoes varied from one another due to factors such as tree size, location of knots, and wood grain. Although the methods were similar, every craftsman made them a little different, to the point where each canoe was a unique creation.

The performance of modern canoes not only improved, but using modern computer design programs such as SOLIDWORKS, the performance changes and hydrodynamic properties can be predicted by using mathematical formulas, and studied without a “trial­and­error” approach that would have been otherwise needed to test each canoe manufactured. Since a new canoe is not needed each time to test performance, there is less waste of material and time.

These factors however, do not necessarily mean modern canoes are superior to ancient canoes. Modern canoes for example, have an average life of approximately ten years due to a phenomenon called blistering which delaminates the material. This is caused by water getting under the gel coating. The life of the canoe can be extended with proper care, such as fresh­water rinses when not in use, complete drying, and minimizing exposure to direct sunlight. However, traditional canoes (made of wood) can in many instances last much longer.

From a subjective standpoint, the reasons for using canoes have evolved just as the manufacturing has, and it would not be fair to say that modern canoes are superior. Ancient Hawaiian canoes had much more uses than modern canoes and were valued by the Hawaiians. They were unique pieces of art as well, and symbols of the communities that built them.

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5. Conclusion The focus of this research was an analysis of the materials and manufacturing process

involved in the building of traditional Hawaiian and modern single hulled outrigger canoes with the ultimate goal to compare similarities and differences. By applying modern theory on the manufacturing processes to such a specific and local product with tremendous cultural history, we were able to identify some of the indigenous knowledge of ancient Hawaiian culture, as well as some of the modern advancements in composite manufacturing.

In summary, our research showed that traditional canoes were carved out of Koa wood, then cured, and their surface treated with natural oils and paint to improve the material properties, mitigate fatigue life, and ensure longevity of the canoe. Modern manufactures on the other hand strive to design and build lighter, stronger, and faster canoes by optimizing their designs through simulation software (computer software), composite materials, and composites manufacturing techniques such as vacuum bagging.

An objective and subjective comparison showed that there are parallels in the manufacturing processes and that modern canoes are still modelled after ancient designs. While mechanical properties and the manufacturing processes are far superior to traditional ones in terms of weight, strength, and production time, the cultural value, uniqueness, and the ancient engineering knowledge embedded in a traditional Hawaiian outrigger canoe are remarkable.

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Appendix A

A.1 Tables

Table 2: CFRP Material Properties based on a weight ratio of 60% carbon fiber to 40% epoxy resin[9].

Carbon Fiber Reinforced Polymer (CFRP)

Test Results Comments

Density (kg/m³) 1.79g/cm3

Tensile Modulus 245 GPa ASTM D3039

Tensile Strength, Ultimate 4620 MPa ASTM D3039

Elongation at Failure 1.8%

Table 3: S­glass Properties[9]. Owens Corning S­glass Test Results Comments

Density 2.49 g/cm3

Tensile Modulus 88 GPa ISO 527­5

Tensile Strength 1550 MPa ISO 527­5

Poissons Ratio 0.27 ASTM D638 ­ 0.27

Table 4: Divinycell Material Properties[11]. Divinycell H80 Test Results Comments

Tensile Strength, Ultimate 2.20 MPa ASTM D1623

Elongation at Break 18% Shear Strain

Tensile Modulus 0.0800 GPa

Compressive Strength 1.20 ASTM D1621

Compressive Modulus 0.085 MPa ASTM D1621­B

Poissons Ratio 0.032

Shear Modulus 0.03099 GPa ASTM C273

Shear Strength 0.951 MPa Yield; ASTM C273­00

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Table 5: Coremat Material Properties[12].

Coremat (2mm) Test Results Comments

Dry Weight 96 g/m2

Density Impregnated 540 kg/m3

Flexural strength 8.5 MPa ASTM D790

Flexural Modulus 1250 MPa ASTM D790

Compressive Strength (10% strain) 10 MPa ISO 844

Shear Strength 3 MPa ASTM C273­61

Shear Modulus 25 MPa ASTM C273­61

Table 6: Physical Properties of Cured Epoxy[13]. Cured Epoxy Test Results Comments

Hardness (Shore D) 83 ASTM D­2240

Compression yield 1155 MPa ASTM D­695

Tensile strength 800 MPa ASTM D­695

Tensile elongation 3.4% ASTM D­695

Tensile modulus 41340 MPa ASTM D­695

Flexural strength 1428 MPa ASTM D­790

Flexural modulus 46710 MPa ASTM D­790

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A.2 Figures

Figure 4: Illustration of Ko`i, Hawaiian Adze

Figure 5: Illustration of Nao Wili pump drill

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Figure 5: Picture of CNC Machine at Kamanu Composites

More figures to come for modern canoe

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Acknowledgements We would like to thank Kamanu Composites Inc. for offering their support and letting us visit their company to observe and learn about their manufacturing process at first hand. We would especially like to say Mahalo to Keizo Gates, who went out of his way in showing us around and responding to follow up questions.

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