Unit Nine

First read the two texts below and complete the tables.

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Canoe Materials

Wood Canoes: (high cost, high maintenance)
Recent innovations such as watertight epoxy coatings, improved varnishes and modern production methods have made these canoes lighter, faster, and most importantly more durable than ever before.

Aluminium Canoes: (moderate cost, no care)
Aluminium canoes are corrosion-proof, sturdy, require little maintenance, and do not deteriorate when exposed to sunlight. They are the only canoes that can be left outside and ignored all winter. The disadvantages as well as being heavy, aluminium canoes heat up quickly in the sun and cool off in the cold. They are noisy.

Fibreglass Canoes: (low to moderate cost, minor care)
Fibreglass is the most common material used in manufacturing canoes. The quality of fibreglass canoes can vary widely from excellent to poor. The major difference is; good quality fibreglass canoes are made by laying strips of fibreglass cloth into a mould saturated with resin. Poor quality fibreglass canoes are made using small separate pieces of fibreglass called "chopped fibre" in place of the stronger, more expensive fibreglass cloth.

Kevlar Canoes: (High cost, moderate care)
Kevlar canoes are rapidly becoming more popular each year due to Kevlar’s great strength to light weight ratio. Kevlar produces a lightweight canoe with minimal compromise to strength and durability. With a strength per weight ratio marketed as being "stronger than steel" making boats of this material very impact resistant.

Carbon & Carbon/Kevlar Canoes: (highest cost, high care)
Carbon is the latest advancement in canoe building technology. Carbon is slightly lighter, stiffer, and is less flexible than Kevlar. When bonded with Kevlar, carbon tends to hold its shape better than other materials - keeping lightweight boats from flexing out of shape. Its primary use is in building the lightest possible performance oriented performance and racing boats. Carbon canoes are lighter but are not as strong as Kevlar canoes.

Polyethylene & ABS Canoes (low cost, low care)
"Plastic, Tupperware and Poly" are just some of the confusing terms used to describe Polyethylene canoes. Polyethylene is extremely tough, but as a soft material is not very rigid. Manufacturers have overcome the stiffness problem in different ways. Some companies brace their canoe interiors with aluminium tubes and struts. This makes a heavy, clunky but acceptable canoe. Other companies continue to produce canoes from single layer polyethylene by adding a keel in a largely unsuccessful attempt to stiffen. Single layer poly canoe hulls tend to "oil-can" and lose shape quickly when paddled. The most successful solution is a patented multi-layer "sandwich approach". A thick foam core is sandwiched between an outer and inner layer of polyethylene to provide stiffness at moderate cost

Royalex & Royalite Canoes: (moderately high cost, minimal care)
These canoes are manufactured in a similar fashion to a quality polyethylene canoe using the "sandwich method". A lighter core is sandwiched first by thin multiple layers of ABS substrate for stiffness, then finished by adding a vinyl inner and outer skin. Royalex canoes weigh less, are more expensive, but are not as strong as a "sandwich" method polyethylene canoe. Royalex canoes with vinyl gunnels are very difficult to damage as they tend to "pop back into shape" better than other materials. Serious white-water paddlers requiring a canoe which is lighter than Polyethylene often choose Royalex. Royalite is simply a thinner, lighter, but more fragile version of Royalex.

Source: Adapted from http://www.frontenac-outfitters.com/onlinetutorials.cfm?id=2

Material	Reason for using it
wood
aluminium
fibreglass
Kevlar
Carbon & Carbon/Kevlar
Polyethylene & ABS
Royalex & Royalite

Then study the ways of describing reasons for an improvement, a design change or choice of materials.

Choose three materials and reasons from the table and make sentences. Use all the ways given in the box. Upload your sentences to the “Reason” forum.

Finally go to the “Listening – test practice “ quiz and complete it.