Got Guts? Project by: Shiko Njuno Hector Torrez Luis Zamudio

Topics to cover General Information General Information Types of racquet strings Types of racquet strings The making of the strings The making of the strings SRJC Lab analysis of a sample SRJC Lab analysis of a sample

General Information ► Over the last two decades, racket heads have become larger and lighter using light-weight materials. ► Wooden rackets and natural gut string were used up to mid 1970’s, along with leather grip handles. Later, Aluminum and Steel became highly useful materials being extremely light and providing durability. ► Today most racket frames are made out of light weight graphite or graphite composites that include titanium, fiberglass (Kevlar) that provides more flexibility and yet remains cost effective. ► During a game, a racket can experience 140 mph impacts. There are about two thousands different models available that have been manufactured to withstand this punishment. ► To the right is a picture of an antique Spalding tennis racket.

Types of Strings Natural Gut (Cow or Sheep) Synthetic

Types of Strings Used Natural Gut: is made of cow or sheep gut. Allows for a very sensitive game but is very susceptible to environmental conditions and is not very durable. It is also more expensive than synthetic string. This is the type of string preferred by the professionals. Synthetic Fiber Strings: are made of Nylon and are almost as good as natural gut due to technological improvements. They come in two subtypes: 1)Monofilament: the string consists of only one filament. This is typically used in cheaper hobby grade metal racquets. 2)Multifilament: the strings consist of many thin filaments braided together. For example: ASHAWAY Flex 21 consists of approx. 750 filaments and the Vantage 20 of approx 3000 separate filaments.

Natural Gut Made of the serosa of the intestine of the cow. Made of the serosa of the intestine of the cow. Its got an internal structure that is very elastic which makes it with- stand a larger number of impacts without fatiguing. Its got an internal structure that is very elastic which makes it with- stand a larger number of impacts without fatiguing.

Process of making the gut string The serosa is removed from the 120 feet long intestine, it is cut into long ribbons in order to clean them. The serosa is removed from the 120 feet long intestine, it is cut into long ribbons in order to clean them.

Ribbons are inspected for blemishes in a control ultra violet room. Next the ribbons are counted to determine the gauges and then cut for length.

The ribbons are bundled and put in a salt solution. They are refrigerated for 30 days to get rid of bacteria. The bundles go through a multistep washing to clean off the impurities. The bright lines in middle of image are a reflection from overhead lighting.

The ribbons are attached to a twisting machine to make into a set of Natural Gut

Natural Gut String Vs Synthetic String Elastic Internal Structure Fatigue resistant Large performance life Very tough High Tensile Strength Break resistance

Types of tests operated on Strings

Data: Length (cm)96.5 Lo (mm)16.49 Diameter (mm)1.12 Area (m2)3.94E-06 Results: Weight (g)L f (mm)Force (N)∆l (mm)Stress,σ (N/m2)Strain,Є (m) E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E-04

Any Questions??