Mavic: "A Closer Look at Clothing and Weather Conditions"

"A Closer Look at Clothing and Weather Conditions"  

article by Mike Crotty 

Being comfortable on the bike is fundamental in not only enjoying your ride but also getting the most from your own athletic ability. Whilst there are many different disciplines in cycling, from the highest level of professional racing all the way through to leisure riding for the pure escapism of the open road, what remains a constant for everyone are the conditions that you may face as soon as you step out of the door and into the elements. From sun, wind, rain and cold as the seasons rotate throughout the year, what you wear can certainly be the difference between a great day and survival if you’re not equipped correctly.

1.         Material World

Whilst there are an untold number of material types, compositions and finishes it’s the key elements that each of these technologies bring to the final garment that will ultimately give it superior fit, warmth, breathability or waterproofing to make it comfortable. Mavic engineers and material scientists consider all of the properties of each material – how they work on their own, together, and as part of a finished garment. Most importantly they analyse all of the options available, selecting the most appropriate in each instance for the required application. It’s often helpful to have a general understanding of some of the technologies when selecting kit for your own specific needs as a cyclist.

Woven materials are hard wearing and offer good resistance against abrasion whereas knitted fabrics are generally lighter weight and offer a naturally high level of stretch, fit and comfort. Mesh goes one step further to increase the aeration properties of the fabric to once again improve the overall comfort.

Synthetic composites are regularly used to provide specific advantages compared to natural fabrics, for example polyester drys quickly and offers good moisture management compared to cotton and wool, polyamide increases durability and abrasion resistance with elastan increasing the stretch of the fabric to provide a better fit to the body.

How a fabric is finished or used together in a layered construction is also important, depending on its intended final purpose. A Durable Water Repellent (DWR) coating may be added to the outer layer of the fabric, or a membrane used, to increase resistance to water. To improve the ability of the textile to move sweat from the skin to the outer surface, and to promote faster drying of the material, a hydrophilic finish may be used. Brushed fabrics that are generally found on the inside of jackets not only increase thermal insulation and warmth but also give a comfortable feel against the skin.

2.         Enter the Elements

Where and when certain materials and technologies are used will depend on the intended purpose along with the conditions that they will face in use. It’s important to integrate materials and designs appropriately with real-world riding conditions to ensure that they maintain their intended performance characteristics throughout. The four main elements that cycling kit will be subject to (heat, wind, rain and cold) are detailed below. To ensure that a garment performs exactly as it is intended, offering the rider the highest level of protection and performance, comprehensive lab studies are conducted using a library of fabrics to analyse a number of key areas. Unless otherwise stated, each study is undertaken in a controlled environment of 20℃ +/- 2℃ and 65% relative humidity +/- 2℃ with samples subject to this environment for a minimum of 4 hours.

Heat

As the temperature rises, naturally you’ll wear less on the bike. In the height of summer you’ll need to try and keep your core temperature down to maintain comfort and perform optimally. Fabrics will be lighter weight and specifically designed to wick sweat away from your skin quickly. A knitted material construction with naturally good stretch, comfort and fit is often used for the main body. Mesh is normally located in the side panelling and under the arms to further aid ventilation as does the front zipper which can vary in length. One very important area that should not be overlooked is the UV rating of the garment. Despite being lightweight technical fabrics can still offer a high level of protection against harmful rays.

As one of the most important attributes for any fabric being used in hot conditions is to transfer sweat away from the skin it is important to validate this function in the lab. This is done by conducting a moisture management test on to determine its water vapour transfer properties. Here is a description of the test protocol.

– Using a 100cm² sample size the dry weight of the sample is recorded using a digital scale accurate to 1/10th of a milligram.
– A drop of distilled water is placed on the scale and weight recorded. It is important to note that when repeating the test the weight of the water droplet is consistent.
– Centre the fabric over the droplet and place into position.
– Start the recorder to begin the test.
– At 2 minute intervals the mass of the sample is recorded until it has returned to its original mass.

For the fabric to pass it must take less than 30 minutes to return to its original weight. It must also absorb the droplet of water within 2 seconds. This study is performed on synthetic fabrics including 100% Polyester, Polyester/Elastan and Polyester/Nylon with a knit construction and hydrophilic finish. To ensure the longevity of the performance it is conducted with new fabric and also repeated after five wash and five dry cycles.

Wind

In the right direction the wind can make cycling feel effortless but when you’re met with it head on this can be a completely different story as you battle against it. As well as this you’ll also notice that it feels as though it’s cutting straight through you, chilling your core and significantly reducing your body temperature. In part this is emphasised by moisture, in the form of sweat, that may have dampened your clothing – further adding to this chilling effect.

As riding conditions worsen trying to maintain levels of comfort are paramount which is where the use of technical fabrics and well designed garments come into their own. A jacket that has been specifically developed to be used in windy conditions may utilise a combination of technologies to achieve the required performance levels. For example, a knitted polyester construction with hydrophilic finish may be used to aid moisture management, stretch, comfort and fit, combined with a fleece backing to increases thermal insulation and a wind / water resistant inner membrane with Durable Water Repellent (DWR) surface treatment to further aid water repellency. Overall the goal is to carefully combine the performance values of each fabric, technology or treatment so that they all work together to provide maximum protection against the elements.

For woven and knit fabrics with a membrane, coating or polyurethane film it is crucial to understand exactly how windproof the construction is so that the material’s specific performance attributes can be utilised fully and in the most appropriate way. To do this an air permeability test is conducted as detailed in the following steps.

– Using a fabric size of 20cm², the sample is positioned onto the head of the air permeability tester and held under a force of 50N +/- 5N.
– It’s important that the fabric is flat with no creases as this will affect the result of the test.
– A flow meter is used to measure the air velocity through the test sample, recorded in mm/s.
– The test is repeated five times to attain an average result for the fabric.
– Results are recorded and entered into a database to rank the fabric in accordance to its specific performance properties.

From the results, fabrics are carefully chosen to provide more or less wind protection in certain areas of the garment using the following scale >50 mm/s = no wind protection, 10-50 mm/s = wind repellent, 0-10 mm/s = windproof.

Rain

Whilst we may all dream of riding in the dry the unfortunate reality is that at times you may find yourself dodging showers or at worst caught in an unavoidable downpour. If this sounds familiar, or it’s a necessity to ride in the rain, then you’ll already know about the importance of having a good rain jacket to hand should the weather turn. Depending on the level of protection required, technologies, surface treatments and membranes have been developed to offer varying levels of waterproofing and are rated in millimetres – for example you may see a jacket with a 10,000mm waterproof rating, but what does this actually mean? If you imagine putting a tube with inner dimensions of 25.4mm x 25.4mm (1 inch square) over the fabric you could then fill the tube with water to a height of 10,000mm before water would begin to seep through. The higher the number the more waterproof the fabric and better protection it will offer.

Testing water penetration of a fabric under hydrostatic pressure, which is the pressure exerted by a fluid at equilibrium at a given point within the fluid due to the force of gravity, provides important data essential to engineers during the development phase of a product. More about this process is highlighted below.

– For this test a 20cm² sample size is used, making sure that the fabric has no creases.
– The sample is fitted to the test equipment with the membrane or coating facing the distilled water source (controlled to be at PH 6-7 and 21℃ +/- 2℃).
– Once the test is started the water pressure increases at a rate set to 60 mbar/min.
– The hydrostatic pressure is recorded at the moment when water droplets penetrate the fabric in three different places
– For accuracy the test is repeated and the average hydrostatic pressure calculated using new samples plus those that have been subject to three wash cycles.

For a fabric to be considered waterproof it must be rated above 2,000mm. However, in cycling waterproof ratings between 5,000mm and 10,000mm are most frequently offered, catering for even the harshest conditions. To further improve the overall waterproofing of a garment seams are sealed to cover the tiny holes that are made by the needle when stitching two fabrics together. Seams can also be bonded by heat or glue but normally they will be sewn first and then taped. If you are riding in extreme conditions then a fully taped jacket, which has all seams sealed, will offer more protection than a garment that only has critical areas taped – such as the shoulders, neck and chest. Either way, without adequate seam sealing no matter how waterproof the fabric is you will still get wet so it’s worth keeping this in mind.

Cold

In the winter, and during times of extreme cold, the primary function of your cycling kit will be to retain your body heat and provide thermal insulation against the outside. Much the same as garments that are specifically designed for the wind a similar combination of fabrics, technologies and treatments will be used to do this, albeit refined in each area to bring about the right levels of thermal insulation. PrimaLoft® is a proprietary technology that uses ultra-fine fibres to form a very tight collection of air pockets that trap heat from your body and keep the cold out. As well as the fibres being water resistant their ultra-fine diameter makes them softer and more comfortable whilst at the same time being more compressible to keep the overall bulk of the clothing down. Even when it’s cold it’s important that your clothing works with you at all times so that you’re able to maintain or regulate your body temperature. In some cases the fabrics will do this for you (like a hydrophilic finish that will draw moisture away from your skin) whilst technical details like a high collar and zippered vents on sleeves or underarm can further aid the micro-adjustability of your comfort.

In one study a protocol was established to determine the thermal resistance of 5 Mavic and 4 non Mavic garments to specifically identify what areas lose most heat and where improvements could be made. The thermal resistance of each item of clothing was initially measured to give an understanding of the  garments “Clo” level. 0 Clo corresponds to a naked person. 1 Clo = 0.155 m2K/W which corresponds to the insulating value of clothing needed to maintain a person in comfort sitting at rest in a room at 21℃ with air movement of 0.1 m/s and humidity less than 50% (typically a person wearing a business suit). Further examples of clothing insulation are detailed below:

– 2 Clo: Skiwear
– 3 Clo: Lightweight fleece equipment
– 4 Clo: Heavy polar equipment
– 8 Clo: Polar Down

For this test the heating plate is set to 36.3℃ (which gives a surface temperature of 26℃) and the sample to be analysed is loaded into position. The flowmeter records the difference in temperature between the back plate and the top surface of the material to obtain a measure of Clo.

Using a cold chamber and thermal imaging camera, a series of tests were then conducted in order to validate the thermal insulation of each garment based on heat images and subjective analysis from the test rider. The chamber was regulated at – 20℃ with no airflow. The test rider would start by riding on a static trainer for 1 minute outside of the cold chamber to heat the clothing internally.

The subject is then moved into the cold chamber where they repeat the static riding for a further 2 minutes to regulate the body temperature. The timer is then started and the amount of time it takes for the test rider to start to feel the cold is recorded. The rider indicates each area where they feel the cold – for example lower back, shoulder blades, fore arms, sides, under arm, chest, belly. Thermal images are taken to validate this subjective assessment. The blue areas in the images show good thermal insulation where green, yellow and red show increasing areas of heat from the subject’s body. Testing was repeated at separate intervals throughout the day to confirm results with a panel of riders.

The conclusion of this study confirmed how fit directly influences thermal insulation and that the main areas of thermal loss were in the shoulder (blade) area and arms. Using this information allows further development of garments to provide more or less protection depending on their application.

3.         Bringing It All Together – The Importance of Layering

Wearing a number of layers, as opposed to just one thicker layer, will not only protect you more effectively from the weather during your ride but will ensure that you are as comfortable as possible. Dressing in this way will also mean that you have more options to regulate your body temperature depending on how the conditions may change. There are three key areas to consider when layering, each of which serves a specific purpose.

– Base layer. As this is the first layer that you put on, the primary function of the base layer is to wick sweat and transfer it away from your skin so that you remain dry.
– Mid layer. This helps to trap air inside to keep you warm whilst at the same time being breathable and offering some protection against the outside.
– Outer layer. Generally this will be your final barrier of protection against the weather and can come in various forms – from a lightweight packable gilet or cape to help block wind on an alpine descent through to a fully seam sealed waterproof rain jacket.

4.         Conclusion

Through careful development, analysis, design and testing fabrics and materials have been constructed to allow you to perform to your highest level despite the conditions that you face. Whilst it may be less pleasurable in the rain, wind or cold knowing that you are well protected should bring an extra level of confidence, allowing you to keep riding when you may otherwise have to stop.

The important thing when selecting clothing is to firstly identify the type of terrain and conditions you are likely to encounter the majority of the time and then look for suitable garments to compliment this. Today there is a vast selection of rider equipment to choose from, so it can sometimes feel like it’s hard to know where to start. By carefully taking the time to identify your specific needs you may find that you don’t need as much kit as you originally thought, and that a few key items that you continually come back to time and time again offer both the performance and versatility to make your time in the saddle as comfortable and fulfilling as it can be.

From the Mavic development team we wish you a safe and enjoyable ride!

http://www.engineerstalk.mavic.com/closer-look-at-clothing-characteristics-for-changing-weather-conditions/