Dyneema has a negative coefficient of thermal expansion, meaning that it expands as it cools. When you tune your rigging for summer sailing, it will become rediculously slack in the winter. This is known as "Winters Stretch" and can be used to your advantage!
During the year, thimbles and clevis pins will move and shimmy while you sail. They are under tremendous tension and there is no way possible for you to push them back into place without untying the stay and then retensioning it. You need to untie everything to remove the tension on the stay, but in winter, the tension is removed as the stay elongates temporarily!
When your rigging goes slack, you are presented with the opportunity of the year to push everything back into place and line it all up perfectly! That thimble that rotated a bit when you set up your rigging can now be spun vertically with ease. That clevis pin that spun around and has the cotter pin upside down can now be rotated to line the cotter pin head up and keep it from falling out.
All of these little jobs that would take hours to perform and correct in the summer can be accomplished in a few minutes with no tools, all thanks to the chilling effects of winter.
