In mast furling main - tri-radial vs cross cut

[cmedsailor]

Hello,
I am considering purchasing a new in mast furling main sail. Could someone explain me what are the differences (besides cost) between a tri-radial cut and a cross cut construction?
Thanks

 

[gardenshed]

If you take a piece of fabric and pull it in different directions, you will find that it deforms more/less depending on how you pull it. Depending on how the fabric was woven, it will move less in the direction of threads that it is made from, as opposed to at 45deg to the direction of the threads. Tri radial construction tries to align the pieces of cloth with the way that the sail is tensioned to minimise this distortion.
As with all these issues, there is no universal answer. If you select the right cloth (one designed to be used loaded in one direction such as Dimension Hydranet) then it will make a great triradial sail. If you use a standard sailcloth you won't get as big an improvement as you want but as there are a lot more panels, the labour needed and hence cost will rise.
what is the benefit: As the wind rises, a tridadial sail made from cloth designed to used in a tri radial layout, will distort far less, keep its intended shape and give you more control. It should also keep its shape for a longer period.
Cheap cloth, cross cut will stretch and distort making your sail baggy when you need it flat and it will lose its intended shape quicker than one made with better cloth and assembled in a way that makes best use of the cloth.

Simples? No?

A discussion with a good sailmaker should confirm these basic principles and give more details of the cloth types and panel layouts and the impact this has on shape, shape retention and longlevity.
The golden rule is to invest into good quality sailcloth, that's where you get the best bang for your buck.

If you move from cloth to laminated materials, then similar principles apply, but the complications greatly increase as some will not like being rolled up very tight and may de-laminate, different cloths can be used in different parts of the sail and there are a great variety of base materails, thread/load bearing materials and taffetas etc used to protect the load bearing threads.

UK sails, North sails, quantum etc have web sites that take you through the various options/cuts/cloths that they offer and may help your decision making