Bi radial vs cross cut?

[rogerroger]

I'm going to replace my sails and am told there's 2 types of genoa - bi radial or cross cut.

Could someone please explain the difference - not the technicalities but the difference the choice will actually make - boat's a Beneteau First 27 not used for racing.

cheers

Roger Holden
www.first-magnitude.co.uk

 

[charles_reed]

Functional comparison Bi-radial/Crosscut roller

The theory was that the radial sail could be cut with varying different weights of fabric for the rolled and unrolled conditions.
It was also maintained that the sail would set better because the stress lines could be laid along the warp of the fabric.
Whilst this latter certainly makes a hanked or foil genoa with radial cut a better setting sail than a crosscut sail, it was not borne out in practice with a roller genoa.
In practice it was discovered that biradial genoas on roller furler lost shape far more quickly than their cross cut relations, though, when new and fully unrolled they do give better drive.
In practice a good (for you) sailmaker would advise you to purchase the cheaper crosscut sail (with ample foam luff) as one likely to give good service for about 5/6 years compared to the 3/4 years of a radial sail (I'm talking here of a seasonal mileage of 2,000-4,000M), with the following provisos:

1. Don't go above about 150% of foretriangle - the added weight in the crosscut sail doesn't make it a good lightweight sail.
2. Don't expect a roller sail to be any use after it's rolled below 60% of its total area - roller reefing REDUCES does not ELIMINATE headsail changes.

Hope this helps (besides the crosscut is cheaper).

My (reasonably satisfactory) headsail wardrobe (after many errors of judgement and thanks to Jeremy's guidance)is:

355% triradial spinnaker
350% reaching asymmetric (sets on 1.8m sprit)
150% crosscut roller genoa
100% solent
65% biradial roller yankee

As the last rolls to a far more comfortable 8% than the storm jib the latter is now redundant

 

[rogerroger]

Re: Functional comparison Bi-radial/Crosscut roller

thanks for that lengthly and detailed reply.

I think you've made my mind up for me - a cross cut it is!

Roger Holden
www.first-magnitude.co.uk