6.3

If you want to maximise performance from your sail/mast, buy the same brand sail as your mast, or at least closely match it. So look at the website of your mast brand, and have a look at the specs of the sail which match your requirements.

jjwilliams7 said..
hi, anyone know the largest sail i could buy to rig on a 400 mast? new or second hand
currently have a 5.7m but want bigger without buying new mast etc. have up to a 34 extension.
thanks.

The problem with your question here is that you are expecting too much, and trying to save money - rather than to go for what will work.

A 5.7m sail - the one you have - is already 'big' for a 4m mast, and that's not just because of the rigging luff length but because of the mast stiffness.

The change-up size from that 5.7m rig would be a 6.2m or probably a 6.5m, and that bigger sail size really needs a 430 mast because of the IMCS stiffness rating. If you try and rig a 6m+ sail on a 4m mast any extensions used will mean the mast is very soft, and the sail will set very flat, giving you little power gain over your 5.7m, plus any big sail rigged on too soft a mast will also have poor wind range.

Most windsurfing quivers need planning with forwards thinking, and if you want to get going in lighter winds then you need the right mast to go with a bigger sail. Plus you might consider using a bigger board with your existing sails, as that is often the other earlier-planing solution.

You could try a tip extension too. I made a couple of 15cm ones out of an old broken mast following an example of Manu's posted on here some time ago.

Basher's right about avoiding over extending your mast but if you're a lightweight like me you'll be well served by doing that to all your masts, for camless sails anyway.

thanks very much everyone !