I just purchased some new gear. My mast extension is 40cm and I will be using 15cm of extension leaving 25cm up the mast. This is being used on a 580cm Point 7 mast with a 11.8m Point 7 AC2 sail.

Is there enough extension( 25cm) into the mast?

I do have a 50cm extension but I cannot use my downhaul winch on it.

Thanks

Absolute minimum 150mm, 200 better. With a big Formula sail like that which will have crap loads of downhaul tension the more the better but I can't see that you should have any issues if you have 250mm inside the mast.

Length of the mast ferrule is a good guide.

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vando said..
Length of the mast ferrule is a good guide.

read somewhere that a ferrule/sleeve should be at least 3X the diametre.

These guys say 3x when bonding but then advertise their own extension booms with about 2x diametre ferrules.. www.carbonfibertubeshop.com/bonded%20assemblies.html

I'd go with Martin's figures (15-20cm)

Great, thanks guys.