buying a larger sail

Question
QUESTION: hi windlover, im 19 and after trying windsurfing for my last two summer holidays i have fallen in love with the sport, at the end of last summer we bought a hi-fly 240l board and a 4.0m sail which has gone brilliantly this summer.
last time i was out in 24 gusting 34kts and managed to do loads of planing.
So in order windsurf more often i need a bigger sail, as well as a harness. the average summer wind at my spot, malahide estuary, Dublin, Ireland is about 10-12kts according to the stats. After the new sail i figure a smaller board around the 120L volume is in order.
I am about 6ft 1 inch and 13 stone , around 182 lbs and what i really want to know is what size sail i should go for?
my mast is 405cm tall and my boom extends to 205cm.
oh and while im on to you i was wondering what the story is with how far back or forward you place the universal joint? what factors you should take into account etc?
anyway sorry about all the writing and many thanks for your time.

ANSWER: Hey Aaron,

It's great to hear that we have another sailor hooked on windsurfing. It sounds like you enjoy it as much as the rest of us.

If your average winds are 10-12kts. and you plan to use the 240l board for light wind sailing, you could get as large as an 11.0 sail. You could actually plane with a sail this big. If you want to sail a larger range of wind, you would probably want something around 9.0. You may not plane in the lower range but you could sail in winds as high as 15kts.

If you do get a board around 120L, then you could use the 9.0 on light wind days and be planing in about 12-15kts. You could also go as low as a 5.0 in winds up to around 22-25kts.

As for your mast, a 405cm is only good for about your 4.0 and smaller. For a 5.0-6.5 you will probably need a 460cm. Anything larger you will need like a 500cm or longer. You will also need a longer boom for any sails bigger than a 6.5. If you don't already have one, you will need to get a long mast base. That way you can adjust your mast length to accomodate a variety of sail sizes.
I use a 460cm with a long base and can use 4.5-7.0 sails.

For universal joint placement, it is all about the strength of the wind and the size of your sail. In light winds or when you want to go upwind alot, move your mast forward. In higher winds and for better offwind speed, move the mast back. If your fin is adjustable, you need to move it the way you move your mast. Forward for upwind, back for speed offwind. If you move your mast 1-2", then move your fin about 1/2-3/4".

Hope this will help you.
Keep on sailing,
Windlover

---------- FOLLOW-UP ----------

QUESTION: thanks, when you say a long mast base, do you mean the insert you put into the mast?
Also my mast doesnt curve, it goes straight up, will any of the larger sails accomodate that or will i have to get a curved mast?
thank you
ANSWER: Hey Aaron,

Yes, the insert you put into the mast is called a 'mast base'. They come in a variety of lengths. There are multiple holes drilled into them so that you can adjust the length to accomodate a variety of sail sizes.

As for your mast curve, all masts are straight until they are rigged. Then they bend due to the design of the sail. When you downhaul a sail, it causes a pull from the top of the mast to the bottom via the 'luff' of the sail. When the mast bends, it helps shape the sail to be a more efficient foil or wing. Some sails cause more bend in the mast than others.

The main thing to consider when putting different sails on the same mast is the stiffness of the mast. All sails require a specific stiffness mast to be rigged correctly. If you know the stiffness of the mast (it should say on the bottom, MCS #), then try to find sails that use something close to that stiffness of mast. If you need to buy a new or used mast, try to match it to the sail you are considering buying.

Hope this helps.
Keep on sailing,
Windlover

---------- FOLLOW-UP ----------

QUESTION: ive read that term downhauling a fair bit but im afraid i dont know what it means?
thank you

Answer
Hey Aaron,

Downhaul is the rope at the bottom of the mast that connects to the bottom of the sail. Downhauling tightens the leech of the sail.

Outhaul is the rope that is on the end of the boom and connects to the corner of the sail farthest from the mast.

Hope this helps.
Keep on sailing,
Windlover