Looking at getting a bigger sail. I measured my boom, from the leading edge where the mast fits to the end and it is 224cm. Now the sail I am looking at has a boom length of 222cm. Is this too close? Is the sail measured flat so you never tighten it to 222cm anyway? I am trying to get the biggest possible sail without getting a new boom.
Any thoughts or experiences would be appreciated. Thanks

Sail tunings are usually accurate to +-1cm if it's a relatively new saill (last 5 years). That is, with the recommended mast etc, to get the proper sail shape. You will probably be OK, though you won't have much room for any positive outhaul adjustment, should you wish to depower (flatten) the sail with postive downhaul/outhaul combination. Bottom line is the outhaul setting is the ideal rigging for that sail +-1cm, so you should theoretically have 2cm of wiggle room.

I just got me a new sail, a 6.6 Ezzy Infinity and went through the same measuring deal you are now. My old sail was a 6.0. I measured my max. reasonable boom length at 200 cm. This allowed about 6cm from the 194 printed on the sail. I also didn't want to get an extension (as I'm of Scottish heritage) so tortured over the luff length as well. I've rigged the sail three times now (it's ready for wind) and low and behold their numbers (the one's on the sail) were spot on, allowing full use of the sail. Theoretically you should be ok. You may want to see if your boom is stiff enough when that extended. It would be nice for you if the seller would just let you rig it up before you buy.

It sounds like you are looking to purchase a 7.5 to 8.5 M sail? These larger sails put tremendous forces on booms and using a boom near the limit of its extension is not going to provide a solid rig and as a result you would compromise a lot of the sails performance and wind range. (Need to keep the rig tensioned and draft locked in place) Further you will likely overstress your boom which will likely result in a premature failure. In sails of this size you should be using a carbon boom with a maximum of 60-70% of its extension range. Using extensions beyond this the boom becomes too soft and overstressed with large sails. This also has something to do with your physical size and sailing ability. If you are a strong sailor of medium to large build this is even more important since you are able to handle the forces and use the sail in stronger winds. In summary the performance of a sail is very sensitive to use of the proper mast, carbon boom (in this size with at least 30-40% of extension left in the tubes) and proper rigging. Without the correct mast or boom the sail will have limited speed, controlability and wind range. Also note not all carbon booms are created equal. You need one which is very rigid under a classic static test where you extend it to the lenght you need and stand on one arm and pull up on the other. If you can move it much (2-3 inches or more) think of what it will do under pressure with tons of outhaul forces trying to compress it. This would not be good. Hope this helps. Call if you have more questions!

tomv 656-0998

ditto, you'll break it if you are anything over anorexia weight fa sure or you do more than stand there to hold the thing up in 2 knots a wind....boom limits of up to 2ft extension are only a selling feature .....as Tom says ya need 2-3 settings below max to gain some stiffness and actually give the larger sails a chance to perform.

Hey thanks for all the input. As Clownboy is Scottish, I am of Dutch decent, basically cheap as well. Thats how copper wire was invented, his great grandfather and mine found a penny at the same time!!
Anyway I am after the biggest sail possible for light winds, however it seems I am better off getting a slightly smaller sail that doesn't max out my boom and mast as this will not only prolong the life of the boom but a smaller sail will perform more effeciently in light winds as well. I guess it is back to measuring and looking, thanks for all the help.
Obviously this is a very general question with many diferent factors but at what wind speed would a big board, like a GO 150L be able to get planning with a 7.5 or so sail. Average size/ability sailor, little chop etc.
Like Bobson was, I need more TOW, as I am getting back into windsurfing this is still a thrill.

Cheers

This is getting into "unofficial" terrritory but you may wish to try going to your local metal supply (Metral Supermarkets at 2111 Keating Cross in Saanichton) to purchase longer aluminum extension tubes for your booms.
I was in your position; another 3-4 inches on each end would make the extension more reasonable (stiffer) so I went there and purchased tubes about a foot longer than the old ones. The guy and I picked out the right diameter and he cut it for nothing. I think it cost about $15! I particularly like my old booms' width and oval grip. Of course, I had to drill a few holes and insert the spring clips. They are now very solid with at least 6 inches of insert depth on both ends. I gave about three inches of length before the clip hole to further increase stiffness.They do weigh a few ounces more but I seem to be tolerating it. They are not anodized so they will be prone to sticking but disassembly after use and rinsing have solved that problem. I fixed the grip tears with Aquaseal (from Whites) and all seems well. When I hit some moola again some super-light, super-stiff expensive carbonies will be sweet but for now I'm sailing at about 90% of my boom potential for a very low price.

I got a 7.5 sail last year, and was at first upset when it was about 2 cm too long for my new-that-spring booms (my others were late 80's). Bought a new aluminum from Excel, great deal (just over $200 I think, but check their website), now I can have two sails rigged, I really don't regret the extra money. I haven't had any problems (that I can attribute to the booms, at least) by having aluminum rather than carbon for the 7.5. It was fine last night gusting over 20 kt when kiters were "way overpowered on 12m", although perhaps carbon would have been less back-handed in the gusts. It wasn't so much a problem downhauled quite a bit but outhauled just a few cm from neutral. If it had got any stronger I would have just moved my harness lines back a bit and added a little more downhaul/outhaul - or rigged a smaller sail if there was time. Excel also has really good deals on carbon too, though when you can afford it.

I remember some pics in the rec.windsurfing site this summer that showed how some $-stressed Formula guys were stiffening their alu booms by cutting a small slit in their sail (Intentionally!!!!) and connecting the two boom halfs with a high-tech non-stretch line. Same or better rigidity as carbon, apparently, for a fraction of the cost.

Hey Chewy, email me() if you want. I might have a boom big enough for you if you want. How big of a sail are you thinking of going..?? I'm thinking for a GO 150 and your size you'd need about 12kts to start planing. Do you have or are getting a GO..?? You can try my hypersonic or Formula if you would like.