Regardless of what you decide I don't think using a 5.7 on that board is a good idea except in a very flat water or for non planing practice. The board is too wide and youl'll have a hard time controlling it. For the well being of it and your own get a fitting board first-something around 65 cm wide, no more. Then you'll realize/like I just did/ that the 6 to 7 sail range is more fun just then for just blasting and you'll want to replace that 6.5 Cheetah with a wave sail. This torture won't end soon, Im telling you. Not until we get to expert level and narrow our equipment to what we like to do best, until we find our way in other words.

Mast and Sail compatibility....

That's a subject for when the wind is not blowing. But, below are some links to a Unifiber chart that is updated nearly every year. Why every year??? Well, it turns out that some manufacturers change their sail-mast bend curvesfrom one year to the next. This is a good thing as windsurfing equipment is constantly evolving along with fins and boards.

For instance. Back in 2011 some of stiffest masts on the market were used on Maui Sails, Gaastra, Naish and Severn. But, for 2017 (found on the 2015 Unifiber chart link below) all of these manufacturers have softened up their masts and have reshaped their new sail luff sleeves and their sail twist characteristics. Also, notice that some new names have emerged for sails (e.g., Vandal, Attitude, Avanti, Bull and Challenger. And, I see S2 Maui is not on the list yet).

Either way, the charts are interesting and may provide an 'aha' moment for why some sails just don't look right when rigged on masts with bend curves that do not match the sail design. Again, some sail manufacturers change their bend characteristics from one year to the next. So getting the right year chart may make a difference.

Hope this helps a bit.......

www.unifiber.net/2011/mast-selector
www.unifiber.net/2012/mast-selector
www.unifiber.net/2014/mast-selector
www.unifiber.net/2015/mast-selector (now includes the 2017 sail year)

I just don't understand why Ezzy keep labeling their masts as constant curve when they are soft top -bend curve 15-on par with Neil Pryde. On the Unifiber chart they should be 3 squares to the right and Sailworks should be one square to the left.

Ady,
You make a good point. And I will not presume to know the finer details about mast bend curves.

Discussion:
The Ezzy website (www.ezzy.com/masts/mast-overview/) offers the following: "Ezzy mast bend curves are tip: 75% to 79% and base: 62% to 65%". This would make the Ezzy mast softer at the top than at its base making it more of a Flex-Top than a pure Constant Curve. That seems to be reflected in the Unifiber chart where the dots are over towards the 'Flex-Top category on the Unifiber chart.

The Ezzy mast is definitely not as soft as a Neil Pryde mast, especially in the Top., Also, consider that PowerEx offers a special flex-top mast with a special "NP" designation specifically for use with Neil Pryde sails. www.powerexmasts.com/products/details.php?product=8

This past spring I rigged a 460 PowerEx Mast on an older mono-film Neil Pryde sail and found it hard to downhaul to the point of loosening the leech. After getting the leech a little loose, the upper battens (head of the sail) were still not completely flat. The mast was notably a 'little' too stiff in the top.. I told my friend to be aware and careful not to get catapulted as there was quite a bit of power in the head of the sail. He came off the water a couple of hours late and said it was the fastest he's ever gone with that sail. Ah...., that's the beauty of an older mono-film Neil Pryde sail. Light and fast.

By the way. I just saw the picture of your beautiful 'duck-jibe'.
Man, I wish I could that. It's one of the fastest, smoothest, planing ways to turn a board.
OK then! I now have a new goal.............

Douglas King wrote: This seasons trophy together with the Helly Tack Im late actually, it was supposed to happen last year, but after the initial failures I decided to postpone it until I get a better board for the task. After realizing that there will be no new board this year I restarted the effort and it finally clicked. Im dead set on the Forward Loop now , but with the lack of strong wind for my 86L board this will probably not happen any time soon.

Ady,
Did you say 'Forward Loop'??
I like the music on this "How To" video......... "The Secret of the Forward Loop"...
And, it simply wears me out just watching it......

That video is awesome!

Now, back to my sail issue. I can put my hands on a new 2017 Severne Blade 5.7 for 15% off. I know: this doesn't necessarily make the sail exactly what I need cause this one is really a wave sail, but it is such a nice piece of gear that I'm tempted to buy it and hang it over my bed!

BLADE

The 017 Blade is a 5 batten wave sail with the perfect blend of power and control. Sail profiles are designed for maximum stability and wind range. Moderate head tension allows responsive twist.

Here is the claim:
Constructed entirely out of premium X-Ply, the Blade is one of the most durable sails on the market, yet intelligent design means it’s also one of the lightest. SpiderFibre technology has radically reduced swing weight whilst also creating a much stronger clew. New Dyneema window X-Ply allows for improved vision. Upper panels in eM3 reduce swing weight, and heavy duty heX-Ply in the foot for impact strength.
The 017 Blade is the sail to choose for all-round high performance.

The sail is surely fantastic, but what about the mast again? If you are moving away from the soft top youll be better with the Sailworks Revo and Sumo masts I believe -for costumer service, availability etc.

Mast Compatibility.... Yes Indeed.......
Gregory, Is your mast an Ezzy 430 RDM?
If so, the 2017 Severn sail will require a much stiffer RDM mast in the top.

BTW I can sell you a very decent 5.8 for blasting its a crossover from Ka Sails that will work on the Ezzy mast. It may be a temporary solution, but for 150$ ?!

Doug, Ady,
These are the comparative data I got directly from Severne on a 400 mast
EZZY: 64.2 19 76.3
SV: 63.2 19.5 75.7
Are the differences that significant?

Not on paper, but I can bet the haus that the Ezzy numbers are way off. Where did you get them, they look like Sailworks numbers!