“-1- Cost limitations
a class 5 mast can be homebuilt by an absolute amateur.”
>If you are talking about a new carbon mast, I would have to agree with you…but there is a lot of used equipment on the market…especially now that kite boarding has taken off and a lot of windsurfers have made a switch…at least in my area.
“-2- Sail efficiency.
A sailboat rig at this time can have a significantly higher aspect ratio then the windsurf rig.
I'm not sure that the current lower aspect surfer sails can easily be scaled up while retaining their excellent behavior.”
>The windsurfer rigs have been all over the place in respect to aspect ratio, but have settled into the sweet spot about twelve years ago after trying all the extremes, including much higher aspects than are available in the current offerings.
>For a while they felt that longer boom length with lower aspect was needed for low end power, and then went to extremes with high aspect for speed sailing to “reduce drag”. In the mid-eighties Gastra sails came out with “camber inducers” to force an air foil shape into the sail which gave a lot of stability to the foil of the sail…particularly noticeable in larger sails when sailing thru a lull, and building on the use of full length battens and the RAF (rotating asymmetrical foil) shape sails that Neal Pryde was offering at the time.
>Fast forward to the nineties… the sails went to monofilm and the cuts became better. Centered on a flexible yet quick resetting carbon mast (which allows the sail to maintain its ideal design shape a larger percentage of the time) with very stiff carbon booms (outhaul stability, if the boom flexes the sail draft increases and moves back…now you are looking at a “face plant”)
>Windsurfing moved away from the pin head sails and started putting more and more area in the head. By using a large square top design it allowed them to put more area in the sail for power to get up on a plane sooner as well as lowering the wind speed necessary to plane in the first place. The older style sales (especially in the larger sizes) quickly got out of control… but these new sails were cut flatter and were designed to have a complexly floppy leach at the top 30%+- of the sail. As the sail powers up, the top of the sail twists off and the draft (power center) moves down and forward…turning a gust into pure forward momentum. So they achieved a “best of both worlds” scenario. More sail area for light winds and a “self regulating” sail in high wind or gusty conditions…When properly tuned it’s like an automatic transmission for your car.
“-3- A cat is significantly different from a surfboard”
>I agree…this is where it could get interesting…to see if they are as different as they appear…
“Having the sail respond to a gust while it is not necessary means losing performance.”
>Again I agree…but at least when used in conjunction with a properly designed sailboard the sail design has been so dialed in that there is very little wasted energy. What would have blown you over, or caused a draft shift to the rear of the sail causing an “over the handlebars” situation in the past now gets converted to pure forward power and very balanced feel.
“At this time I feel a more conventional catamaran rig is more suited to getting optimal performance over the full range of conditions from light to strong.”
>That may prove to be the case, but we won’t know until it is seriously tried…the possibilities are exciting if the positive attribute will transfer over to the f12.
“It not about holding a sail down in all conditions, it is also about getting maximal performance in all of these conditions.”
>”Holding down the sail” was more in reference to the idea that, as in the past, windsurfers are forever changing the size of their sails to meet the changing wind conditions…I might add most catamarans are doing little more than “holding it down” in 25mph wind wouldn’t you say?
“-4- Windsurf sails don't really have a mainsheet system that affects the leech tension.”
While you are correct in saying that they don’t have a mainsheet system that affects leach tension… The outhaul tension, in conjunction with the down haul controls the leach tension to a very fine degree. Top of the line windsurfing sails are extremely “tunable”. This is generally done on the beach, however as I stated in my prior post some racers have used “on the fly” outhaul and downhaul adjustments to give the sail a fuller shape when course racing on downwind legs.
“I understand catamaran sails to a large extend and surf sails to a much lesser extend. In effect I do what I know best. Maybe somebody else needs to do the design work involved with F12 windsurfer sails?”
>I would have loved to be more deeply involved in this aspect of the F12 but family/business restraints have my plate overflowing…that said…any experience I have in this area that can be of help I freely offer…
>One of the coolest things about the windsurfer rig is… if can be set up with a way to accept a standard windsurfing mast base, you can try an endless variety of sails by just releasing the spring clip and snapping another on.
>Most serious sailors have a whole “quiver” of sails of the same brand and style, so you could see exactly how far to push the size limit before it became a point of diminishing returns. Same way with sail shape/style.
>It might be worth approaching some of the top windsurf sail manufactures, or a local windsurfing shop to see if they might want to become involved by offering sails/masts/booms/bases for the prototype in exchange for advertising exposure. I am sure they are feeling their revenue fall off drastically as Kite boarding as taken a big bite out of their market. Might be an easy sell with the prospect of opening a new market for their equipment… Wouter… with your track record with the F16 Class you might have the credibility to make that happen…