I've been talking about these crazy wing sails for my TI for about a year now, I have finally completed my first wing sail ( 33 sq ft jib) and it actually survived my first wind tests (mounted on the boat (static)).
With Tropical storm Andrea going on, I ended up testing the sail out with the boat on the trailer in the front yard (way safer), since we had around 6 inches of rain, 40 mph winds and, and at least 6 tornados in the area today, plus huge surf (why I didn’t go out in the water).
About a year ago I read that wing sails are much more efficient (Americas cup and all), and because the way they work, there is much less heeling moment (the force trying to tip you over) when using wing sails. That was one of my issues with my original 35 sq ft jib (designed and built for my TI 3 yrs ago), when on a reach in higher winds, you could easily tip the boat over with all the sails deployed, plus severe weather helm when really pushing the boat (more so with the old rudder system). My original jib sail built 3 yrs ago finally wore out, and I have been studying for a year now learning all I can about wing sails with plans to replace all my sails with wing sails on my TI (talking about my plans on this forum, thus the reason for this post)). The reason being wing sails have an efficiency of 1.9 ( type E) (according to this article I read ( http://smalltridesign.com/masts/rig-mast_options.html
), whereas the standard TI sail (like my old jib) the best you can do is sail .85 (type A) times the wind according to this article. This stands to reason since TI's typically work out speed wise to about .6 to .8 of the available wind speed.
Here is the sail open (33 sq ft sail area)
Here is the sail all furled up ( I furled it and unfurled it around 50 times today, I was even able to furl it easily in 30 mph gusts (Tropical Storm Andria was going on today)
With the jib furled in a couple turns, it works as just a regular jib (the thick part is collapsed) ( discovered that today)
I now need two control lines to control the sail (the two lines work like the control bar on a kite so you can vary the shape and camber to suit), I'm still working on improving the control system.
Just like the old jib, it only takes a second or so to furl/unfurl the jib (I'm using the same 1 “ dia aluminum mast and PVC furler I had on my old jib, which works without any issues).
I had the sail out for a couple hours today in the front yard with winds 15-30 mph, making sure everything holds together, and flexing everything over and over again. When the gusts from the storm got really strong, I would furl it up and wait till things settle down (don't want to trash the darn thing before I get to use it).
The design I used is a conservative design with the average thickness of the wing being around 3 1/2 inches (about 10%), with the widest point being around 15% to 20% back from the front edge of the ‘length cord of the wing’. Since the wing is a soft wing and still flex's like a regular sail, I figured going too thick would be too low a reynolds number (too much drag in low wind conditions).
Wing sails are really complex, I probably wouldn't have started if I had known what I know now.
My original (non wing) jib sail 3 yrs ago took me a couple weeks to design and about a week to build, and around $30 bucks in materials (not including the cost of the old worn out Hobie kayak sail, that I used as a starting point). I used the jib for 3 yrs until it finally wore out. I've been designing this crazy wing sail for a year now, and construction has been over a month to this point, and I think I have at least another month of tweaking and adjustments. Was it worth it ( probably not). I’m over $100 dollars materials cost now (way over my limit).
Will I continue with my other wing sail designs, probably not for a while, I’m pretty burned out on all this now, though my wing spinnaker (screacher), would probably be really cool.
Is there any practical use for it (probably not)
Will it be more efficient than a standard jib of the same size, probably, but based on what I’ve learned, I now know why all boats don’t have wing sails (way too complex).
Will I do it again (NO) just wasn’t worth all the effort, too much thinking and not enough just enjoying sailing. Sails have been working just fine for 2000 yrs now with little to no change, who am I to change all that.
Are wing sails in all of our futures, probably yes, but let somebody else figure it all out, I’m pretty burned out on the subject now.
Some of my study sources are:
Tom Spear ( http://tspeer.com/
Several boat design forums (Doug Lord and others).
This guys website has some interesting information ( http://wingsails.com/
This guys rigid wing sail is novel but no way would I ever put anything like that on my TI (http://www.solidwingsails.com/
analysis and software used: Xfoil,Javafoil, and several others. All the 3D design work was done in Solidworks