Has anyone done any speculative design for a wing sail for the Iceflyer?

I have been thinking about building a solid wing sail for my Ice Flyer. I know Wally Hall had discussed it at one time and his conclusion (I think) was that the pilot in front of the sail would disrupt the air flow too much. I would still like to build one if I can find some usable plans. If it doesn't work on the Ice Flyer, I can try it on the DN. Another project for next summer.

Roger Livingston

Roger,

Thanks for the reply! Searching around the net, I found several interesting projects folks have been doing with wingsails. One in particular seemed reasonably low tech, although perhaps a bit futzy in construction, but interesting as heck! The url to the site is:

http://www.trikini.com/Cheapwingsail

The wingsail is patterned after a chinese junk sail, but on a much smaller scale. The fellow uses it on small dinghy. Because of the relatively narrow bottom cord of the sail, and its lack of stays, I could envision a version that might perhaps be usable on an iceflyer. The sail bottom would have to be elevated so that would clear the pilot and be in free air, but perhaps it would make an interesting starting point for initial modelling on a small scale.

I will keep looking and doodling. Thanks again!

Regards,
Greg Paschak

Some day I may also experimenent with another type of sail on a boat similar to the iceflyer but at the moment Im fairly happy using the windsurfing sail but my sail is pretty fast (see this thread http://www.network54.com/Forum/151343/thread/1135202659/last-1135721904/RAF+versus+camber+sails ) and it makes a fun boat to sail..

Keep in mind that Im not an expert on sail design (I have basically an internet and trial and error education) but here is what I think about going to a higher perormance type of sail.

The windsuring industry has over the years put out "double luft" sails or wide luft sleeve sails and they sort of look like wing masted sails but they dont peform anywhere near as good as a wing masted sail (a wing mast sail has a foil shaped mast that might be 20% of the chord distance and the back end of the sail is some soft of cloth with battens). In my opinion, I think the difference is that the wing mast carefully maintains a partiular shape over the lee side of the sail where the wind is accelerated. The very leading edge of a wing mast must also be critcal and important since a windsurfing sail can have a nice looking lee shape but still not get the performance of a wing mast. On the windward side were the wind velocity is slowed down, the wing mast still has some pretty bad shape and still has a seperation bubble about where the mast ends but this doesnt seem to matter that much since wing mast sails perform reasonably well against slotted foil sails which probably have better control of the wind flow over the entire sail area.

So I think if you were to make some sort of foil sail, you need to pay a lot of attention to the first 20% and I think it should be fairly rigid so that it cannot deform under the potontially high pressure diferentials that "could" happen. In the land sailing world, they have been messing with mast shapes for a long time and I would be inclined to try and copy what works well.

Some other things to consider..

* the wing masted boats I have seen have a seperate control on the mast and a seperate control on the sheet. This allows the mast to be specifcally and optimally pointed and I think you need the independent control to really make it work well. Also, the mast can voilently oscillate if you just let it sit in the wind (for example, doing a tack at high speed) and on the one boat I sailed, you had to pull in on the mast sheet to constrain the mast from oscillating when you tacked the boat. The big rear sail ice boats out east must use some soft of self aligning wing mast config since they cant see the mast and how they do this, I dont know. Maybe it has something to do with where the mast pivots?

* You probably already know about this but there is a great resource here http://groups.msn.com/LandsailerandIceboatdesignandconstruction/messages.msnw on slotted flap sails. Its interesting that even with a five square meter limitation, these sails were becoming very high aspect which results in a higher center of effort and then a larger platform to handle it (much larger than either an Iceflyer or DN). Im not sure how important the platform size is to you (ie, 8 or 9 foot wide and 12 foot long) but its possible that a fairly small area slotted flap sail might work reasonably well. However, its still not certian that the very small size sail would peform better than a modified windurfing sail and Im fairly certain that it would not have the wind range of windsurfing sail - so Im not sure about the benifits of doing this.

If you do go to a slotted flap sail, you must worry about it oscillating. The boats like Phil Rothrock and John Eisenlohr build (see the msn link above) have a chain link between a hand held wheel and the sprocket which is rigidly attached to the bottom of the mast. The wheel has something like a 10 to 1 ratio for rotating the sail but this direct connection is important for keeping the sail from oscillating.

Alternatively, you can mass balance the sail and this means that the sail center of gravity should be in front of the sails rotational axis. In general, this wont be true if the sail rotation point is put close to the sail center of effort (which makes sheeting the sail easier). In general, mass balancing places a mass out in front of the sail leading edge (see http://www.windjet.co.uk/ - I believe the bar sticking out in front of the mast both is for mass balancing and also so that the pilot can look up and see where the sail is pointed but Im not sure). I personally dont like the idea of dealing with the mass so the rigid control of the sail would be the way I would go (similar to what Phil and John have done). Some of these boats are getting such a high aspect and tall mast that they still have to mass balance the top of the sail even with the rigid attachment at the bottom.

Anyhow, I still like the windsuring sail for this applicaiton but that is partly because of some of the places that I sail which are either small and gusty high winds or have areas that require a lot of maneuverbility and a sail which doesnt require a lot of attention. And I think the windsurfing sail can be made fairly fast. A few weeks ago I sailed with an ice flyer that had been in "moth balls" for a few years with a not well tuned and stock windsurfing sail and I was a really a lot faster. So I think messing with the windsuring sail is still a reasonable thing to do and they are non-linear enough that who knows what will work well.

I forgot to mention about the sail behind the pilot.

Overall, I dont think it is bad at all having the pilot right in front of the sail like on the iceflyer because while the lift of the sail in that area is probably reduced in that area, the free flow drag of the pilot is also reduced - possibly by a fair amount. It allows the pilot to sit upright and wear a heavier and safer helmet with a full face shield which is comforable and sort of like having your head in its own little enclosed cockpit. This is hard to tell for sure but I beleive the sail behind somehow reduces the effective wind on the pilot also adding to comfort without the "going into the water safety risk" of a real enclosed cockpit.

You need a larger platform in order to lay down like this but here is Phil Rothrocks solution http://groups.msn.com/LandsailerandIceboatdesignandconstruction/visittonalsaacabout1998.msnw?action=ShowPhoto&PhotoID=428
on a boat he had around 1998. This looked to me like one of the best balanced rear sail landyachts Ive seen so might be worth taking a good look at for ideas.

Thanks for the response on this topic WH, and the great links for additional information that you yourself have researched! Starting slowly to work on my first Iceflyer Classic, but the mind wanders and having been a pilot in my youth, it naturally struck me that this could be an intersting application for a wing. Will digest all this information as I go along, and will keep a close watch on the forum to see if you perhaps do eventually try such a planform for the excellent design of the Iceflyer. Again, thanks for all the information and your thoughts on the subject. This forum is an excellent venue to gain knowledge from experienced builders and sailors.