When I made my wing jib sail I had the idea to make it convertible so I could use it as both a jib sail, or a kayak sail on my Tandem Island (for sailing without the AMA's).
I have tried to use a standard Hobie kayak sail on my TI, and it's just too small for such a big boat (not worth putting up). I also tried kayak sailing with the main sail furled up, but it's just too big and top heavy to be able to kayak sail, even when furled way in, it makes the boat too top heavy.
As avid kayakers from way back we enjoy taking our TI as a kayak up river exploring, and to places where it just isn't practical to take all the rigging and AMA's.
When I designed and built my wing jib one thing I noticed right away was that the wing sail doesn't create hardly any side force (the force that is always trying to tip you over). And also when in the neutral position (not powered) it doesn't seem to create any drag, the wind just harmlessly skims past it not giving any driving force, or creating any measurable resistance.
All these traits are perfect for a kayak sail, a sail that when it's up and not powered, it can't tip you over, and it doesn't luff and shake around in the wind like the Hobie kayak sail does when lufting in the wind.
Here is a pic of my TI with the kayak wing sail
We have a long history of kayak sailing on Oasis and Revo's (we did that for years before getting the TI) so after my tests today I would compare the performance to be slightly better than a Revo with a kayak sail (I'm sure most everyone on here has kayak sailed, and understands the performance). The winds were 4-6 mph and I was able to sail upwind (about 30 degrees off the wind) at around 2+mph without pedaling. On a reach I got up to 4mph without pedaling, which was actually decent (maybe a little better than the revo would do in 5-6 mph winds). Downwind was quite a bit better than the revo (kayak sailing downwind on a revo isn't too impressive), I got up to around 4mph. Of course when I pedaled everything came alive (just like with the revo) and I got up to around 6+mph on a reach (while pedaling).
The wind kicked up to 8-9 mph as a storm was coming in, I was still able to do figure 8's easily with the sail up with no fear of tipping over. When in neutral the sail doesn't appear to create enough drag to worry about. I would probably by ok up to around 20 mph wind before wanting to furl it and take it down.
It's really odd looking going down wind with the sail pointing completely backwards, but hey it works (the sail freely pivots 360 degrees).
The sail furls and unfurls quickly and easily just like our Hobie kayak sails with the PVC furlers installed. The boom on the bottom, I'm not sure it's necessary when in kayak mode, (I could probably leave it off when kayaking). But it doesn't seem to get in my way at all, and helps keep the wing rigid.
Will I take it on my next kayak river adventure, probably not the dang thing is 18 ft long, and is really designed as a jib so a lot of efficiency is lost trying to use it as a mainsail. Yea it fits over the hull when furled up for transporting but not like a Hobie kayak sail that you can just attach to the paddle bungy on the side of the boat and your good to go.
Now that I know it works, if I get in the mood I will build a 4 ft by 12 foot tall square top furlable wing sail (about 45 sq ft) for use when we are kayak sailing (without AMA's), should be fun.
I did have 50 lbs of ballast in the hull, but if I had a second passenger, I don't think I would have needed it. The 50 lb ballast weight was left over from our old Oasis, so it lives on in yet another boat. LOL