• To see how I made a disc sail click this
• This is how it worked first time out in a packraft
• This is how it worked first time out in my Incept kayak
• And this is a proper Pacific Action ‘V’ sail fitted on my K40
• Here’s a post about using the PA in strong winds in Western Australia. There’s a video too
  
• Andy Pink’s kayak sailing page (French translated)
• My current sail – a knock-off ‘Windpaddle’
• Giving up on the cheap Windpaddle
• Trying out a WindPaddle Adventure II sail on my Seawave
  
• MRS Packraft with WindPaddle II

Updated summer 2019

You may have read in the Shark Bay story what a relief it was to turn into the wind at Cape Peron, get Jeff to flick up his Pacific Action sail (below left) and shoot down across the Reach, with me clinging to Jeff’s hefty sea kayak. There’s a bit more Pacific Action sailing action attached to an Incept K40 in this video.
To me, sailing a kayak or packraft is a smart idea in the right conditions and with kayaks, some people think so too. The now moribund US-dominated packraft forum didn’t get so excited when a bloke demo’d his WindPaddle (see below); perhaps in the US most packrafters do rivers, not lakes or certainly not sea. In Scotland where the lochs can be long wind-channels and the boggy ground alongside horrible to walk over with a full pack, sailing a packraft down a 20-km valley full of water in half the time it would take to paddle makes sense.

V-sails and Umbrella sailing
I never got round to fitting a Pacific Action sail [video and left] onto the Sunny IK. In the UK they cost around £250 but it’s more or less two sticks and a sheet and some string. Here is a great thread on SotP about making your own V-sail, although now I notice the original model of the PA sails going for as little as £160 in the UK to make way for the new, mostly clear models.
I read about a guy who mentioned he umbrella-sailed his packraft back across an Arizona lake on an afternoon breeze. So with an old brolly I’ve barely used in 20 years, I gave it a go.
First time was in the Sunny kayak on a very windy day – too windy in fact. I found an out-of-the-way loch on the north side of Stac Polly mountain, hacked into the 20 mph headwind, turned round and opened up the umbrella expecting to catch the wind and rip back to the shore like an ekranoplan. No such luck. In a way the good thing with a brolly is that it inverts long before it drags you out of the boat and across the lake like a character from a cartoon. But because of that in-built safety overload I couldn’t get going. Oddly, all that happened was instead of the bow coming round down wind, the boat kept getting side-on until the brolly inverting on a gust. Why side on? Was it the fact that the sail’s pivot point was effectively my shoulder in the middle of the boat, and not a point fixed on the front end? Could be.
A few days later I tried with my much lighter Llama packraft, but this rare day there was not enough wind to prove anything. As you can see left, I tried to use the paddle as a rudder, but on that day it would have been better used in its traditional role.

Flip-out disc sails
Since then ‘flip-out’ disc sails came to my attention: lighter, simpler and more compact than a PA. They work like those clever flip-out tents (see below): release a sling and it springs into shape on an unfurling hoop or batten. I made myself one from a spare tent.
Here is a great IK page by a French gonflard, Andypink picturing all sorts of kayak sails and having assessed all out there, he designed a 1.2m2 ‘spoon sail‘ which is now being sold by Bic (right) for about £50 – just under half the price of a smaller US-made WindPaddle (good canoer’s review here). As you’d expect, the places selling the Bic in the UK merely parrot the blurb from Bic  with no detailed analysis or photos of it in use. To do that you have to dig into Andy P’s blog; there are photos of an actual Bic-in-action here and here and especially here (also left, his picture cropped for clarity). You can see there are no less than three attachment points on each side of the sail.
Having used my similar but ultra-basic home-made version, I’d say the properly designed Bic differs in the following ways:

• It has a window – always nice to see what’s ahead.
• I assumed the inverted teardrop shape would make it unstable, but I suspect the close base-mount points make it easier to pull the sail hard down to one side for angling off the wind at up to 45°. And like a PA, it’s bigger up top where there’s significantly more wind.
• The ‘control string’ attaches to the side of the sail at three points and then is attached to the hull (not one point and held in the hand like my MYO disc). I presume they are all chosen in position and length to maintain a certain optimal form. 
• It appears the dishing as featured on a WindPaddle and its knock-offs is not necessary.

Here’s a good intro to kayak sailing on Douglas Wilcox’s inspiring Scottish sea kayaking blog. DW paddles hardshells mostly, has actual sail boat experience and these days uses a fixed Flat Earth sail (a jib?) which I don’t think would work on an IK.
Douglas told me that on the faster boats they all use (proper sea kayaks with bows sharp enough to cut week-old brie) the WindPaddle proved to have a fairly narrow range of operational effectiveness (same with the Bic I imagine). In a strong wind the flexible hoop distorts and loses effectiveness; and in a light wind they find it’s barely worth the bother. But don’t forget this is in a slick kayak that can easily be paddled at 5mph while slicing through the swell. A packraft manages about half that and fast IK like a Seawave or Incept maybe 70-80% of that speed. So at the lower wind speeds I can paddle, a sail may be worthwhile – and in sail-distorting high winds; well, it didn’t happen with mine in 20mph winds (F4-5). I didn’t go that fast, but I can’t see me voluntarily being out at sea at wind speeds of 30mph, which is F6. It’s F7 out the window right now, pelting down and the sea looks utterly grim.
A ‘0.9m2’ WindPaddle is the same size as my disc sail, left (ie: 1m diametre which = a radius of 0.5m x 0.5m x π actually = 0.785 m2, but perhaps the dishing makes a bigger area?). As this guy suggests, this may not represent great value for money for a nylon sheet in a hoop plus some string. My own disc sail seems to work OK, but I may end up trying a Pacific Action – see below. My only reservations might be that it’s yet more stuff and a Bic or PA may be a little more complicated to rig and operate than a plain old disc sail.

More kayak and packraft sailing thoughts
I forget of course that my disc sail was primarily made as a portable sail for my packraft; I never really expected it to work on what was my Incept IK, but having done so anyway, I think at 0.78m2 it’s too small and too low. I block much of the backwind and I’ve been told the higher a sail the better it works; it’s just that too much height can affect stability in a gust. We don’t want that.
We were out yesterday on Loch Broom with Steve and Micheal in the Feathercrafts and me in the K40. By the time we finally put in at the back of the loch near the river, it had gotten windy and the fetch up the valley was pushing up a short chop which mid-loch, made forward progress slow. But now I have a nifty way of carrying my disc sail securely and out of the way on the Incept (right), I went right ahead and deployed it for the return. As before, I found that a stiff headwind paddled into at 2-3mph (see graph, left), didn’t correspond into a scintillating downwind glide under sail. Top speed was just over 4mph at which point things begin to get interesting and you want more. But most of the time Steve was able to keep up and even take pictures between paddling his Kahuna, so all I was gaining was some rest rather than extra speed.
Nothing wrong with resting on the move, but compact and handy though it is, I think my home-made disc sail is too small to get the K40 moving with my weight in it, let alone adding a camping payload. Researching more about V-sails, including the SotP thread mentioned above, I see that here and there PA sails are getting discounted to nearly the same price as a WindPaddle.
Having thought it over and actually seen one in use, a PA is more like the real thing compared to any disc sail, whose USP is that they’re compact and deploy in a flash. What a WindPaddle, Bic or my home-made disc sail can’t do so easily on the water in anything longer than a packraft is fold up easily. On an Alpacka you just reach forward and twist the disc sail down out of the way and clamp it, but alone on a choppy sea in a long kayak, it’s far out of reach on the bow of my Incept, unless I just pull it back and lash it down over my knees. A headwind would hold it in place like that, but one may have other things on one’s mind in heavy conditions and a side- or backwind gust could catch it where it might dig into the water and act as an unwanted sea anchor, upsetting the boat. We don’t want that either.
Update – a cheap Windpaddle knock-off (above left).
So, having experimented with the concept of kayak sailing for little outlay, I can now see the value in actually buying something like a PA that’s made for the job, partly because we’re intending to paddle the Ningaloo this September where a sail will be useful, and sail-savvy Jeff (left) will be there to give me some tuition in the art. Short version: it didn’t go so well for me.
Where’s a windy day when you want one? Not today, but the next time I must take the Alpacka Yak out with the disc sail and see if the new shape and a bit more experience makes any difference. As you can see here, it wasn’t so conclusive with the old shape Llama on a reservoir in Surrey, but the pointier Yak, a bit of paddle rudder finesse and a stiff Hebridean breeze may make a difference.

Pic below:  not given up on WindPaddle sailing yet.